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Merge pull request #1737 from citusdata/fix_writeability_checks 

Fix issues in WaitForAllConnections
pull/1743/head
Marco Slot 2017-10-31 13:16:06 +01:00 committed by GitHub
parent d85a3952f5 2bb46bb5ee
commit bc3bdeaac8
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 44 additions and 12 deletions
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56
src/backend/distributed/connection/remote_commands.c
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@ -831,7 +831,6 @@ WaitForAllConnections(List *connectionList, bool raiseInterrupts)
}
connection = (MultiConnection *) event->user_data;
connectionIndex = event->pos + pendingConnectionsStartIndex;
if (event->events & WL_SOCKET_WRITEABLE)
{
@ -844,12 +843,18 @@ WaitForAllConnections(List *connectionList, bool raiseInterrupts)
else if (sendStatus == 0)
{
/* done writing, only wait for read events */
ModifyWaitEvent(waitEventSet, connectionIndex, WL_SOCKET_READABLE,
ModifyWaitEvent(waitEventSet, event->pos, WL_SOCKET_READABLE,
NULL);
}
}
if (event->events & WL_SOCKET_READABLE)
/*
* Check whether the connection is done is the socket is either readable
* or writable. If it was only writable, we performed a PQflush which
* might have read from the socket, meaning we may not see the socket
* becoming readable again, so better to check it now.
*/
if (event->events & (WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE))
{
int receiveStatus = PQconsumeInput(connection->pgConn);
if (receiveStatus == 0)
@ -866,7 +871,21 @@ WaitForAllConnections(List *connectionList, bool raiseInterrupts)
if (connectionIsReady)
{
/*
* All pending connections are kept at the end of the allConnections
* array and the connectionReady array matches the allConnections
* array. The wait event set corresponds to the pending connections
* subarray so we can get the index in the allConnections array by
* taking the event index + the offset of the subarray.
*/
connectionIndex = event->pos + pendingConnectionsStartIndex;
connectionReady[connectionIndex] = true;
/*
* When a connection is ready, we should build a new wait event
* set that excludes this connection.
*/
rebuildWaitEventSet = true;
}
}
@ -877,9 +896,24 @@ WaitForAllConnections(List *connectionList, bool raiseInterrupts)
{
if (connectionReady[connectionIndex])
{
/*
* Replace the ready connection with a connection from
* the start of the pending connections subarray. This
* may be the connection itself, in which case this is
* a noop.
*/
allConnections[connectionIndex] =
allConnections[pendingConnectionsStartIndex];
/* offset of the pending connections subarray is now 1 higher */
pendingConnectionsStartIndex++;
/*
* We've moved a pending connection into this position,
* so we must reset the ready flag. Otherwise, we'd
* falsely interpret it as ready in the next round.
*/
connectionReady[connectionIndex] = false;
}
}
}
@ -907,8 +941,8 @@ WaitForAllConnections(List *connectionList, bool raiseInterrupts)
/*
* BuildWaitEventSet creates a WaitEventSet for the given array of connections
* which can be used to wait for any of the sockets to become read-ready, or
* write-ready in case there is data to send.
* which can be used to wait for any of the sockets to become read-ready or
* write-ready.
*/
static WaitEventSet *
BuildWaitEventSet(MultiConnection **allConnections, int totalConnectionCount,
@ -926,14 +960,12 @@ BuildWaitEventSet(MultiConnection **allConnections, int totalConnectionCount,
{
MultiConnection *connection = allConnections[connectionIndex];
int socket = PQsocket(connection->pgConn);
int eventMask = WL_SOCKET_READABLE;
int sendStatus = PQflush(connection->pgConn);
if (sendStatus == 1)
{
/* we have data to send, wake up when the socket is ready to write */
eventMask = WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE;
}
/*
* Always start by polling for both readability (server sent bytes)
* and writeability (server is ready to receive bytes).
*/
int eventMask = WL_SOCKET_READABLE | WL_SOCKET_WRITEABLE;
AddWaitEventToSet(waitEventSet, eventMask, socket, NULL, (void *) connection);
}