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Add PQping and PQpingParams to libpq to allow detection of the server's
status, including a status where the server is running but refuses a postgres connection. Have pg_ctl use this new function. This fixes the case where pg_ctl reports that the server is not running (cannot connect) but in fact it is running.
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+146
-16
lines changed

5 files changed

+146
-16
lines changed

‎doc/src/sgml/libpq.sgml

Lines changed: 68 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1511,6 +1511,74 @@ int PQbackendPID(const PGconn *conn);
15111511
</listitem>
15121512
</varlistentry>
15131513

1514+
<varlistentry id="libpq-pqpingparams">
1515+
<term><function>PQpingParams</function><indexterm><primary>PQpingParams</></></term>
1516+
<listitem>
1517+
<para>
1518+
<function>PQpingParams</function> indicates the status of the
1519+
server. The currently recognized parameter key words are the
1520+
same as <function>PQconnectParams</>.
1521+
1522+
<synopsis>
1523+
PGPing PQpingParams(const char **keywords, const char **values, int expand_dbname);
1524+
</synopsis>
1525+
1526+
It returns one of the following values:
1527+
1528+
<variablelist>
1529+
<varlistentry id="libpq-pqpingparams-pqaccess">
1530+
<term><literal>PQACCESS</literal></term>
1531+
<listitem>
1532+
<para>
1533+
The server is running and allows access.
1534+
</para>
1535+
</listitem>
1536+
</varlistentry>
1537+
1538+
<varlistentry id="libpq-pqpingparams-pqreject">
1539+
<term><literal>PQREJECT</literal></term>
1540+
<listitem>
1541+
<para>
1542+
The server is running but rejected a connection request.
1543+
</para>
1544+
</listitem>
1545+
</varlistentry>
1546+
1547+
<varlistentry id="libpq-pqpingparams-pqnoresponse">
1548+
<term><literal>PQNORESPONSE</literal></term>
1549+
<listitem>
1550+
<para>
1551+
The server did not respond.
1552+
</para>
1553+
</listitem>
1554+
</varlistentry>
1555+
</variablelist>
1556+
1557+
</para>
1558+
1559+
</listitem>
1560+
</varlistentry>
1561+
1562+
<varlistentry id="libpq-pqping">
1563+
<term><function>PQping</function><indexterm><primary>PQping</></></term>
1564+
<listitem>
1565+
<para>
1566+
Returns the status of the server.
1567+
1568+
<synopsis>
1569+
PGPing PQping(const char *conninfo);
1570+
</synopsis>
1571+
</para>
1572+
1573+
<para>
1574+
This function uses the same <literal>conninfo</literal> parameter
1575+
key words as <function>PQconnectdb</>. It returns the same
1576+
values as <function>PQpingParams</> above.
1577+
</para>
1578+
1579+
</listitem>
1580+
</varlistentry>
1581+
15141582
<varlistentry id="libpq-pqconnectionneedspassword">
15151583
<term><function>PQconnectionNeedsPassword</function><indexterm><primary>PQconnectionNeedsPassword</></></term>
15161584
<listitem>

‎src/bin/pg_ctl/pg_ctl.c

Lines changed: 13 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -136,7 +136,7 @@ static char **readfile(const char *path);
136136
static int start_postmaster(void);
137137
static void read_post_opts(void);
138138

139-
static bool test_postmaster_connection(bool);
139+
static PGPing test_postmaster_connection(bool);
140140
static bool postmaster_is_alive(pid_t pid);
141141

142142
static char postopts_file[MAXPGPATH];
@@ -400,11 +400,10 @@ start_postmaster(void)
400400
* Note that the checkpoint parameter enables a Windows service control
401401
* manager checkpoint, it's got nothing to do with database checkpoints!!
402402
*/
403-
static bool
403+
static PGPing
404404
test_postmaster_connection(bool do_checkpoint)
405405
{
406-
PGconn *conn;
407-
bool success = false;
406+
PGPing ret = PQACCESS; /* assume success for zero wait */
408407
int i;
409408
char portstr[32];
410409
char *p;
@@ -508,18 +507,10 @@ test_postmaster_connection(bool do_checkpoint)
508507

509508
for (i = 0; i < wait_seconds; i++)
510509
{
511-
if ((conn = PQconnectdb(connstr)) != NULL &&
512-
(PQstatus(conn) == CONNECTION_OK ||
513-
PQconnectionNeedsPassword(conn)))
514-
{
515-
PQfinish(conn);
516-
success = true;
517-
break;
518-
}
510+
if ((ret = PQping(connstr)) != PQNORESPONSE)
511+
return ret;
519512
else
520513
{
521-
PQfinish(conn);
522-
523514
#if defined(WIN32)
524515
if (do_checkpoint)
525516
{
@@ -543,7 +534,8 @@ test_postmaster_connection(bool do_checkpoint)
543534
}
544535
}
545536

546-
return success;
537+
/* value of last call to PQping */
538+
return ret;
547539
}
548540

549541

@@ -746,9 +738,11 @@ do_start(void)
746738

747739
if (do_wait)
748740
{
741+
int status;
742+
749743
print_msg(_("waiting for server to start..."));
750744

751-
if (test_postmaster_connection(false) == false)
745+
if ((status = test_postmaster_connection(false)) == PQNORESPONSE)
752746
{
753747
write_stderr(_("%s: could not start server\n"
754748
"Examine the log output.\n"),
@@ -759,6 +753,9 @@ do_start(void)
759753
{
760754
print_msg(_(" done\n"));
761755
print_msg(_("server started\n"));
756+
if (status == PQREJECT)
757+
write_stderr(_("warning: could not connect, perhaps due to invalid authentication or\n"
758+
"misconfiguration.\n"));
762759
}
763760
}
764761
else

‎src/interfaces/libpq/exports.txt

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -157,3 +157,5 @@ PQescapeLiteral 154
157157
PQescapeIdentifier 155
158158
PQconnectdbParams 156
159159
PQconnectStartParams 157
160+
PQping 158
161+
PQpingParams 159

‎src/interfaces/libpq/fe-connect.c

Lines changed: 53 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -285,6 +285,7 @@ static bool connectOptions1(PGconn *conn, const char *conninfo);
285285
static bool connectOptions2(PGconn *conn);
286286
static int connectDBStart(PGconn *conn);
287287
static int connectDBComplete(PGconn *conn);
288+
static PGPing internal_ping(PGconn *conn);
288289
static PGconn *makeEmptyPGconn(void);
289290
static void fillPGconn(PGconn *conn, PQconninfoOption *connOptions);
290291
static void freePGconn(PGconn *conn);
@@ -375,6 +376,20 @@ PQconnectdbParams(const char **keywords,
375376

376377
}
377378

379+
PGPing
380+
PQpingParams(const char **keywords,
381+
const char **values,
382+
int expand_dbname)
383+
{
384+
PGconn *conn = PQconnectStartParams(keywords, values, expand_dbname);
385+
PGPing ret;
386+
387+
ret = internal_ping(conn);
388+
PQfinish(conn);
389+
390+
return ret;
391+
}
392+
378393
/*
379394
* PQconnectdb
380395
*
@@ -408,6 +423,18 @@ PQconnectdb(const char *conninfo)
408423
return conn;
409424
}
410425

426+
PGPing
427+
PQping(const char *conninfo)
428+
{
429+
PGconn *conn = PQconnectStart(conninfo);
430+
PGPing ret;
431+
432+
ret = internal_ping(conn);
433+
PQfinish(conn);
434+
435+
return ret;
436+
}
437+
411438
/*
412439
* PQconnectStartParams
413440
*
@@ -2513,6 +2540,32 @@ PQconnectPoll(PGconn *conn)
25132540
}
25142541

25152542

2543+
/*
2544+
* internal_ping
2545+
* Determine if a server is running and if we can connect to it.
2546+
*/
2547+
PGPing
2548+
internal_ping(PGconn *conn)
2549+
{
2550+
if (conn && conn->status != CONNECTION_BAD)
2551+
{
2552+
(void) connectDBComplete(conn);
2553+
2554+
/*
2555+
* If the connection needs a password, we can consider the
2556+
* server as accepting connections.
2557+
*/
2558+
if (conn && (conn->status != CONNECTION_BAD ||
2559+
PQconnectionNeedsPassword(conn)))
2560+
return PQACCESS;
2561+
else
2562+
return PQREJECT;
2563+
}
2564+
else
2565+
return PQNORESPONSE;
2566+
}
2567+
2568+
25162569
/*
25172570
* makeEmptyPGconn
25182571
* - create a PGconn data structure with (as yet) no interesting data

‎src/interfaces/libpq/libpq-fe.h

Lines changed: 10 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -107,6 +107,13 @@ typedef enum
107107
PQERRORS_VERBOSE /* all the facts, ma'am */
108108
} PGVerbosity;
109109

110+
typedef enum
111+
{
112+
PQACCESS, /* connected to server */
113+
PQREJECT, /* server rejected access */
114+
PQNORESPONSE /* server did not respond */
115+
} PGPing;
116+
110117
/* PGconn encapsulates a connection to the backend.
111118
* The contents of this struct are not supposed to be known to applications.
112119
*/
@@ -403,6 +410,9 @@ extern int PQendcopy(PGconn *conn);
403410
extern int PQsetnonblocking(PGconn *conn, int arg);
404411
extern int PQisnonblocking(const PGconn *conn);
405412
extern int PQisthreadsafe(void);
413+
extern PGPing PQping(const char *conninfo);
414+
extern PGPing PQpingParams(const char **keywords,
415+
const char **values, int expand_dbname);
406416

407417
/* Force the write buffer to be written (or at least try) */
408418
extern int PQflush(PGconn *conn);

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