Patent Publication Number: US-11656902-B2

Title: Distributed container image construction scheduling system and method

Description:
CROSS REFERENCE TO RELATED APPLICATION(S) 
     This application claims the priority to Chinese Patent Application No. 202010034706.5, filed with the China National Intellectual Property Administration (CNIPA) on Jan. 14, 2020 and entitled “DISTRIBUTED CONTAINER IMAGE CONSTRUCTION SCHEDULING SYSTEM AND METHOD”, which is incorporated herein by reference in its entirety. 
     TECHNICAL FIELD 
     The present disclosure relates to the technical field of cloud computing, and in particular, to a distributed container image construction scheduling system and method. 
     BACKGROUND ART 
     With the development of cloud computing technologies, microservices can be deployed in containers to greatly improve resource utilization. However, as cloud computing services become increasingly diversified and complex, it is much complicated for software engineers to manually compile container image files to call continuous integration and continuous delivery (CI/CD) tools to construct images. In addition, constructing massive container images on a single node may lead to performance bottleneck and tough maintenance. This cannot meet current requirements, especially when container image files for most applications are normalized. In view of this, a distributed container image construction system is required to optimize existing container image construction methods so as to expedite image construction, efficiently utilize resources, and simplify processes. 
     A wide variety of businesses involve cloud computing. Different users construct different container images based on their program dependencies. In addition, image construction needs to be iterated accordingly. As a result, new image construction tasks continuously emerge with time. Therefore, how to send and run these image construction tasks in a distributed image construction system is an urgent problem to be resolved. In particular, an optimization solution is required to properly distribute and run these tasks on corresponding construction nodes to ensure satisfied image construction efficiency. 
     SUMMARY 
     Currently, container image construction in cloud computing features low efficiency, complex process, and low reliability. Given this, the present disclosure provides a distributed container image construction scheduling system and method. 
     To this end, an embodiment of the present disclosure provides a distributed system for constructing and scheduling a container image that includes a management node and a construction node, where 
     the management node is configured to manage generation and scheduling of a task for constructing the container image in a distributed manner and the management node includes a console and a scheduler, where 
     the console is configured to obtain a task parameter, create a task, transmit the task to the scheduler, and feed an image construction status back to a user, and 
     the scheduler is configured to receive the task transmitted from the console, generate a task message, transmit the task message to a corresponding construction node for running, and wait and receive a task execution result from the corresponding construction node; and 
     the construction node is configured to perform a task issued by the management node, where each construction node includes an image constructor, and 
     the image constructor is configured to receive the task message transmitted from the scheduler, and return an execution result to the scheduler. 
     Further, the scheduler is a web server and the image constructor is a Google Remote Procedure Call (gRPC) server. 
     Further, the scheduling system includes at least three management nodes and multiple construction nodes. 
     Further, only one management node is active at a time, and management nodes can be seamlessly switched by using a heartbeat detection technology and virtual IP (VIP) technology. 
     According to another aspect, an embodiment of the present disclosure provides a scheduling method for constructing a distributed container image, including: 
     initializing the management node and the construction node, where the initializing the management node and construction node includes: setting a scheduler on the management node to a web server in a block listening status and an image constructor on the construction node to a gRPC server in a block listening status; 
     creating, by the console, an image construction task, and performing, by the scheduler, a check and generating a task message; 
     determining construction nodes to which the task message can be sent; 
     determining an optimal working node from the determined construction nodes; 
     sending, by the scheduler, the task message to the optimal working node and generating a task object; 
     performing, by the optimal working node, the task and sending feedback on a construction status to the management node; 
     informing, by the management node, a user of the feedback on the construction status; and 
     entering an initialization status of the management node and construction node again. 
     Further, setting an image constructor on the construction node to a gRPC server in a block listening status includes: 
     initiating the scheduler on the management node; checking, by the scheduler, whether a profile of the scheduler exists; and reading, if the profile exists, IP addresses and gRPC service ports of all construction nodes from the profile and storing the IP addresses and gRPC service ports to a cache, where the profile includes a list of IP addresses and gRPC service ports of construction nodes; 
     setting, by the scheduler, a number of concurrent threads in the cache as workers, and setting a task list to empty; 
     checking, by the scheduler, whether a Transport Layer Security (TLS) public key and private key that are used to encrypt web communication and gRPC communication exist on the current management node; and using, if the TLS public key and private key exist, the TLS public key and private key to enable a TLS authentication-enabled web server in the scheduler to block monitoring, and enabling the console to wait for the user to create a task; and 
     if the profile of the scheduler does not exist or the TLS public key and private key that are used to encrypt web communication and gRPC communication do not exist, recording, by the scheduler, a cause of failure, generating and recording a message locally, sending fault information to an operation and maintenance (O&amp;M) engineer, and exiting a scheduler program; and 
     the setting an image constructor on the construction node to a gRPC server in a block listening status includes: 
     initiating the image constructor on the construction node; and attempting, by the image constructor, to interface to a container engine on the current construction node and setting, if the image constructor is interfaced to the container engine, values of a status variable, health variable, and image construction quantity variable in a cache of the construction node into true, healthy, and zero respectively; 
     checking, by the image constructor, whether a TLS public key and private key that are used to encrypt gRPC communication exist on the current construction node; and using, if the TLS public key and private key exist, the TLS public key and private key to enable a TLS authentication-enabled gRPC server in the image constructor to block monitoring, and waiting for the scheduler to obtain node information of the image constructor or issue a task; and 
     if the image constructor fails to interface to the container engine or the TLS public key and private key that are used to encrypt gRPC communication do not exist, recording, by the image constructor, a cause of failure, generating and recording a message locally, sending fault information to an O&amp;M engineer, and exiting an image constructor program. 
     Further, the creating, by the console, an image construction task, and performing, by the scheduler, a check and generating a task message includes: 
     creating, by the console on the management node, the task, where before the task is created, an image name, a graphics processing unit (GPU) value, a name and version of a development framework, and a third-party dependency are specified and a heterogeneous resource value and test mode value are entered; 
     serializing, by the console, the task into a structural object and sending the structural object to the scheduler; and 
     checking, by the scheduler, whether the structural object is valid, where the checking whether the structural object is valid includes: 
     checking whether the image name is empty; and if the image name is empty, generating an error message that indicates an empty image name, sending the error message to the console to inform the user, canceling generating the task, and entering a blocking status again to wait for the user to create a task on the console; or 
     if the image name is not empty, continuing, by the scheduler, to check whether the heterogeneous resource value in the structural object is true; and if the heterogeneous resource value is not true or is empty, generating an error message that indicates an invalid heterogeneous resource value, sending the error message to the console to inform the user, canceling generating the task, and entering a blocking status again to wait for the user to create a task on the console; or 
     if the heterogeneous resource value is true, continuing to check whether the development framework in the structural object is specified; and if the development framework is unspecified, generating an error message that indicates an unspecified development framework, sending the error message to the console to inform the user, canceling generating the task, and entering a blocking status again to wait for the user to create a task on the console; or 
     if the development framework is specified, continuing to check whether the test mode value in the structural object is true; and if the test mode value is not true or is empty, generating an error message that indicates an invalid test mode value, sending the error message to the console to inform the user, canceling generating the task, and entering a blocking status again to wait for the user to create a task on the console; or 
     if the test mode value is true, determining that the task passes the check, and generating, by the scheduler, the task message based on task content. 
     Further, the determining construction nodes to which the task message can be sent include: 
     creating, by the scheduler on the management node, a table of active construction nodes in a cache, where the table includes IP addresses, gRPC service ports, and communication statuses of construction nodes; 
     performing communication tests between all construction nodes in the cache of the scheduler and gRPC services of these construction nodes by using the IP addresses and gRPC service ports, and saving construction nodes that successfully communicate with the gRPC services into the table of active construction nodes in the cache; 
     determining whether the number of active construction nodes in the table of active construction nodes is greater than that of workers; if the number of active construction nodes is greater than that of workers, performing no operation; and if the number of active construction nodes is less than that of workers, setting, by the scheduler, the number of active construction nodes to that of workers, and enabling multiple threads to concurrently obtain resource information and status information of each construction node in the table of active construction nodes, where the resource information of each construction node includes a number of central processing units (CPUs), a CPU clock speed, a total memory capacity, and an available memory capacity of the construction node and a system load, and the status information of each construction node includes a status variable, health variable, and image construction quantity variable of the construction node; 
     determining, by the scheduler one after another, whether a value of the status variable of a construction node in the table of active construction nodes is true; and performing no operation if the value of the status variable is true, or deleting the construction node from the table of active construction nodes if the value of the status variable is false; 
     determining, by the scheduler one after another after values of status variables of all construction nodes are determined, whether a value of the health variable of a construction node in the table of active construction nodes is set to healthy; and performing no operation if the value of the health variable is set to healthy, or deleting the construction node from the table of active construction nodes if the value of the health variable is not set to healthy; and 
     using, after values of health variables of all construction nodes are determined, remaining construction nodes in the table of active construction nodes as the construction nodes to which the task message can be sent. 
     Further, determining an optimal working node from the determined construction nodes includes: 
     calculating a performance score and task score for each construction node in the table of active construction nodes, where 
     
       
         
           
             
               
                 Perform 
                 ⁢ 
                     
                 Score 
               
               = 
               
                 
                   
                     ( 
                     
                       
                         CpuCores 
                         
                           Max 
                           ⁢ 
                           CpuCores 
                         
                       
                       + 
                       
                         CpuFrequency 
                         
                           Max 
                           ⁢ 
                           CpuFrequency 
                         
                       
                     
                     ) 
                   
                   × 
                   100 
                   × 
                   CpuWeight 
                 
                 + 
                 
                   
                     ( 
                     
                       1 
                       - 
                       
                         SystemLoad 
                         CpuCores 
                       
                     
                     ) 
                   
                   × 
                   100 
                   × 
                   LoadWeight 
                 
                 + 
                 
                   
                     ( 
                     
                       
                         
                           FreeMemory 
                           TotalMemory 
                         
                         × 
                         3 
                       
                       + 
                       
                         
                           FreeMemory 
                           
                             Max 
                             ⁢ 
                             FreeMemory 
                           
                         
                         × 
                         7 
                       
                     
                     ) 
                   
                   × 
                   100 
                   × 
                   MemoryWeight 
                 
               
             
             ⁢ 
             
 
             
               
                 Task 
                 ⁢ 
                     
                 Score 
               
               = 
               
                 
                   ( 
                   
                     
                       
                         Max 
                         ⁢ 
                         BuildNumber 
                       
                       - 
                       BuildNumber 
                     
                     
                       Max 
                       ⁢ 
                       BuildNumber 
                     
                   
                   ) 
                 
                 × 
                 100 
                 × 
                 TaskWeight 
               
             
           
         
       
     
     Perform Score indicates the performance score, Task Score indicates the task score, CpuWeight indicates a CPU weight, LoadWeight indicates a load weight, MemoryWeight indicates a memory weight, TaskWeight indicates a task weight, CpuCores indicates the number of CPUs of the construction node, CpuFrequency indicates the clock speed of the construction node, TotalMemory indicates the total memory capacity of the construction node, FreeMemory indicates the available memory capacity of the construction node, BuildNumber indicates the image construction quantity variable, SystemLoad indicates the system load, MaxCpuCores indicates a number of CPUs of a construction node whose CPU quantity is greater than that of any other construction node in the table of active construction nodes, MaxCpuFrequency indicates a clock speed of a construction node whose clock speed is greater than that of any other construction node in the table of active construction nodes, MaxFreeMemory indicates an available memory capacity of a construction node whose available memory capacity is greater than that of any other construction node in the table of active construction nodes, and MaxBuildNumber indicates an image construction quantity of a construction node whose image construction quantity is greater than that of any other construction node in the table of active construction nodes; 
     using, by the scheduler, a sum of the performance score and task score as a final total score of the construction node and storing the final total score to the cache; and 
     determining, by the scheduler, a construction node having a highest total score as the optimal working node. 
     Further, the sending, by the scheduler, the task message to the optimal working node and generating a task object includes: 
     obtaining, by the scheduler, an IP address and a gRPC service port of the optimal working node; 
     encrypting, by the scheduler, the task message in a gRPC mode by using a TLS public key and private key of the management node, sending the encrypted task message to the optimal working node based on the IP address and gRPC service port of the optimal working node, and asynchronously generating the task object, where the task object includes the task message, a scheduling node, and the construction status, where the scheduling node is the optimal working node and the construction status is set to false; and 
     entering a blocking state of the scheduler and waiting for the optimal working node to send the feedback on the construction status. 
     Further, the performing, by the optimal working node, the task and sending feedback on a construction status to the management node includes: 
     determining, by an image constructor of the optimal working node, whether values of the status variable and health variable on the optimal working node in a cache of the construction node are true and healthy respectively; and if the values of the status variable and health variable are false and unhealthy respectively, using the values of these two variables as the feedback on the construction status, attaching an error tag, decrementing a value of the image construction quantity variable in the cache of the construction node by one, and sending the feedback on the construction status to the management node, or 
     if the values of the status variable and health variable are true and healthy respectively, incrementing a value of the image construction quantity variable in the cache of the construction node by one; extracting, from the task message, an image name, a GPU value, a name and version of a development framework, a third-party dependency, a heterogeneous resource value, and a test mode value; calling a container engine to construct an image based on these parameters; using, after the image is constructed, a construction completion result from the container engine as the feedback on the construction status, attaching a completion tag, decrementing the value of the image construction quantity variable in the cache of the construction node by one, and sending the feedback on the construction status to the management node; and 
     using, if an error occurs when the image is being constructed by calling the container engine and image construction is stopped, an error message returned by the container engine as the feedback on the construction status, attaching an error tag, decrementing the value of the image construction quantity variable in the cache of the construction node by one, and sending the feedback on the construction status to the management node. 
     Further, the informing, by the management node, a user of the feedback on the construction status includes: 
     checking, by the scheduler on the management node after receiving the feedback on the construction status, whether the feedback on the construction status includes an error tag, and setting, if the feedback on the construction status does not include an error tag, the construction status in the task object to true to indicate that the task is constructed; or 
     checking, by the scheduler if the feedback on the construction status includes an error tag, whether an error message in the feedback on the construction status indicates an unhealthy construction node; and rescheduling the task if the error message indicates an unhealthy construction node, or sending, if the error message does not indicate an unhealthy construction node, the feedback on the construction status to the console to inform the user of the error message and content. 
     According to the specific embodiments provided in the present disclosure, the present disclosure discloses the following technical effects: 
     The present disclosure provides a distributed system for constructing a container image and uses the distributed system to expedite container image construction. Compared with those of constructing massive container images on a single node, performance bottleneck and maintenance challenges of this system are alleviated. This system uses a scheduler to distribute construction tasks rationally and balances a task load on a construction node so that resources on the construction node can be efficiently utilized, thereby ensuring system stability and improving efficiency in container image construction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To describe the technical solutions in the embodiments of the present disclosure or in the prior art more clearly, the accompanying drawings required for the embodiments are briefly described below. Apparently, the accompanying drawings in the following description show merely some embodiments of the present disclosure, and a person of ordinary skill in the art may still derive other accompanying drawings from these accompanying drawings without creative efforts. 
         FIG.  1    is an architecture diagram of a distributed system for constructing a container image according to an embodiment of the present disclosure; 
         FIG.  2    is a flowchart of a management node in a distributed system for constructing a container image according to an embodiment of the present disclosure; and 
         FIG.  3    is a flowchart of an optimal working node in a distributed system for constructing a container image according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The technical solutions of the embodiments of the present disclosure are clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are merely some rather than all of the embodiments of the present disclosure. All other examples obtained by a person of ordinary skill in the art based on the examples of the present disclosure without creative efforts shall fall within the protection scope of the present disclosure. 
     To make the foregoing objectives, features, and advantages of the present disclosure clearer and more comprehensible, the present disclosure is now further described in detail below with reference to the accompanying drawings and specific embodiments. 
     One aspect of the present disclosure provides a distributed system for constructing and scheduling a container image, as shown in  FIG.  1   . The system includes a construction node  12  and a management node  11 . The management node  11  is configured to manage generation and scheduling of a task for constructing a container image in a distributed manner. The management node  11  includes a console  111  and a scheduler  112 . 
     The console  111  is configured to obtain parameters required by a user  10 , such as a development dependency library, development framework, version, heterogeneous resource value, and test mode value, and transmit tasks of generating these parameters to the scheduler  112 , and feed an image construction status back to the user  10 . 
     The scheduler  112  is a web server and is configured to: receive the tasks transmitted from the console  111 , filter the tasks, send tasks that are obtained after filtering to corresponding construction nodes  12  for running, and wait and receive task execution results from the corresponding construction nodes  12 . 
     The construction node  12  is configured to run the tasks issued by the management node  11 . Each construction node  12  includes an image constructor  121 . 
     The image constructor  121  is a gRPC server and is configured to receive tasks sent from the scheduler  112 , run the tasks, and return execution results to the scheduler  112  after these tasks are run. 
     In an actual production environment, at least three management nodes  11  and multiple construction nodes  12  are set. A quantity of nodes can be increased or decreased as needed. 
     Only one management node  11  is operating at a time and other management nodes  11  are in the idle state. Management nodes  11  can be seamlessly switched by using a heartbeat detection technology and virtual IP technology in cloud computing. This ensures an efficient and available system and avoids a single point of failure. 
     Another aspect of the present disclosure provides a distributed method for constructing and scheduling a container image. The method includes the following steps: 
     1. System Initialization 
     Construction Node  12 : 
     In step  201 , an image constructor  121  is initiated on the construction node  12 . The image constructor  121  first attempts to interface to a container engine  122  on the current construction node  12 . If the image constructor  121  is interfaced to the container engine  122 , the image constructor  121  sets values of a status variable, health variable, and image construction quantity variable of construction node  12  in a cache of the construction node  12  into true, healthy, and zero respectively. 
     In step  202 , the image constructor  121  checks whether a TLS public key and private key that are used to encrypt gRPC communication exist on the current construction node  12 . If the TLS public key and private key exist, the image constructor  121  calls the TLS public key and private key to enable a TLS authentication-enabled gRPC server in the image constructor  121  to block monitoring, and waits for the scheduler  121  to obtain node information of the image constructor  121  or issue a task. 
     In step  203 , if the image constructor  121  fails to interface to the container engine  122  or the TLS public key and private key that are used to encrypt gRPC communication do not exist, the image constructor  121  records a cause of failure, generates a message, records the message locally, sends fault information to an O&amp;M engineer by email, and exits an image constructor  121  program. 
     Management Node  11 : 
     A scheduler  112  is initiated on the management node  11 . The scheduler  112  first checks whether a profile of the scheduler  112  exists. The profile includes a list of IP addresses and gRPC service ports of construction nodes  12 . If the profile exists, the scheduler  112  reads the IP addresses and gRPC service ports of all construction nodes  12  from the profile and saves the IP addresses and gRPC service ports to a cache. Then, the scheduler  112  sets a number of concurrent threads as workers to an initial value of 5, and sets a task list to empty. An initial number of workers in a production environment can be adjusted based on actual needs. 
     The scheduler  112  checks whether a TLS public key and private key that are used to encrypt web and gRPC communications exist on the current management node  11 . If the TLS public key and private key exist, the scheduler  112  calls the TLS public key and private key to enable a TLS authentication-enabled web server in the scheduler  112  to block monitoring, and in step  204 , the scheduler enables the console  111  to wait for the user to create a task. 
     If the profile of the scheduler  112  does not exist or the TLS public key and private key that are used to encrypt web and gRPC communications do not exist, the scheduler  112  records a cause of failure, generates a message, records the message locally, sends fault information to an O&amp;M engineer, and exits a scheduler  112  program. 
     2. Generation and Check of an Image Construction Task 
     Referring to  FIG.  2   , a user  10  creates a task by using a console  111  on a management node  11 . Before the task is created, an image name, a GPU value, a name and version of a development framework, and a third-party dependency are specified and a heterogeneous resource value and test mode value are entered. 
     In step  205 , the console  111  serializes the task into a structural object and sends the structural object into a scheduler  112 . 
     Specifically, in step  206 , the scheduler  112  checks whether the structural object is valid. The details are as follows: 
     The scheduler  112  first checks whether the image name is empty. If the image name is empty, the scheduler  112  generates (step  207 ) an error message that indicates an empty image name, sends (step  212 ) the error message to the console  111  to inform the user  10 , cancels generating the task, and enters a blocking status again to wait for the user  10  to create a task on the console  111 . 
     If the image name is not empty, the scheduler  112  continues to check whether the heterogeneous resource value in the structural object is true. If the heterogeneous resource value is not true or is empty, the scheduler  112  generates (step  207 ) an error message that indicates an invalid heterogeneous resource value, sends (step  212 ) the error message to the console  111  to inform the user  10 , cancels generating the task, and enters a blocking status again to wait for the user  10  to create a task on the console  111 . 
     If the heterogeneous resource value is true, the scheduler  112  continues to check whether the development framework in the structural object is specified. If the development framework is unspecified, the scheduler  112  generates (step  207 ) an error message that indicates an unspecified development framework, sends (step  212 ) the error message to the console  111  to inform the user  10 , cancels generating the task, and enters a blocking status again to wait for the user  10  to create a task on the console  111 . 
     If the development framework is specified, the scheduler  112  continues to check whether the test mode value in the structural object is true. If the test mode value is not true or is empty, the scheduler  112  generates (step  207 ) an error message that indicates an invalid test mode value, sends (step  212 ) the error message to the console  111  to inform the user  10 , cancels generating the task, and enters a blocking status again to wait for the user  10  to create a task on the console  111 . 
     If the test mode value is true, it indicates that the task passes the check. In this case, the scheduler  112  generates a task message based on task content and then performs Step  3 . 
     3. Filtering (Step  208 ) Construction Nodes  12 . 
     Referring to  FIG.  2   , the scheduler  112  on the management node  11  first creates a table of active construction nodes  12  in the cache. The table includes IP addresses, gRPC service ports, and communication statuses of construction nodes  12 . Then, the scheduler  112  attempts to perform asynchronous communication tests between all construction nodes  12  in the cache of the scheduler  112  in Step  1  and gRPC services of these construction nodes  12  by using the IP addresses and gRPC service ports and saves construction nodes  12  that successfully communicate with the gRPC services into the table of active construction nodes in the cache. 
     After that, the scheduler  112  determines whether the number of active construction nodes in the table of active construction nodes is greater than that of workers in Step  1 . If the number of active construction nodes is greater than that of workers, the scheduler  112  performs no operation. If the number of active construction nodes is less than that of workers, the scheduler  112  sets the number of active construction nodes to that of workers and uses multiple threads to concurrently obtain resource information of each construction node  12  in the table of active construction nodes and status information of each construction node  12  in the cache in Step  1 . The resource information of each construction node  12  includes a number of CPUs, a CPU clock speed, a total memory capacity, and an available memory capacity of the construction node  12  and a system load. The status information of each construction node  12  includes a status variable, health variable, and image construction quantity variable of the construction node  12 . A number of concurrent threads that are used to obtain information about the active construction nodes equal the number of concurrent threads, that is, the number of workers, in the cache. In other words, threads whose quantity equals to that of workers are used to consume all construction nodes  12  that are available for communication and obtain resource information and status information of these construction nodes  12 . Then, the scheduler  112  caches the information. 
     After information of the last construction node is cached, the scheduler  112  determines, one after another, whether a value of the status variable of a construction node  12  in the table of active construction nodes is true. If the value of the status variable is true, the scheduler  112  performs no operation. If the value of the status variable is false, the scheduler  112  deletes the construction node  12  from the table of active construction nodes. After values of status variables of all construction nodes  12  are determined, the scheduler  112  determines, one after another, whether a value of the health variable of a construction node  12  in the table of active construction nodes is set to healthy. If the value of the health variable is set to healthy, the scheduler  112  performs no operation. If the value of the health variable is not set to healthy, the scheduler  112  deletes the construction node  12  from the table of active construction nodes. After values of health variables of all construction nodes  12  are determined, the scheduler  112  performs Step  4 . 
     4. Calculation (Step  209 ) of Scores for a Construction Node  12 . 
     Referring to  FIG.  2   , the scheduler  112  first obtains a number of CPUs of a construction node  12  whose CPU quantity is greater than that of any other construction node  12  in the table of active construction nodes, a clock speed of a construction node  12  whose clock speed is greater than that of any other construction node  12  in the table of active construction nodes  12 , an available memory capacity of a construction node  12  whose available memory capacity is greater than that of any other construction node  12  in the table of active construction nodes, and an image construction quantity of a construction node  12  whose image construction quantity is greater than that of any other construction node  12  in the table of active construction nodes. Then, the scheduler  112  uses MaxCpuCores, MaxCpuFrequency, MaxCpuFrequency, and MaxFreeMemory to indicate the number of CPUs, clock speed, available memory capacity, and image construction quantity respectively. 
     The scheduler  112  uses CpuCores, CpuFrequency, TotalMemory, FreeMemory, BuildNumber, SystemLoad to indicate the number of CPUs, clock speed, total memory capacity, available memory capacity, and image construction quantity variable of the construction node  12 , and the system load that are obtained in Step  3  respectively. Then, the scheduler  112  asynchronously calculates a performance score and a task score for each construction node  12  in the table of active construction nodes based on the information, where the performance score and task score are indicated by Perform Score and Task Score respectively. 
     The performance score and task score are calculated based on the following formulas 
     
       
         
           
             
               
                 Perform 
                 ⁢ 
                     
                 Score 
               
               = 
               
                 
                   
                     ( 
                     
                       
                         CpuCores 
                         
                           Max 
                           ⁢ 
                           CpuCores 
                         
                       
                       + 
                       
                         CpuFrequency 
                         
                           Max 
                           ⁢ 
                           CpuFrequency 
                         
                       
                     
                     ) 
                   
                   × 
                   100 
                   × 
                   CpuWeight 
                 
                 + 
                 
                   
                     ( 
                     
                       1 
                       - 
                       
                         SystemLoad 
                         CpuCores 
                       
                     
                     ) 
                   
                   × 
                   100 
                   × 
                   LoadWeight 
                 
                 + 
                 
                   
                     ( 
                     
                       
                         
                           FreeMemory 
                           TotalMemory 
                         
                         × 
                         3 
                       
                       + 
                       
                         
                           FreeMemory 
                           
                             Max 
                             ⁢ 
                             FreeMemory 
                           
                         
                         × 
                         7 
                       
                     
                     ) 
                   
                   × 
                   100 
                   × 
                   MemoryWeight 
                 
               
             
             ⁢ 
             
 
             
               
                 Task 
                 ⁢ 
                     
                 Score 
               
               = 
               
                 
                   ( 
                   
                     
                       
                         Max 
                         ⁢ 
                         BuildNumber 
                       
                       - 
                       BuildNumber 
                     
                     
                       Max 
                       ⁢ 
                       BuildNumber 
                     
                   
                   ) 
                 
                 × 
                 100 
                 × 
                 TaskWeight 
               
             
           
         
       
     
     Perform Score indicates the performance score, Task Score indicates the task score, CpuWeight indicates a CPU weight, LoadWeight indicates a load weight, Score MemoryWeight indicates a memory weight, TaskWeight indicates a task weight, CpuCores indicates the number of CPUs of the construction node  12 , CpuFrequency indicates the clock speed of the construction node  12 , TotalMemory indicates the total memory capacity of the construction node  12 , FreeMemory indicates the available memory capacity of the construction node  12 , BuildNumber indicates the image construction quantity variable, SystemLoad indicates the system load, MaxCpuCores indicates the number of CPUs of the construction node  12  whose CPU quantity is greater than that of any other construction node  12  in the table of active construction nodes, MaxCpuFrequency indicates the clock speed of the construction node  12  whose clock speed is greater than that of any other construction node  12  in the table of active construction nodes, MaxFreeMemory indicates the available memory capacity of the construction node  12  whose available memory capacity is greater than that of any other construction node  12  in the table of active construction nodes, and MaxBuildNumber indicates the image construction quantity of the construction node  12  whose image construction quantity is greater than that of any other construction node  12  in the table of active construction nodes. 
     Default values of CpuWeight, LoadWeight, MemoryWeight, and TaskWeight are 2, 2, 3, and 3 respectively. 
     After the performance score and task score are calculated, the scheduler  112  uses a sum of the two scores as a final total score and stores the final total score into the cache. 
     After a total score is calculated for the last construction node  12  in the table of active construction nodes, the scheduler  112  determines a construction node  12  having highest total score in the table of active construction nodes as an optimal working node and performs Step  5 . 
     5. Distribution (Step  210 ) of an Image Construction Task. 
     Referring to  FIG.  2   , the scheduler  112  first obtains an IP address and a gRPC service port of the optimal working node that is obtained in Step  4  from the cache that is generated in Step  1 . 
     Then, the scheduler  112  encrypts the task message that is generated in Step  2  in a gRPC mode by using the TLS public key and private key of the management node that are obtained in Step  1 , sends an encrypted task message to the optimal working node based on the IP address and gRPC service port of the optimal working node, and asynchronously generates a task object. The task object includes a task message, a scheduling node, and a construction status. The scheduler  112  sets the task message to the task message that is generated by the scheduler  112  in Step  2 , the scheduling node to the optimal working node that is obtained in Step  4 , and the construction status to false. After that, the scheduler  112  enters a blocking state and waits (step  304 ) for the optimal working node to send feedback on construction status. 
     After the optimal working node receives the task message, an image constructor  121  on the optimal working node performs Step  6 . 
     6. Performing an Image Construction Task. 
     Referring to  FIG.  3   , after receiving the task message from the management node  11 , the image constructor  121  first determines (step  305 ) values of the status variable and health variable on the optimal working node in a cache of the construction node  12  are true and healthy respectively. If the values of the status variable and health variable are false and unhealthy respectively, the image constructor  121  uses (step  307 ) the values of these two variables as the feedback on the construction status, attaches an error tag, and performs Step  7 . 
     If the values of the status variable and health variable are true and healthy respectively, the image constructor  121  increments (step  306 ) the value of the image construction quantity variable in the cache of the construction node  12  by one. Then, the image constructor  121  extracts, from the task message, the image name, GPU value, name and version of the development framework, third-party dependency, heterogeneous resource value, and test mode value, and calls (step  308 ) a container engine  122  to construct an image based on these parameters. 
     After the image is constructed, the image constructor  121  uses (step  310 ) a construction completion result from the container engine  122  as (step  211 ) the feedback on the construction status, attaches a completion tag, and performs Step  7 . 
     If an error occurs when the image is being constructed (step  309 ) by calling the container engine  122  and image construction is stopped, the image constructor  121  uses (step  307 ) an error message returned by the container engine  122  as the feedback on the construction status, attaches an error tag, and performs Step  7 . 
     7. Feedback of a Construction Status. 
     Referring to  FIG.  3   , the image constructor  121  decrements (step  311 ) the value of the image construction quantity variable in the cache of the construction node  12  by one and sends (step  312 ) the feedback on the construction status to the management node  11 . 
     After receiving the feedback on the construction status, the scheduler  112  on the management node  11  checks whether the feedback includes an error tag. If the feedback on the construction status does not include an error tag, the scheduler  112  sets the construction status in the task object in Step  5  to true to indicate that construction is complete. If the feedback on the construction status includes an error tag, the scheduler  112  checks whether an error message in the feedback on the construction status indicates an unhealthy construction node  12 . If the error message indicates an unhealthy construction node, the scheduler  112  makes the task go to Step  3  and reschedules the task. If the error message does not indicate an unhealthy construction node, the scheduler  112  sends (step  212 ) the feedback on the construction status to the console  111  to inform the user  10  of the error message and content. 
     After that, the image constructor  121  on the construction node  12  enters the block monitoring status as in Step  1  and waits for a new task to be issued. The scheduler  112  on the management node  11  enters the block monitoring status as in Step  1  and waits for a new task to be issued. 
     Each example of the present specification is described in a progressive manner, each example focuses on the difference from other examples, and the same and similar parts between the examples may refer to each other. Since the system disclosed in the embodiments corresponds to the method disclosed in the embodiments, the description is relatively simple, and reference can be made to the method description. 
     In this specification, several specific embodiments are used for illustration of the principles and implementations of the present disclosure. The description of the foregoing embodiments is used to help illustrate the method of the present disclosure and the core ideas thereof. In addition, those of ordinary skill in the art can make various modifications in terms of specific implementations and the scope of application in accordance with the ideas of the present disclosure. In conclusion, the content of this specification shall not be construed as a limitation to the present disclosure.