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Motivation

Ignite provide many ways to execute user provided code:

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

Description

It proposed to add new entity to Ignite - IgniteClassPath.

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• 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.

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$ ./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.