Re: connect_timeout parameter in libpq

New version of patch. Documentation updates, accurate remaining time calculation etc.

On Mon, Aug 12, 2002 at 11:35:17PM -0400, Tom Lane wrote:
> Shouldn't such a patch include documentation updates? (And not
> only user-level documentation; this patch adds not even a single
> comment to explain what it's doing or why.)
>
> I'm also not thrilled with the way that the patch imposes the
> overhead of calculating the timeout whether the user wants it or not.
> The time() kernel calls should be skipped unless needed.
>
> A final comment is that the patch's timeout accuracy is quite poor, since
> time()'s result is quantized to seconds. gettimeofday() might be a
> better choice. Also it seems to assume that select() does not modify its
> timeout argument, which is not a portable assumption. On some platforms
> the timeout struct is decremented by the elapsed time.
>
> regards, tom lane

*** postgresql-7.2.1/doc/src/sgml/libpq.sgml.orig Вт Авг 13 12:34:51 2002
--- postgresql-7.2.1/doc/src/sgml/libpq.sgml Вт Авг 13 14:18:15 2002
***************
*** 172,177 ****
--- 172,186 ----
</varlistentry>

<varlistentry>
+ <term><literal>connect_timeout</literal></term>
+ <listitem>
+ <para>
+ Time space in seconds given to connect routine. Zero or not set means infinite.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
<term><literal>options</literal></term>
<listitem>
<para>
*** postgresql-7.2.1/src/interfaces/libpq/fe-connect.c.orig Чт Авг 8 12:22:46 2002
--- postgresql-7.2.1/src/interfaces/libpq/fe-connect.c Вт Авг 13 15:50:43 2002
***************
*** 114,119 ****
--- 114,122 ----
{"password", "PGPASSWORD", DefaultPassword, NULL,
"Database-Password", "*", 20},

+ {"connect_timeout", "PGCONNECT_TIMEOUT", NULL, NULL,
+ "Connect-timeout", "", 10}, /* strlen( INT32_MAX) == 10 */
+
{"dbname", "PGDATABASE", NULL, NULL,
"Database-Name", "", 20},

***************
*** 307,312 ****
--- 310,317 ----
conn->pguser = tmp ? strdup(tmp) : NULL;
tmp = conninfo_getval(connOptions, "password");
conn->pgpass = tmp ? strdup(tmp) : NULL;
+ tmp = conninfo_getval(connOptions, "connect_timeout");
+ conn->connect_timeout = tmp ? strdup(tmp) : NULL;
#ifdef USE_SSL
tmp = conninfo_getval(connOptions, "requiressl");
conn->require_ssl = tmp ? (tmp[0] == '1' ? true : false) : false;
***************
*** 1050,1061 ****
{
PostgresPollingStatusType flag = PGRES_POLLING_WRITING;

if (conn == NULL || conn->status == CONNECTION_BAD)
return 0;

! for (;;)
{
/*
* Wait, if necessary. Note that the initial state (just after
* PQconnectStart) is to wait for the socket to select for
* writing.
--- 1055,1093 ----
{
PostgresPollingStatusType flag = PGRES_POLLING_WRITING;

+ struct timeval remains, *rp = NULL, finish_time, start_time;
+
if (conn == NULL || conn->status == CONNECTION_BAD)
return 0;

! /*
! * Prepare to time calculations, if connect_timeout isn't zero.
! */
! if (conn->connect_timeout != NULL)
{
+ remains.tv_sec = atoi(conn->connect_timeout);
+ if (!remains.tv_sec)
+ {
+ conn->status = CONNECTION_BAD;
+ return 0;
+ }
+ remains.tv_usec = 0;
+ rp = &remains;
+ }
+
+
+ while (NULL == rp || remains.tv_sec > 0 || remains.tv_sec == 0 && remains.tv_usec > 0)
+ {
/*
+ * If connecting timeout is set, get current time.
+ */
+ if ( NULL != rp && -1 == gettimeofday(&start_time, NULL))
+ {
+ conn->status = CONNECTION_BAD;
+ return 0;
+ }
+
+ /*
* Wait, if necessary. Note that the initial state (just after
* PQconnectStart) is to wait for the socket to select for
* writing.
***************
*** 1069,1075 ****
return 1; /* success! */

case PGRES_POLLING_READING:
! if (pqWait(1, 0, conn))
{
conn->status = CONNECTION_BAD;
return 0;
--- 1101,1107 ----
return 1; /* success! */

case PGRES_POLLING_READING:
! if (pqWaitTimed(1, 0, conn, rp))
{
conn->status = CONNECTION_BAD;
return 0;
***************
*** 1077,1083 ****
break;

case PGRES_POLLING_WRITING:
! if (pqWait(0, 1, conn))
{
conn->status = CONNECTION_BAD;
return 0;
--- 1109,1115 ----
break;

case PGRES_POLLING_WRITING:
! if (pqWaitTimed(0, 1, conn, rp))
{
conn->status = CONNECTION_BAD;
return 0;
***************
*** 1094,1100 ****
--- 1126,1156 ----
* Now try to advance the state machine.
*/
flag = PQconnectPoll(conn);
+
+ /*
+ * If connecting timeout is set, calculate remain time.
+ */
+ if (NULL != rp) {
+ if (-1 == gettimeofday(&finish_time, NULL))
+ {
+ conn->status = CONNECTION_BAD;
+ return 0;
+ }
+ if (0 > (finish_time.tv_usec -= start_time.tv_usec))
+ {
+ remains.tv_sec++;
+ finish_time.tv_usec += 1000000;
+ }
+ if (0 > (remains.tv_usec -= finish_time.tv_usec))
+ {
+ remains.tv_sec--;
+ remains.tv_usec += 1000000;
+ }
+ remains.tv_sec -= finish_time.tv_sec - start_time.tv_sec;
+ }
}
+ conn->status = CONNECTION_BAD;
+ return 0;
}

/* ----------------
***************
*** 1929,1934 ****
--- 1985,1992 ----
free(conn->pguser);
if (conn->pgpass)
free(conn->pgpass);
+ if (conn->connect_timeout)
+ free(conn->connect_timeout);
/* Note that conn->Pfdebug is not ours to close or free */
if (conn->notifyList)
DLFreeList(conn->notifyList);
*** postgresql-7.2.1/src/interfaces/libpq/fe-misc.c.orig Чт Авг 8 16:33:34 2002
--- postgresql-7.2.1/src/interfaces/libpq/fe-misc.c Вт Авг 13 16:16:57 2002
***************
*** 748,757 ****
--- 748,766 ----
int
pqWait(int forRead, int forWrite, PGconn *conn)
{
+ return pqWaitTimed( forRead, forWrite, conn, (const struct timeval *) NULL);
+ }
+
+ int
+ pqWaitTimed(int forRead, int forWrite, PGconn *conn, const struct timeval *timeout)
+ {
fd_set input_mask;
fd_set output_mask;
fd_set except_mask;

+ struct timeval tmp_timeout;
+ struct timeval *ptmp_timeout = NULL;
+
if (conn->sock < 0)
{
printfPQExpBuffer(&conn->errorMessage,
***************
*** 770,778 ****
if (forWrite)
FD_SET(conn->sock, &output_mask);
FD_SET(conn->sock, &except_mask);
! if (select(conn->sock + 1, &input_mask, &output_mask, &except_mask,
! (struct timeval *) NULL) < 0)
{
if (SOCK_ERRNO == EINTR)
goto retry;
printfPQExpBuffer(&conn->errorMessage,
--- 779,796 ----
if (forWrite)
FD_SET(conn->sock, &output_mask);
FD_SET(conn->sock, &except_mask);
!
! if (NULL != timeout)
{
+ /*
+ * select may modify timeout argument on some platforms use copy
+ */
+ tmp_timeout = *timeout;
+ ptmp_timeout = &tmp_timeout;
+ }
+ if (select(conn->sock + 1, &input_mask, &output_mask,
+ &except_mask, ptmp_timeout) < 0)
+ {
if (SOCK_ERRNO == EINTR)
goto retry;
printfPQExpBuffer(&conn->errorMessage,
*** postgresql-7.2.1/src/interfaces/libpq/libpq-int.h.orig Чт Авг 8 16:37:56 2002
--- postgresql-7.2.1/src/interfaces/libpq/libpq-int.h Вт Авг 13 14:37:54 2002
***************
*** 279,284 ****
--- 279,286 ----
PQExpBufferData workBuffer; /* expansible string */

int client_encoding; /* encoding id */
+
+ char *connect_timeout;
};

/* String descriptions of the ExecStatusTypes.
***************
*** 324,329 ****
--- 326,332 ----
extern int pqReadData(PGconn *conn);
extern int pqFlush(PGconn *conn);
extern int pqWait(int forRead, int forWrite, PGconn *conn);
+ extern int pqWaitTimed(int forRead, int forWrite, PGconn *conn, const struct timeval* timeout);
extern int pqReadReady(PGconn *conn);
extern int pqWriteReady(PGconn *conn);

--
Regards
Denis