[LOGSTASH] crashes with pipeline exception (5.6.10)

[Karthik_Mahadevan]

we see no issue when starting logstash, it was running for months without any issue.
suddenly we see traceback provided below and logstash in state to reject incoming logs.
traceback:
'[2019-04-24T22:20:18,855][ERROR][logstash.pipeline ] Exception in pipelineworker, the pipeline stopped processing new events, please check your filter configuration and restart Logstash. {"exception"=>"-1", "backtrace"=>["java.util.ArrayList.elementData(ArrayList.java:422)", "java.util.ArrayList.remove(ArrayList.java:499)", "org.logstash.FieldReference.parse(FieldReference.java:73)", "org.logstash.PathCache.parseToCache(PathCache.java:24)", "org.logstash.PathCache.cache(PathCache.java:20)", "org.logstash.ext.JrubyEventExtLibrary$RubyEvent.ruby_set_field(JrubyEventExtLibrary.java:125)", "org.logstash.ext.JrubyEventExtLibrary$RubyEvent$INVOKER$i$2$0$ruby_set_field.call(JrubyEventExtLibrary$RubyEvent$INVOKER$i$2$0$ruby_set_field.gen)", "org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:202)", "rubyjit.LogStash::Filters::Json$$filter_40ff8d4c1569dcd49c050f4a5093a76d6c4d61381252169911.block_2$RUBY$file(/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-json-3.0.5/lib/logstash/filters/json.rb:106)", "rubyjit$LogStash::Filters::Json$$filter_40ff8d4c1569dcd49c050f4a5093a76d6c4d61381252169911$block_2$RUBY$file.call(rubyjit$LogStash::Filters::Json$$filter_40ff8d4c1569dcd49c050f4a5093a76d6c4d61381252169911$block_2$RUBY$file)", "org.jruby.runtime.CompiledBlock19.yield(CompiledBlock19.java:135)", "org.jruby.runtime.Block.yield(Block.java:142)", "org.jruby.RubyHash$13.visit(RubyHash.java:1355)", "org.jruby.RubyHash.visitLimited(RubyHash.java:648)", "org.jruby.RubyHash.visitAll(RubyHash.java:634)", "org.jruby.RubyHash.iteratorVisitAll(RubyHash.java:1306)", "org.jruby.RubyHash.each_pairCommon(RubyHash.java:1351)", "org.jruby.RubyHash.each19(RubyHash.java:1342)", "org.jruby.RubyHash$INVOKER$i$0$0$each19.call(RubyHash$INVOKER$i$0$0$each19.gen)", "org.jruby.runtime.callsite.CachingCallSite.callBlock(CachingCallSite.java:143)", "org.jruby.runtime.callsite.CachingCallSite.callIter(CachingCallSite.java:154)", "rubyjit.LogStash::Filters::Json$$filter_40ff8d4c1569dcd49c050f4a5093a76d6c4d61381252169911.file(/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-json-3.0.5/lib/logstash/filters/json.rb:106)", "rubyjit.LogStash::Filters::Json$$filter_40ff8d4c1569dcd49c050f4a5093a76d6c4d61381252169911.file(/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-json-3.0.5/lib/logstash/filters/json.rb)", "org.jruby.internal.runtime.methods.JittedMethod.call(JittedMethod.java:201)", "org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:336)", "org.jruby.runtime.callsite.CachingCallSite.callBlock(CachingCallSite.java:179)", "org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:183)", "rubyjit.LogStash::Filters::Base$$do_filter_8e8403dcfdf01a35ffca12ed35ec4e79455489071252169911.file(/usr/share/logstash/logstash-core/lib/logstash/filters/base.rb:145)", "rubyjit.LogStash::Filters::Base$$do_filter_8e8403dcfdf01a35ffca12ed35ec4e79455489071252169911.file(/usr/share/logstash/logstash-core/lib/logstash/filters/base.rb)", "org.jruby.internal.runtime.methods.JittedMethod.call(JittedMethod.java:201)", "org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:336)", "org.jruby.runtime.callsite.CachingCallSite.callBlock(CachingCallSite.java:179)", "org.jruby.runtime.callsite.CachingCallSite.callIter(CachingCallSite.java:188)", "rubyjit.LogStash::Filters::Base$$multi_filter_6c0dea8219a042f89f5a5b41e60697f8088a7c451252169911.block_0$RUBY$file(/usr/share/logstash/logstash-core/lib/logstash/filters/base.rb:164)", "rubyjit$LogStash::Filters::Base$$multi_filter_6c0dea8219a042f89f5a5b41e60697f8088a7c451252169911$block_0$RUBY$file.call(rubyjit$LogStash::Filters::Base$$multi_filter_6c0dea8219a042f89f5a5b41e60697f8088a7c451252169911$block_0$RUBY$file)", "org.jruby.runtime.CompiledBlock19.yield(CompiledBlock19.java:135)",
..................... (removed some part because of limitation to number of characters)
"org.jruby.internal.runtime.methods.ProcMethod.call(ProcMethod.java:64)", "org.jruby.internal.runtime.methods.DynamicMethod.call(DynamicMethod.java:210)", "org.jruby.internal.runtime.methods.DynamicMethod.call(DynamicMethod.java:206)", "org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:326)", "org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:170)", "rubyjit.LogStash::Pipeline$$filter_batch_052b78d27259f9bcbc13f5e343ec3d67811edf031252169911.chained_0_rescue_1$RUBY$SYNTHETIC__file__(/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:398)", "rubyjit.LogStash::Pipeline$$filter_batch_052b78d27259f9bcbc13f5e343ec3d67811edf031252169911.file(/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb)", "rubyjit.LogStash::Pipeline$$filter_batch_052b78d27259f9bcbc13f5e343ec3d67811edf031252169911.file(/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb)", "org.jruby.internal.runtime.methods.JittedMethod.call(JittedMethod.java:181)", "org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:326)", "org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:170)", "org.jruby.ast.FCallOneArgNode.interpret(FCallOneArgNode.java:36)", "org.jruby.ast.NewlineNode.interpret(NewlineNode.java:105)", "org.jruby.ast.BlockNode.interpret(BlockNode.java:71)", "org.jruby.ast.WhileNode.interpret(WhileNode.java:131)", "org.jruby.ast.NewlineNode.interpret(NewlineNode.java:105)", "org.jruby.ast.BlockNode.interpret(BlockNode.java:71)", "org.jruby.evaluator.ASTInterpreter.INTERPRET_METHOD(ASTInterpreter.java:74)", "org.jruby.internal.runtime.methods.InterpretedMethod.call(InterpretedMethod.java:225)", "org.jruby.internal.runtime.methods.DefaultMethod.call(DefaultMethod.java:219)", "org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:202)", "org.jruby.ast.FCallTwoArgNode.interpret(FCallTwoArgNode.java:38)", "org.jruby.ast.NewlineNode.interpret(NewlineNode.java:105)", "org.jruby.ast.BlockNode.interpret(BlockNode.java:71)", "org.jruby.evaluator.ASTInterpreter.INTERPRET_BLOCK(ASTInterpreter.java:112)", "org.jruby.runtime.Interpreted19Block.evalBlockBody(Interpreted19Block.java:206)", "org.jruby.runtime.Interpreted19Block.yield(Interpreted19Block.java:194)", "org.jruby.runtime.Interpreted19Block.call(Interpreted19Block.java:125)", "org.jruby.runtime.Block.call(Block.java:101)", "org.jruby.RubyProc.call(RubyProc.java:300)", "org.jruby.RubyProc.call(RubyProc.java:230)", "org.jruby.internal.runtime.RubyRunnable.run(RubyRunnable.java:103)", "java.lang.Thread.run(Thread.java:748)"]}'
version of logstash is 5.6.10. this do not seem like a configuration issue. can anyone help us understand what went wrong?