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@@ -460,14 +460,21 @@ public class CacheReplicationMonitor extends Thread implements Closeable {
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directive.getReplication()) * blockInfo.getNumBytes();
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cachedTotal += cachedByBlock;
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- if (mark != ocblock.getMark()) {
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- // Mark hasn't been set in this scan, so update replication and mark.
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+ if ((mark != ocblock.getMark()) ||
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+ (ocblock.getReplication() < directive.getReplication())) {
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+ //
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+ // Overwrite the block's replication and mark in two cases:
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+ //
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+ // 1. If the mark on the CachedBlock is different from the mark for
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+ // this scan, that means the block hasn't been updated during this
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+ // scan, and we should overwrite whatever is there, since it is no
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+ // longer valid.
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+ //
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+ // 2. If the replication in the CachedBlock is less than what the
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+ // directive asks for, we want to increase the block's replication
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+ // field to what the directive asks for.
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+ //
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ocblock.setReplicationAndMark(directive.getReplication(), mark);
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- } else {
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- // Mark already set in this scan. Set replication to highest value in
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- // any CacheDirective that covers this file.
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- ocblock.setReplicationAndMark((short)Math.max(
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- directive.getReplication(), ocblock.getReplication()), mark);
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}
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}
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}
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@@ -483,6 +490,36 @@ public class CacheReplicationMonitor extends Thread implements Closeable {
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}
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}
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+ private String findReasonForNotCaching(CachedBlock cblock,
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+ BlockInfo blockInfo) {
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+ if (blockInfo == null) {
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+ // Somehow, a cache report with the block arrived, but the block
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+ // reports from the DataNode haven't (yet?) described such a block.
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+ // Alternately, the NameNode might have invalidated the block, but the
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+ // DataNode hasn't caught up. In any case, we want to tell the DN
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+ // to uncache this.
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+ return "not tracked by the BlockManager";
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+ } else if (!blockInfo.isComplete()) {
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+ // When a cached block changes state from complete to some other state
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+ // on the DataNode (perhaps because of append), it will begin the
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+ // uncaching process. However, the uncaching process is not
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+ // instantaneous, especially if clients have pinned the block. So
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+ // there may be a period of time when incomplete blocks remain cached
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+ // on the DataNodes.
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+ return "not complete";
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+ } else if (cblock.getReplication() == 0) {
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+ // Since 0 is not a valid value for a cache directive's replication
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+ // field, seeing a replication of 0 on a CacheBlock means that it
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+ // has never been reached by any sweep.
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+ return "not needed by any directives";
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+ } else if (cblock.getMark() != mark) {
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+ // Although the block was needed in the past, we didn't reach it during
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+ // the current sweep. Therefore, it doesn't need to be cached any more.
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+ return "no longer needed by any directives";
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+ }
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+ return null;
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+ }
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+
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/**
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* Scan through the cached block map.
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* Any blocks which are under-replicated should be assigned new Datanodes.
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@@ -508,11 +545,17 @@ public class CacheReplicationMonitor extends Thread implements Closeable {
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iter.remove();
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}
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}
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- // If the block's mark doesn't match with the mark of this scan, that
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- // means that this block couldn't be reached during this scan. That means
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- // it doesn't need to be cached any more.
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- int neededCached = (cblock.getMark() != mark) ?
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- 0 : cblock.getReplication();
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+ BlockInfo blockInfo = blockManager.
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+ getStoredBlock(new Block(cblock.getBlockId()));
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+ String reason = findReasonForNotCaching(cblock, blockInfo);
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+ int neededCached = 0;
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+ if (reason != null) {
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+ if (LOG.isDebugEnabled()) {
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+ LOG.debug("not caching " + cblock + " because it is " + reason);
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+ }
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+ } else {
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+ neededCached = cblock.getReplication();
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+ }
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int numCached = cached.size();
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if (numCached >= neededCached) {
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// If we have enough replicas, drop all pending cached.
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@@ -612,8 +655,10 @@ public class CacheReplicationMonitor extends Thread implements Closeable {
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BlockInfo blockInfo = blockManager.
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getStoredBlock(new Block(cachedBlock.getBlockId()));
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if (blockInfo == null) {
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- LOG.debug("Not caching block " + cachedBlock + " because it " +
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- "was deleted from all DataNodes.");
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+ if (LOG.isDebugEnabled()) {
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+ LOG.debug("Not caching block " + cachedBlock + " because there " +
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+ "is no record of it on the NameNode.");
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+ }
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return;
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}
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if (!blockInfo.isComplete()) {
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Andrew Wang