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Redesign archive modules

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A new callback named startup_cb, called shortly after a module is
loaded, is added.  This makes possible the initialization of any
additional state data required by a module.  This initial state data can
be saved in a ArchiveModuleState, that is now passed down to all the
callbacks that can be defined in a module.  With this design, it is
possible to have a per-module state, aimed at opening the door to the
support of more than one archive module.

The initialization of the callbacks is changed so as
_PG_archive_module_init() does not anymore give in input a
ArchiveModuleCallbacks that a module has to fill in with callback
definitions.  Instead, a module now needs to return a const
ArchiveModuleCallbacks.

All the structure and callback definitions of archive modules are moved
into their own header, named archive_module.h, from pgarch.h.
Command-based archiving follows the same line, with a new set of files
named shell_archive.{c,h}.

There are a few more items that are under discussion to improve the
design of archive modules, like the fact that basic_archive calls
sigsetjmp() by itself to define its own error handling flow.  These will
be adjusted later, the changes done here cover already a good portion
of what has been discussed.

Any modules created for v15 will need to be adjusted to this new
design.

Author: Nathan Bossart
Reviewed-by: Andres Freund
Discussion: https://postgr.es/m/20230130194810.6fztfgbn32e7qarj@awork3.anarazel.de
This commit is contained in:
Michael Paquier
2023-02-17 14:26:42 +09:00
parent d2ea2d310d
commit 35739b87dc
15 changed files with 253 additions and 90 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
src/backend/postmaster/Makefile
View File

@@ -22,7 +22,6 @@ OBJS = \
interrupt.o \
pgarch.o \
postmaster.o \
shell_archive.o \
startup.o \
syslogger.o \
walwriter.o

1
src/backend/postmaster/meson.build
View File

@@ -10,7 +10,6 @@ backend_sources += files(
'interrupt.c',
'pgarch.c',
'postmaster.c',
'shell_archive.c',
'startup.c',
'syslogger.c',
'walwriter.c',

27
src/backend/postmaster/pgarch.c
View File

@@ -31,6 +31,8 @@
#include "access/xlog.h"
#include "access/xlog_internal.h"
#include "archive/archive_module.h"
#include "archive/shell_archive.h"
#include "lib/binaryheap.h"
#include "libpq/pqsignal.h"
#include "pgstat.h"
@@ -97,7 +99,8 @@ char *XLogArchiveLibrary = "";
*/
static time_t last_sigterm_time = 0;
static PgArchData *PgArch = NULL;
static ArchiveModuleCallbacks ArchiveContext;
static const ArchiveModuleCallbacks *ArchiveCallbacks;
static ArchiveModuleState *archive_module_state;
/*
@@ -406,8 +409,8 @@ pgarch_ArchiverCopyLoop(void)
HandlePgArchInterrupts();
/* can't do anything if not configured ... */
if (ArchiveContext.check_configured_cb != NULL &&
!ArchiveContext.check_configured_cb())
if (ArchiveCallbacks->check_configured_cb != NULL &&
!ArchiveCallbacks->check_configured_cb(archive_module_state))
{
ereport(WARNING,
(errmsg("archive_mode enabled, yet archiving is not configured")));
@@ -508,7 +511,7 @@ pgarch_archiveXlog(char *xlog)
snprintf(activitymsg, sizeof(activitymsg), "archiving %s", xlog);
set_ps_display(activitymsg);
ret = ArchiveContext.archive_file_cb(xlog, pathname);
ret = ArchiveCallbacks->archive_file_cb(archive_module_state, xlog, pathname);
if (ret)
snprintf(activitymsg, sizeof(activitymsg), "last was %s", xlog);
else
@@ -814,7 +817,7 @@ HandlePgArchInterrupts(void)
/*
* LoadArchiveLibrary
*
* Loads the archiving callbacks into our local ArchiveContext.
* Loads the archiving callbacks into our local ArchiveCallbacks.
*/
static void
LoadArchiveLibrary(void)
@@ -827,8 +830,6 @@ LoadArchiveLibrary(void)
errmsg("both archive_command and archive_library set"),
errdetail("Only one of archive_command, archive_library may be set.")));
memset(&ArchiveContext, 0, sizeof(ArchiveModuleCallbacks));
/*
* If shell archiving is enabled, use our special initialization function.
* Otherwise, load the library and call its _PG_archive_module_init().
@@ -844,12 +845,16 @@ LoadArchiveLibrary(void)
ereport(ERROR,
(errmsg("archive modules have to define the symbol %s", "_PG_archive_module_init")));
(*archive_init) (&ArchiveContext);
ArchiveCallbacks = (*archive_init) ();
if (ArchiveContext.archive_file_cb == NULL)
if (ArchiveCallbacks->archive_file_cb == NULL)
ereport(ERROR,
(errmsg("archive modules must register an archive callback")));
archive_module_state = (ArchiveModuleState *) palloc0(sizeof(ArchiveModuleState));
if (ArchiveCallbacks->startup_cb != NULL)
ArchiveCallbacks->startup_cb(archive_module_state);
before_shmem_exit(pgarch_call_module_shutdown_cb, 0);
}
@@ -859,6 +864,6 @@ LoadArchiveLibrary(void)
static void
pgarch_call_module_shutdown_cb(int code, Datum arg)
{
if (ArchiveContext.shutdown_cb != NULL)
ArchiveContext.shutdown_cb();
if (ArchiveCallbacks->shutdown_cb != NULL)
ArchiveCallbacks->shutdown_cb(archive_module_state);
}

129
src/backend/postmaster/shell_archive.c
View File

@@ -1,129 +0,0 @@
/*-------------------------------------------------------------------------
*
* shell_archive.c
*
* This archiving function uses a user-specified shell command (the
* archive_command GUC) to copy write-ahead log files. It is used as the
* default, but other modules may define their own custom archiving logic.
*
* Copyright (c) 2022-2023, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/postmaster/shell_archive.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <sys/wait.h>
#include "access/xlog.h"
#include "common/percentrepl.h"
#include "pgstat.h"
#include "postmaster/pgarch.h"
static bool shell_archive_configured(void);
static bool shell_archive_file(const char *file, const char *path);
static void shell_archive_shutdown(void);
void
shell_archive_init(ArchiveModuleCallbacks *cb)
{
cb->check_configured_cb = shell_archive_configured;
cb->archive_file_cb = shell_archive_file;
cb->shutdown_cb = shell_archive_shutdown;
}
static bool
shell_archive_configured(void)
{
return XLogArchiveCommand[0] != '\0';
}
static bool
shell_archive_file(const char *file, const char *path)
{
char *xlogarchcmd;
char *nativePath = NULL;
int rc;
if (path)
{
nativePath = pstrdup(path);
make_native_path(nativePath);
}
xlogarchcmd = replace_percent_placeholders(XLogArchiveCommand, "archive_command", "fp", file, nativePath);
if (nativePath)
pfree(nativePath);
ereport(DEBUG3,
(errmsg_internal("executing archive command \"%s\"",
xlogarchcmd)));
fflush(NULL);
pgstat_report_wait_start(WAIT_EVENT_ARCHIVE_COMMAND);
rc = system(xlogarchcmd);
pgstat_report_wait_end();
if (rc != 0)
{
/*
* If either the shell itself, or a called command, died on a signal,
* abort the archiver. We do this because system() ignores SIGINT and
* SIGQUIT while waiting; so a signal is very likely something that
* should have interrupted us too. Also die if the shell got a hard
* "command not found" type of error. If we overreact it's no big
* deal, the postmaster will just start the archiver again.
*/
int lev = wait_result_is_any_signal(rc, true) ? FATAL : LOG;
if (WIFEXITED(rc))
{
ereport(lev,
(errmsg("archive command failed with exit code %d",
WEXITSTATUS(rc)),
errdetail("The failed archive command was: %s",
xlogarchcmd)));
}
else if (WIFSIGNALED(rc))
{
#if defined(WIN32)
ereport(lev,
(errmsg("archive command was terminated by exception 0x%X",
WTERMSIG(rc)),
errhint("See C include file \"ntstatus.h\" for a description of the hexadecimal value."),
errdetail("The failed archive command was: %s",
xlogarchcmd)));
#else
ereport(lev,
(errmsg("archive command was terminated by signal %d: %s",
WTERMSIG(rc), pg_strsignal(WTERMSIG(rc))),
errdetail("The failed archive command was: %s",
xlogarchcmd)));
#endif
}
else
{
ereport(lev,
(errmsg("archive command exited with unrecognized status %d",
rc),
errdetail("The failed archive command was: %s",
xlogarchcmd)));
}
return false;
}
pfree(xlogarchcmd);
elog(DEBUG1, "archived write-ahead log file \"%s\"", file);
return true;
}
static void
shell_archive_shutdown(void)
{
elog(DEBUG1, "archiver process shutting down");
}