Parallel builds

[sknop]

It looks like the asciidoctor gradle plugin does not support parallel builds.
We have a repository with multiple (independent) documents, and it would be great if these could be build in parallel.

[ysb33r]

In the current 2.x context:

• If --parallel is specified on the command-line and there are multiple asciidoctorX tasks they should be able to run in parallel if Gradle decides to schedule them so.
• There is a parallelMode property that is on by default for asciidoctorX tasks. If there are more than one backend in the specific tasks, processing for those backends will happen in parallel. If inProcess==JAVA_EXC the parallel mode is ignored. Currently only the generic AsciidoctorTask type supports this parallel feature.

The idea of generating independent documents in parallel is an excellent concept in principle, so let's explore it.

• In order to to achieve this, multiple AsciidoctorJ instances must be made available. This can either be done via the worker API (keeping in mind the current limitations of this API and related open issues with Gradle) or inside the worker of external Java process, multiple Asciidoctor instances can simply be created.
• Depending on the model of operation this will need to be separate processes or threads.
• Assuming that the documents come from the same task, we can safely assume that the classpath, GEM requirements, and extensions will be the same thus making multiple threads or actors a possibility.
• As this parallel processing could be highly contextual to the environment of the script author parameters such as memory and concurrency limit should be configurable.
• There is no guarantee that processing the documents in parallel will be faster as start-up time for instance could be more than the time saved in concurrency. Therefore this will need to be configurable behaviour and turned off by default.

It is possible that the curretn parallelMode implementation could be extended to accommodate the above all be it with additional DSL.

[shevek]

Failing miserably for us; tends to crash the JVM.

[ysb33r]

@shevek parallel builds are not supported in anything prior to 2.0.0.