Disable macro/plugin class loader caching, by default #6412
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And change the relevant settings to be evolvable into a policy selection rather than just a on/off toggle.
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The main rationale here is that when we merged #6314 we didn't consider the risk of exposing concurrency bugs or memory leaks due to the sharing of state in top level objects (aka Java statics) across a cached classloader, which could be used in parallel or held onto for a long time. We should enable caching by default in 2.13.x, but do so with a good release note for macro and plugin authors showing how to avoid problems, and perhaps incorporating with a time-based invalidation of cached classloaders. The UI change is trying to incorporate #6381. |
jvican
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Mar 12, 2018
| object None extends CachePolicy("none", "Don't cache class loader") | ||
| object LastModified extends CachePolicy("last-modified", "Cache class loader, using file last-modified time to invalidate") | ||
| // TODO Jorge to add new policy. Think about whether there is a benefit to the user on offering this as a separate policy or unifying with the previous one. | ||
| // object ZipMetadata extends CachePolicy("zip-metadata", "Cache classloade, using file last-modified time, then ZIP file metadata to invalidate") |
lrytz
approved these changes
Mar 12, 2018
neko-kai
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…(however, this supposedly breaks macros with global mutable state...) scala/scala#6412 https://twitter.com/olafurpg/status/1191299377064824832 > The caching logic for compiler plugins is enabled by default in Bloop and that one does make a difference, around 20/30%, see scala/scala-dev#458
neko-kai
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* renames for Project fields * Disable eta-sam lint scala/bug#11644 * Enable compiler plugin & macro classloader caching for faster builds (however, this supposedly breaks macros with global mutable state...) scala/scala#6412 https://twitter.com/olafurpg/status/1191299377064824832 > The caching logic for compiler plugins is enabled by default in Bloop and that one does make a difference, around 20/30%, see scala/scala-dev#458 * Don't use -Xsource: since it's not recommended scala/bug#11661 * fix Ybackend-parallelism option * empty `enabled` default parameter for Plugins
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#6314 introduced classpath caching for compiler plugins and macros, and enabled it by default. This PR switches the default in order to be conservative in a 2.12 minor release.
Currently, the only caching strategy is
last-modified, which checks the last modified date of the JAR file. Caching can be enabled using-Ycache-plugin-class-loader:last-modified/-Ycache-macro-class-loader:last-modifiedChange the relevant settings to be evolvable into a policy selection rather than just a on/off toggle.