[gatein-issues] [JBoss JIRA] Work started: (GTNPORTAL-1545) Concurrency problem (HashMap used in class ConfigurationManager in multithreaded environment)

[Minh Hoang TO (JIRA)]

     [ https://jira.jboss.org/browse/GTNPORTAL-1545?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on GTNPORTAL-1545 started by Minh Hoang TO.

> Concurrency problem (HashMap used in class ConfigurationManager in multithreaded environment)
> ---------------------------------------------------------------------------------------------
>
>                 Key: GTNPORTAL-1545
>                 URL: https://jira.jboss.org/browse/GTNPORTAL-1545
>             Project: GateIn Portal
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: WebUI
>    Affects Versions: 3.1.0-GA
>         Environment: GateIn trunk (revision 4282) on EAP5
>            Reporter: Marek Posolda
>            Assignee: Minh Hoang TO
>         Attachments: exception-stacktrace.txt, GTNPORTAL-1545-20101025.patch
>
>   Original Estimate: 6 hours
>  Remaining Estimate: 6 hours
>
> Sometimes I can see exception during startup of performance. Exception is something like: 
> java.lang.reflect.InvocationTargetException: ...
> Caused by: java.lang.Exception: Cannot find the configuration for the component org.exoplatform.portal.webui.container.UIContainerList, configId null
> 	at org.exoplatform.webui.application.WebuiApplication.createUIComponent(WebuiApplication.java:110)
> 	at org.exoplatform.webui.core.UIContainer.addChild(UIContainer.java:197)
> 	at org.exoplatform.portal.webui.portal.UIPortalComposer.<init>(UIPortalComposer.java:97)
> 	... 71 more
> Whole stacktrace is attached. I am not seeing it in every test run, only sometimes. And usually the component is different in each case (sometimes it fails with different component that UIContainerList). 
> After investigation, I founded that problem is in class org.exoplatform.webui.application.ConfigurationManager which is shared by more clients (threads) but it's using HashMap "configs_". This piece of code in ConfigurationManager.getComponentConfig(Class<?> type, String id)
>       //
>       Component config = configs_.get(key);
>       if (config != null)
>       {
>          return config;
>       }
>       //
>       process(type);
>       //
>       return configs_.get(key);
> is read component configuration (in case that this configuration is missing in map) and then it saves into HashMap and returns it. But in multithreaded environment, sometimes can still happen that this method returns null because "config_" HashMap is not thread-safe -> Exception is thrown in WebuiApplication.createUIComponent(WebuiApplication.java:110).
> See this article http://java.dzone.com/articles/concurrency-and-hashmap with nice simple example, which is doing very similar scenario as ConfigurationManager.

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