[GitHub] ivankelly commented on a change in pull request #832: Issue 620: Close the fileChannels for read when they are idle

[GitBox <gi...@apache.org>]

ivankelly commented on a change in pull request #832: Issue 620: Close the fileChannels for read when they are idle
URL: https://github.com/apache/bookkeeper/pull/832#discussion_r159850836
 
 

 ##########
 File path: bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/EntryLogger.java
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 @@ -330,54 +334,115 @@ private int readFromLogChannel(long entryLogId, BufferedReadChannel channel, Byt
      * A thread-local variable that wraps a mapping of log ids to bufferedchannels
      * These channels should be used only for reading. logChannel is the one
      * that is used for writes.
+     * We use this Guava cache to store the BufferedReadChannel.
+     * When the BufferedReadChannel is removed, the underlying fileChannel's refCnt decrease 1,
+     * temporally use 1h to relax replace after reading.
      */
-    private final ThreadLocal<Map<Long, BufferedReadChannel>> logid2Channel =
-            new ThreadLocal<Map<Long, BufferedReadChannel>>() {
+    private final ThreadLocal<Cache<Long, BufferedReadChannel>> logid2Channel =
+            new ThreadLocal<Cache<Long, BufferedReadChannel>>() {
         @Override
-        public Map<Long, BufferedReadChannel> initialValue() {
+        public Cache<Long, BufferedReadChannel> initialValue() {
             // Since this is thread local there only one modifier
             // We dont really need the concurrency, but we need to use
             // the weak values. Therefore using the concurrency level of 1
-            return new MapMaker().concurrencyLevel(1)
-                .weakValues()
-                .makeMap();
+            return CacheBuilder.newBuilder().concurrencyLevel(1)
+                    .expireAfterAccess(readChannelCacheExpireTimeMs, TimeUnit.MILLISECONDS)
+                    //decrease the refCnt
+                    .removalListener(removal -> logid2FileChannel.get(removal.getKey()).release())
+                    .build(readChannelLoader);
 
 Review comment:
   build(this::getChannelForLogId) should work here, i think, so you don't have to define the loader at all.

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