Patent Publication Number: US-10311242-B2

Title: Distributed system resource liens

Description:
TECHNICAL FIELD 
     This disclosure relates to assessing liens on resources of distributed systems. 
     BACKGROUND 
     A distributed system may include many interconnected hardware and software resources. Due to the vast number of resources in a distributed system, some distributed systems are very complex and difficult to understand. Moreover, in large distributed systems, some resources may affect the operation of other resources. As the size of a distributed system increases, it becomes increasingly difficult to ascertain the effect of a particular resource on other resources in the distributed system. 
     SUMMARY 
     One aspect of the disclosure provides a method for accessing liens on resources of distributed systems. The method includes receiving, at data processing hardware, an operation control request. The operation control request identifies a lien requestor, a resource of a distributed system, and at least one restricted operation for the resource of the distributed system. The method also includes associating, by the data processing hardware, an operation control lien with the resource of the distributed system based on the operation control request. The operation control lien identifies the lien requestor and the at least one restricted operation for the resource of the distributed system. The method further includes: receiving, at the data processing hardware, an operation request to execute a corresponding operation on the resource of the distributed system; determining, by the data processing hardware, that the corresponding operation of the operation request is a restricted operation identified by the operation control lien associated with the resource of the distributed system; and restricting, by the data processing hardware, execution of the corresponding operation of the operation request. 
     Implementations of the disclosure may include one or more of the following optional features. In some implementations, restricting execution of the corresponding operation includes denying execution of the corresponding operation. The method may also include: receiving, at the data processing hardware, a subsequent operation request to execute the corresponding operation on the resource of the distributed system; determining, by the data processing hardware that the corresponding operation of the subsequent operation request is an unrestricted operation not identified by any operation control lien associated with the resource of the distributed system; and allowing, by the data processing hardware, unrestricted execution of the corresponding operation. 
     In some examples, the method includes receiving, at the data processing hardware, a lien requestor existence indicator indicating that the lien requestor of the operation control request no longer exists and disassociating, by the data processing hardware, any operation control liens based on any operation control requests of the lien requestor from any corresponding resources of the distributed system. The method may also include receiving, at the data processing hardware, a remove request from the lien requestor and disassociating, by the data processing hardware, the corresponding operation control lien from the resource of the distributed system. The remove request may identify the resource of the distributed system and the corresponding associated operation control lien previously requested by the lien requestor. 
     In some implementations, the method includes returning, from the data processing hardware, a message indicating the corresponding restricted operation for the resource of the distributed system. The message may indicate the lien requestor. The operation control request may also identify an operation control description and the message may indicate the operation control description. Determining that the corresponding operation of the operation request is the restricted operation may include: determining a parent-child relationship between the resource of the distributed system and other resources of the distributed system; determining that the resource of the distributed system is a parent resource having at least one depending child resource; and determining that the parent resource has at least one associated operation control lien. The method may further include receiving, at the data processing hardware, an update request from the lien requestor and updating, by the data processing hardware, the corresponding operation control lien associated with the of the resource of the distributed system as identifying the at least one updated restricted operation. The update request may identify the resource of the distributed system, the corresponding associated operation control lien, and at least one updated restricted operation for the control lien. 
     Another aspect of the disclosure provides a system for accessing liens on resources of distributed systems. The system includes data processing hardware and memory hardware in communication with the data processing hardware. The memory hardware stores instructions that when executed on the data processing hardware cause the data processing hardware to perform operations. The operations include receiving an operation control request and associating an operation control lien with the resource of the distributed system based on the operation control request. The operation control request identifies a lien requestor, a resource of a distributed system, and at least one restricted operation for the resource of the distributed system. The operation control lien identifies the lien requestor and the at least one restricted operation for the resource of the distributed system. The operations also include: receiving an operation request to execute a corresponding operation on the resource of the distributed system; determining that the corresponding operation of the operation request is a restricted operation identified by the operation control lien associated with the resource of the distributed system; and restricting execution of the corresponding operation of the operation request. 
     This aspect may include one or more of the following optional features. In some implementations, restricting execution of the corresponding operation includes denying execution of the corresponding operation. The operations may also include receiving a subsequent operation request to execute the corresponding operation on the resource of the distributed system, determining that the corresponding operation of the subsequent operation request is an unrestricted operation not identified by any operation control lien associated with the resource of the distributed system, and allowing unrestricted execution of the corresponding operation. The operations may further include receiving a lien requestor existence indicator indicating that the lien requestor of the operation control request no longer exists and disassociating any operation control liens based on any operation control requests of the lien requestor from any corresponding resources of the distributed system. 
     In some examples, the operations include receiving a remove request from the lien requestor and disassociating the corresponding operation control lien from the resource of the distributed system. The remove request may identify the resource of the distributed system and the corresponding associated operation control lien previously requested by the lien requestor. The operations may also include returning, from the data processing hardware, a message indicating the corresponding restricted operation for the resource of the distributed system. The message may indicate the lien requestor. 
     In some implementations, the operation control request further identifies an operation control description and the message indicates the operation control description. Determining that the corresponding operation of the operation request is the restricted operation may include: determining a parent-child relationship between the resource of the distributed system and other resources of the distributed system; determining that the resource of the distributed system is a parent resource having at least one depending child resource; and determining that the parent resource has at least one associated operation control lien. The operations may further include receiving an update request from the lien requestor and updating the corresponding operation control lien associated with the resource of the distributed system as identifying the at least one updated restricted operation. The update request may identify the resource of the distributed system, the corresponding associated operation control lien, and at least one updated restricted operation for the control lien. 
     Yet another aspect of the disclosure provides a second method for accessing liens on resources of distributed systems. The method includes receiving, at the data processing hardware, an operation request to execute a corresponding operation on a resource of a distributed system and determining, by the data processing hardware, that the resource of the distributed system has an associated operation control lien. The operation control lien identifies a lien requestor and at least one restricted operation for the resource of the distributed system. The method also includes determining, by the data processing hardware, that the corresponding operation of the operation request is a restricted operation identified by the operation control lien associated with the resource of the distributed system and restricting, by the data processing hardware, execution of the corresponding operation of the operation request on the resource of the distributed system. 
     This aspect may include one or more of the following optional features. In some implementations, restricting execution of the corresponding operation of the operation request may include denying execution of the corresponding operation. The method may also include: receiving, at the data processing hardware, a subsequent operation request to execute the corresponding operation on the resource of the distributed system; determining, by the data processing hardware that the corresponding operation of the subsequent operation request is an unrestricted operation not identified by any operation control lien associated with the resource of the distributed system; and allowing, by the data processing hardware, unrestricted execution of the corresponding operation. The method may also include receiving, at the data processing hardware, a lien requestor existence indicator indicating that the lien requestor no longer exists and disassociating, by the data processing hardware, any operation control liens identifying the lien requestor from any corresponding resources of the distributed system. 
     In some examples, the method includes receiving, at the data processing hardware, a remove request from the lien requestor and disassociating, by the data processing hardware, the corresponding operation control lien from the resource of the distributed system. The remove request may identify the resource of the distributed system and the corresponding associated operation control lien previously requested by the lien requestor. The method may further include returning, from the data processing hardware, a message indicating the corresponding restricted operation for the resource of the distributed system, the message indicating the lien requestor. 
     Yet another aspect of the disclosure provides a system for accessing liens on resources of distributed systems. The system includes data processing hardware and memory hardware in communication with the data processing hardware. The memory hardware stores instructions that when executed on the data processing hardware cause the data processing hardware to perform operations. The operations include receiving an operation request to execute a corresponding operation on a resource of a distributed system and determining that the resource of the distributed system has an associated operation control lien. The operation control lien identifies a lien requestor and at least one restricted operation for the resource of the distributed system. The operations also include determining that the corresponding operation of the operation request is a restricted operation identified by the operation control lien associated with the resource of the distributed system and restricting execution of the corresponding operation of the operation request on the resource of the distributed system. 
     This aspect may include one or more of the following optional features. In some implementations, restricting execution of the corresponding operation of the operation request includes denying execution of the corresponding operation. The operations may also include receiving a subsequent operation request to execute the corresponding operation on the resource of the distributed system, determining that the corresponding operation of the subsequent operation request is an unrestricted operation not identified by any operation control lien associated with the resource of the distributed system and allowing unrestricted execution of the corresponding operation. The operations may further include receiving a lien requestor existence indicator indicating that the lien requestor no longer exists and disassociating any operation control liens identifying the lien requestor from any corresponding resources of the distributed system. 
     In some examples, the operations include receiving a remove request from the lien requestor and disassociating the corresponding operation control lien from the resource of the distributed system. The remove request may identify the resource of the distributed system and the corresponding associated operation control lien previously requested by the lien requestor. The operations may also include returning, from the data processing hardware, a message indicating the corresponding restricted operation for the resource of the distributed system, the message indicating the lien requestor. 
     The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of an example resource lien environment. 
         FIG. 2A-2C  are block diagrams of example operation control lien modules. 
         FIG. 3A-3C  are example arrangements of operations for evaluating an operation request. 
         FIG. 4  is an example arrangement of operations performed by an operation control lien module. 
         FIG. 5  is a block diagram of an example distributed system. 
         FIG. 6  is a block diagram of an example distributed system. 
         FIG. 7  is a schematic view of an example computing device that may be used to implement the systems and methods described in this document. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     Typically, a distributed system offers several advantages. The distributed system may have a greater amount of system resources accessible to users of the distributed system and also have a greater amount of computing power to perform operations for users. However, because distributed systems share system resources, the use of one resource may become dependent on another resource. With such dependencies, modification or deletion of a resource may have a detrimental or a catastrophic impact on tasks or resources depending on the modified or the deleted resource. For example, applications that rely on a resource or resources for interoperability become inoperable without those underlying resources. Thus, systems with shared resources have a need to warn or to prevent other users that attempt to modify or to delete a resource within the system that is being used in other capacities. Much like how a property lien stakes a legal claim on tangible property, a resource lien serves to indicate a computing claim on a distributed system resource. Therefore, the resource lien may function as a recordation of the use of a resource and prevent damage to other tasks or resources depending on that resource. For example, a system and/or method of assessing a resource lien may provide reference to a resource with a lien, may provide a representation of who or what generated the resource lien, and may provide an explanation of why the resource lien exists while constraining or permitting various actions on the resource lien, such as creating a new resource lien, updating an existing lien, or removing an existing lien. 
       FIG. 1  depicts an example resource lien environment  10  for managing a distributed system  100  with an operation control lien module  200 . The operation control lien module  200  can access the distributed system  100  via a network  130 . An entity, such as a resource owner  20  or a resource user  30 , may use a computer  120  (e.g.,  120   a  and  120   b ) to access the distributed system  100  and/or the operation control lien module  200 . Although, in the example of  FIG. 1 , the operation control lien module  200  is shown as separate from the distributed system  100 , in other implementations the operation control lien module  200  may be a part of the distributed system  100 . In other words, the operation control lien module  200  may be implemented using the resources  110  of the distributed system  100 . 
     The resource lien environment  10  includes the resource owner  20  who is an entity in charge of a resource  110  of the distributed system  100 . For example, the resource owner  20  is a creator of a resource  110  or an entity designated with privileges/permissions to manage the resource  110 . As the entity in charge of the resource  110 , the resource owner  20  has access privileges (e.g., root privileges) to the corresponding resource  110 , such as read or write access. Therefore, the resource owner  20  may modify or delete the resource  110  managed by the resource owner  20 . In the resource lien environment  10 , when the resource owner  20  seeks to perform an operation (e.g., modify, edit, update, delete, etc.) on the resource  110 , the resource owner  20  generates an operation request  230 . The operation control lien module  200  receives the operation request  230  from the resource owner  20  and informs the resource owner  20  if the operation is encumbered by an operation control lien  220 . Each resource  110  of the distributed system  100  has a corresponding resource owner  20 . In some examples, if the resource owner  20  corresponding to a given resource  110  is undefined, the distributed system  100  may designate a default resource owner  20 . 
     Referring further to  FIG. 1 , the resource lien environment  10  includes the resource user  30 . The resource user  30  is an entity that decides to use a resource  110  that corresponds to the resource owner  20 . For example, the resource user  30  may be an entity that has access to resources  110  of the distributed system  100 . When the resource user  30  decides to use a resource  110  of the distributed system  100 , the resource user  30  generates an operation control request  210  to identify the use of the corresponding resource  110  by the resource user  30 . The operation control lien module  200  receives the operation control request  210  from the resource user  30  and generates an operation control lien  220  for the corresponding resource  110 . 
     Generally, resources  110  of the distributed system  100  may include hardware resources  110   h  and software resources  110   s . The hardware resources  110   h  include data processing hardware  112  and memory hardware  114 . The software resources  110   s  may include software applications, software services, application programming interfaces (APIs) or the like. The software resources  110   s  may reside on the hardware resources  110   h  (e.g., stored in the memory hardware  114 ) or may include instructions executed on the data processing hardware  112 . 
     A software application (i.e., a software resource  110   s ) may refer to computer software that causes a computing device to perform a task. In some examples, a software application may be referred to as an “application,” an “app,” or a “program.” Example applications include, but are not limited to, system diagnostic applications, system management applications, system maintenance applications, word processing applications, spreadsheet applications, messaging applications, media streaming applications, social networking applications, and gaming applications. 
     The memory hardware  114  is non-transitory memory that may be physical devices used to store programs (e.g., sequences of instructions) or data (e.g., program state information) on a temporary or permanent basis for use by data processing hardware  112 . The memory hardware  114  may be volatile and/or non-volatile addressable semiconductor memory. Examples of non-volatile memory include, but are not limited to, flash memory and read-only memory (ROM)/programmable read-only memory (PROM)/erasable programmable read-only memory (EPROM)/electronically erasable programmable read-only memory (EEPROM) (e.g., typically used for firmware, such as boot programs) as well as disks or tapes. Examples of volatile memory include, but are not limited to, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), and phase change memory (PCM). 
       FIG. 2A  illustrates an example operation control lien module  200 . The operation control lien module  200  receives the operation control request  210 . The operation control request  210  identifies a lien requestor  212 , at least one resource identifier  214  corresponding to at least one resource  110 , and at least one restricted operation  216  for the at least one resource  110  of the distributed system  100 . In some examples, the lien requestor  212  is the resource user  30 . However, the lien requestor  212  may also be an entity besides the resource user  30  that the resource user  30  designates as the lien requestor  212 , such as a manager or a project owner corresponding to the use of the at least one resource  110  relating to the at least one resource identifier  214 . Additionally or alternatively, the lien requestor  212  may be a data string providing a name of the lien requestor  212 , an identifier of the lien requestor  212 , or contact information regarding the lien requestor  212 . The at least one restricted operation  216  may be any operation capable of being performed on the at least one resource  110 . Some examples of the at least one restricted operation  216  include modifying, editing, updating, or deleting the at least one resource  110 . In some examples, the operation control request  210  includes additional fields and/or custom fields, such as a field identifying other resources  110  linked to the at least one resource  110  of the at least one resource identifier  214 , a field describing a use of the at least one resource  110 , a field identifying a level of severity of the use of the at least one resource  110 , or a field of contact information relating to the lien requestor  212  or the resource user  30 . 
     Referring further to  FIG. 2A , based on the operation control request  210 , the operation control lien module  200  associates an operation control lien  220  with the at least one resource  110  of the at least one resource identifier  214  identified by the operation control request  210 . The operation control lien  220  identifies the lien requestor  212 , the at least one restricted operation  216 , and the at least one resource identifier  214  relating to the at least one restricted operation  216  of the at least one resource  110 . In some examples, such as where an operation control lien module  200  seeks to minimize data storage related to an operation control lien  220 , the operation control lien  220  may minimally identify the at least one resource  110  via the at least one resource identifier  214  and a related at least one restricted operation  216 . Each operation control lien  220  generated by the operation control lien module  200  may be stored within the distributed system  100 . 
     Unlike an access control list (ACL), which is simply a list of permissions attached to an object, the operation control lien  220  identifies the lien requestor  212  and optionally a reason why the operation control lien  220  exists. Moreover, the operation control lien  220  may be agnostic as to specific user permissions and may have a global restriction (e.g., does not allow deletion by anyone). In contrast, a typical ACL merely specifies which users or system processes are granted access to objects, as well as what operations are allowed on given objects. Each entry in a typical ACL specifies a subject and an operation. For instance, a file object having an ACL containing “(Ann: read, write; Brian: read)” provides Ann permission to read and write the file and Brian permission to only read the file. The ACL fails to indicate the author or originator of the ACL or any reason why the ACL exists. 
     As  FIG. 2A  illustrates, the operation control lien module  200  may receive an operation request  230  from the resource owner  20  to execute a corresponding operation on a resource  110  of the distributed system  100 . In some implementations, the operation request  230  includes a request operation  232  and an operation request resource identifier  234  identifying at least one resource  110 . Much like the at least one restricted operation  216 , the request operation  232  is a request to execute an operation that modifies, edits, updates, or deletes the at least one resource  110  of the corresponding operation request  230 . Additionally or alternatively, the operation request  230  also identifies an operation control description  236  describing the request operation  232  on the at least one resource  110  related to the operation request resource identifier  234 . 
       FIG. 2B  is another example of an operation control lien module  200 . Rather than a lien request process where an operation control lien module  200  receives an operation control request  210  and converts the operation control request  210  to an operation control lien  220 , a lien requestor  212  generates an operation control lien  220  based on at least one restricted operation  216  and a corresponding resource  110  of at least one identifier  214 . A database  240  of operation control liens  220  may store the operation control lien  220  generated by the lien requestor  212 . The database  240  may be part of the distributed system  100  or a separate database accessible to the operation control lien module  200 . In some examples, the operation control lien module  200  receives the operation request  230  to execute a corresponding operation on the at least one resource  110  related to the operation request  230  and determines whether the at least one resource  110  has an associated operation control lien  220 . For example, the operation control lien module  200  queries the database  240  for operation control liens  220  that relate to the at least one resource  110  of the operation request resource identifier  234 . 
     Optionally, the operation control lien module  200  automatically generates the operation control lien  220  when a resource user  30  uses a resource  110  of the distributed system  100 . In some implementations, when the operation control lien module  200  automatically generates the operation control lien  220 , the operation control lien module  200  may default the corresponding restricted operation  216  related to the resource  110  of the resource user  30  and/or default the lien requestor  212  as the resource user  30 . 
       FIG. 2C  illustrates additional functions of an operation control lien module  200 . Although  FIG. 2C  depicts the operation control lien module  200  performing each function, an operation control lien module  200  may perform any combination of these functions (e.g.,  250 - 270 ). In some examples, the operation control lien module  200  receives a remove request  250  from the lien requestor  212 . The remove request  250  identifies a resource  110  of the distributed system  100  and a corresponding operation control lien  220  related to the resource  110 . In response to the remove request  250 , the operation control lien module  200  disassociates  252  the corresponding operation control lien  220  from the resource  110 . In these examples, only the lien requestor  212  can remove operation control liens  220  related to a resource  110 . By allowing only the lien requestor  212  to remove operation control liens  220 , the operation control lien module  200  prevents an entity from disregarding inherent safeguards of an operation control lien  220 , such as warning or preventing an entity from performing at least one restricted operation  216  on a resource  110  being used by a resource user  30 . 
     In some implementations, the operation control lien module  200  receives a lien requestor existence indicator  260 . The lien requestor existence indicator  260  indicates that a lien requestor  212  corresponding to an operation control request  210  no longer exists. In these implementations, when the operation control lien module  200  receives the lien requestor existence indicator  260 , the operation control lien module  200  dissociates  262  any operation control liens  220  based on any operation control requests  210  of the lien requestor  212  for any corresponding resources  110  of the distributed system  100 . 
     Referring further to  FIG. 2C , the operation control lien module  200  may receive an update request  270  from the lien requestor  212 . The update request  270  identifies a resource  110  of the distributed system  100  to be updated, an operation control lien  220  corresponding to the resource  110 , and at least one restricted operation  216  to be updated for the operation control lien  220 . When the operation control lien module  200  receives the update request  270  from the lien requestor  212 , the operation control lien module  200  updates  272  the operation control lien  220  associated with the resource  110  with the identified at least one restricted operation  216  corresponding to the update request  270 . 
       FIG. 3A  illustrates an example method  300  for accessing liens on resources  110  of distributed systems  100 . Operations associated with the method  300  begin when the operation control lien module  200  receives an operation request  230  to execute a request operation  232  on an at least one resource  110 . Referring to  FIG. 3A , at  302 , the operation control lien module  200  determines whether the operation request resource identifier  234  identifies the resource  110  associated with an operation control lien  220 . When the operation request resource identifier  234  identifies the resource  110  associated with the operation control lien  220 , the method  300 , at  304 , determines if the request operation  232  of the operation request  230  is at least one restricted operation  216  identified by the operation control lien  220 . At  306 , when the operation control lien module  200  determines that the operation request resource identifier  234  does not identify the resource  110  of at least one operation control lien  220  or that the request operation  232  is not at least one restricted operation  216  (e.g., an unrestricted operation not identified by any operation control lien  220 ), the operation control lien module  200  allows unrestricted execution of the request operation  232  on the resource  110  identified by the operation request resource identifier  234 . When, however, the request operation  232  is the at least one restricted operation  216  (e.g., a restricted request operation), at  308 , the operation control lien module  200  restricts execution of the request operation  232  corresponding to the operation request  230 . In some examples, the operation control lien module  200  restricts execution by denying execution of the corresponding request operation  232 . 
     In other implementations as illustrated by  FIG. 3B , the operation control lien module  200  restricts execution of the request operation  232  according to passive restrictions  310 . The passive restrictions  310  function to prevent immediate performance of the request operation  232  without outright denying the execution of the request operation  232 . An operation control lien module  200  may perform any combination of the passive restrictions  310  when the operation control lien module  200 , at  308 , restricts execution of the request operation  232 . 
     Optionally, at  308   a , the operation control lien module  200  returns a message to an entity (e.g., the resource owner  20 ) that attempts to execute the request operation  232 . The message may indicate the at least one restricted operation  216  corresponding to the request operation  232  or the message may indicate other parameters of at least one operation control lien  220  related to the at least one restricted operation  216 , such as the lien requestor  212 , contact information regarding the lien requestor  212 , or any information describing why the lien requestor  212  generated the at least one operation control lien  220 . 
     As another example, at  308   b , the operation control lien module  200  prompts an entity (e.g., the resource owner  20 ) attempting to execute the request operation  232  with a message prompt. The message prompt may ask the entity if the entity wants to proceed with the request operation  232  corresponding to at least one restricted operation  216  in light of the related operation control lien  220  on the resource  110  (e.g., “Are you sure you want to perform this operation when a resource user is using this resource?”). The message prompt functions to give the entity pause for contemplation of any foreseeable consequences of the request operation  232 . 
     In yet other examples, at  308   c , the operation control lien module  200  restricts execution of the request operation  232  by contacting the lien requestor  212  associated with the operation control lien  220 . For example, at  308   c , the operation control lien module  200  requires permission from the lien requestor  212  associated with the operation control lien  220  with the at least one restricted operation  216 . In other examples, instead of requiring permission, the operation control lien module  200  communicates with the lien requestor  212  associated with the operation control lien  220  of the resource  110  to indicate that an entity may perform at least one restricted operation  216  identified by at least one operation control lien  220  relating to the lien requestor  212 . The communication may allow the lien requestor  212  to prepare for the request operation  232  or communicate further with the entity of the operation request  230 . Additionally or alternatively, the operation control lien module  200  may channel communication between the lien requestor  212  and the entity of the request operation  232 . 
     Referring further to  FIG. 3B , the operation control lien module  200  may restrict execution of a request operation  232  according the passive restriction  310  at  308   d . At  308   d , the operation control lien module  200  copies the at least one resource  110  identified by the operation request resource identifier  234 . The operation control lien module  200  may copy the at least one resource  110  by producing a full copy of the at least one resource  110  or an image of the at least one resource  110 . The operation control lien module  200  may copy the at least one resource  110  automatically or may prompt the entity (e.g., resource owner  20 ) to copy the at least one resource  110 . In some examples, the operation control lien module  200  stores the copied version of the at least one resource  110  in the distributed system  100 , but in other examples, the operation control lien module  200  communicates the copy to the lien requestor  212 . Additionally or alternatively, the copy of the at least one resource  110  is a temporary file that expires in a pre-determined amount of time after creation (e.g., a default thirty days). 
       FIG. 3C  illustrates an example method  300  for accessing liens on resources  110  of distributed systems  100 . Much like  FIG. 3A , operations associated with the method  300  begin when the operation control lien module  200  receives an operation request  230  to execute a request operation  232  on an at least one resource identified by an operation request resource identifier  234 . Yet unlike the example method  300  of  FIG. 3A , in  FIG. 3C , when the operation control lien module  200  determines that a request operation  232  is at least one restricted operation  216  of at least one operation control lien  220 , the operation control lien module  200 , at  302   a , also determines whether an resource  110  identified by an operation request resource identifier  234  has a parent-child relationship  110   p ,  110   c  with another resource  110  of the distributed system  100 . A parent resource  110   p  is a resource  110  that a child resource  110   c  depends upon (e.g., for some operation, task, or function). For example, a parent resource  110   p  is a segment of code used within a larger segment of code (e.g., a function or a compiled set of functions). The child resource  110   c  is the larger segment of code that depends upon the segment of code of the parent resource  110   p . With complex distributed systems  100 , resources  110  may have several layers of dependencies with parent-child relationships  110   p ,  110   c . In the case of complicated parent-child relationships  110   p ,  110   c , the dependencies of a resource  110  may not be as apparent to an entity, such as a resource owner  20 . For example, if resource A depends on resource B that depends on resource C, a resource user  30  of resource A may not be aware that resource B actually depends on resource C. Therefore, the resource user  30  or the operation control lien module  200  may only associate and/or request an operation control lien  220  for resource B leaving resource C unencumbered by a use of resource A. The unencumbered use of resource A may become an issue when a resource owner  20  of resource C may perform request operations  232  on resource C with unrestricted execution; potentially harming a functionality of resource A. 
     To prevent such harm, the method  300  of  FIG. 3C  determines the parent-child relationship  110   p ,  110   c  of a resource  110 . In some examples, the operation control lien module  200  determines a parent-child relationship  110   p ,  110   c  between the resource  110  identified by the operation request resource identifier  234  and other resources  110  of the distributed system  100 . At  302   b , when the operation control lien module  200  determines a parent-child relationship  110   p ,  110   c , the operation control lien module  200  determines whether the resource  110  is a parent resource  110   p  having at least one depending child resource  110   c . When the resource  110  is a child resource  110   c  or unrelated to a parent-child relationship  110   p ,  110   c , the method  300  may proceed to  306  and execute the request operation  232  as a child resource  110   c  does not have any other resources  110  that depend from the child resource  110   c  (i.e. subject to an operation control lien  220 ). When the method  300  determines the resource  110  is a parent resource  110   p , at  302 , the operation control lien module  200  determines whether the resource  110  identified by the operation request resource identifier  234  is also associated with an operation control lien  220 . When the resource  110  is associated with the operation control lien  220 , the method  300 , at  304 , determines if the request operation  232  of the operation request  230  is at least one restricted operation  216  identified by the operation control lien  220 . At  306 , when the operation control lien module  200  determines that the resource  110  is not the resource  110  of at least one operation control lien  220  or that the request operation  232  is not at least one restricted operation  216  (e.g., an unrestricted operation not identified by any operation control lien  220 ), the operation control lien module  200  allows unrestricted execution of the request operation  232  on the resource  110  identified by the operation request resource identifier  234 . When, however, the request operation  232  is the at least one restricted operation  216  (e.g., a restricted request operation), at  308 , the operation control lien module  200  restricts execution of the request operation  232  corresponding to the operation request  230 . 
       FIG. 4  illustrates a method  400  for accessing liens on resources  110  of distributed systems  100 . At  402 , the method  400  includes receiving, at data processing hardware  112 , an operation control request  210 . The operation control request  210  identifies a lien requestor  212 , a resource  110  of a distributed system  100 , and at least one restricted operation  216  for the resource  110  of the distributed system  100 . At  404 , the method  400  also includes associating, by the data processing hardware  112 , an operation control lien  220  with the resource  110  of the distributed system  100  based on the operation control request  210 . The operation control lien  220  identifies the lien requestor  212  and the at least one restricted operation  216  for the resource  110  of the distributed system  100 . At  406 , the method  400  includes receiving, at the data processing hardware  112 , an operation request  230  to execute a corresponding operation  232  on the resource  110  of the distributed system  100 . At  408 , the method  400  includes determining, by the data processing hardware  112 , that the corresponding operation  232  of the operation request  230  is a restricted operation  216  identified by the operation control lien  220  associated with the resource  110  of the distributed system  100 . At  410 , the method  400  further includes restricting, by the data processing hardware  112 , execution of the corresponding operation  232  of the operation request  230 . 
       FIG. 5  illustrates an example distributed system  500 . The distributed system  500  includes resources  110 . The resources  110  include loosely coupled hardware resources  110 ,  110   h  (e.g., data processing devices such as computers or servers), each having data processing hardware  112  (e.g., one or more central processing units (CPUs) or other computing resource) in communication with memory hardware  114  (e.g., memory, flash memory, dynamic random access memory (DRAM), phase change memory (PCM), and/or disks having spindles) that may be used for storing software resources  110 ,  110   s . A storage abstraction (e.g., key/value store or file system) overlain on the resources  110  allows scalable use of resources  110  of the distributed system  500 , such as network interface controllers  118 ,  118   a - c , data processing hardware  112 ,  112   a - c , and memory hardware  114 ,  114   a - c , by one or more clients  140 ,  140   a - n  (e.g., resource users  30 ). The clients  140 ,  140   a - c  may communicate with the resources  110  and/or communicate an operation control request  210  through a network  130 . The distributed system  500  may include multiple layers of redundancy where resources  110  are replicated and/or encoded and stored in multiple data centers. The distributed system  500  with the network interface controller (NIC)  118  may allow a client  140  to directly interface with hardware resources  110 ,  110   h  or software resources  110 ,  110   s  without requiring execution of a routine on data processing hardware  112 . In some implementations, a transaction application programming interface (API)  502  (e.g., a single-sided transactional system client library) is responsible for accessing the underlying resources  110 . 
       FIG. 6  illustrates an example resource lien environment  10  with multiple layers. The resource lien environment  10  includes an application layer  610 , a virtual machine layer  620  (VM layer) and a distributed system layer  102 . Each layer of the resource lien environment  10  may use resources  110  for various operations. For example, the application layer  610  includes applications  110   s ,  110   sa - sb , such as a first application  110   sa  and a second application  110   sb , that utilize software resources  110 ,  110   s . Each software application  110   s ,  110   sa - b  may include protocols and functions compiled from shared resources  110  (e.g., code or instructions) within a distributed system  100 . In some implementations, hardware resources  110 ,  110   h  from the distributed system layer  102  may store or may execute each application  110   s ,  110   sa - sb . For example, memory hardware  114  of the hardware resources  110 ,  110   h  stores the applications  110   s ,  110   sa - sb , while data processing hardware  112  of the hardware resources  110 ,  110   h  executes the applications  110   s ,  110   sa - sb . In some examples, a virtual machine  630  (e.g.,  630   a  and  630   b ) of the VM layer  620  executes the applications  110   s ,  110   sa - sb . As depicted in  FIG. 6 , a first virtual machine  630 ,  630   a  executes the first application  110   sa  and a second virtual machine  630 ,  630   b  executes the second application  110   sb . A host machine, such as a server (e.g.,  110 ,  110   h ) may independently operate one or more virtual machines  630  (e.g.,  630 ,  630   a - b ). When a host machine operates virtual machines  630 , a virtual processor  632  of the virtual machine  630  may share the hardware resources  110 ,  110   h  of the distributed system  100  associated with the distributed system layer  102 . For example, a virtual machine  630  may execute an application, such as the first application  110   sa , by emulating a portion  113  of data processing hardware  112  available within the distributed system  100 . 
     Referring further to  FIG. 6 , a resource user  30  associated with aspects of each layer of the resource lien environment  10  may generate an operation control request  210  and/or a corresponding operation control lien  220 . In some examples, a resource user  30  related to the application  110   s ,  110   sa  generates an operation control request  210  and/or corresponding operation control lien  220  for the following resources  110 : software resources  110 ,  110   s  related to the application  110   s ,  110   sa ; hardware resources  110 ,  110   h , such as data processing hardware  112  and memory hardware  114  storing and executing the application  110   s ,  110   sa  at a distributed system layer  102 ; and hardware resources  110 ,  110   h  that may be operating a virtual processor  632  of a virtual machine  630  executing the application  110   s ,  110   sa  on a VM layer  620 . 
       FIG. 7  is schematic view of an example computing device  700  that may be used to implement the systems and methods described in this document. The computing device  700  is intended to represent various forms of digital computers, such as laptops, desktops, workstations, personal digital assistants, servers, blade servers, mainframes, and other appropriate computers. The components shown here, their connections and relationships, and their functions, are meant to be exemplary only, and are not meant to limit implementations of the inventions described and/or claimed in this document. 
     The computing device  700  includes a processor  710 , memory  720 , a storage device  730 , a high-speed interface/controller  740  connecting to the memory  720  and high-speed expansion ports  750 , and a low speed interface/controller  760  connecting to a low speed bus  770  and a storage device  730 . Each of the components  710 ,  720 ,  730 ,  740 ,  750 , and  760 , are interconnected using various busses, and may be mounted on a common motherboard or in other manners as appropriate. The processor  710  can process instructions for execution within the computing device  700 , including instructions stored in the memory  720  or on the storage device  730  to display graphical information for a graphical user interface (GUI) on an external input/output device, such as display  780  coupled to high speed interface  740 . In other implementations, multiple processors and/or multiple buses may be used, as appropriate, along with multiple memories and types of memory. Also, multiple computing devices  700  may be connected, with each device providing portions of the necessary operations (e.g., as a server bank, a group of blade servers, or a multi-processor system). 
     The memory  720  stores information non-transitorily within the computing device  700 . The memory  720  may be a computer-readable medium, a volatile memory unit(s), or non-volatile memory unit(s). The non-transitory memory  720  may be physical devices used to store programs (e.g., sequences of instructions) or data (e.g., program state information) on a temporary or permanent basis for use by the computing device  700 . Examples of non-volatile memory include, but are not limited to, flash memory and read-only memory (ROM)/programmable read-only memory (PROM)/erasable programmable read-only memory (EPROM)/electronically erasable programmable read-only memory (EEPROM) (e.g., typically used for firmware, such as boot programs). Examples of volatile memory include, but are not limited to, random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), phase change memory (PCM) as well as disks or tapes. 
     The storage device  730  is capable of providing mass storage for the computing device  700 . In some implementations, the storage device  730  is a computer-readable medium. In various different implementations, the storage device  730  may be a floppy disk device, a hard disk device, an optical disk device, or a tape device, a flash memory or other similar solid state memory device, or an array of devices, including devices in a storage area network or other configurations. In additional implementations, a computer program product is tangibly embodied in an information carrier. The computer program product contains instructions that, when executed, perform one or more methods, such as those described above. The information carrier is a computer- or machine-readable medium, such as the memory  720 , the storage device  730 , or memory on processor  710 . 
     The high speed controller  740  manages bandwidth-intensive operations for the computing device  700 , while the low speed controller  760  manages lower bandwidth-intensive operations. Such allocation of duties is exemplary only. In some implementations, the high-speed controller  740  is coupled to the memory  720 , the display  780  (e.g., through a graphics processor or accelerator), and to the high-speed expansion ports  750 , which may accept various expansion cards (not shown). In some implementations, the low-speed controller  760  is coupled to the storage device  730  and a low-speed expansion port  790 . The low-speed expansion port  790 , which may include various communication ports (e.g., USB, Bluetooth, Ethernet, wireless Ethernet), may be coupled to one or more input/output devices, such as a keyboard, a pointing device, a scanner, or a networking device such as a switch or router, e.g., through a network adapter. 
     The computing device  700  may be implemented in a number of different forms, as shown in the figure. For example, it may be implemented as a standard server  700   a  or multiple times in a group of such servers  700   a , as a laptop computer  700   b , or as part of a rack server system  700   c.    
     Various implementations of the systems and techniques described herein can be realized in digital electronic and/or optical circuitry, integrated circuitry, specially designed ASICs (application specific integrated circuits), computer hardware, firmware, software, and/or combinations thereof. These various implementations can include implementation in one or more computer programs that are executable and/or interpretable on a programmable system including at least one programmable processor, which may be special or general purpose, coupled to receive data and instructions from, and to transmit data and instructions to, a storage system, at least one input device, and at least one output device. 
     These computer programs (also known as programs, software, software applications or code) include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As used herein, the terms “machine-readable medium” and “computer-readable medium” refer to any computer program product, non-transitory computer readable medium, apparatus and/or device (e.g., magnetic discs, optical disks, memory, Programmable Logic Devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that receives machine instructions as a machine-readable signal. The term “machine-readable signal” refers to any signal used to provide machine instructions and/or data to a programmable processor. 
     The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry. 
     To provide for interaction with a user, one or more aspects of the disclosure can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube), LCD (liquid crystal display) monitor, or touch screen for displaying information to the user and optionally a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. In addition, a computer can interact with a user by sending documents to and receiving documents from a device that is used by the user; for example, by sending web pages to a web browser on a user&#39;s client device in response to requests received from the web browser. 
     A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.