using ehcache to cache the plugin results

scm-plugin-backend/pom.xml

@@ -42,6 +42,12 @@
       <version>0.9.28</version>
     </dependency>
     
+    <dependency>
+      <groupId>net.sf.ehcache</groupId>
+      <artifactId>ehcache-core</artifactId>
+      <version>${ehcache.version}</version>
+    </dependency>
+
   </dependencies>
 
   <build>

scm-plugin-backend/src/main/java/sonia/scm/plugin/rest/PluginResource.java

@@ -38,17 +38,23 @@ package sonia.scm.plugin.rest;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 
+import net.sf.ehcache.Cache;
+import net.sf.ehcache.CacheManager;
+import net.sf.ehcache.Element;
+
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import sonia.scm.plugin.BackendConfiguration;
 import sonia.scm.plugin.PluginBackend;
+import sonia.scm.plugin.PluginBackendListener;
 import sonia.scm.plugin.PluginCenter;
 import sonia.scm.plugin.PluginInformation;
 import sonia.scm.plugin.PluginVersion;
 
 //~--- JDK imports ------------------------------------------------------------
 
+import java.util.Collection;
 import java.util.Collections;
 import java.util.HashSet;
 import java.util.List;
@@ -69,9 +75,15 @@ import javax.ws.rs.core.Response;
  */
 @Singleton
 @Path("{version}/plugins")
-public class PluginResource
+public class PluginResource implements PluginBackendListener
 {
 
+  /** Field description */
+  public static final String CACHE = "sonia.cache.plugin-backend";
+
+  /** Field description */
+  public static final String CONFIG = "/config/ehcache.xml";
+
   /** the logger for PluginResource */
   private static final Logger logger =
     LoggerFactory.getLogger(PluginResource.class);
@@ -91,6 +103,33 @@ public class PluginResource
   {
     this.backend = backend;
     this.configuration = configuration;
+
+    // added listener to clear the cache on a event
+    this.backend.addListener(this);
+
+    CacheManager cacheManager =
+      new CacheManager(PluginResource.class.getResource(CONFIG));
+
+    cache = cacheManager.getCache(CACHE);
+  }
+
+  //~--- methods --------------------------------------------------------------
+
+  /**
+   * Method description
+   *
+   *
+   * @param plugins
+   */
+  @Override
+  public void addedNewPlugins(Collection<PluginInformation> plugins)
+  {
+    if (logger.isDebugEnabled())
+    {
+      logger.debug("clear cache {}", CACHE);
+    }
+
+    cache.removeAll();
   }
 
   //~--- get methods ----------------------------------------------------------
@@ -120,16 +159,65 @@ public class PluginResource
                    version, Boolean.toString(snapshot));
     }
 
-    List<PluginInformation> plugins =
+    PluginCenter pc = null;
-      backend.getPlugins(new DefaultPluginFilter(version, os, arch, snapshot));
+    String key = createCacheKey(version, os, arch, snapshot);
-    PluginCenter pc = new PluginCenter();
+    Element el = cache.get(key);
 
-    pc.setPlugins(getNewestPlugins(plugins));
+    if (el != null)
-    pc.setRepositories(configuration.getRepositories());
+    {
+      if (logger.isDebugEnabled())
+      {
+        logger.debug("load plugin center from cache");
+      }
+
+      pc = (PluginCenter) el.getObjectValue();
+    }
+    else
+    {
+      if (logger.isDebugEnabled())
+      {
+        logger.debug("load plugin center from backend");
+      }
+
+      List<PluginInformation> plugins =
+        backend.getPlugins(new DefaultPluginFilter(version, os, arch,
+          snapshot));
+
+      pc = new PluginCenter();
+      pc.setPlugins(getNewestPlugins(plugins));
+      pc.setRepositories(configuration.getRepositories());
+      cache.put(new Element(key, pc));
+    }
 
     return Response.ok(pc).build();
   }
 
+  //~--- methods --------------------------------------------------------------
+
+  /**
+   * Method description
+   *
+   *
+   * @param version
+   * @param os
+   * @param arch
+   * @param snapshot
+   *
+   * @return
+   */
+  private String createCacheKey(String version, String os, String arch,
+                                boolean snapshot)
+  {
+    StringBuilder key = new StringBuilder(version);
+
+    key.append(":").append(os).append(":").append(arch).append(":");
+    key.append(Boolean.toString(snapshot));
+
+    return key.toString();
+  }
+
+  //~--- get methods ----------------------------------------------------------
+
   /**
    * Method description
    *
@@ -206,6 +294,9 @@ public class PluginResource
   /** Field description */
   private PluginBackend backend;
 
+  /** Field description */
+  private Cache cache;
+
   /** Field description */
   private BackendConfiguration configuration;
 }

scm-plugin-backend/src/main/resources/config/ehcache.xml

@@ -0,0 +1,110 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+
+    Copyright (c) 2010, Sebastian Sdorra
+    All rights reserved.
+
+    Redistribution and use in source and binary forms, with or without
+    modification, are permitted provided that the following conditions are met:
+
+    1. Redistributions of source code must retain the above copyright notice,
+       this list of conditions and the following disclaimer.
+    2. Redistributions in binary form must reproduce the above copyright notice,
+       this list of conditions and the following disclaimer in the documentation
+       and/or other materials provided with the distribution.
+    3. Neither the name of SCM-Manager; nor the names of its
+       contributors may be used to endorse or promote products derived from this
+       software without specific prior written permission.
+
+    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+    DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
+    DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+    (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+    ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+    http://bitbucket.org/sdorra/scm-manager
+
+
+-->
+
+<!--
+    Document   : ehcache.xml
+    Created on : October 14, 2010, 6:54 AM
+    Author     : sdorra
+    Description:
+        Purpose of the document follows.
+-->
+
+<ehcache xmlns="http://ehcache.org/ehcache.xsd">
+
+
+  <!--
+    Sets the path to the directory where cache .data files are created.
+
+    If the path is a Java System Property it is replaced by
+    its value in the running VM.
+
+    The following properties are translated:
+    user.home - User's home directory
+    user.dir - User's current working directory
+    java.io.tmpdir - Default temp file path
+  -->
+  
+  <diskStore path="java.io.tmpdir"/>
+
+
+  <!--
+    Default Cache configuration. These will applied to caches programmatically created through
+    the CacheManager.
+
+    The following attributes are required:
+
+    maxElementsInMemory            - Sets the maximum number of objects that will be created in memory
+    eternal                        - Sets whether elements are eternal. If eternal,  timeouts are ignored and the
+                                     element is never expired.
+    overflowToDisk                 - Sets whether elements can overflow to disk when the in-memory cache
+                                     has reached the maxInMemory limit.
+
+    The following attributes are optional:
+    timeToIdleSeconds              - Sets the time to idle for an element before it expires.
+                                     i.e. The maximum amount of time between accesses before an element expires
+                                     Is only used if the element is not eternal.
+                                     Optional attribute. A value of 0 means that an Element can idle for infinity.
+                                     The default value is 0.
+    timeToLiveSeconds              - Sets the time to live for an element before it expires.
+                                     i.e. The maximum time between creation time and when an element expires.
+                                     Is only used if the element is not eternal.
+                                     Optional attribute. A value of 0 means that and Element can live for infinity.
+                                     The default value is 0.
+    diskPersistent                 - Whether the disk store persists between restarts of the Virtual Machine.
+                                     The default value is false.
+    diskExpiryThreadIntervalSeconds- The number of seconds between runs of the disk expiry thread. The default value
+                                     is 120 seconds.
+  -->
+
+  <defaultCache
+        maxElementsInMemory="20000"
+        eternal="false"
+        overflowToDisk="false"
+        timeToIdleSeconds="1200"
+        timeToLiveSeconds="2400"
+        diskPersistent="false"
+        diskExpiryThreadIntervalSeconds="2400"
+  />
+
+  <cache
+        name="sonia.cache.plugin-backend"
+        maxElementsInMemory="20000"
+        eternal="false"
+        overflowToDisk="false"
+        timeToIdleSeconds="1800"
+        timeToLiveSeconds="3600"
+        diskPersistent="false"
+  />
+
+</ehcache>