From b7214a877cc1d0fc181f207ec332ca1b9dd90dcd Mon Sep 17 00:00:00 2001 From: Bruce Momjian Date: Sat, 17 Aug 2002 12:19:31 +0000 Subject: [PATCH] What I have done for libpgtcl: Everytime if I do PQconsumeInput (when the backend channel gets readable) I check for the return value. (0 == error) and generate a notification manually, e.g. fixed string connection_closed) and pass it to the TCL event queue. The only other thing I had to do is to comment out removing all pending events in PgStopNotifyEventSource whenever the connection was unexpectedly closed (so the manually generated event will not be deleted). A broken backend connection triggers a notify event to the client (fixed notification string "connection_closed") so proper action can be taken to switch to another database server etc. Remember that this is event driven. If you have applications, that have idle database connections most of the time, you'll get immediate feedback of a dying server. Upon connection to the server issue a pg_notify for notify event "connection_closed" and whenever the backend crashes (which it does do in very very rare cases) you get an event driven recovery. (of course the Tcl-Event loop has to be processed). Issuing a notification "connection_closed" on a still working database could be used for switching to another db-server (which I've actually impelemented right now). Gerhard Hintermayer --- src/interfaces/libpgtcl/pgtclCmds.c | 7 +++++-- src/interfaces/libpgtcl/pgtclId.c | 26 +++++++++++++++++++------- src/interfaces/libpgtcl/pgtclId.h | 4 ++-- 3 files changed, 26 insertions(+), 11 deletions(-) diff --git a/src/interfaces/libpgtcl/pgtclCmds.c b/src/interfaces/libpgtcl/pgtclCmds.c index 24f0456707..4b047b1b6e 100644 --- a/src/interfaces/libpgtcl/pgtclCmds.c +++ b/src/interfaces/libpgtcl/pgtclCmds.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/interfaces/libpgtcl/Attic/pgtclCmds.c,v 1.62 2002/06/20 20:29:53 momjian Exp $ + * $Header: /cvsroot/pgsql/src/interfaces/libpgtcl/Attic/pgtclCmds.c,v 1.63 2002/08/17 12:19:31 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -419,8 +419,11 @@ Pg_disconnect(ClientData cData, Tcl_Interp *interp, int argc, char *argv[]) #if TCL_MAJOR_VERSION >= 8 conn = PgGetConnectionId(interp, argv[1], &connid); - if (connid->notifier_channel != NULL) + if (connid->notifier_channel != NULL) { + /* stop listening for NOTIFY events on that channel */ + PgStopNotifyEventSource(connid,1); Tcl_UnregisterChannel(interp, connid->notifier_channel); + } #endif return Tcl_UnregisterChannel(interp, conn_chan); diff --git a/src/interfaces/libpgtcl/pgtclId.c b/src/interfaces/libpgtcl/pgtclId.c index cb6250cdb4..d5474ce61c 100644 --- a/src/interfaces/libpgtcl/pgtclId.c +++ b/src/interfaces/libpgtcl/pgtclId.c @@ -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 1.30 2002/06/20 20:29:53 momjian Exp $ + * $Header: /cvsroot/pgsql/src/interfaces/libpgtcl/Attic/pgtclId.c,v 1.31 2002/08/17 12:19:31 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -277,7 +277,7 @@ PgDelConnectionId(DRIVER_DEL_PROTO) * Turn off the Tcl event source for this connection, and delete any * pending notify events. */ - PgStopNotifyEventSource(connid); + PgStopNotifyEventSource(connid,1); /* Close the libpq connection too */ PQfinish(connid->conn); @@ -441,7 +441,7 @@ PgGetConnByResultId(Tcl_Interp *interp, char *resid_c) *mark = '.'; if (conn_chan && Tcl_GetChannelType(conn_chan) == &Pg_ConnType) { - Tcl_SetResult(interp, Tcl_GetChannelName(conn_chan), TCL_VOLATILE); + Tcl_SetResult(interp, (char *)Tcl_GetChannelName(conn_chan), TCL_VOLATILE); return TCL_OK; } @@ -611,7 +611,9 @@ PgNotifyTransferEvents(Pg_ConnectionId * connid) * closed socket descriptor. */ if (PQsocket(connid->conn) < 0) - PgStopNotifyEventSource(connid); + /* do not remove any pending events, so that the virtual notification + connection_closed will be processed */ + PgStopNotifyEventSource(connid,0); } /* @@ -675,7 +677,17 @@ Pg_Notify_FileHandler(ClientData clientData, int mask) * it internally to libpq; but it will clear the read-ready * condition). */ - PQconsumeInput(connid->conn); + if (!PQconsumeInput(connid->conn)) { + NotifyEvent *event = (NotifyEvent *) ckalloc(sizeof(NotifyEvent)); + + PGnotify *closed = (PGnotify *) ckalloc(sizeof(PGnotify)); + strcpy(closed->relname,"connection_closed"); + event->header.proc = Pg_Notify_EventProc; + event->info= *closed; + event->connid = connid; + Tcl_QueueEvent((Tcl_Event *) event, TCL_QUEUE_TAIL); + ckfree((void *)closed); + } /* Transfer notify events from libpq to Tcl event queue. */ PgNotifyTransferEvents(connid); @@ -724,7 +736,7 @@ PgStartNotifyEventSource(Pg_ConnectionId * connid) } void -PgStopNotifyEventSource(Pg_ConnectionId * connid) +PgStopNotifyEventSource(Pg_ConnectionId * connid, int remove_pending) { /* Remove the event source */ if (connid->notifier_running) @@ -743,5 +755,5 @@ PgStopNotifyEventSource(Pg_ConnectionId * connid) } /* Kill any queued Tcl events that reference this channel */ - Tcl_DeleteEvents(NotifyEventDeleteProc, (ClientData) connid); + if (remove_pending) Tcl_DeleteEvents(NotifyEventDeleteProc, (ClientData) connid); } diff --git a/src/interfaces/libpgtcl/pgtclId.h b/src/interfaces/libpgtcl/pgtclId.h index 55b572bb78..6a918e41f8 100644 --- a/src/interfaces/libpgtcl/pgtclId.h +++ b/src/interfaces/libpgtcl/pgtclId.h @@ -10,7 +10,7 @@ * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: pgtclId.h,v 1.18 2002/06/20 20:29:53 momjian Exp $ + * $Id: pgtclId.h,v 1.19 2002/08/17 12:19:31 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -44,7 +44,7 @@ extern PGresult *PgGetResultId(Tcl_Interp *interp, char *id); extern void PgDelResultId(Tcl_Interp *interp, char *id); extern int PgGetConnByResultId(Tcl_Interp *interp, char *resid); extern void PgStartNotifyEventSource(Pg_ConnectionId * connid); -extern void PgStopNotifyEventSource(Pg_ConnectionId * connid); +extern void PgStopNotifyEventSource(Pg_ConnectionId * connid, int remove_pend); extern void PgNotifyTransferEvents(Pg_ConnectionId * connid); extern void PgNotifyInterpDelete(ClientData clientData, Tcl_Interp *interp);