Motivation

Ignite provide many ways to execute user provided code:

• Compute jobs.
• Services.
• SQL UDF.
• CacheInterceptors
• Query filters
• etc.

Currently, Ignite provides several ways to load user-provided code:

• add user jars to Ignite server node classpath.
• Configure DeploymentSpi implementation via IgniteConfiguration#setDeploymentSpi, IgniteConfiguration#setDeploymentMode.
  Monitored by GridDeploymentInfo, UriDeploymentSpiMBean, LocalDeploymentSpiMBean.
• Add dependencies to client node and enable peer to peer class loading.

However, all this ways lack several crucial features:

• Clear way to know which classes loaded from which nodes.
  It expected that all classes will be the same on all nodes, which is not alway true.
• Tools to view jars available.
• Clear way to update user jars.
• Having several versions of user jars: blue-green, canary deployments.
• Remove classes from Ignite process.
• Restrictions (security) for client nodes to provide classes.
  In real world cases not all client nodes can be treated as trusted
  so in many production cluster p2p class loading disabled and forbidden to enable.

We must reinvent the way Ignite loads user classes to fill the gap. 

Description

It proposed to add new entity to Ignite - IgniteClassPath.

IgniteClassPath properties:

• Name - unique string identifier (app_v1, 01_07_2025, etc).
• Set of libs and resources associated with IgniteClassPath.
• Each instance available on each Ignite node, maybe on demand.
• Can be created and removed runtime - without any restarts.
• Instances independent from each other.

API changes (list will be widen):

• IgniteCache#withClassPath
• IgniteCompute#withClassPath
• ServiceConfiguration#setClassPath
• JDBC driver params to point to classpath used by UDFs and other things during queries execution.
• Deprecation and removal of DeploymentSpi and related configuration properties.
• Deprecation and removal p2p class loading and related configuration properties.
• New security permission to restrict creation/deletion of IgniteClassPath for specific users.

Required tools:

• control.sh command to create/remove/list resources.
• control.sh command to register class path from server node resource.
  In strict environments it often prohibited for process to modify it's code (jars).
  So, regular flow with the "Ignite, please deploy files from the local disk to cluster" not working.
  We must provide a way to register and validate IgniteClassPath from server node local disks. 
• system view to list available instances.

Examples:

$ ./control.sh --ignite-classpath create --name superapp_v1 --files ./my-app-v1.jar,./grpc-context-1.19.0.jar,./error_prone_annotations-2.1.3.jar
$ ./control.sh --ignite-classpath remove --name superapp_v0
$ ./control.sh --system-view IGNITE_CLASSPATHES

Ignite ignite = ...

IgniteCompute compute = ignite.compute(ignite.cluster().forServers());

// Running compute with the provided jars.
compute.withClasspath("superapp_v1").() -> {
    MyLibClass libClass = MyLibClass.getInstance();
    // other code.
};


ServiceConfiguration serviceCfg = new ServiceConfiguration();

serviceCfg.setName("mysuperappService_v1");
serviceCfg.setService(new MySuperappServiceImpl());
serviceCfg.setIgniteClasspath("mysuperapp_v1");

ignite.services().deploy(serviceCfg);

Other systems approaches:

Apache Spark

Provides a special tool - spark-submit  to deploy and execute jobs inside cluster.
It supports --jars argument to list jar files required by job. (1)

Apache Tomcat (2)

J2EE spec itself provide a clear way to:

• pack dependencies to single WAR file
• update application versions by deploying new WAR file to servlet container.
• Well known directories /WEB-INF/classes, /WEB-INF/libs contains all applcation dependencies that added to classpath.
• Tools to deploy/undeploy application provided, also.

Apache Flink (3) (4)

Provides an options to specify job classpath during starttime.

Example: 

$ ./bin/flink run -C /path/to/dependency.jar -c com.example.MyJob my-flink-job.jar

Risks and Assumptions

We assume that p2p and deployment SPI will be removed from Ignite.

Users may want to recompile and refresh classes without changing (remove, create) existing IgniteClassPath during development or hotfix.
Currently, we don't have plans to support this kind of scenario.

We assume the following user scenarios:

Deploy and run first version of application:

1. Pack jar files by regular procedures.
2. Create IgniteClassPath in running cluster.
3. Set name of classpath in app config.
4. Start Ignite client nodes or connect via thin clients.
5. Use classpath when starting jobs, services, etc.

Run second version of application in the same cluster:

1. Pack jar files by regular procedures.
2. Create second IgniteClassPath in running cluster.
3. Restart some instances of user application with the updated version in config.
4. Use updated classpath for new instances of application.
5. When tested update all application instances.

With this approach, we can update applications without any outages.

Discussion Links

// Links to discussions on the devlist, if applicable.

Reference Links

1. https://spark.apache.org/docs/latest/submitting-applications.html
2. https://tomcat.apache.org/tomcat-11.0-doc/deployer-howto.html
3. https://nightlies.apache.org/flink/flink-docs-stable/docs/ops/debugging/debugging_classloading/
4. https://nightlies.apache.org/flink/flink-docs-release-2.2/docs/ops/rest_api/

Tickets

// Links or report with relevant JIRA tickets.