[BUG] openapi-generator-maven-plugin is not marked as threadSafe

[famod]

Description

Building a Maven multimodule project in parallel (e.g. mvn -T2 ...) that uses openapi-generator-maven-plugin yields the following warning for each plugin execution:

[2020-04-08T13:59:47.119Z] [WARNING] *****************************************************************
[2020-04-08T13:59:47.119Z] [WARNING] * Your build is requesting parallel execution, but project      *
[2020-04-08T13:59:47.119Z] [WARNING] * contains the following plugin(s) that have goals not marked   *
[2020-04-08T13:59:47.119Z] [WARNING] * as @threadSafe to support parallel building.                  *
[2020-04-08T13:59:47.119Z] [WARNING] * While this /may/ work fine, please look for plugin updates    *
[2020-04-08T13:59:47.119Z] [WARNING] * and/or request plugins be made thread-safe.                   *
[2020-04-08T13:59:47.119Z] [WARNING] * If reporting an issue, report it against the plugin in        *
[2020-04-08T13:59:47.119Z] [WARNING] * question, not against maven-core                              *
[2020-04-08T13:59:47.119Z] [WARNING] *****************************************************************
[2020-04-08T13:59:47.119Z] [WARNING] The following plugins are not marked @threadSafe in some-module:
[2020-04-08T13:59:47.119Z] [WARNING] org.openapitools:openapi-generator-maven-plugin:4.2.3
[2020-04-08T13:59:47.119Z] [WARNING] Enable debug to see more precisely which goals are not marked @threadSafe.
[2020-04-08T13:59:47.119Z] [WARNING] *****************************************************************

openapi-generator version

4.2.3

OpenAPI declaration file content or url

not relevant

Command line used for generation

mvn clean install -T2 (example)

Steps to reproduce

Build a multimodule project taht is using openapi-generator-maven-plugin in parallel.

Related issues/PRs

n/a

Suggest a fix

Add threadSafe=true to @Mojo: https://github.com/OpenAPITools/openapi-generator/blob/master/modules/openapi-generator-maven-plugin/src/main/java/org/openapitools/codegen/plugin/CodeGenMojo.java#L73
This assumes that the plugin does handle concurrent invocations (form different modules) without concurrency issues!

[famod]

I was torn between bug and "improvement" so feel free to change the issue type.

[wing328]

@famod I wonder if you can file a PR with the suggested fix when you've time.

[famod]

@wing328 I'll gladly do that but is the plugin thread safe after all? I cannot answer this question.

[famod]

By coincidence, we've just hit a sproadic build problem which might be a concurrency issue:

15:55:54  [INFO] --- openapi-generator-maven-plugin:4.2.3:generate (generate-code) @ module-A ---
15:55:54  [INFO] Execution of maven-enforcer-plugin:1.4.1:enforce (enforce-deps) @ module-B took 0.069s
15:55:54  [INFO] 
15:55:54  [INFO] --- maven-enforcer-plugin:1.4.1:enforce (enforce-infix) @ module-B ---
15:55:54  [INFO] Execution of maven-enforcer-plugin:1.4.1:enforce (enforce-infix) @ module-B took 0.001s
15:55:54  [INFO] 
15:55:54  [INFO] --- maven-resources-plugin:3.1.0:resources (resources) @ module-B ---
15:55:54  [INFO] Using 'UTF-8' encoding to copy filtered resources.
15:55:54  [INFO] Copying 1 resource
15:55:54  [INFO] Copying 1 resource
15:55:54  [INFO] Execution of maven-resources-plugin:3.1.0:resources (resources) @ module-B took 0.005s
15:55:54  [INFO] 
15:55:54  [INFO] --- openapi-generator-maven-plugin:4.2.3:generate (generate-code) @ module-B ---
15:55:54  [ERROR] Cannot find a deserializer for non-concrete Map type [map type; class com.google.common.collect.ImmutableMap, [simple type, class java.lang.String] -> [simple type, class java.lang.String]]
15:55:54   at [Source: (File); line: 1, column: 1]
15:55:54  [ERROR] /opt/jenkins/data/jobs/th360-middleware-pr-pipelines-develop/jobs/PR-00048-THMED-2681-exception-handling/workspace/user/api/pro-fe/target/classes/api.json [0:0]: unexpected error in Open-API generation
15:55:54  java.lang.RuntimeException: Unable to deserialize config file: /opt/jenkins/data/jobs/th360-middleware-pr-pipelines-develop/jobs/PR-00048-THMED-2681-exception-handling/workspace/shared/rest/src/main/openapi/generator/import-mappings.json
15:55:54      at org.openapitools.codegen.config.CodegenConfigurator.fromFile (CodegenConfigurator.java:139)
15:55:54      at org.openapitools.codegen.plugin.CodeGenMojo.execute (CodeGenMojo.java:456)
15:55:54      at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
15:55:54      at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
15:55:54      at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
15:55:54      at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
15:55:54      at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
15:55:54      at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:190)
15:55:54      at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:186)
15:55:54      at java.util.concurrent.FutureTask.run (FutureTask.java:264)
15:55:54      at java.util.concurrent.Executors$RunnableAdapter.call (Executors.java:515)
15:55:54      at java.util.concurrent.FutureTask.run (FutureTask.java:264)
15:55:54      at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1128)
15:55:54      at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:628)
15:55:54      at java.lang.Thread.run (Thread.java:834)
15:55:54  [ERROR] 
15:55:54  java.lang.RuntimeException: Unable to deserialize config file: /opt/jenkins/data/jobs/th360-middleware-pr-pipelines-develop/jobs/PR-00048-THMED-2681-exception-handling/workspace/shared/rest/src/main/openapi/generator/import-mappings.json
15:55:54      at org.openapitools.codegen.config.CodegenConfigurator.fromFile (CodegenConfigurator.java:139)
15:55:54      at org.openapitools.codegen.plugin.CodeGenMojo.execute (CodeGenMojo.java:456)
15:55:54      at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo (DefaultBuildPluginManager.java:137)
15:55:54      at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:210)
15:55:54      at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:156)
15:55:54      at org.apache.maven.lifecycle.internal.MojoExecutor.execute (MojoExecutor.java:148)
15:55:54      at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject (LifecycleModuleBuilder.java:117)
15:55:54      at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:190)
15:55:54      at org.apache.maven.lifecycle.internal.builder.multithreaded.MultiThreadedBuilder$1.call (MultiThreadedBuilder.java:186)
15:55:54      at java.util.concurrent.FutureTask.run (FutureTask.java:264)
15:55:54      at java.util.concurrent.Executors$RunnableAdapter.call (Executors.java:515)
15:55:54      at java.util.concurrent.FutureTask.run (FutureTask.java:264)
15:55:54      at java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1128)
15:55:54      at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:628)
15:55:54      at java.lang.Thread.run (Thread.java:834)

You can see that module-A starts generating shortly before module-B and then module-B fails (before module-A has finished).

WDYT?