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);
}
}
/// <summary>Scan through the cached block map.</summary>
/// <remarks>
/// Scan through the cached block map.
/// Any blocks which are under-replicated should be assigned new Datanodes.
/// Blocks that are over-replicated should be removed from Datanodes.
/// </remarks>
private void RescanCachedBlockMap()
{
for (IEnumerator <CachedBlock> cbIter = cachedBlocks.GetEnumerator(); cbIter.HasNext
();)
{
scannedBlocks++;
CachedBlock cblock = cbIter.Next();
IList <DatanodeDescriptor> pendingCached = cblock.GetDatanodes(DatanodeDescriptor.CachedBlocksList.Type
.PendingCached);
IList <DatanodeDescriptor> cached = cblock.GetDatanodes(DatanodeDescriptor.CachedBlocksList.Type
.Cached);
IList <DatanodeDescriptor> pendingUncached = cblock.GetDatanodes(DatanodeDescriptor.CachedBlocksList.Type
.PendingUncached);
// Remove nodes from PENDING_UNCACHED if they were actually uncached.
for (IEnumerator <DatanodeDescriptor> iter = pendingUncached.GetEnumerator(); iter
.HasNext();)
{
DatanodeDescriptor datanode = iter.Next();
if (!cblock.IsInList(datanode.GetCached()))
{
Log.Trace("Block {}: removing from PENDING_UNCACHED for node {} " + "because the DataNode uncached it."
, cblock.GetBlockId(), datanode.GetDatanodeUuid());
datanode.GetPendingUncached().Remove(cblock);
iter.Remove();
}
}
BlockInfoContiguous blockInfo = blockManager.GetStoredBlock(new Block(cblock.GetBlockId
()));
string reason = FindReasonForNotCaching(cblock, blockInfo);
int neededCached = 0;
if (reason != null)
{
Log.Trace("Block {}: can't cache block because it is {}", cblock.GetBlockId(), reason
);
}
else
{
neededCached = cblock.GetReplication();
}
int numCached = cached.Count;
if (numCached >= neededCached)
{
// If we have enough replicas, drop all pending cached.
for (IEnumerator <DatanodeDescriptor> iter_1 = pendingCached.GetEnumerator(); iter_1
.HasNext();)
{
DatanodeDescriptor datanode = iter_1.Next();
datanode.GetPendingCached().Remove(cblock);
iter_1.Remove();
Log.Trace("Block {}: removing from PENDING_CACHED for node {}" + "because we already have {} cached replicas and we only"
+ " need {}", cblock.GetBlockId(), datanode.GetDatanodeUuid(), numCached, neededCached
);
}
}
if (numCached < neededCached)
{
// If we don't have enough replicas, drop all pending uncached.
for (IEnumerator <DatanodeDescriptor> iter_1 = pendingUncached.GetEnumerator(); iter_1
.HasNext();)
{
DatanodeDescriptor datanode = iter_1.Next();
datanode.GetPendingUncached().Remove(cblock);
iter_1.Remove();
Log.Trace("Block {}: removing from PENDING_UNCACHED for node {} " + "because we only have {} cached replicas and we need "
+ "{}", cblock.GetBlockId(), datanode.GetDatanodeUuid(), numCached, neededCached
);
}
}
int neededUncached = numCached - (pendingUncached.Count + neededCached);
if (neededUncached > 0)
{
AddNewPendingUncached(neededUncached, cblock, cached, pendingUncached);
}
else
{
int additionalCachedNeeded = neededCached - (numCached + pendingCached.Count);
if (additionalCachedNeeded > 0)
{
AddNewPendingCached(additionalCachedNeeded, cblock, cached, pendingCached);
}
}
if ((neededCached == 0) && pendingUncached.IsEmpty() && pendingCached.IsEmpty())
{
// we have nothing more to do with this block.
Log.Trace("Block {}: removing from cachedBlocks, since neededCached " + "== 0, and pendingUncached and pendingCached are empty."
, cblock.GetBlockId());
cbIter.Remove();
}
}
}
/// <summary>Apply a CacheDirective to a file.</summary>
/// <param name="directive">The CacheDirective to apply.</param>
/// <param name="file">The file.</param>
private void RescanFile(CacheDirective directive, INodeFile file)
{
BlockInfoContiguous[] blockInfos = file.GetBlocks();
// Increment the "needed" statistics
directive.AddFilesNeeded(1);
// We don't cache UC blocks, don't add them to the total here
long neededTotal = file.ComputeFileSizeNotIncludingLastUcBlock() * directive.GetReplication
();
directive.AddBytesNeeded(neededTotal);
// The pool's bytesNeeded is incremented as we scan. If the demand
// thus far plus the demand of this file would exceed the pool's limit,
// do not cache this file.
CachePool pool = directive.GetPool();
if (pool.GetBytesNeeded() > pool.GetLimit())
{
Log.Debug("Directive {}: not scanning file {} because " + "bytesNeeded for pool {} is {}, but the pool's limit is {}"
, directive.GetId(), file.GetFullPathName(), pool.GetPoolName(), pool.GetBytesNeeded
(), pool.GetLimit());
return;
}
long cachedTotal = 0;
foreach (BlockInfoContiguous blockInfo in blockInfos)
{
if (!blockInfo.GetBlockUCState().Equals(HdfsServerConstants.BlockUCState.Complete
))
{
// We don't try to cache blocks that are under construction.
Log.Trace("Directive {}: can't cache block {} because it is in state " + "{}, not COMPLETE."
, directive.GetId(), blockInfo, blockInfo.GetBlockUCState());
continue;
}
Block block = new Block(blockInfo.GetBlockId());
CachedBlock ncblock = new CachedBlock(block.GetBlockId(), directive.GetReplication
(), mark);
CachedBlock ocblock = cachedBlocks.Get(ncblock);
if (ocblock == null)
{
cachedBlocks.Put(ncblock);
ocblock = ncblock;
}
else
{
// Update bytesUsed using the current replication levels.
// Assumptions: we assume that all the blocks are the same length
// on each datanode. We can assume this because we're only caching
// blocks in state COMPLETE.
// Note that if two directives are caching the same block(s), they will
// both get them added to their bytesCached.
IList <DatanodeDescriptor> cachedOn = ocblock.GetDatanodes(DatanodeDescriptor.CachedBlocksList.Type
.Cached);
long cachedByBlock = Math.Min(cachedOn.Count, directive.GetReplication()) * blockInfo
.GetNumBytes();
cachedTotal += cachedByBlock;
if ((mark != ocblock.GetMark()) || (ocblock.GetReplication() < directive.GetReplication
()))
{
//
// Overwrite the block's replication and mark in two cases:
//
// 1. If the mark on the CachedBlock is different from the mark for
// this scan, that means the block hasn't been updated during this
// scan, and we should overwrite whatever is there, since it is no
// longer valid.
//
// 2. If the replication in the CachedBlock is less than what the
// directive asks for, we want to increase the block's replication
// field to what the directive asks for.
//
ocblock.SetReplicationAndMark(directive.GetReplication(), mark);
}
}
Log.Trace("Directive {}: setting replication for block {} to {}", directive.GetId
(), blockInfo, ocblock.GetReplication());
}
// Increment the "cached" statistics
directive.AddBytesCached(cachedTotal);
if (cachedTotal == neededTotal)
{
directive.AddFilesCached(1);
}
Log.Debug("Directive {}: caching {}: {}/{} bytes", directive.GetId(), file.GetFullPathName
(), cachedTotal, neededTotal);
}