/// <summary>Pull a slot out of a preexisting shared memory segment.</summary>
/// <remarks>
/// Pull a slot out of a preexisting shared memory segment.
/// Must be called with the manager lock held.
/// </remarks>
/// <param name="blockId">The blockId to put inside the Slot object.</param>
/// <returns>
/// null if none of our shared memory segments contain a
/// free slot; the slot object otherwise.
/// </returns>
private ShortCircuitShm.Slot AllocSlotFromExistingShm(ExtendedBlockId blockId)
{
if (this.notFull.IsEmpty())
{
return(null);
}
KeyValuePair <ShortCircuitShm.ShmId, DfsClientShm> entry = this.notFull.FirstEntry
();
DfsClientShm shm = entry.Value;
ShortCircuitShm.ShmId shmId = shm.GetShmId();
ShortCircuitShm.Slot slot = shm.AllocAndRegisterSlot(blockId);
if (shm.IsFull())
{
if (DfsClientShmManager.Log.IsTraceEnabled())
{
DfsClientShmManager.Log.Trace(this + ": pulled the last slot " + slot.GetSlotIdx(
) + " out of " + shm);
}
DfsClientShm removedShm = Sharpen.Collections.Remove(this.notFull, shmId);
Preconditions.CheckState(removedShm == shm);
this.full[shmId] = shm;
}
else
{
if (DfsClientShmManager.Log.IsTraceEnabled())
{
DfsClientShmManager.Log.Trace(this + ": pulled slot " + slot.GetSlotIdx() + " out of "
+ shm);
}
}
return(slot);
}
/// <summary>Stop tracking a slot.</summary>
/// <remarks>
/// Stop tracking a slot.
/// Must be called with the EndpointShmManager lock held.
/// </remarks>
/// <param name="slot">The slot to release.</param>
internal virtual void FreeSlot(ShortCircuitShm.Slot slot)
{
DfsClientShm shm = (DfsClientShm)slot.GetShm();
shm.UnregisterSlot(slot.GetSlotIdx());
if (shm.IsDisconnected())
{
// Stale shared memory segments should not be tracked here.
Preconditions.CheckState(!this.full.Contains(shm.GetShmId()));
Preconditions.CheckState(!this.notFull.Contains(shm.GetShmId()));
if (shm.IsEmpty())
{
if (DfsClientShmManager.Log.IsTraceEnabled())
{
DfsClientShmManager.Log.Trace(this + ": freeing empty stale " + shm);
}
shm.Free();
}
}
else
{
ShortCircuitShm.ShmId shmId = shm.GetShmId();
Sharpen.Collections.Remove(this.full, shmId);
// The shm can't be full if we just freed a slot.
if (shm.IsEmpty())
{
Sharpen.Collections.Remove(this.notFull, shmId);
// If the shared memory segment is now empty, we call shutdown(2) on
// the UNIX domain socket associated with it. The DomainSocketWatcher,
// which is watching this socket, will call DfsClientShm#handle,
// cleaning up this shared memory segment.
//
// See #{DfsClientShmManager#domainSocketWatcher} for details about why
// we don't want to call DomainSocketWatcher#remove directly here.
//
// Note that we could experience 'fragmentation' here, where the
// DFSClient allocates a bunch of slots in different shared memory
// segments, and then frees most of them, but never fully empties out
// any segment. We make some attempt to avoid this fragmentation by
// always allocating new slots out of the shared memory segment with the
// lowest ID, but it could still occur. In most workloads,
// fragmentation should not be a major concern, since it doesn't impact
// peak file descriptor usage or the speed of allocation.
if (DfsClientShmManager.Log.IsTraceEnabled())
{
DfsClientShmManager.Log.Trace(this + ": shutting down UNIX domain socket for " +
"empty " + shm);
}
this.Shutdown(shm);
}
else
{
this.notFull[shmId] = shm;
}
}
}
/// <exception cref="System.IO.IOException"/>
public void Visit(Dictionary <DatanodeInfo, DfsClientShmManager.PerDatanodeVisitorInfo
> info)
{
NUnit.Framework.Assert.IsTrue(info[datanode].full.IsEmpty());
NUnit.Framework.Assert.IsFalse(info[datanode].disabled);
NUnit.Framework.Assert.AreEqual(1, info[datanode].notFull.Values.Count);
DfsClientShm shm = info[datanode].notFull.Values.GetEnumerator().Next();
NUnit.Framework.Assert.IsFalse(shm.IsDisconnected());
}
internal void Shutdown(DfsClientShm shm)
{
try
{
shm.GetPeer().GetDomainSocket().Shutdown();
}
catch (IOException e)
{
DfsClientShmManager.Log.Warn(this + ": error shutting down shm: got IOException calling "
+ "shutdown(SHUT_RDWR)", e);
}
}
public virtual void FreeSlot(ShortCircuitShm.Slot slot)
{
Lock.Lock();
try
{
DfsClientShm shm = (DfsClientShm)slot.GetShm();
shm.GetEndpointShmManager().FreeSlot(slot);
}
finally
{
Lock.Unlock();
}
}
/// <exception cref="System.IO.IOException"/>
public void Visit(Dictionary <DatanodeInfo, DfsClientShmManager.PerDatanodeVisitorInfo
> info)
{
NUnit.Framework.Assert.IsTrue(info[datanode].full.IsEmpty());
NUnit.Framework.Assert.IsFalse(info[datanode].disabled);
NUnit.Framework.Assert.AreEqual(1, info[datanode].notFull.Values.Count);
DfsClientShm shm = info[datanode].notFull.Values.GetEnumerator().Next();
for (IEnumerator <ShortCircuitShm.Slot> iter = shm.SlotIterator(); iter.HasNext();)
{
ShortCircuitShm.Slot slot = iter.Next();
if (slot.IsValid())
{
this._enclosing.done.SetValue(false);
}
}
}
/// <summary>Ask the DataNode for a new shared memory segment.</summary>
/// <remarks>
/// Ask the DataNode for a new shared memory segment. This function must be
/// called with the manager lock held. We will release the lock while
/// communicating with the DataNode.
/// </remarks>
/// <param name="clientName">The current client name.</param>
/// <param name="peer">The peer to use to talk to the DataNode.</param>
/// <returns>
/// Null if the DataNode does not support shared memory
/// segments, or experienced an error creating the
/// shm. The shared memory segment itself on success.
/// </returns>
/// <exception cref="System.IO.IOException">
/// If there was an error communicating over the socket.
/// We will not throw an IOException unless the socket
/// itself (or the network) is the problem.
/// </exception>
private DfsClientShm RequestNewShm(string clientName, DomainPeer peer)
{
DataOutputStream @out = new DataOutputStream(new BufferedOutputStream(peer.GetOutputStream
()));
new Sender(@out).RequestShortCircuitShm(clientName);
DataTransferProtos.ShortCircuitShmResponseProto resp = DataTransferProtos.ShortCircuitShmResponseProto
.ParseFrom(PBHelper.VintPrefixed(peer.GetInputStream()));
string error = resp.HasError() ? resp.GetError() : "(unknown)";
switch (resp.GetStatus())
{
case DataTransferProtos.Status.Success:
{
DomainSocket sock = peer.GetDomainSocket();
byte[] buf = new byte[1];
FileInputStream[] fis = new FileInputStream[1];
if (sock.RecvFileInputStreams(fis, buf, 0, buf.Length) < 0)
{
throw new EOFException("got EOF while trying to transfer the " + "file descriptor for the shared memory segment."
);
}
if (fis[0] == null)
{
throw new IOException("the datanode " + this.datanode + " failed to " + "pass a file descriptor for the shared memory segment."
);
}
try
{
DfsClientShm shm = new DfsClientShm(PBHelper.Convert(resp.GetId()), fis[0], this,
peer);
if (DfsClientShmManager.Log.IsTraceEnabled())
{
DfsClientShmManager.Log.Trace(this + ": createNewShm: created " + shm);
}
return(shm);
}
finally
{
IOUtils.Cleanup(DfsClientShmManager.Log, fis[0]);
}
goto case DataTransferProtos.Status.ErrorUnsupported;
}
case DataTransferProtos.Status.ErrorUnsupported:
{
// The DataNode just does not support short-circuit shared memory
// access, and we should stop asking.
DfsClientShmManager.Log.Info(this + ": datanode does not support short-circuit "
+ "shared memory access: " + error);
this.disabled = true;
return(null);
}
default:
{
// The datanode experienced some kind of unexpected error when trying to
// create the short-circuit shared memory segment.
DfsClientShmManager.Log.Warn(this + ": error requesting short-circuit shared memory "
+ "access: " + error);
return(null);
}
}
}