Patent Publication Number: US-11388228-B2

Title: Methods, systems and computer readable media for self-replicating cluster appliances

Description:
TECHNICAL FIELD 
     The subject matter described herein relates to distributed computing environments. More particularly, the subject matter described herein relates to methods, systems, and computer readable media for self-replicating cluster appliances. 
     BACKGROUND 
     Containers, also referred to as virtual containers, application containers, or software containers, are units of software that packages or contains code, configurations, and code dependencies. Containers may share an operating system (OS) installed on a physical or virtual machine but each container may run resource-isolated processes. A popular type of containers are Docker containers. 
     Container or cluster orchestration software, such as Kubernetes, can be used to send containers out to different nodes (e.g., a machine or computing platform for running one or more containers), manage clusters (e.g., one or more nodes, usually a master node and one or more worker nodes) and/or pods (e.g., one or mode containers that can share workload, a local network, and resources), and start up additional containers as demand increases. For example, Kubernetes can be used to configure a Kubernetes service that defines a logical set of pods running somewhere in a cluster (e.g., across multiple nodes), and that all provide the same functionality. In this example, the Kubernetes service may be assigned a unique IP address (also referred to as a clusterIP). This IP address may be tied to the lifespan of the Kubernetes service, e.g., the IP address may not change while the Kubernetes service is alive. Pods can be configured to talk to a Kubernetes service front-end, and communication to the Kubernetes service can be automatically load-balanced by the service front-end to a pod member of the Kubernetes service. 
     While containers and related orchestration software can be useful for providing cluster related applications or microservices, issues can arise when setting up nodes to act as cluster appliances. 
     SUMMARY 
     The subject matter described herein includes methods, systems, and computer readable media for self-replicating cluster appliances. A method for self-replicating cluster appliances includes at a controller node configured for controlling a cluster of one or more network testing and/or visibility nodes: receiving node information associated with a first computing node, wherein the first computing node includes a preconfigured operating system (OS); determining, using the node information, OS data for configuring the first computing node to be in the cluster; and providing, via a communications interface, the OS data to the first computing node. The method also includes at the first computing node: receiving the OS data; and using the OS data to configure the first computing node to be in the cluster and to provide at least one network testing or visibility service. 
     A system for self-replicating cluster appliances includes at least one processor, a memory and a controller node implemented using the at least one processor and the memory. The controller node is configured for controlling a cluster of one or more network testing and/or visibility nodes. The controller node is further configured for: receiving node information associated with a first computing node, wherein the first computing node includes a preconfigured OS; determining, using the node information, OS data for configuring the first computing node to be in the cluster; and providing, via a communications interface, the OS data to the first computing node. The first computing node is further configured for: receiving the OS data; and using the OS data to configure the first computing node to be in the cluster and to provide at least one network testing or visibility service. 
     The subject matter described herein may be implemented in software in combination with hardware and/or firmware. For example, the subject matter described herein may be implemented in software executed by a processor. In one example implementation, the subject matter described herein may be implemented using a computer readable medium having stored thereon computer executable instructions that when executed by the processor of a computer control the computer to perform steps. Example computer readable media suitable for implementing the subject matter described herein include non-transitory devices, such as disk memory devices, chip memory devices, programmable logic devices, and application-specific integrated circuits. In addition, a computer readable medium that implements the subject matter described herein may be located on a single device or computing platform or may be distributed across multiple devices or computing platforms. 
     As used herein, the term “node” refers to at least one physical computing platform including one or more processors and memory. 
     As used herein, each of the terms “function”, “engine”, and “module” refers to hardware, firmware, or software in combination with hardware and/or firmware for implementing features described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the subject matter described herein will now be explained with reference to the accompanying drawings, wherein like reference numerals represent like parts, of which: 
         FIG. 1  is a block diagram illustrating an example cluster containing nodes for performing network testing and/or visibility related services; 
         FIG. 2  is a block diagram illustrating an example cluster-based service environment; 
         FIGS. 3A and 3B  depict a message flow diagram illustrating a worker node joining a cluster; 
         FIG. 4  is a diagram illustrating a memory partition schema associated with a reboot-less or hot-boot based architecture; and 
         FIG. 5  is a flow chart illustrating an example process for self-replicating cluster appliances. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various embodiments of the subject matter described herein, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  is a block diagram illustrating an example cluster  100  containing nodes for performing network testing and/or visibility related services. Referring to  FIG. 1 , cluster  100  may include a master node  102 , worker nodes  110 - 116 , and a user  118 . 
     Master node  102  may represent any suitable entity (e.g., one or more computing platforms or a device implemented using at least one processor) for performing various aspects associated with controlling cluster  100  and for configuring one or more worker nodes  110 - 116 , e.g., network testing and/or visibility nodes. Master node  102  may include cluster controller  104 , data storage  106 , and one or more communications interface(s)  108 . 
     Cluster controller  104  may represent any suitable entity or entities (e.g., software executing on at least one processor) for controlling cluster  100  and/or various nodes therein. In some embodiments, cluster controller  104  may also include functionality for detecting a new worker node, authorizing the new worker node, and providing a configuration or boot image and/or other data to the new worker node such that the new worker node can join cluster  100 . For example, cluster controller  104  may utilize node information received from a new worker node during an authentication process to select an appropriate OS for the new worker node. In this example, after the new worker node has received the appropriate OS, the new worker node may execute software, such as a cluster configuration agent, to receive additional cluster configuration information and complete joining cluster  100 . 
     In some embodiments, cluster controller  104  may utilize container or cluster orchestration software, such as Kubernetes, for providing containers (e.g., containerized applications) to one or more of worker nodes  110 - 116  and/or for configuring pods (e.g., groups of related containers with similar or same functionality) and services (e.g., microservices) that utilize the containers and pods. 
     Data storage  106  may represent any suitable entity (e.g., a computer readable medium, a database, a storage device, or memory) for storing configuration or boot images (e.g., operating system (OS) or kernel images), containers (e.g., containerized applications, various software and/or applications, cluster configuration information, authentication information, active services, pod related information, cluster related resource utilization information, and/or other data. For example, data storage  106  may store one or more repository containing different OS images or related software (e.g., various versions of a client-side cluster configuration agent to install on worker nodes  110 - 116 ). 
     Communications interface(s)  108  may represent any suitable entities (e.g., network interface cards (NICs), port modules, and/or other hardware or software) for receiving and sending communications via various communications protocols and/or data formats. For example, communications interface(s)  108  may include a configuration and monitoring interface for communicating with worker nodes  110 - 116 . In another example, communications interface(s)  108  may include a user interface (UI), a graphical UI (GUI), and/or an application programming interface (API) for allowing user  118  or another entity to interact with master node  102 . 
     User  118  may be any entity (e.g., an automated system or a device or system controlled or controllable by a human user) for selecting, viewing, and/or configuring various aspects associated with master node  102  or cluster  100 . For example, user  118  may provide configuration information to master node  102  via communications interface(s)  108 . Example UIs for interacting with master node  102  or cluster  100  may support automation (e.g., via one or more scripting languages), a representation state transfer (REST) API, a command line, and/or a web based GUI. 
     Each of worker nodes  110 - 116  may represent any suitable entity (e.g., one or more computing platforms or a device implemented using at least one processor) for performing various aspects associated with performing network testing and/or visibility related tasks or functions. For example, each of worker nodes  110 - 116  may include hardware (e.g., a network testing and/or visibility platform or a related device) from Keysight of Santa Clara, Calif. In this example, each of worker nodes  110 - 116  may execute an OS and/or other software provided by master node  102  or cluster controller  104 , e.g., after being communicatively coupled to master node  102 . Continuing with this example, the provided OS and/or other software may allow each of worker nodes  110 - 116  to act as a cluster appliance and/or provide cluster-based services and/or functions. 
     In some embodiments, an authentication process (e.g., a handshake process) between master node  102  and each of worker nodes  110 - 116  may be performed, e.g., when cabled to or otherwise connected to master node  102  and prior to being configured for cluster  100 . In such embodiments, the handshake or authentication process be for confirming that worker nodes  110 - 116  are licensed or have approved hardware (e.g., worker nodes  110 - 116  are from an approved manufacturer or retailer) and meet version, functionality, and/or sanity requirements. 
     In some embodiments, a handshake or authentication process may be used to gather node related information for determining an appropriate configuration or boot image or related data from a repository of boot and/or configuration related data (e.g., stored in data storage  106 ). For example, e.g., during an initial authentication process, each of worker nodes  110 - 116  may provide master node  102  or cluster controller  104  with detailed information related to its constituent components (e.g., processing blade information, load module information, chassis information, software information, etc.). In this example authentication related messages and/or related node information may be exchanged, for example, via a proprietary protocol or other communications protocol. 
     In some embodiments, master node  102  may be configured to analyze node information provided by a worker node (e.g., worker node  116 ) and to create or access an appropriate configuration image for the worker node, where the appropriate configuration image (e.g., an OS image and/or additional data) can be downloaded to and/or deployed on the worker node. 
     In some embodiments, a configuration image may include software, configuration data, and/or other information for booting a worker node with a particular OS and related software such that the worker node is subsequently controlled by master node  102 . In some embodiments, a configuration image may also include information for creating one or more pods and associated containerized applications that run within the pod(s). For example, a configuration image may include an OS image along with a cluster configuration agent that communicates with master node  102  or entities therein (e.g., cluster controller  104  or a Docker registry) to configure various aspects of a worker node for cluster related entities, functions, or services. 
     In some embodiments, master node  102  may provide configuration images (e.g., boot or OS images) to worker nodes  110 - 116  for various reasons, e.g., during an initial configuration of new hardware prior to or concurrently with being added cluster  100  or during a software or configuration update of a worker node that is already part of cluster  100 . For example, in response to user  118  requesting upgrades or purchasing new features for worker node  110 , master node  102  may select or create a configuration image for worker node  110  (which master node  102  already controls), where the configuration image includes an updated version of the OS running on worker node  110 . In this example, the updated OS may provide new features, functions, and/or improve existing features and/or functions. 
     In some embodiments, worker nodes  110 - 116  may utilize a reboot-less or hot-boot architecture for deploying configuration images. In some embodiments, a reboot-less or hot-boot architecture may allow user  118  (e.g., via master node  102  or another entity) to make significant changes to a running system without requiring a full or hard reboot, thereby reducing the effective “downtime” of the system. For example, master node  102  or a related entity may provide an updated OS and/or kernel image to worker node  110  while worker node  110  is running a prior OS and/or kernel version. In this example, worker node  110  may be configured to receive and store the updated OS and/or kernel image from master node  102 . Continuing with this example, worker node  110  may utilize a kexec system call or a similar command, which may allow worker node  110  to load the image (e.g., into random access memory (RAM)) and hot-boot directly into the updated OS and/or kernel from the currently running OS image and/or kernel. 
     In some embodiments, a reboot-less or hot-boot architecture may involve a launcher OS and a target OS, where the launcher OS hot-boots into the target OS and where the target OS can be received and stored while a worker node is running. For example, each of worker nodes  110 - 116  may store and utilize a launcher configuration image (e.g., a “pre-loaded” OS image) in a read-only memory partition. In such embodiments, while running, each of worker nodes  110 - 116  may be capable of receiving an updated configuration image from master node  102  or a related entity and storing the updated configuration image (e.g., in a read-only memory partition). After storing the updated configuration image, each of worker nodes  110 - 116  may be capable of hot-booting the updated configuration image using a read and write allowed memory partition (e.g., RAM or volatile memory). 
     In some embodiments, e.g., where a launcher OS is limited to just hot-booting into another OS, the related attack surface (and the need to completely update the launcher OS) is minimal. However, in some embodiments, the launcher OS may be updated as well, e.g., by deploying a binary image (e.g., via a file copy or dd command) to the read-only memory partition storing the launcher OS. 
     In some embodiments, a reboot-less or hot-boot architecture may provide various advantages over traditional OS deployment and management. For example, in lieu of apt-managed software updates used by some Linux based OSes, which have the potential to put the system into an indeterminate state, a reboot-less or hot-boot architecture allow worker nodes  110 - 116  to be updated with up-to-date OS functionality via configuration images. Moreover, since the configuration image or related OS may be a self-contained package, traditional (e.g., piece-meal) software and/or OS updates may be mitigated. Further, a reboot-less or hot-boot architecture can provide significant freedom and ease for OS changes to worker nodes  110 - 116  in the future, e.g., a switch from one Linux variant to another Linux variant, or from Linux to Windows, etc. 
     In some embodiments, user  118  may access master node  102  and view a comprehensive resource map associated with cluster  100  or related node(s) therein. For example, user  118  may reserve resources for various cluster related services or features. In this example, resource reservation information may be maintained by master node  102  and/or stored at data storage  106  and such information may be accessible or visible to some or all cluster-based entities and/or users. 
     In some embodiments, master node  102  or a related entity (e.g., cluster controller  104  or a scheduler) may include functionality for scheduling resource usage, e.g., compute, network, and data storage related resources. In such embodiments, master node  102  or a related entity may identify and manage or arbitrate resource contention among various users, nodes, or other entities. For example, assuming two users are attempting to setup different services that require a significant amount of compute resources and cluster  100  can only support one user&#39;s service, master node  102  or a related entity may notify these users and/or may prioritize (and setup) one service over another service based on one or more factors, e.g., user priority, service priority, predicted workload, current workload, and/or preferences set by a network operator or cluster operator (e.g., user  118 ). 
     It will be appreciated that  FIG. 1  is for illustrative purposes and that various depicted entities, their locations, and/or their functions described above in relation to  FIG. 1  may be changed, altered, added, or removed. It will also be appreciated that while intermediate nodes  106 - 108  are shown in  FIG. 1 , there could be more or less intermediate nodes. 
       FIG. 2  is a block diagram illustrating an example cluster-based service environment  200 . Referring to  FIG. 2 , cluster-based service environment  200  may also include a service front-end (SFE)  202  for interacting with or communicating with cluster  100  or entities therein, e.g., worker nodes  110 - 112  and/or related pods and containers. 
     SFE  202  may represent any suitable entity or entities (e.g., software executing on at least one processor, a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or a combination of software, an ASIC, or an FPGA) for performing one or more aspects associated with receiving service requests and distributing (e.g., load sharing) these service requests to one or more containerized applications associated with one or more pods hosted on worker nodes  110 - 112 . 
     In some embodiments, various features or functions associated with SFE  202  may be performed by an ingress controller  204 . For example, ingress controller  204  may represent any suitable entity or entities (e.g., software executing on at least one processor) for receiving service requests from various sources (e.g., from the internet or another network), where the service requests are for requesting one or more network testing or network visibility related microservices. In this example, ingress controller  204  may distribute service requests to relevant pods based on an internet protocol (IP) data tuple (e.g., source IP, source port, destination IP, destination port, and protocol), a destination IP address (e.g., associated with a service), and/or other information. 
     Data storage  206  may represent any suitable entity (e.g., a computer readable medium, a database, a storage device, or memory) for storing various data associated with providing one or more cluster related and/or container related service, e.g., microservices. Example data stored in data storage  206  may include service requests, pod configuration data, network address information, cluster related information, load sharing algorithm, and/or other information. In some embodiments, data storage  206  may be used to store state or other information such that related service requests (e.g., requests from a same client) are sent to the same pod for handling. 
     In some embodiments, SFE  202  may be a separate node and/or entity from master node  102  and may be configured to access or communicate with cluster related resources, e.g., master node  102 , worker nodes  110 - 112 , containers, pods, etc. In some embodiments, SFE  202  may be master node  102  or include some similar functionality. For example, SFE  202  may be capable of configuring a new worker node  300  to be part of providing a service, e.g., a network testing or visibility microservice. 
     In some embodiments, each of worker nodes  110 - 112  may be a Kubernetes worker node with one or more pods comprising one or more containerized applications (e.g., Docker containers). For example, Kubernetes worker node may be controlled and administered via a Kubernetes master node. In this example, a Kubernetes master node and one or more Kubernetes worker nodes may be referred to as a Kubernetes cluster. 
     In some embodiments, each of worker nodes  110 - 112  may include a number of processes and/or software for cluster related communications and/or functions. For example, a Kubernetes worker node may include a Kubelet process usable for sending communications between the Kubernetes master node and the Kubernetes worker node. In this example, the Kubelet process may manage the pods and the containers running on the Kubernetes worker node. 
     In some embodiments, each of worker nodes  110 - 112  may include a container runtime (e.g., Docker, rkt) usable for obtaining a container image from a container registry (e.g., a Docker registry at master node  102 ), unpacking the container, and running the container or a related application. In some embodiments, each of worker nodes  110 - 112  may include a host operating system and related infrastructure usable for executing the container runtime, the containerized applications, and/or related software. 
     In  FIG. 2 , SFE  202  or ingress controller  204  may receive and distribute service requests for one or more different services, e.g., Service X and Service Y. For example, each service may represent an abstraction that includes a logical set of pods running somewhere in cluster  100 , where the pods provide the same functionality. When created, each service may be assigned a unique IP address (also called clusterIP). For example, as depicted in  FIG. 2 , Service X may be associated with IP address ‘20.100.3.12’ and Service Y may be associated with IP address ‘20.100.3.26’. A clusterIP address may be tied to its respective service for the service&#39;s lifespan and may not change while the service is active. 
     In some embodiments, SFE  202  or ingress controller  204  may load share or distribute communications sent to a clusterIP address via one or more pods associated with a related service. For example, as depicted in  FIG. 2 , Pods  1  and  2  may be associated with Service X and Pods  3  and  4  may be associated with Service Y. In this example, after selecting a particular pod to handle a service request, SFE  202  or ingress controller  204  may provide the service request to the appropriate pod by sending the service request to the pod using the pod&#39;s IP address. For example, Pod  1  may be associated with IP address ‘10.100.0.17’ and Pod  2  may be associated with IP address ‘10.100.0.28’, while Pod  3  may be associated with IP address ‘10.100.1.46’ and Pod  4  may be associated with IP address ‘10.100.1.37’. 
     In some embodiments, each pod may be associated with a cluster-private IP address. Cluster-private IP addresses are generally unreachable by nodes outside the cluster (except via SFE  202 ), but can be used for inter-pod and inter-node communications. In some embodiments, pods associated with a particular service may also be associated with a same subnet or related subnet mask. By utilizing cluster-private IP addresses, containers within a given pod can reach each other&#39;s ports via localhost, and all pods in a cluster can see each other without NAT, thereby alleviating the need to explicitly create links between pods or to map container ports to host ports. 
     In contrast to using cluster-private IP address and pod related addressing as described above, some container based solutions may use host-private networking whereby containers can communicate with each other only if they are on the same host or node. For example, with a host-private networking, in order for Docker containers to communicate across nodes, there must be allocated ports on a Docker node&#39;s own IP address, which are then forwarded or proxied to the containers. In this example, containers must either coordinate which ports they use very carefully or ports must be allocated dynamically for such internode container communications to work. Since host-private networking requires port mappings to deliver internode communications, it can be very difficult to scale, particularly across developers, and can expose users to cluster-level issues outside of their control. 
     It will be appreciated that  FIG. 2  is for illustrative purposes and that various depicted entities, their locations, and/or their functions described above in relation to  FIG. 2  may be changed, altered, added, or removed. 
       FIGS. 3A-3B  depict a message flow diagram illustrating a worker node  300  joining cluster  100 . In some embodiments, a customer (e.g., user  118 ) may purchase a new worker node  300  that includes hardware capable of being configured for cluster based applications. For example, worker node  300  may be a network testing or visibility platform from Keysight of Santa Clara, Calif. In this example, worker node  300  may include an OS preloaded by the manufacturer that may not include all features or capabilities of a newer available OS and/or may be incapable of connecting to cluster  100  without additional configuration (e.g., by master node  102 ). In some embodiments, to initiate or trigger a process for adding worker node  300  to cluster  100 , worker node  300  may be communicatively coupled (e.g., connected via an Ethernet or network cable) to master node  102  in cluster  100 . 
     Referring to  FIG. 3A , in step  301 , worker node  300  may power on and a network and/or preboot execution environment (PXE) may boot a default OS (e.g., a launcher or base OS initially loaded at time of manufacture). 
     In step  302 , master node  102  may detect connection to worker node  300  and in response may initiate a handshake with worker node  300 . For example, master node  102  may include or interact with a DHCP server. In this example, worker node  300  may send a DHCP discovery and a subsequent DHCP request message for requesting an IP address. In this example, in response to worker node  300  requesting an IP address, master node  102  may attempt to authenticate worker node  300  via a handshake and/or other mechanisms. 
     In some embodiments, a handshake or authentication process between master node  102  and worker node  300  may be for confirming that worker node  300  is authorized to receive an updated configuration image (e.g., an OS and kernel image) and/or to join cluster  100 . For example, a handshake or authentication process between master node  102  and worker node  300  may confirm that worker node  300  is licensed or has approved hardware, that worker node  300  meets version, functionality, and/or sanity requirements. In some embodiments, a handshake or authentication process between master node  102  and worker node  300  may be used to gather node related information for determining an appropriate configuration image or related data from a repository of boot and/or configuration related data. 
     In step  303 , e.g., as part of a handshake or authentication process, master node  102  may request node information (e.g., hardware component, system IDs and/or serial numbers, etc.) from worker node  300 . 
     In step  304 , worker node  300  may send node information about worker node  300  to master node  102 . 
     In step  305 , master node  102  may select or create a configuration image (e.g., an OS or kernel image) based on the node information from worker node  300 . For example, master node  102  may use node information (e.g., hardware component information) from worker node  300  to create or access a configuration image for worker node  300 . In this example, the configuration image may configure (e.g., using a provided cluster configuration agent) worker node  300  for joining cluster  100  and performing or helping perform one or more cluster-based services. In some embodiments, selecting or creating an configuration image may utilize a repository containing images and related data for various OSes, platforms, and/or architectures. 
     In step  306 , master node  102  may send the configuration image and/or related data to worker node  300 . For example, master node  102  may provide a configuration image comprising an OS image and a cluster configuration agent to worker node  300 . 
     Referring to  FIG. 3B , in step  307 , worker node  300  may perform a hot-boot to effectively deploy or utilize the received configuration image and/or run a cluster configuration agent provided by master node  102 . For example, cluster configuration agent may be software or code usable for joining cluster  100  and/or setting up cluster-based services. In this example, cluster configuration agent may request various cluster related data from master node  102  such that worker node  300  can set up and run pods and/or related containers for providing microservices or other functionality. 
     In step  308 , worker node  300  may request cluster configuration information from master node  102 . For example, worker node  300  may request information such that worker node  300  can join and communicate with cluster  100 . 
     In step  309 , master node  102  may send the cluster configuration information to worker node  300 . For example, master node  102  may provide a number of container images, pod configuration data, and/or file system data, resource reservation data, and/or other information. 
     In step  310 , worker node  300  may join cluster  100  using the cluster configuration information from master node  102 . For example, after joining cluster  100  using the cluster configuration information from master node  102 , worker node  300  may be configured as a cluster-based worker node and may subsequently administered and/or controlled via master node  102  (e.g., by user  118 ). 
     It will be appreciated that  FIGS. 3A-3B  are for illustrative purposes and that various depicted messages and details for configuring worker node  300  and/or adding worker node  300  to cluster  100  described above in relation to  FIG. 2  may be changed, altered, added, or removed. 
       FIG. 4  is a diagram illustrating a memory partition schema  400  associated with a reboot-less or hot-boot based architecture. In some embodiments, worker nodes  110 - 116  may utilize a reboot-less or hot-boot architecture for deploying configuration images. In some embodiments, master node  102  may store a plurality of OSes in various memory partitions with different read and/or write permissions as represented by memory partition schema  400 . 
     Referring to  FIG. 4 , memory partition schema  400  is depicted using a table representing associations between partition identifiers (IDs), descriptions, and read-write permissions. In some embodiments, memory partition schema  400  may indicate how master node  102  stores configuration images (e.g., OS images) for worker nodes  110 - 116 , e.g., in persistent memory. In some embodiments, memory partition schema  400  may indicate which memory partition a worker node store a given OS image and access permissions associated with those memory partitions. 
     A first OS image depicted in memory partition schema  400  may represent a factory restore OS image and may be stored in a read-only memory partition (e.g., so that the factory restore OS image cannot be inadvertently modified). For example, a factory restore OS may be the original OS of master node  102 . In another example, a factory restore OS may be the original OS of worker node  300  (e.g., prior to receiving a configuration image from master node  102 ). In this example, the factory restore OS may also act as a launcher OS and may be capable of allowing worker node  110  to receive a configuration image while worker node  110  is running and to hot-boot this configuration image or a related OS. 
     A second OS image depicted in memory partition schema  400  may represent a current base OS (e.g., a target OS) and may be stored in a read-only memory partition (e.g., so that the base OS image cannot be inadvertently modified). For example, a base OS image may represent a current (e.g., actively running) OS of master node  102 . In another example, a base OS image may be an up-to-date OS for worker node  300  and may be provided to worker node  300  by master node  102 . In this example, while the base OS image may be stored in a read-only memory partition, worker node  300  may load the base OS image into RAM and hot-boot into the base OS, where the hot-booted OS in RAM may be modifiable. 
     User data depicted in memory partition schema  400  may represent various data that can be modified and may be stored in a read and write allowed memory partition. For example, user data may represent current state information related to cluster related operations stored in write allowed memory in master node  102 . In another example, user data may include a hot-booted OS of worker node  300  loaded in RAM and, while running, worker node  300  may modify or change the hot-booted OS. In this example, if worker node  300  is powered off, the OS and related data stored in RAM is lost. Continuing with this example, when powered back on, worker node  300  may load the unmodified base OS image (from a read-only memory partition) back into RAM and hot-boot into the base OS. 
     It will be appreciated that memory partition schema  400  in  FIG. 4  is for illustrative purposes and that different and/or additional information may also be stored or maintained. 
       FIG. 5  is a diagram illustrating an example process  500  for self-replicating cluster appliances. In some embodiments, process  500 , or portions thereof, may be performed by or at master node  102 , cluster controller  104 , worker node  300 , and/or another node or module. In some embodiments, process  500  may include steps  502 ,  504 , and/or  506 . 
     Referring to process  500 , in step  502 , node information associated with a first computing node may be received, wherein the first computing node may include a preconfigured OS. In some embodiments, node information may include processing blade information, load module information, chassis information, and/or loaded software information. 
     In step  504 , OS data for configuring the first computing node to be in the cluster may be determining using the node information. In some embodiments, OS data may include an OS image, a cluster configuration agent, a container OS, a kernel, or a filesystem. 
     In step  506 , the OS data may be provided, via a communications interface, to the first computing node. For example, the OS data may be provided from master node  102  via a file transfer protocol (FTP) or a trivial FTP (TFTP). 
     In some embodiments, process  500  may include actions (e.g., steps  502 - 506 ) performed by a controller node (e.g., master node  102 ) and may include additional actions performed by or a first computing node (e.g., worker node  300 ). For example, a first computing node may be configured for receiving OS data (e.g., an OS image and a cluster configuration agent) from a controller node; and for using the OS data to configure the first computing node to be in the cluster and to provide at least one network testing or visibility service. 
     In some embodiments, using OS data to configure a first computing node may include rebooting the first computing node in response to receiving a reboot command from the controller node via an IPMI. For example, a baseboard management controller (BMC) in worker node  300  may communicate with a bootstrap supervisor agent in master node  102  and may receive a command (e.g., ‘ipmitool chassis bootdev pxe’) for changing the boot order of worker node  300  and may receive a reboot command (e.g., ‘ipmitool chassis power reset’) for trigger worker node  300  to reboot and use the new boot order. 
     In some embodiments, a network testing or visibility service associated with cluster  100  may use at least one pod in the cluster, wherein the at least one pod may include one or more containers. In some embodiments, the at least one pod or containers therein may execute on the first computing node or another node in the cluster, wherein service requests may be load balanced using the at least one pod. 
     In some embodiments, receiving node information may be associated with an authentication process for determining that a first computing node is authorized to receive OS data. For example, master node  102  may perform a handshake with worker node  300  to determine that worker node  300  is authorized equipment for receiving a new OS image which would allow worker node  300  to join a cluster. In this example, to determine that worker node  300  is authorized, worker node  300  may send node information about itself to master node  102 . 
     In some embodiments, a controller node (e.g., master node  102 ) may be a Kubernetes master node and a first computing node may be a Kubernetes worker node (e.g., worker node  300 ). 
     In some embodiments, a first computing node may store a first OS (e.g., a base or launcher OS) in a read-only memory, wherein the first OS may unpack a second OS (e.g., from an OS image provided by master node  102 ) in a read and write allowed memory (e.g., RAM) and may load the second OS capable of providing at least one network testing or visibility service. 
     In some embodiments, a controller node may support resource reservations or resource contention arbitration associated with a cluster. 
     It will be appreciated that process  500  is for illustrative purposes and that different and/or additional actions may be used. It will also be appreciated that various actions described herein may occur in a different order or sequence. 
     It should be noted that master node  102 , cluster controller  104 , worker node  300 , and/or functionality described herein may constitute a special purpose computing device. Further, master node  102 , cluster controller  104 , worker node  300 , and/or functionality described herein can improve the technological field of node and cluster configuration for various cluster related applications or microservices, e.g., network testing and/or visibility services. For example, master node  102  or cluster controller  104  can be configured to self-replicate cluster appliances by configuring a new node to act a cluster appliance (e.g., worker node  300 ). In this example, master node  102  or cluster controller  104  can authenticate a new node, select appropriate OS data (e.g., an OS image and a cluster configuration agent) for the new node based on the node&#39;s capabilities (e.g., a node&#39;s hardware and software resources), and provide the OS data to the new node such that the new node can be added to the cluster and that the new node can provide or help provide a microservice, e.g., at least one network testing or visibility service. Also, master node  102  or cluster controller  104  may improve the technological field of cluster management and related services by providing resource reservations and resource contention arbitration for nodes within a cluster. Also, worker node  300  and/or functionality described herein can improve the technological field of OS and/or node configuration by storing a launcher or base OS/kernel in a read-only memory partition and a newer OS/kernel (e.g., from master node  102 ) in a read-write memory partition, where the launcher OS/kernel hot-boots the newer OS/kernel. For example, a launcher OS/kernel can be configured to unpack and load a newer OS/kernel into RAM (e.g., overwriting any previous in-memory OS/kernel instance) and to utilize the newer kernel/OS instance. 
     It will be understood that various details of the subject matter described herein may be changed without departing from the scope of the subject matter described herein. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation, as the subject matter described herein is defined by the claims as set forth hereinafter.