erb_concurrency_test.rb

require 'erb'

NUM_THREADS = 400

puts "Thread with string"
threads = NUM_THREADS.times.map {
  Thread.new do
    '1'
  end
}
threads.each(&:join)

puts "Thread with ERB"
threads = NUM_THREADS.times.map {
  Thread.new do
    ERB.new('1').result
  end
}
threads.each(&:join)

output

bbrowning@bbrowning-mbp:~/tmp$ jruby -v
jruby 1.7.3 (1.9.3p385) 2013-02-21 dac429b on Java HotSpot(TM) 64-Bit Server VM 1.8.0-ea-b74 +indy [darwin-x86_64]
bbrowning@bbrowning-mbp:~/tmp$ jruby erb_concurrency_test.rb
Thread with string
Thread with ERB
Exception in thread "RubyThread-724: erb_concurrency_test.rb:1" java.lang.ArrayIndexOutOfBoundsException
	at java.lang.System.arraycopy(Native Method)
	at org.jruby.RubyString.cat(RubyString.java:1419)
	at org.jruby.RubyString.cat19(RubyString.java:1324)
	at org.jruby.RubyString.cat19(RubyString.java:1317)
	at org.jruby.RubyString.append19(RubyString.java:2580)
	at org.jruby.RubyString.concat19(RubyString.java:2611)
	at org.jruby.RubyString$INVOKER$i$1$0$concat19.call(RubyString$INVOKER$i$1$0$concat19.gen)
	at org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:326)
	at org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:170)
	at org.jruby.ast.CallOneArgNode.interpret(CallOneArgNode.java:57)
	at org.jruby.ast.NewlineNode.interpret(NewlineNode.java:105)
	at org.jruby.ast.BlockNode.interpret(BlockNode.java:71)
	at org.jruby.ast.RootNode.interpret(RootNode.java:129)
	at org.jruby.evaluator.ASTInterpreter.INTERPRET_EVAL(ASTInterpreter.java:96)
	at org.jruby.evaluator.ASTInterpreter.evalWithBinding(ASTInterpreter.java:175)
	at org.jruby.RubyKernel.evalCommon(RubyKernel.java:1103)
	at org.jruby.RubyKernel.eval19(RubyKernel.java:1066)
	at rubyjit.ERB$$result_DB39BCF7DCAE0101E3C2162508E49164D98727E2178030112.__file__(/Users/bbrowning/.rvm/rubies/jruby-1.7.3/lib/ruby/1.9/erb.rb:838)
	at rubyjit.ERB$$result_DB39BCF7DCAE0101E3C2162508E49164D98727E2178030112.__file__(/Users/bbrowning/.rvm/rubies/jruby-1.7.3/lib/ruby/1.9/erb.rb)
	at org.jruby.ast.executable.AbstractScript.__file__(AbstractScript.java:38)
	at org.jruby.internal.runtime.methods.JittedMethod.call(JittedMethod.java:141)
	at erb_concurrency_test.block_3$RUBY$__file__(erb_concurrency_test.rb:16)
	at erb_concurrency_test$block_3$RUBY$__file__.call(erb_concurrency_test$block_3$RUBY$__file__)
	at org.jruby.runtime.CompiledBlock19.yield(CompiledBlock19.java:163)
	at org.jruby.runtime.CompiledBlock19.call(CompiledBlock19.java:91)
	at org.jruby.runtime.Block.call(Block.java:89)
	at org.jruby.RubyProc.call(RubyProc.java:261)
	at org.jruby.RubyProc.call(RubyProc.java:213)
	at org.jruby.internal.runtime.RubyRunnable.run(RubyRunnable.java:98)
	at java.lang.Thread.run(Thread.java:722)