[jira] [Created] (VELOCITY-992) VelocityEngine multi-thread deadlock

vincent royer created VELOCITY-992:
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             Summary: VelocityEngine multi-thread deadlock
                 Key: VELOCITY-992
                 URL: https://issues.apache.org/jira/browse/VELOCITY-992
             Project: Velocity
          Issue Type: Bug
          Components: Engine
    Affects Versions: 2.4.1
            Reporter: vincent royer


When using one VelocityEngine instance in a multithread app, I get the following dead lock:

"{*}javamail-executor-thread-1{*}@20270" tid=0xe0 nid=NA waiting for monitor entry
  java.lang.Thread.State: BLOCKED
     waiting for {*}javamail-executor-thread-2{*}@20366 to release lock on <0x5094> (a int[])
      at org.apache.velocity.runtime.directive.RuntimeMacro.init(RuntimeMacro.java:133)
      at org.apache.velocity.runtime.parser.node.ASTDirective.init(ASTDirective.java:197)
      - locked <0x5093> (a org.apache.velocity.runtime.parser.node.ASTDirective)
      at org.apache.velocity.runtime.parser.node.SimpleNode.init(SimpleNode.java:400)
      at org.apache.velocity.runtime.parser.node.ASTprocess.init(ASTprocess.java:64)
      at org.apache.velocity.Template.initDocument(Template.java:230)
      at org.apache.velocity.Template.process(Template.java:146)
      at org.apache.velocity.runtime.resource.ResourceManagerImpl.loadResource(ResourceManagerImpl.java:429)
      at org.apache.velocity.runtime.resource.ResourceManagerImpl.getResource(ResourceManagerImpl.java:346)
      at org.apache.velocity.runtime.RuntimeInstance.getTemplate(RuntimeInstance.java:1696)
      at org.apache.velocity.runtime.directive.Parse.getTemplate(Parse.java:356)
      at org.apache.velocity.runtime.directive.Parse.render(Parse.java:220)
      at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:304)
      at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:439)
      at org.apache.velocity.Template.merge(Template.java:358)
      at org.apache.velocity.Template.merge(Template.java:262)
      at org.apache.velocity.app.VelocityEngine.mergeTemplate(VelocityEngine.java:295)
      at io.micronaut.views.velocity.VelocityViewsRenderer.render(VelocityViewsRenderer.java:92)

"{*}javamail-executor-thread-2{*}@20366" tid=0xe2 nid=NA runnable
  java.lang.Thread.State: RUNNABLE
      at org.apache.velocity.runtime.directive.RuntimeMacro.init(RuntimeMacro.java:133)
      at org.apache.velocity.runtime.parser.node.ASTDirective.init(ASTDirective.java:197)
      - locked <{*}0x5095{*}> (a org.apache.velocity.runtime.parser.node.ASTDirective)
      at org.apache.velocity.runtime.parser.node.SimpleNode.init(SimpleNode.java:400)
      at org.apache.velocity.runtime.parser.node.ASTprocess.init(ASTprocess.java:64)
      at org.apache.velocity.Template.initDocument(Template.java:230)
      at org.apache.velocity.Template.process(Template.java:146)
      at org.apache.velocity.runtime.resource.ResourceManagerImpl.loadResource(ResourceManagerImpl.java:429)
      at org.apache.velocity.runtime.resource.ResourceManagerImpl.getResource(ResourceManagerImpl.java:346)
      at org.apache.velocity.runtime.RuntimeInstance.getTemplate(RuntimeInstance.java:1696)
      at org.apache.velocity.runtime.directive.Parse.getTemplate(Parse.java:356)
      at org.apache.velocity.runtime.directive.Parse.render(Parse.java:220)
      at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:304)
      at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:439)
      at org.apache.velocity.Template.merge(Template.java:358)
      at org.apache.velocity.Template.merge(Template.java:262)
      at org.apache.velocity.app.VelocityEngine.mergeTemplate(VelocityEngine.java:295)
      at io.micronaut.views.velocity.VelocityViewsRenderer.render(VelocityViewsRenderer.java:92)

 

This is probably because the reentrant Node.init() is synchronized in the ASTDirective.
{color:#b3ae60}@Override
{color}{color:#cf8e6d}public synchronized {color}Object {color:#56a8f5}init{color}(InternalContextAdapter context, Object data)
{color:#cf8e6d}throws {color}TemplateInitException
{
Token t;

{color:#7a7e85}/* method is synchronized to avoid concurrent directive initialization **/
{color}{color:#7a7e85}
{color}{color:#7a7e85} {color}{color:#cf8e6d}if {color}(!{color:#c77dbb}isInitialized{color})
See [https://github.com/apache/velocity-engine/blob/master/velocity-engine-core/src/main/java/org/apache/velocity/runtime/parser/node/ASTDirective.java#L101]

My velocity template defines a runtime macro for i18n, processed as an ASTDirective, and the content of the macro is also processed as an ASTDirective, causing the reentrant deadlock.
#macro(msg $key) $messages.getMessage($key, $key, $locale) #end
#parse("templates/header.vm")



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