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pg_on_connection_loss command for libpgtcl. Patch from 

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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

105
doc/src/sgml/libpgtcl.sgml
View File

@ -72,6 +72,10 @@
<ENTRY><function>pg_listen</function></ENTRY>
<ENTRY>establish a callback for NOTIFY messages</ENTRY>
</ROW>
<ROW>
<ENTRY><function>pg_on_connection_loss</function></ENTRY>
<ENTRY>establish a callback for unexpected connection loss</ENTRY>
</ROW>
<ROW>
<ENTRY><function>pg_lo_creat</function></ENTRY>
@ -1245,7 +1249,7 @@ pg_listen <REPLACEABLE CLASS="PARAMETER">dbHandle</REPLACEABLE> <REPLACEABLE CLA
<REPLACEABLE CLASS="PARAMETER">callbackCommand</REPLACEABLE>
</TERM>
<LISTITEM>
<PARA>If present and not empty, provides the command string to execute
<PARA>If present, provides the command string to execute
when a matching notification arrives.
</PARA>
</LISTITEM>
@ -1312,6 +1316,105 @@ invoke the SQL NOTIFY statement using <FUNCTION>pg_exec</FUNCTION>.
<!-- ********************************************************** -->
<REFENTRY ID="PGTCL-PGON_CONNECTION_LOSS">
<REFMETA>
<REFENTRYTITLE>pg_on_connection_loss</REFENTRYTITLE>
<REFMISCINFO>PGTCL - Asynchronous Notify</REFMISCINFO>
</REFMETA>
<REFNAMEDIV>
<REFNAME>pg_on_connection_loss
</REFNAME>
<REFPURPOSE>set or change a callback for unexpected connection loss
</REFPURPOSE>
<INDEXTERM
ID="IX-PGTCL-PGON_CONNECTION_LOSS-1"><PRIMARY>pgtcl</PRIMARY><SECONDARY>connection loss</SECONDARY></INDEXTERM>
<INDEXTERM ID="IX-PGTCL-PGON_CONNECTION_LOSS-2"><PRIMARY>connection loss</PRIMARY></INDEXTERM>
</REFNAMEDIV>
<REFSYNOPSISDIV>
<REFSYNOPSISDIVINFO>
<DATE>2002-09-02</DATE>
</REFSYNOPSISDIVINFO>
<SYNOPSIS>
pg_on_connection_loss <REPLACEABLE CLASS="PARAMETER">dbHandle</REPLACEABLE> <REPLACEABLE CLASS="PARAMETER">callbackCommand</REPLACEABLE>
</SYNOPSIS>
<REFSECT2 ID="R2-PGTCL-PGON_CONNECTION_LOSS-1">
<REFSECT2INFO>
<DATE>2002-09-02</DATE>
</REFSECT2INFO>
<TITLE>Inputs
</TITLE>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
<REPLACEABLE CLASS="PARAMETER">dbHandle</REPLACEABLE>
</TERM>
<LISTITEM>
<PARA>Specifies a valid database handle.
</PARA>
</LISTITEM>
</VARLISTENTRY>
<VARLISTENTRY>
<TERM>
<REPLACEABLE CLASS="PARAMETER">callbackCommand</REPLACEABLE>
</TERM>
<LISTITEM>
<PARA>If present, provides the command string to execute
when connection loss is detected.
</PARA>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
<REFSECT2 ID="R2-PGTCL-PGON_CONNECTION_LOSS-2">
<REFSECT2INFO>
<DATE>2002-09-02</DATE>
</REFSECT2INFO>
<TITLE>Outputs
</TITLE>
<VARIABLELIST>
<VARLISTENTRY>
<TERM>
None
</TERM>
<LISTITEM>
<PARA>
</PARA>
</LISTITEM>
</VARLISTENTRY>
</VARIABLELIST>
</REFSECT2>
</REFSYNOPSISDIV>
<REFSECT1 ID="R1-PGTCL-PGON_CONNECTION_LOSS-1">
<REFSECT1INFO>
<DATE>2002-09-02</DATE>
</REFSECT1INFO>
<TITLE>Description
</TITLE>
<PARA><FUNCTION>pg_on_connection_loss</FUNCTION> creates, changes, or cancels
a request to execute a callback command if an unexpected loss of connection
to the database occurs.
With a <parameter>callbackCommand</>
parameter, the request is established, or the command string of an already
existing request is replaced. With no <parameter>callbackCommand</>
parameter, a prior request is canceled.
</PARA>
<para>
The callback command string is executed from the Tcl idle loop. That is the
normal idle state of an application written with Tk. In non-Tk Tcl shells,
you can
execute <FUNCTION>update</FUNCTION> or <FUNCTION>vwait</FUNCTION> to cause
the idle loop to be entered.
</Para>
</REFSECT1>
</REFENTRY>
<!-- ********************************************************** -->
<REFENTRY ID="PGTCL-PGLOCREAT">
<REFMETA>
<REFENTRYTITLE>pg_lo_creat</REFENTRYTITLE>

9
src/interfaces/libpgtcl/pgtcl.c
View File

@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/interfaces/libpgtcl/Attic/pgtcl.c,v 1.25 2002/06/20 20:29:53 momjian Exp $
* $Header: /cvsroot/pgsql/src/interfaces/libpgtcl/Attic/pgtcl.c,v 1.26 2002/09/02 21:51:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -151,8 +151,13 @@ Pgtcl_Init(Tcl_Interp *interp)
"pg_listen",
Pg_listen,
(ClientData) NULL, (Tcl_CmdDeleteProc *) NULL);
Tcl_CreateCommand(interp,
"pg_on_connection_loss",
Pg_on_connection_loss,
(ClientData) NULL, (Tcl_CmdDeleteProc *) NULL);
Tcl_PkgProvide(interp, "Pgtcl", "1.3");
Tcl_PkgProvide(interp, "Pgtcl", "1.4");
return TCL_OK;
}

84
src/interfaces/libpgtcl/pgtclCmds.c
View File

@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/interfaces/libpgtcl/Attic/pgtclCmds.c,v 1.65 2002/09/02 06:11:43 momjian Exp $
* $Header: /cvsroot/pgsql/src/interfaces/libpgtcl/Attic/pgtclCmds.c,v 1.66 2002/09/02 21:51:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -1876,6 +1876,7 @@ Pg_listen(ClientData cData, Tcl_Interp *interp, int argc, char *argv[])
notifies = (Pg_TclNotifies *) ckalloc(sizeof(Pg_TclNotifies));
notifies->interp = interp;
Tcl_InitHashTable(&notifies->notify_hash, TCL_STRING_KEYS);
notifies->conn_loss_cmd = NULL;
notifies->next = connid->notify_list;
connid->notify_list = notifies;
Tcl_CallWhenDeleted(interp, PgNotifyInterpDelete,
@ -1970,3 +1971,84 @@ Pg_listen(ClientData cData, Tcl_Interp *interp, int argc, char *argv[])
ckfree(caserelname);
return TCL_OK;
}
/***********************************
Pg_on_connection_loss
create or remove a callback request for unexpected connection loss
syntax:
pg_on_connection_loss conn ?callbackcommand?
With a third arg, creates or changes the callback command for
connection loss; without, cancels the callback request.
Callbacks can occur whenever Tcl is executing its event loop.
This is the normal idle loop in Tk; in plain tclsh applications,
vwait or update can be used to enter the Tcl event loop.
***********************************/
int
Pg_on_connection_loss(ClientData cData, Tcl_Interp *interp, int argc, char *argv[])
{
char *callback = NULL;
Pg_TclNotifies *notifies;
Pg_ConnectionId *connid;
PGconn *conn;
if (argc < 2 || argc > 3)
{
Tcl_AppendResult(interp, "wrong # args, should be \"",
argv[0], " connection ?callback?\"", 0);
return TCL_ERROR;
}
/*
* Get the command arguments.
*/
conn = PgGetConnectionId(interp, argv[1], &connid);
if (conn == (PGconn *) NULL)
return TCL_ERROR;
if ((argc > 2) && *argv[2])
{
callback = (char *) ckalloc((unsigned) (strlen(argv[2]) + 1));
strcpy(callback, argv[2]);
}
/* Find or make a Pg_TclNotifies struct for this interp and connection */
for (notifies = connid->notify_list; notifies; notifies = notifies->next)
{
if (notifies->interp == interp)
break;
}
if (notifies == NULL)
{
notifies = (Pg_TclNotifies *) ckalloc(sizeof(Pg_TclNotifies));
notifies->interp = interp;
Tcl_InitHashTable(&notifies->notify_hash, TCL_STRING_KEYS);
notifies->conn_loss_cmd = NULL;
notifies->next = connid->notify_list;
connid->notify_list = notifies;
Tcl_CallWhenDeleted(interp, PgNotifyInterpDelete,
(ClientData) notifies);
}
/* Store new callback setting */
if (notifies->conn_loss_cmd)
ckfree((void *) notifies->conn_loss_cmd);
notifies->conn_loss_cmd = callback;
if (callback)
{
/*
* Start the notify event source if it isn't already running.
* The notify source will cause Tcl to watch read-ready on the
* connection socket, so that we find out quickly if the connection
* drops.
*/
PgStartNotifyEventSource(connid);
}
return TCL_OK;
}

11
src/interfaces/libpgtcl/pgtclCmds.h
View File

@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: pgtclCmds.h,v 1.26 2002/06/20 20:29:53 momjian Exp $
* $Id: pgtclCmds.h,v 1.27 2002/09/02 21:51:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -21,7 +21,7 @@
#define RES_START 16
/*
* From Tcl verion 8.0 on we can make large object access binary.
* From Tcl version 8.0 on we can make large object access binary.
*/
#ifdef TCL_MAJOR_VERSION
#if (TCL_MAJOR_VERSION >= 8)
@ -36,6 +36,9 @@
* deleted while the connection remains open. A free side benefit is that
* multiple interpreters can be registered to listen for the same notify
* name. (All their callbacks will be called, but in an unspecified order.)
*
* We use the same approach for pg_on_connection_loss callbacks, but they
* are not kept in a hashtable since there's no name associated.
*/
typedef struct Pg_TclNotifies_s
@ -48,6 +51,8 @@ typedef struct Pg_TclNotifies_s
* got round to deleting the Pg_TclNotifies structure.
*/
Tcl_HashTable notify_hash; /* Active pg_listen requests */
char *conn_loss_cmd; /* pg_on_connection_loss cmd, or NULL */
} Pg_TclNotifies;
typedef struct Pg_ConnectionId_s
@ -128,5 +133,7 @@ extern int Pg_lo_export(
ClientData cData, Tcl_Interp *interp, int argc, char *argv[]);
extern int Pg_listen(
ClientData cData, Tcl_Interp *interp, int argc, char *argv[]);
extern int Pg_on_connection_loss(
ClientData cData, Tcl_Interp *interp, int argc, char *argv[]);
#endif /* PGTCLCMDS_H */

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);
}

5
src/interfaces/libpgtcl/pgtclId.h
View File

@ -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 1.20 2002/08/18 01:39:43 momjian Exp $
* $Id: pgtclId.h,v 1.21 2002/09/02 21:51:47 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -44,8 +44,9 @@ 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, bool allevents);
extern void PgNotifyTransferEvents(Pg_ConnectionId * connid);
extern void PgConnLossTransferEvents(Pg_ConnectionId * connid);
extern void PgNotifyInterpDelete(ClientData clientData, Tcl_Interp *interp);
/* GetFileProc is needed in Tcl 7.6 *only* ... it went away again in 8.0 */