[GROOVY-8097] Add an argument to set the resolution cache path in @Grab

• Type: New Feature
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 2.4.8
• Component/s: Grape
• Assignee: Unassigned
• Reporter: Ion Alberdi
• Created: 22/Feb/17 10:12
• Updated: 14/Mar/17 08:34

Description

Ivy does not support concurrent access to its resolution cache
https://issues.apache.org/jira/browse/IVY-654

Grape relies on Ivy. For this reason, Grape cannot support concurrent access to its resolution cache neither.

When using the @Grab annotation in jenkins groovyCommand or systemGroovyCommand, the related code is vulnerable to race conditions. When the race condition appears in a systemGroovyCommand, we have no choice but to reboot jenkins as all consecutive calls to @Grab fail.

Among the two solutions we tried:

• Protect the calls to grab with a lock similar to ivy's "artifact-lock-nio" strategy. Works but slow.
• Set Ivy's lock on the repository cache and setup Grab to use a different cache resolution cache for each concurrent jobs. The following code permits to fix a test we did to reproduce the race condition.

    static IvySettings createIvySettings(String resolutionPath, boolean dumpSettings) {
        // Copy/Paste/Purged from GrapeIvy.groovy
        IvySettings settings = new IvySettings()

        settings.load(new File(GROOVY_HOME, "grapeConfig.xml"))
        // set up the cache dirs
        settings.defaultCache = new File(GRAPES_HOME)
        settings.setVariable("ivy.default.configuration.m2compatible", "true")
        settings.setDefaultResolutionCacheBasedir(resolutionPath)
        return settings
    }

    static GrapeIvy ivyWithCustomResolutionPath(String resolutionPath) {
        Class<?> grapeIvyClass = Class.forName("groovy.grape.GrapeIvy");
        Object instance = grapeIvyClass.newInstance()
        Field field = grapeIvyClass.getDeclaredField("ivyInstance");
        field.setAccessible(true);
        field.set(instance, Ivy.newInstance(createIvySettings(resolutionPath)));
        return ((GrapeIvy)instance)
    }

We'd like to propose to add an additional argument to Grab to setup Ivy's resolution cache directory.

Note that this solution seems to have been adopted by these users too
https://rbcommons.com/s/twitter/r/3436/

Would you agree on such a feature ? We'd be glad to propose a PR.