File descriptors from stdlib jars are leaked when ScriptingContainers are terminated #3928
Description
Environment
JRuby 9.1.1.0, run from a Java program via ScriptingContainer, with setCompileMode set to OFF.
Expected Behavior
ScriptingContainer instances should be able to be created and terminated without leaking memory or other resources, such as file descriptors.
Actual Behavior
When a ScriptingContainer is constructed and executes any Ruby code that results in certain jar-based libraries being loaded from jruby-stdlib, there are file descriptors opened pointing to the relevant library jars. When a ScriptingContainer is terminated, these descriptors (which seem to be referenced in a global cache) are not cleaned up.
The cache appears to use weak references, so presumably at some point the memory used by these objects could be reclaimed, but because there is also an open file descriptor associated with each cache entry, it is likely that a program that is recycling ScriptingContainer instances will exceed the open file descriptor limit and crash before there is enough memory pressure to cause these objects to be GC'd.
Here is a reproducer that illustrates the issue:
In the reproducer, we just do requires on a few libraries like openssl, psych, json/ext. Here is some lsof output that shows file descriptors for jars that definitely seem related to those libraries (bouncycastle, etc.):
java 16802 cprice 145r REG 8,1 673715 1848479 /tmp/jruby-16802/jruby4231261797459246050bcpkix-jdk15on-1.54.jar
java 16802 cprice 146r REG 8,1 3277268 1848480 /tmp/jruby-16802/jruby2526682390458341590bcprov-jdk15on-1.54.jar
java 16802 cprice 147r REG 8,1 1029206 1848481 /tmp/jruby-16802/jruby8134376450898266715jopenssl.jar
java 16802 cprice 148r REG 8,1 29184 1848482 /tmp/jruby-16802/jruby2150106223798361691parser.jar
java 16802 cprice 149r REG 8,1 36598 1848483 /tmp/jruby-16802/jruby8382658838024689723generator.jar
java 16802 cprice 150r REG 8,1 673715 1848486 /tmp/jruby-16802/jruby791041166383033485bcpkix-jdk15on-1.54.jar
java 16802 cprice 151r REG 8,1 3277268 1848487 /tmp/jruby-16802/jruby8183181496442107777bcprov-jdk15on-1.54.jar
java 16802 cprice 152r REG 8,1 1029206 1848488 /tmp/jruby-16802/jruby2262201270422384640jopenssl.jar
java 16802 cprice 153r REG 8,1 29184 1848489 /tmp/jruby-16802/jruby7381052665382428377parser.jar
java 16802 cprice 154r REG 8,1 36598 1848490 /tmp/jruby-16802/jruby8249386243245178423generator.jar
java 16802 cprice 155r REG 8,1 673715 1848493 /tmp/jruby-16802/jruby2517646537378734847bcpkix-jdk15on-1.54.jar
java 16802 cprice 156r REG 8,1 3277268 1848494 /tmp/jruby-16802/jruby6109779259907062980bcprov-jdk15on-1.54.jar
java 16802 cprice 157r REG 8,1 1029206 1848495 /tmp/jruby-16802/jruby4734983808548108497jopenssl.jar
java 16802 cprice 158r REG 8,1 29184 1848496 /tmp/jruby-16802/jruby1658078054671173220parser.jar
java 16802 cprice 159r REG 8,1 36598 1848497 /tmp/jruby-16802/jruby3451778285607680674generator.jar