Re: [HACKERS] loading libraries on Postmaster startup

More recent patch applied.

---------------------------------------------------------------------------

Joe Conway wrote:
> Tom Lane wrote:
> > Joe Conway <mail(at)joeconway(dot)com> writes:
> >>[ what about autoloading libraries into the postmaster? ]
> >
> > I can see a couple possible downsides: (a) the library might have some
> > weird behavior across fork boundaries; (b) the additional memory space
> > that has to be duplicated into child processes will cost something per
> > child launch, even if the child never uses it. But these are only
> > arguments that it might not *always* be a prudent thing to do, not that
> > we shouldn't give the DBA the tool to do it if he wants. So fire away.
>
> Here is a patch for the above, including a documentation update. It
> creates a new GUC variable "preload_libraries", that accepts a list in
> the form:
>
> preload_libraries = '$libdir/mylib1:initfunc,$libdir/mylib2'
>
> If ":initfunc" is omitted or not found, no initialization function is
> executed, but the library is still preloaded. If "$libdir/mylib" isn't
> found, the postmaster refuses to start.
>
> In my testing with PL/R, it reduces the first call to a PL/R function
> (after connecting) from almost 2 seconds, down to about 8 ms.
>
> If there are no objections, please apply.
>
> Thanks,
>
> Joe

> Index: doc/src/sgml/runtime.sgml
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/doc/src/sgml/runtime.sgml,v
> retrieving revision 1.169
> diff -c -r1.169 runtime.sgml
> *** doc/src/sgml/runtime.sgml 19 Feb 2003 04:06:28 -0000 1.169
> --- doc/src/sgml/runtime.sgml 22 Feb 2003 05:59:08 -0000
> ***************
> *** 1781,1786 ****
> --- 1781,1815 ----
> </varlistentry>
>
> <varlistentry>
> + <term><varname>PRELOAD_LIBRARIES</varname> (<type>string</type>)</term>
> + <indexterm><primary>preload_libraries</></>
> + <listitem>
> + <para>
> + This variable specifies one or more shared libraries that are to be
> + preloaded at Postmaster start. An initialization function can also be
> + optionally specified by adding a colon followed by the name of the
> + initialization function after the library name. For example
> + <literal>'$libdir/mylib:init_mylib'</literal> would cause <literal>mylib</>
> + to be preloaded and <literal>init_mylib</> to be executed. If more than
> + one library is to be loaded, they must be delimited with a comma.
> + </para>
> +
> + <para>
> + If <literal>mylib</> is not found, the postmaster will fail to start.
> + However, if <literal>init_mylib</> is not found, <literal>mylib</> will
> + still be preloaded without executing the initialization function.
> + </para>
> +
> + <para>
> + By preloading a shared library (and initializing it if applicable),
> + the library startup time is avoided when the library is used later in a
> + specific backend. However there is a cost in terms of memory duplication
> + as every backend is forked, whether or not the library is used.
> + </para>
> + </listitem>
> + </varlistentry>
> +
> + <varlistentry>
> <term><varname>REGEX_FLAVOR</varname> (<type>string</type>)</term>
> <indexterm><primary>regular expressions</></>
> <listitem>
> Index: src/backend/postmaster/postmaster.c
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/backend/postmaster/postmaster.c,v
> retrieving revision 1.306
> diff -c -r1.306 postmaster.c
> *** src/backend/postmaster/postmaster.c 25 Jan 2003 05:19:46 -0000 1.306
> --- src/backend/postmaster/postmaster.c 22 Feb 2003 04:29:44 -0000
> ***************
> *** 205,210 ****
> --- 205,212 ----
> bool Log_connections = false;
> bool Db_user_namespace = false;
>
> + /* list of library:init-function to be preloaded */
> + char *preload_libraries_string = NULL;
>
> /* Startup/shutdown state */
> static pid_t StartupPID = 0,
> ***************
> *** 644,649 ****
> --- 646,658 ----
> if (EnableSSL)
> secure_initialize();
> #endif
> +
> + /*
> + * process any libraries that should be preloaded and
> + * optionally pre-initialized
> + */
> + if (preload_libraries_string)
> + process_preload_libraries(preload_libraries_string);
>
> /*
> * Fork away from controlling terminal, if -S specified.
> Index: src/backend/utils/init/miscinit.c
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/backend/utils/init/miscinit.c,v
> retrieving revision 1.100
> diff -c -r1.100 miscinit.c
> *** src/backend/utils/init/miscinit.c 27 Jan 2003 00:51:06 -0000 1.100
> --- src/backend/utils/init/miscinit.c 22 Feb 2003 04:29:44 -0000
> ***************
> *** 1044,1046 ****
> --- 1044,1135 ----
> "which is not compatible with this version %s.",
> file_major, file_minor, version_string);
> }
> +
> + /*-------------------------------------------------------------------------
> + * Library preload support
> + *-------------------------------------------------------------------------
> + */
> +
> + #if defined(__mc68000__) && defined(__ELF__)
> + typedef int32 ((*func_ptr) ());
> + #else
> + typedef char *((*func_ptr) ());
> + #endif
> +
> + /*
> + * process any libraries that should be preloaded and
> + * optionally pre-initialized
> + */
> + void
> + process_preload_libraries(char *preload_libraries_string)
> + {
> + char *rawstring;
> + List *elemlist;
> + List *l;
> +
> + if (preload_libraries_string == NULL)
> + return;
> +
> + /* Need a modifiable copy of string */
> + rawstring = pstrdup(preload_libraries_string);
> +
> + /* Parse string into list of identifiers */
> + if (!SplitIdentifierString(rawstring, ',', &elemlist))
> + {
> + /* syntax error in list */
> + pfree(rawstring);
> + freeList(elemlist);
> + elog(LOG, "invalid list syntax for preload_libraries configuration option");
> + }
> +
> + foreach(l, elemlist)
> + {
> + char *tok = (char *) lfirst(l);
> + char *sep = strstr(tok, ":");
> + char *filename = NULL;
> + char *funcname = NULL;
> + func_ptr initfunc;
> +
> + if (sep)
> + {
> + /*
> + * a colon separator implies there is an initialization function
> + * that we need to run in addition to loading the library
> + */
> + size_t filename_len = sep - tok;
> + size_t funcname_len = strlen(tok) - filename_len - 1;
> +
> + filename = (char *) palloc(filename_len + 1);
> + memset(filename, '\0', filename_len + 1);
> + snprintf(filename, filename_len + 1, "%s", tok);
> +
> + funcname = (char *) palloc(funcname_len + 1);
> + memset(funcname, '\0', funcname_len + 1);
> + snprintf(funcname, funcname_len + 1, "%s", sep + 1);
> + }
> + else
> + {
> + /*
> + * no separator -- just load the library
> + */
> + filename = pstrdup(tok);
> + funcname = NULL;
> + }
> +
> + initfunc = (func_ptr) load_external_function(filename, funcname, false, NULL);
> + if (initfunc)
> + (*initfunc)();
> +
> + elog(LOG, "preloaded library %s with initialization function %s", filename, funcname);
> +
> + if (filename != NULL)
> + pfree(filename);
> +
> + if (funcname != NULL)
> + pfree(funcname);
> + }
> +
> + pfree(rawstring);
> + freeList(elemlist);
> + }
> +
> Index: src/backend/utils/misc/guc.c
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/backend/utils/misc/guc.c,v
> retrieving revision 1.114
> diff -c -r1.114 guc.c
> *** src/backend/utils/misc/guc.c 6 Feb 2003 20:25:33 -0000 1.114
> --- src/backend/utils/misc/guc.c 22 Feb 2003 06:01:33 -0000
> ***************
> *** 61,66 ****
> --- 61,67 ----
> extern int CommitDelay;
> extern int CommitSiblings;
> extern bool FixBTree;
> + extern char *preload_libraries_string;
>
> #ifdef HAVE_SYSLOG
> extern char *Syslog_facility;
> ***************
> *** 817,822 ****
> --- 818,829 ----
> {
> {"lc_time", PGC_USERSET}, &locale_time,
> "C", locale_time_assign, NULL
> + },
> +
> + {
> + {"preload_libraries", PGC_POSTMASTER, GUC_LIST_INPUT | GUC_LIST_QUOTE},
> + &preload_libraries_string,
> + "", NULL, NULL
> },
>
> {
> Index: src/backend/utils/misc/postgresql.conf.sample
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/backend/utils/misc/postgresql.conf.sample,v
> retrieving revision 1.70
> diff -c -r1.70 postgresql.conf.sample
> *** src/backend/utils/misc/postgresql.conf.sample 6 Feb 2003 20:25:33 -0000 1.70
> --- src/backend/utils/misc/postgresql.conf.sample 22 Feb 2003 04:29:44 -0000
> ***************
> *** 213,216 ****
> --- 213,217 ----
> #transform_null_equals = false
> #statement_timeout = 0 # 0 is disabled, in milliseconds
> #db_user_namespace = false
> + #preload_libraries = ''
>
> Index: src/include/miscadmin.h
> ===================================================================
> RCS file: /opt/src/cvs/pgsql-server/src/include/miscadmin.h,v
> retrieving revision 1.115
> diff -c -r1.115 miscadmin.h
> *** src/include/miscadmin.h 9 Jan 2003 18:00:24 -0000 1.115
> --- src/include/miscadmin.h 22 Feb 2003 04:29:44 -0000
> ***************
> *** 292,297 ****
> --- 292,298 ----
> unsigned long id2);
>
> extern void ValidatePgVersion(const char *path);
> + extern void process_preload_libraries(char *preload_libraries_string);
>
> /* these externs do not belong here... */
> extern void IgnoreSystemIndexes(bool mode);

>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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+ Christ can be your backup. | Newtown Square, Pennsylvania 19073