Convert most classes to use `@CompileStatic` about gretty

[javabrett]

Noting that Gretty 2.x still claims in docs to support Gradle 1.10 !!, although surely hardly anyone relies on that (nor should they) and we certainly don't test it. I understand @CompileStatic would require Groovy 2.x making Gradle 2.x minimum. So it's another one to add to the support-matrix deprecation list for the next-release, and depending on the branch/version we might deprecate Gradle 2.x support too.

[javabrett]

Hoping that @wolfs or @rwinch can validate an initial/basic approach for this, and the results, or anyone else with @CompileStatic or Gradle/Groovy performance-tuning experience.

Here's what I tried:

Baseline data:

• There's 324 *.groovy files in the project, including a handful of atypical source files for build etc.
• Full integration-test for a specific test-config ranges from 10m42s to 17m15s for a range of containers.

Approach

• Add a config.groovy containing ast(groovy.transform.CompileStatic) and reference it.
• For each location using dynamic Groovy, or other code which causes a static-compilation Java check to fail, just annotate the entire class with @CompileStatic(TypeCheckingMode.SKIP). No attempt to limit this to specific methods at this point.
• The above results in 60 classes that are skipped and not statically-compiled, retaining dynamic Groovy.
• Make other minor fixes e.g. adding required casts to fix remaining static-compilation errors.

Results

Completely unscientific, anecdotal from a single run.

• Jetty 7 test failed with a java.lang.IllegalAccessError. Not a huge concern as Jetty 7 support is scheduled for deprecation. Another container failed but with a known fragile-test issue and passed on re-run.
• Test execution times (single run, these times are also sometimes a blend of containers and not all containers run all tests):

Container	Dynamic Compilation	Selective Static Compilation	Change
jetty7	10m42s	failed	X
jetty8	15m40s	15m12s	-22s
jetty9.2	14m51s	13m15s	-1m36s
tomcat7	13m17	13m30s	+13s
tomcat8	17m15s	12m16s	-4m59s
tomcat8.5	12m30s	11m56s	-34s
tomcat9	13m21s	12m49s	-32s

Comment

Seems like an overall improvement, but apart from one dynamic change, nothing spectacular.

Questions

• Is the above approach reasonable, or how could it be improved?
• Any way of further validating what has been done?
• Any point in doing hotspot analysis to try and apply more static-compilation by being more selective with exclusion using method-annotations, or "fixing" bits of code so they work statically?

[wolfs]

@javabrett Thank you for trying it out!

Regarding your numbers above: I don't understand why these improvements would be caused by adding CompileStatic: CompileStatic will only improve the execution time of scripts, since less dynamic invocations need to be done, which may be expensive.

So the improvement would be in configuration time of the build. I guess all the above projects are small, right? So you wouldn't even notice configuration time improvements. Did you restart the daemon between runs? If not, then the time improvement is due to having a warm daemon.

If you want to do some performance measurements, please use gradle-profiler. That would allow you to get more accurate measurements.

Moreover, for testing the configuration time improvements, you would need a sufficiently big project (maybe 100 sub-projects), each applying the Jetty plugin.

Note that it is not necessary to convert all classes to CompileStatic, only the ones which are executed when the plugin is applied (as opposed to when the plugin's tasks are executed) would be enough.

[javabrett]

Thanks @wolfs for the comments and help.

Note that it is not necessary to convert all classes to CompileStatic

I think that was my reaction to the issue summary "Convert most classes to use @CompileStatic" and "Using CompileStatic on a significant number if not on all classes" :).

... only the ones which are executed when the plugin is applied (as opposed to when the plugin's tasks are executed) would be enough.

So that might be in GrettyPlugin#apply and everything called from there? Note that this had compile-errors when compiled Java static, so it was excluded for the first-pass approach.

There's also https://github.com/gretty-gradle-plugin/gretty/blob/master/integrationTests/buildSrc/gretty-integrationTest/src/main/groovy/org/akhikhl/gretty/internal/integrationTests/BasePlugin.groovy#L109 for dev.

So the improvement would be in configuration time of the build.

I think this refers to a Gradle build of a project which applies the Gretty project once or more (rather than the build of the Gretty project itself).

Regarding your numbers above: I don't understand why these improvements would be caused by adding CompileStatic: CompileStatic will only improve the execution time of scripts, since less dynamic invocations need to be done, which may be expensive. So the improvement would be in configuration time of the build. I guess all the above projects are small, right? So you wouldn't even notice configuration time improvements. Did you restart the daemon between runs? If not, then the time improvement is due to having a warm daemon.

The timing numbers refer to builds which run integrationTests, which run on Travis, where I believe the Gradle Daemon is disabled by-default, or at least each build runs in a clean Docker. Per above at least one important class has been disabled. Probably any reduction is coindidental.

Moreover, for testing the configuration time improvements, you would need a sufficiently big project (maybe 100 sub-projects), each applying the Jetty plugin.

I was tempted to ask what a canonical test for performance-improvements might look like before I started - sounds like this is it.

[javabrett]

The configuration-time performance improvement from adding @CompileStatic should now be available in Gretty 2.3.0-SNAPSHOT and 3.0.0-SNAPSHOT. A 2.3.0 release shouldn't be too far away.

A subsequent buildscan for spring-security is available at https://scans.gradle.com/s/o6jlskwqa7k3y .

Thanks @rwinch for the report and @wolfs and @oehme for the profiler support.