Implement support for TCP_KEEPCNT, TCP_KEEPIDLE, TCP_KEEPINTVL (was Re: [HACKERS] Feature freeze date for 8.1) - Mailing list pgsql-patches

Tom Lane wrote:
> Oliver Jowett <oliver@opencloud.com> writes:
>
>>Tom Lane wrote:
>>
>>>I'm not convinced that Postgres ought to provide
>>>a way to second-guess the TCP stack ...
>
>
>>Would you be ok with a patch that allowed configuration of the
>>TCP_KEEPCNT / TCP_KEEPIDLE / TCP_KEEPINTVL socket options on backend
>>sockets?
>
>
> [ shrug... ]  As long as it doesn't fail to build on platforms that
> don't offer those options, I couldn't complain too hard.  But do we
> really need all that?

Here's a patch that adds four new GUCs:

  tcp_keepalives (defaults to on, controls SO_KEEPALIVE)
  tcp_keepalives_idle (controls TCP_KEEPIDLE)
  tcp_keepalives_interval (controls TCP_KEEPINTVL)
  tcp_keepalives_count (controls TCP_KEEPCNT)

They're ignored for AF_UNIX connections and when running standalone.

tcp_keepalives_* treat 0 as "use system default". If the underlying OS
doesn't provide the TCP_KEEP* socket options, the GUCs are present but
reject any value other than 0.

SHOW reflects the currently-in-use value or 0 if not applicable or not
known. i.e. if you set it to 0 and you have the socket options
available, SHOW will show the result of getsockopt() which is non-zero.

A default install on my Linux system produces:

template1=# show all;
              name              |                   setting

--------------------------------+----------------------------------------------
[...]
 tcp_keepalives                 | on
 tcp_keepalives_count           | 9
 tcp_keepalives_idle            | 7200
 tcp_keepalives_interval        | 75
[...]

I haven't had a chance to check it builds on other systems or to test
that this handles actual network failures nicely yet.

-O
Index: doc/src/sgml/runtime.sgml
===================================================================
RCS file: /projects/cvsroot/pgsql/doc/src/sgml/runtime.sgml,v
retrieving revision 1.315
diff -c -r1.315 runtime.sgml
*** doc/src/sgml/runtime.sgml    23 Apr 2005 03:27:40 -0000    1.315
--- doc/src/sgml/runtime.sgml    3 May 2005 01:44:02 -0000
***************
*** 889,894 ****
--- 889,961 ----
        </listitem>
       </varlistentry>

+      <varlistentry id="guc-tcp-keepalives" xreflabel="tcp_keepalives">
+       <term><varname>tcp_keepalives</varname> (<type>boolean</type>)</term>
+       <indexterm>
+        <primary><varname>tcp_keepalives</> configuration parameter</primary>
+       </indexterm>
+       <listitem>
+        <para>
+         Controls the use of TCP keepalives on client connections. When enabled,
+         idle connections will be periodically probed to check that the client
+         is still present. If sufficient probes are lost, the connection will
+         be broken. This option is ignored for connections made via a
+         Unix-domain socket.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry id="guc-tcp-keepalives-idle" xreflabel="tcp_keepalives_idle">
+       <term><varname>tcp_keepalives_idle</varname> (<type>integer</type>)</term>
+       <indexterm>
+        <primary><varname>tcp_keepalives_idle</> configuration parameter</primary>
+       </indexterm>
+       <listitem>
+        <para>
+         On systems that support the TCP_KEEPIDLE socket option, specifies the
+         number of seconds between sending keepalives on an otherwise idle
+         connection. A value of 0 uses the system default. If TCP_KEEPIDLE is
+         not supported, this parameter must be 0. This option is ignored for
+         connections made via a Unix-domain socket, and will have no effect
+         unless the <varname>tcp_keepalives</varname> option is enabled.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry id="guc-tcp-keepalives-interval" xreflabel="tcp_keepalives_interval">
+       <term><varname>tcp_keepalives_interval</varname> (<type>integer</type>)</term>
+       <indexterm>
+        <primary><varname>tcp_keepalives_interval</> configuration parameter</primary>
+       </indexterm>
+       <listitem>
+        <para>
+         On systems that support the TCP_KEEPINTVL socket option, specifies how
+         long, in seconds, to wait for a response to a keepalive before
+         retransmitting. A value of 0 uses the system default. If TCP_KEEPINTVL
+         is not supported, this parameter must be 0. This option is ignored
+         for connections made via a Unix-domain socket, and will have no effect
+         unless the <varname>tcp_keepalives</varname> option is enabled.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry id="guc-tcp-keepalives-count" xreflabel="tcp_keepalives_count">
+       <term><varname>tcp_keepalives_count</varname> (<type>integer</type>)</term>
+       <indexterm>
+        <primary><varname>tcp_keepalives_count</> configuration parameter</primary>
+       </indexterm>
+       <listitem>
+        <para>
+         On systems that support the TCP_KEEPCNT socket option, specifies how
+         many keepalives may be lost before the connection is considered dead.
+         A value of 0 uses the system default. If TCP_KEEPINTVL is not
+         supported, this parameter must be 0. This option is ignored for
+         connections made via a Unix-domain socket, and will have no effect
+         unless the <varname>tcp_keepalives</varname> option is enabled.
+        </para>
+       </listitem>
+      </varlistentry>
+
       </variablelist>
       </sect3>
       <sect3 id="runtime-config-connection-security">
Index: src/backend/libpq/pqcomm.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/libpq/pqcomm.c,v
retrieving revision 1.176
diff -c -r1.176 pqcomm.c
*** src/backend/libpq/pqcomm.c    22 Feb 2005 04:35:57 -0000    1.176
--- src/backend/libpq/pqcomm.c    3 May 2005 01:44:03 -0000
***************
*** 87,93 ****
  #include "libpq/libpq.h"
  #include "miscadmin.h"
  #include "storage/ipc.h"
!

  /*
   * Configuration options
--- 87,93 ----
  #include "libpq/libpq.h"
  #include "miscadmin.h"
  #include "storage/ipc.h"
! #include "utils/guc.h"

  /*
   * Configuration options
***************
*** 577,582 ****
--- 577,583 ----
      if (!IS_AF_UNIX(port->laddr.addr.ss_family))
      {
          int            on;
+         socklen_t   size;

  #ifdef    TCP_NODELAY
          on = 1;
***************
*** 587,599 ****
              return STATUS_ERROR;
          }
  #endif
!         on = 1;
!         if (setsockopt(port->sock, SOL_SOCKET, SO_KEEPALIVE,
!                        (char *) &on, sizeof(on)) < 0)
          {
!             elog(LOG, "setsockopt(SO_KEEPALIVE) failed: %m");
              return STATUS_ERROR;
          }
      }

      return STATUS_OK;
--- 588,645 ----
              return STATUS_ERROR;
          }
  #endif
!
!         if (pq_setkeepalives(tcp_keepalives, port) != STATUS_OK)
!             return STATUS_ERROR;
!
!         /* Grab default keepalive values, then apply
!          * our GUC settings.
!          */
! #ifdef TCP_KEEPIDLE
!         if (getsockopt(port->sock, SOL_TCP, TCP_KEEPIDLE,
!                        (char *) &port->default_keepalives_idle, &size) < 0)
!         {
!             elog(LOG, "getsockopt(TCP_KEEPIDLE) failed: %m");
!             return STATUS_ERROR;
!         }
! #else
!         port->default_keepalives_idle = 0;
! #endif
!
! #ifdef TCP_KEEPINTVL
!         if (getsockopt(port->sock, SOL_TCP, TCP_KEEPINTVL,
!                        (char *) &port->default_keepalives_interval, &size) < 0)
          {
!             elog(LOG, "getsockopt(TCP_KEEPINTVL) failed: %m");
              return STATUS_ERROR;
          }
+ #else
+         port->default_keepalives_idle = 0;
+ #endif
+
+ #ifdef TCP_KEEPCNT
+         if (getsockopt(port->sock, SOL_TCP, TCP_KEEPCNT,
+                        (char *) &port->default_keepalives_count, &size) < 0)
+         {
+             elog(LOG, "getsockopt(TCP_KEEPCNT) failed: %m");
+             return STATUS_ERROR;
+         }
+ #else
+         port->default_keepalives_idle = 0;
+ #endif
+
+         /* Set default keepalive parameters. This should also catch
+          * misconfigurations (non-zero values when socket options aren't
+          * supported)
+          */
+         if (pq_setkeepalivesidle(tcp_keepalives_idle, port) != STATUS_OK)
+             return STATUS_ERROR;
+
+         if (pq_setkeepalivesinterval(tcp_keepalives_interval, port) != STATUS_OK)
+             return STATUS_ERROR;
+
+         if (pq_setkeepalivescount(tcp_keepalives_count, port) != STATUS_OK)
+             return STATUS_ERROR;
      }

      return STATUS_OK;
***************
*** 1158,1160 ****
--- 1204,1305 ----
      /* in non-error case, copy.c will have emitted the terminator line */
      DoingCopyOut = false;
  }
+
+ int
+ pq_setkeepalives(bool onoff, Port *port)
+ {
+     int on = (onoff ? 1 : 0);
+
+     if (IS_AF_UNIX(port->laddr.addr.ss_family))
+         return STATUS_OK;
+
+     if (setsockopt(port->sock, SOL_SOCKET, SO_KEEPALIVE,
+                    (char *) &on, sizeof(on)) < 0)
+     {
+         elog(LOG, "setsockopt(SO_KEEPALIVE) failed: %m");
+         return STATUS_ERROR;
+     }
+
+     return STATUS_OK;
+ }
+
+ int
+ pq_setkeepalivesidle(int idle, Port *port)
+ {
+     if (IS_AF_UNIX(port->laddr.addr.ss_family))
+         return STATUS_OK;
+
+ #ifdef TCP_KEEPIDLE
+     if (idle == 0)
+         idle = port->default_keepalives_idle;
+
+     if (setsockopt(port->sock, SOL_TCP, TCP_KEEPIDLE,
+                    (char *) &idle, sizeof(idle)) < 0)
+     {
+         elog(LOG, "setsockopt(TCP_KEEPIDLE) failed: %m");
+         return STATUS_ERROR;
+     }
+ #else
+     if (idle != 0)
+     {
+         elog(LOG, "setsockopt(TCP_KEEPIDLE) not supported");
+         return STATUS_ERROR;
+     }
+ #endif
+
+     return STATUS_OK;
+ }
+
+ int
+ pq_setkeepalivesinterval(int interval, Port *port)
+ {
+     if (IS_AF_UNIX(port->laddr.addr.ss_family))
+         return STATUS_OK;
+
+ #ifdef TCP_KEEPINTVL
+     if (interval == 0)
+         interval = port->default_keepalives_interval;
+
+     if (setsockopt(port->sock, SOL_TCP, TCP_KEEPINTVL,
+                    (char *) &interval, sizeof(interval)) < 0)
+     {
+         elog(LOG, "setsockopt(TCP_KEEPINTVL) failed: %m");
+         return STATUS_ERROR;
+     }
+ #else
+     if (interval != 0)
+     {
+         elog(LOG, "setsockopt(TCP_KEEPINTVL) not supported");
+         return STATUS_ERROR;
+     }
+ #endif
+
+     return STATUS_OK;
+ }
+
+ int
+ pq_setkeepalivescount(int count, Port *port)
+ {
+     if (IS_AF_UNIX(port->laddr.addr.ss_family))
+         return STATUS_OK;
+
+ #ifdef TCP_KEEPCNT
+     if (count == 0)
+         count = port->default_keepalives_count;
+
+     if (setsockopt(port->sock, SOL_TCP, TCP_KEEPCNT,
+                    (char *) &count, sizeof(count)) < 0)
+     {
+         elog(LOG, "setsockopt(TCP_KEEPCNT) failed: %m");
+         return STATUS_ERROR;
+     }
+ #else
+     if (count != 0)
+     {
+         elog(LOG, "setsockopt(TCP_KEEPCNT) not supported");
+         return STATUS_ERROR;
+     }
+ #endif
+
+     return STATUS_OK;
+ }
Index: src/backend/utils/misc/guc.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/utils/misc/guc.c,v
retrieving revision 1.261
diff -c -r1.261 guc.c
*** src/backend/utils/misc/guc.c    1 May 2005 18:56:19 -0000    1.261
--- src/backend/utils/misc/guc.c    3 May 2005 01:44:08 -0000
***************
*** 113,118 ****
--- 113,125 ----
  static bool assign_transaction_read_only(bool newval, bool doit, GucSource source);
  static const char *assign_canonical_path(const char *newval, bool doit, GucSource source);

+ static bool assign_tcp_keepalives(bool newval, bool doit, GucSource source);
+ static bool assign_tcp_keepalives_idle(int newval, bool doit, GucSource source);
+ static bool assign_tcp_keepalives_interval(int newval, bool doit, GucSource source);
+ static bool assign_tcp_keepalives_count(int newval, bool doit, GucSource source);
+ static const char *show_tcp_keepalives_idle(void);
+ static const char *show_tcp_keepalives_interval(void);
+ static const char *show_tcp_keepalives_count(void);

  /*
   * GUC option variables that are exported from this module
***************
*** 154,159 ****
--- 161,170 ----
  char       *IdentFileName;
  char       *external_pid_file;

+ bool        tcp_keepalives = true;
+ int         tcp_keepalives_idle;
+ int         tcp_keepalives_interval;
+ int         tcp_keepalives_count;

  /*
   * These variables are all dummies that don't do anything, except in some
***************
*** 860,865 ****
--- 871,885 ----
  #endif
      },

+     {
+         {"tcp_keepalives", PGC_USERSET, CLIENT_CONN_OTHER,
+              gettext_noop("Use keepalives on client TCP connections."),
+              NULL,
+         },
+         &tcp_keepalives,
+         true, assign_tcp_keepalives, NULL
+     },
+
      /* End-of-list marker */
      {
          {NULL, 0, 0, NULL, NULL}, NULL, false, NULL, NULL
***************
*** 1333,1338 ****
--- 1353,1387 ----
          BLCKSZ, BLCKSZ, BLCKSZ, NULL, NULL
      },

+     {
+         {"tcp_keepalives_idle", PGC_USERSET, CLIENT_CONN_OTHER,
+              gettext_noop("Seconds between issuing TCP keepalives."),
+              gettext_noop("A value of 0 uses the system default."),
+         },
+         &tcp_keepalives_idle,
+         0, 0, INT_MAX, assign_tcp_keepalives_idle, show_tcp_keepalives_idle
+     },
+
+     {
+         {"tcp_keepalives_interval", PGC_USERSET, CLIENT_CONN_OTHER,
+              gettext_noop("Seconds between TCP keepalive retransmits."),
+              gettext_noop("A value of 0 uses the system default."),
+         },
+         &tcp_keepalives_interval,
+         0, 0, INT_MAX, assign_tcp_keepalives_interval, show_tcp_keepalives_interval
+     },
+
+     {
+         {"tcp_keepalives_count", PGC_USERSET, CLIENT_CONN_OTHER,
+              gettext_noop("Maximum number of TCP keepalive retransmits."),
+              gettext_noop("This controls the number of consecutive keepalive retransmits that can be "
+                           "lost before a connection is considered dead. A value of 0 uses the "
+                           "system default."),
+         },
+         &tcp_keepalives_count,
+         0, 0, INT_MAX, assign_tcp_keepalives_count, show_tcp_keepalives_count
+     },
+
      /* End-of-list marker */
      {
          {NULL, 0, 0, NULL, NULL}, NULL, 0, 0, 0, NULL, NULL
***************
*** 5677,5681 ****
--- 5726,5802 ----
          return newval;
  }

+ static bool
+ assign_tcp_keepalives(bool newval, bool doit, GucSource source)
+ {
+     if (doit && MyProcPort != NULL)
+     {
+         pq_setkeepalives(newval, MyProcPort);
+     }
+     return true;
+ }
+
+ static bool
+ assign_tcp_keepalives_idle(int newval, bool doit, GucSource source)
+ {
+     if (doit && MyProcPort != NULL)
+     {
+         return (pq_setkeepalivesidle(newval, MyProcPort) == STATUS_OK);
+     }
+
+     return true;
+ }
+
+ static const char *
+ show_tcp_keepalives_idle(void)
+ {
+     static char nbuf[32];
+     snprintf(nbuf, sizeof(nbuf), "%d",
+              (tcp_keepalives_idle != 0 || MyProcPort == NULL)
+              ? tcp_keepalives_idle : MyProcPort->default_keepalives_idle);
+     return nbuf;
+ }
+
+ static bool
+ assign_tcp_keepalives_interval(int newval, bool doit, GucSource source)
+ {
+     if (doit && MyProcPort != NULL)
+     {
+         return (pq_setkeepalivesinterval(newval, MyProcPort) == STATUS_OK);
+     }
+
+     return true;
+ }
+
+ static const char *
+ show_tcp_keepalives_interval(void)
+ {
+     static char nbuf[32];
+     snprintf(nbuf, sizeof(nbuf), "%d",
+              (tcp_keepalives_interval != 0 || MyProcPort == NULL)
+              ? tcp_keepalives_interval : MyProcPort->default_keepalives_interval);
+     return nbuf;
+ }
+
+ static bool
+ assign_tcp_keepalives_count(int newval, bool doit, GucSource source)
+ {
+     if (doit && MyProcPort != NULL)
+     {
+         return (pq_setkeepalivescount(newval, MyProcPort) == STATUS_OK);
+     }
+
+     return true;
+ }
+
+ static const char *
+ show_tcp_keepalives_count(void)
+ {
+     static char nbuf[32];
+     snprintf(nbuf, sizeof(nbuf), "%d",
+              (tcp_keepalives_count != 0 || MyProcPort == NULL)
+              ? tcp_keepalives_count : MyProcPort->default_keepalives_count);
+     return nbuf;
+ }

  #include "guc-file.c"
Index: src/backend/utils/misc/postgresql.conf.sample
===================================================================
RCS file: /projects/cvsroot/pgsql/src/backend/utils/misc/postgresql.conf.sample,v
retrieving revision 1.140
diff -c -r1.140 postgresql.conf.sample
*** src/backend/utils/misc/postgresql.conf.sample    21 Apr 2005 19:18:13 -0000    1.140
--- src/backend/utils/misc/postgresql.conf.sample    3 May 2005 01:44:08 -0000
***************
*** 66,71 ****
--- 66,77 ----
  #krb_server_keyfile = ''
  #db_user_namespace = false

+ # - TCP Keepalives -
+ # see 'man 7 tcp' for details
+ #tcp_keepalives = on            # enables use of TCP keepalives
+ #tcp_keepalives_idle = 0        # TCP_KEEPIDLE, in seconds; 0 uses the system default.
+ #tcp_keepalives_interval = 0    # TCP_KEEPINTVL, in seconds; 0 uses the system default.
+ #tcp_keepalives_count = 0       # TCP_KEEPCNT, in seconds; 0 uses the system default.

  #---------------------------------------------------------------------------
  # RESOURCE USAGE (except WAL)
Index: src/bin/psql/tab-complete.c
===================================================================
RCS file: /projects/cvsroot/pgsql/src/bin/psql/tab-complete.c,v
retrieving revision 1.125
diff -c -r1.125 tab-complete.c
*** src/bin/psql/tab-complete.c    21 Apr 2005 19:18:13 -0000    1.125
--- src/bin/psql/tab-complete.c    3 May 2005 01:44:10 -0000
***************
*** 595,600 ****
--- 595,604 ----
          "superuser_reserved_connections",
          "syslog_facility",
          "syslog_ident",
+         "tcp_keepalives",
+         "tcp_keepalives_idle",
+         "tcp_keepalives_interval",
+         "tcp_keepalives_count",
          "temp_buffers",
          "TimeZone",
          "trace_notify",
Index: src/include/libpq/libpq-be.h
===================================================================
RCS file: /projects/cvsroot/pgsql/src/include/libpq/libpq-be.h,v
retrieving revision 1.49
diff -c -r1.49 libpq-be.h
*** src/include/libpq/libpq-be.h    31 Dec 2004 22:03:32 -0000    1.49
--- src/include/libpq/libpq-be.h    3 May 2005 01:44:10 -0000
***************
*** 92,100 ****
--- 92,113 ----
      char        peer_cn[SM_USER + 1];
      unsigned long count;
  #endif
+
+     /*
+      * Default TCP keepalive values found after accept(); 0 if unsupported or AF_UNIX.
+      */
+     int         default_keepalives_idle;
+     int         default_keepalives_interval;
+     int         default_keepalives_count;
  } Port;


  extern ProtocolVersion FrontendProtocol;

+ /* TCP keepalives configuration. These are no-ops on an AF_UNIX socket. */
+ extern int pq_setkeepalives(bool onoff, Port *port);
+ extern int pq_setkeepalivesidle(int idle, Port *port);
+ extern int pq_setkeepalivesinterval(int interval, Port *port);
+ extern int pq_setkeepalivescount(int count, Port *port);
+
  #endif   /* LIBPQ_BE_H */
Index: src/include/utils/guc.h
===================================================================
RCS file: /projects/cvsroot/pgsql/src/include/utils/guc.h,v
retrieving revision 1.60
diff -c -r1.60 guc.h
*** src/include/utils/guc.h    25 Mar 2005 16:17:28 -0000    1.60
--- src/include/utils/guc.h    3 May 2005 01:44:10 -0000
***************
*** 133,138 ****
--- 133,142 ----
  extern char *IdentFileName;
  extern char *external_pid_file;

+ extern bool tcp_keepalives;
+ extern int  tcp_keepalives_idle;
+ extern int  tcp_keepalives_interval;
+ extern int  tcp_keepalives_count;

  extern void SetConfigOption(const char *name, const char *value,
                  GucContext context, GucSource source);