private string FindReasonForNotCaching(CachedBlock cblock, BlockInfoContiguous blockInfo
)
{
if (blockInfo == null)
{
// Somehow, a cache report with the block arrived, but the block
// reports from the DataNode haven't (yet?) described such a block.
// Alternately, the NameNode might have invalidated the block, but the
// DataNode hasn't caught up. In any case, we want to tell the DN
// to uncache this.
return("not tracked by the BlockManager");
}
else
{
if (!blockInfo.IsComplete())
{
// When a cached block changes state from complete to some other state
// on the DataNode (perhaps because of append), it will begin the
// uncaching process. However, the uncaching process is not
// instantaneous, especially if clients have pinned the block. So
// there may be a period of time when incomplete blocks remain cached
// on the DataNodes.
return("not complete");
}
else
{
if (cblock.GetReplication() == 0)
{
// Since 0 is not a valid value for a cache directive's replication
// field, seeing a replication of 0 on a CacheBlock means that it
// has never been reached by any sweep.
return("not needed by any directives");
}
else
{
if (cblock.GetMark() != mark)
{
// Although the block was needed in the past, we didn't reach it during
// the current sweep. Therefore, it doesn't need to be cached any more.
// Need to set the replication to 0 so it doesn't flip back to cached
// when the mark flips on the next scan
cblock.SetReplicationAndMark((short)0, mark);
return("no longer needed by any directives");
}
}
}
}
return(null);
}
/// <summary>Add new entries to the PendingCached list.</summary>
/// <param name="neededCached">The number of replicas that need to be cached.</param>
/// <param name="cachedBlock">The block which needs to be cached.</param>
/// <param name="cached">A list of DataNodes currently caching the block.</param>
/// <param name="pendingCached">
/// A list of DataNodes that will soon cache the
/// block.
/// </param>
private void AddNewPendingCached(int neededCached, CachedBlock cachedBlock, IList
<DatanodeDescriptor> cached, IList <DatanodeDescriptor> pendingCached)
{
// To figure out which replicas can be cached, we consult the
// blocksMap. We don't want to try to cache a corrupt replica, though.
BlockInfoContiguous blockInfo = blockManager.GetStoredBlock(new Block(cachedBlock
.GetBlockId()));
if (blockInfo == null)
{
Log.Debug("Block {}: can't add new cached replicas," + " because there is no record of this block "
+ "on the NameNode.", cachedBlock.GetBlockId());
return;
}
if (!blockInfo.IsComplete())
{
Log.Debug("Block {}: can't cache this block, because it is not yet" + " complete."
, cachedBlock.GetBlockId());
return;
}
// Filter the list of replicas to only the valid targets
IList <DatanodeDescriptor> possibilities = new List <DatanodeDescriptor>();
int numReplicas = blockInfo.GetCapacity();
ICollection <DatanodeDescriptor> corrupt = blockManager.GetCorruptReplicas(blockInfo
);
int outOfCapacity = 0;
for (int i = 0; i < numReplicas; i++)
{
DatanodeDescriptor datanode = blockInfo.GetDatanode(i);
if (datanode == null)
{
continue;
}
if (datanode.IsDecommissioned() || datanode.IsDecommissionInProgress())
{
continue;
}
if (corrupt != null && corrupt.Contains(datanode))
{
continue;
}
if (pendingCached.Contains(datanode) || cached.Contains(datanode))
{
continue;
}
long pendingBytes = 0;
// Subtract pending cached blocks from effective capacity
IEnumerator <CachedBlock> it = datanode.GetPendingCached().GetEnumerator();
while (it.HasNext())
{
CachedBlock cBlock = it.Next();
BlockInfoContiguous info = blockManager.GetStoredBlock(new Block(cBlock.GetBlockId
()));
if (info != null)
{
pendingBytes -= info.GetNumBytes();
}
}
it = datanode.GetPendingUncached().GetEnumerator();
// Add pending uncached blocks from effective capacity
while (it.HasNext())
{
CachedBlock cBlock = it.Next();
BlockInfoContiguous info = blockManager.GetStoredBlock(new Block(cBlock.GetBlockId
()));
if (info != null)
{
pendingBytes += info.GetNumBytes();
}
}
long pendingCapacity = pendingBytes + datanode.GetCacheRemaining();
if (pendingCapacity < blockInfo.GetNumBytes())
{
Log.Trace("Block {}: DataNode {} is not a valid possibility " + "because the block has size {}, but the DataNode only has {}"
+ "bytes of cache remaining ({} pending bytes, {} already cached.", blockInfo.GetBlockId
(), datanode.GetDatanodeUuid(), blockInfo.GetNumBytes(), pendingCapacity, pendingBytes
, datanode.GetCacheRemaining());
outOfCapacity++;
continue;
}
possibilities.AddItem(datanode);
}
IList <DatanodeDescriptor> chosen = ChooseDatanodesForCaching(possibilities, neededCached
, blockManager.GetDatanodeManager().GetStaleInterval());
foreach (DatanodeDescriptor datanode_1 in chosen)
{
Log.Trace("Block {}: added to PENDING_CACHED on DataNode {}", blockInfo.GetBlockId
(), datanode_1.GetDatanodeUuid());
pendingCached.AddItem(datanode_1);
bool added = datanode_1.GetPendingCached().AddItem(cachedBlock);
System.Diagnostics.Debug.Assert(added);
}
// We were unable to satisfy the requested replication factor
if (neededCached > chosen.Count)
{
Log.Debug("Block {}: we only have {} of {} cached replicas." + " {} DataNodes have insufficient cache capacity."
, blockInfo.GetBlockId(), (cachedBlock.GetReplication() - neededCached + chosen.
Count), cachedBlock.GetReplication(), outOfCapacity);
}
}