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  1. Apache Knox
  2. KNOX-1165

Knox - Another unnamed CacheManager already exists in the same VM.


    • Type: Bug
    • Status: Open
    • Priority: Critical
    • Resolution: Unresolved
    • Affects Version/s: 0.12.0
    • Fix Version/s: 1.2.0
    • Component/s: KnoxSSO, Server
    • Labels:
    • Environment:
      JDK 1.8
      CentOS-6 (64bit)


      Issue is described on the note ""Error:Shiro environment initialization failed" when starting KNOX";

      ERROR env.EnvironmentLoader (EnvironmentLoader.java:initEnvironment(146)) - Shiro environment initialization failed
      org.apache.shiro.cache.CacheException: net.sf.ehcache.CacheException: Another unnamed CacheManager already exists in the same VM. Please provide unique names for each CacheManager in the config or do one of following:

      After implementing the solution of creating a new ehcache.xml and reference as <ehcache name="knox-mytopology1"> we still see the issue:

      Caused by: net.sf.ehcache.CacheException: Another CacheManager with same name 'knox-tp' already exists in the same VM. Please provide unique names for each CacheManager in the config or do one of following:

      When enabling the following parameters:


      MORE INFO:
      This KNOX-804 was open to solve this same issue but is not documented anywhere, but we can see the coding changes in GitHub.

      -> The issue seems to be a racing condition on the Shiro lib class, in which depending on the processing power of the server there are two threads within the same "if" statement;

      ref: https://github.com/apache/shiro/blob/master/support/ehcache/src/main/java/org/apache/shiro/cache/ehcache/EhCacheManager.java

      1. The Default constructor only builds the Object, and does not do much:

      • Default no argument constructor
        public EhCacheManager() {

      2. Accordingly with shiro documentation:

      • Initializes this instance.
      • <p/>
      • If a {@link #setCacheManager CacheManager}

        has been

      • explicitly set (e.g. via Dependency Injection or programmatically) prior to calling this
      • method, this method does nothing.
      • <p/>
      • However, if no {@code CacheManager}

        has been set, the default Ehcache singleton will be initialized, where

      • Ehcache will look for an {@code ehcache.xml}

        file at the root of the classpath. If one is not found,

      • Ehcache will use its own failsafe configuration file.
      • <p/>
      • Because Shiro cannot use the failsafe defaults (fail-safe expunges cached objects after 2 minutes,
      • something not desirable for Shiro sessions), this class manages an internal default configuration for
      • this case.
      • @throws org.apache.shiro.cache.CacheException
      • if there are any CacheExceptions thrown by EhCache.
      • @see net.sf.ehcache.CacheManager#create
        public final void init() throws CacheException { ensureCacheManager(); }

      private net.sf.ehcache.CacheManager ensureCacheManager()

      { ***It fails in here. }

      2.1 This is the head of the exception:
      The source of the existing CacheManager is: InputStreamConfigurationSource [stream=java.io.BufferedInputStream@675ffd1d]
      at org.apache.shiro.cache.ehcache.EhCacheManager.ensureCacheManager(EhCacheManager.java:224)
      at org.apache.shiro.cache.ehcache.EhCacheManager.init(EhCacheManager.java:199)
      at org.apache.shiro.util.LifecycleUtils.init(LifecycleUtils.java:45)
      at org.apache.shiro.util.LifecycleUtils.init(LifecycleUtils.java:40)

      3. Starting from Knox-804, the KnoxCacheManager was introduced.
      public class KnoxCacheManager extends EhCacheManager {
      + public KnoxCacheManager()

      { + setCacheManager(net.sf.ehcache.CacheManager.create()); + }


      *Remember that Init() will do nothing if anything in case the setCacheManager is explicitly set.





            • Assignee:
              emattosHWX Ernani Pereira de Mattos Junior
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              • Created: