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pg_on_connection_loss command for libpgtcl. Patch from

Browse Source 
Gerhard Hintermayer, revised and documented by Tom Lane.

This patch also fixes a 'must fix' bug: libpgtcl's LISTEN/NOTIFY
support was broken by the recent changes to the PGnotify structure.
Guess that change wasn't quite so safe as we thought.
This commit is contained in:
Tom Lane
2002-09-02 21:51:47 +00:00
parent b356b969ef
commit 8c8aa53953
6 changed files with 310 additions and 35 deletions
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131
src/interfaces/libpgtcl/pgtclId.c
View File

@ -13,7 +13,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/interfaces/libpgtcl/Attic/pgtclId.c,v 1.32 2002/08/18 01:39:43 momjian Exp $
* $Header: /cvsroot/pgsql/src/interfaces/libpgtcl/Attic/pgtclId.c,v 1.33 2002/09/02 21:51:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -268,6 +268,8 @@ PgDelConnectionId(DRIVER_DEL_PROTO)
entry = Tcl_NextHashEntry(&hsearch))
ckfree((char *) Tcl_GetHashValue(entry));
Tcl_DeleteHashTable(&notifies->notify_hash);
if (notifies->conn_loss_cmd)
ckfree((void *) notifies->conn_loss_cmd);
Tcl_DontCallWhenDeleted(notifies->interp, PgNotifyInterpDelete,
(ClientData) notifies);
ckfree((void *) notifies);
@ -275,9 +277,9 @@ PgDelConnectionId(DRIVER_DEL_PROTO)
/*
* Turn off the Tcl event source for this connection, and delete any
* pending notify events.
* pending notify and connection-loss events.
*/
PgStopNotifyEventSource(connid);
PgStopNotifyEventSource(connid, true);
/* Close the libpq connection too */
PQfinish(connid->conn);
@ -495,7 +497,8 @@ error_out:
typedef struct
{
Tcl_Event header; /* Standard Tcl event info */
PGnotify info; /* Notify name from SQL server */
PGnotify *notify; /* Notify event from libpq, or NULL */
/* We use a NULL notify pointer to denote a connection-loss event */
Pg_ConnectionId *connid; /* Connection for server */
} NotifyEvent;
@ -506,7 +509,6 @@ Pg_Notify_EventProc(Tcl_Event *evPtr, int flags)
{
NotifyEvent *event = (NotifyEvent *) evPtr;
Pg_TclNotifies *notifies;
Tcl_HashEntry *entry;
char *callback;
char *svcallback;
@ -516,7 +518,11 @@ Pg_Notify_EventProc(Tcl_Event *evPtr, int flags)
/* If connection's been closed, just forget the whole thing. */
if (event->connid == NULL)
{
if (event->notify)
PQfreeNotify(event->notify);
return 1;
}
/*
* Preserve/Release to ensure the connection struct doesn't disappear
@ -541,17 +547,29 @@ Pg_Notify_EventProc(Tcl_Event *evPtr, int flags)
/*
* Find the callback to be executed for this interpreter, if any.
*/
entry = Tcl_FindHashEntry(&notifies->notify_hash,
event->info.relname);
if (entry == NULL)
continue; /* no pg_listen in this interpreter */
callback = (char *) Tcl_GetHashValue(entry);
if (event->notify)
{
/* Ordinary NOTIFY event */
Tcl_HashEntry *entry;
entry = Tcl_FindHashEntry(&notifies->notify_hash,
event->notify->relname);
if (entry == NULL)
continue; /* no pg_listen in this interpreter */
callback = (char *) Tcl_GetHashValue(entry);
}
else
{
/* Connection-loss event */
callback = notifies->conn_loss_cmd;
}
if (callback == NULL)
continue; /* safety check -- shouldn't happen */
continue; /* nothing to do for this interpreter */
/*
* We have to copy the callback string in case the user executes a
* new pg_listen during the callback.
* new pg_listen or pg_on_connection_loss during the callback.
*/
svcallback = (char *) ckalloc((unsigned) (strlen(callback) + 1));
strcpy(svcallback, callback);
@ -562,7 +580,10 @@ Pg_Notify_EventProc(Tcl_Event *evPtr, int flags)
Tcl_Preserve((ClientData) interp);
if (Tcl_GlobalEval(interp, svcallback) != TCL_OK)
{
Tcl_AddErrorInfo(interp, "\n (\"pg_listen\" script)");
if (event->notify)
Tcl_AddErrorInfo(interp, "\n (\"pg_listen\" script)");
else
Tcl_AddErrorInfo(interp, "\n (\"pg_on_connection_loss\" script)");
Tcl_BackgroundError(interp);
}
Tcl_Release((ClientData) interp);
@ -578,6 +599,9 @@ Pg_Notify_EventProc(Tcl_Event *evPtr, int flags)
Tcl_Release((ClientData) event->connid);
if (event->notify)
PQfreeNotify(event->notify);
return 1;
}
@ -598,20 +622,45 @@ PgNotifyTransferEvents(Pg_ConnectionId * connid)
NotifyEvent *event = (NotifyEvent *) ckalloc(sizeof(NotifyEvent));
event->header.proc = Pg_Notify_EventProc;
event->info = *notify;
event->notify = notify;
event->connid = connid;
Tcl_QueueEvent((Tcl_Event *) event, TCL_QUEUE_TAIL);
PQfreeNotify(notify);
}
/*
* This is also a good place to check for unexpected closure of the
* connection (ie, backend crash), in which case we must shut down the
* notify event source to keep Tcl from trying to select() on the now-
* closed socket descriptor.
* closed socket descriptor. But don't kill on-connection-loss events;
* in fact, register one.
*/
if (PQsocket(connid->conn) < 0)
PgStopNotifyEventSource(connid);
PgConnLossTransferEvents(connid);
}
/*
* Handle a connection-loss event
*/
void
PgConnLossTransferEvents(Pg_ConnectionId * connid)
{
if (connid->notifier_running)
{
/* Put the on-connection-loss event in the Tcl queue */
NotifyEvent *event = (NotifyEvent *) ckalloc(sizeof(NotifyEvent));
event->header.proc = Pg_Notify_EventProc;
event->notify = NULL;
event->connid = connid;
Tcl_QueueEvent((Tcl_Event *) event, TCL_QUEUE_TAIL);
}
/*
* Shut down the notify event source to keep Tcl from trying to select()
* on the now-closed socket descriptor. And zap any unprocessed notify
* events ... but not, of course, the connection-loss event.
*/
PgStopNotifyEventSource(connid, false);
}
/*
@ -633,7 +682,7 @@ PgNotifyInterpDelete(ClientData clientData, Tcl_Interp *interp)
}
/*
* Comparison routine for detecting events to be removed by Tcl_DeleteEvents.
* Comparison routines for detecting events to be removed by Tcl_DeleteEvents.
* NB: In (at least) Tcl versions 7.6 through 8.0.3, there is a serious
* bug in Tcl_DeleteEvents: if there are multiple events on the queue and
* you tell it to delete the last one, the event list pointers get corrupted,
@ -649,6 +698,22 @@ NotifyEventDeleteProc(Tcl_Event *evPtr, ClientData clientData)
{
Pg_ConnectionId *connid = (Pg_ConnectionId *) clientData;
if (evPtr->proc == Pg_Notify_EventProc)
{
NotifyEvent *event = (NotifyEvent *) evPtr;
if (event->connid == connid && event->notify != NULL)
event->connid = NULL;
}
return 0;
}
/* This version deletes on-connection-loss events too */
static int
AllNotifyEventDeleteProc(Tcl_Event *evPtr, ClientData clientData)
{
Pg_ConnectionId *connid = (Pg_ConnectionId *) clientData;
if (evPtr->proc == Pg_Notify_EventProc)
{
NotifyEvent *event = (NotifyEvent *) evPtr;
@ -675,10 +740,19 @@ Pg_Notify_FileHandler(ClientData clientData, int mask)
* it internally to libpq; but it will clear the read-ready
* condition).
*/
PQconsumeInput(connid->conn);
/* Transfer notify events from libpq to Tcl event queue. */
PgNotifyTransferEvents(connid);
if (PQconsumeInput(connid->conn))
{
/* Transfer notify events from libpq to Tcl event queue. */
PgNotifyTransferEvents(connid);
}
else
{
/*
* If there is no input but we have read-ready,
* assume this means we lost the connection.
*/
PgConnLossTransferEvents(connid);
}
}
@ -686,8 +760,8 @@ Pg_Notify_FileHandler(ClientData clientData, int mask)
* Start and stop the notify event source for a connection.
*
* We do not bother to run the notifier unless at least one pg_listen
* has been executed on the connection. Currently, once started the
* notifier is run until the connection is closed.
* or pg_on_connection_loss has been executed on the connection. Currently,
* once started the notifier is run until the connection is closed.
*
* FIXME: if PQreset is executed on the underlying PGconn, the active
* socket number could change. How and when should we test for this
@ -724,7 +798,7 @@ PgStartNotifyEventSource(Pg_ConnectionId * connid)
}
void
PgStopNotifyEventSource(Pg_ConnectionId * connid)
PgStopNotifyEventSource(Pg_ConnectionId * connid, bool allevents)
{
/* Remove the event source */
if (connid->notifier_running)
@ -742,6 +816,9 @@ PgStopNotifyEventSource(Pg_ConnectionId * connid)
connid->notifier_running = 0;
}
/* Kill any queued Tcl events that reference this channel */
Tcl_DeleteEvents(NotifyEventDeleteProc, (ClientData) connid);
/* Kill queued Tcl events that reference this channel */
if (allevents)
Tcl_DeleteEvents(AllNotifyEventDeleteProc, (ClientData) connid);
else
Tcl_DeleteEvents(NotifyEventDeleteProc, (ClientData) connid);
}