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Rework internal command generation of pg_rewind

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pg_rewind generates and executes internally up to two commands to work
on the target cluster, depending on the options given by its caller:
- postgres -C to retrieve the value of restore_command, when using
-c/--restore-target-wal.
- postgres --single to enforce recovery once and get the target cluster
in a clean shutdown state.

Both commands have been applying incorrect quoting rules, which could
lead to failures when for example using a target data directory with
unexpected characters like CRLFs.  Those commands are now generated with
PQExpBuffer, making use of string_utils.h to quote those commands as
they should.  We may extend those commands in the future with more
options, so this makes any upcoming additions easier.

This is arguably a bug fix, but nobody has complained about the existing
code being a problem either, so no backpatch is done.

Extracted from a larger patch by the same author.

Author: Gunnar "Nick" Bluth
Discussion: https://postgr.es/m/7c59265d-ac50-b0aa-ca1e-65e8bd27642a@pro-open.de
This commit is contained in:
Michael Paquier 2022-03-01 12:52:25 +09:00
parent 7a85073290
commit a33e17f210
1 changed files with 33 additions and 10 deletions
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43
src/bin/pg_rewind/pg_rewind.c
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@ -23,6 +23,7 @@
#include "common/restricted_token.h"
#include "common/string.h"
#include "fe_utils/recovery_gen.h"
#include "fe_utils/string_utils.h"
#include "file_ops.h"
#include "filemap.h"
#include "getopt_long.h"
@ -1016,8 +1017,8 @@ getRestoreCommand(const char *argv0)
{
int rc;
char postgres_exec_path[MAXPGPATH],
postgres_cmd[MAXPGPATH],
cmd_output[MAXPGPATH];
PQExpBuffer postgres_cmd;
if (!restore_wal)
return;
@ -1051,11 +1052,19 @@ getRestoreCommand(const char *argv0)
* Build a command able to retrieve the value of GUC parameter
* restore_command, if set.
*/
snprintf(postgres_cmd, sizeof(postgres_cmd),
"\"%s\" -D \"%s\" -C restore_command",
postgres_exec_path, datadir_target);
postgres_cmd = createPQExpBuffer();
if (!pipe_read_line(postgres_cmd, cmd_output, sizeof(cmd_output)))
/* path to postgres, properly quoted */
appendShellString(postgres_cmd, postgres_exec_path);
/* add -D switch, with properly quoted data directory */
appendPQExpBufferStr(postgres_cmd, " -D ");
appendShellString(postgres_cmd, datadir_target);
/* add -C switch, for restore_command */
appendPQExpBufferStr(postgres_cmd, " -C restore_command");
if (!pipe_read_line(postgres_cmd->data, cmd_output, sizeof(cmd_output)))
exit(1);
(void) pg_strip_crlf(cmd_output);
@ -1067,6 +1076,8 @@ getRestoreCommand(const char *argv0)
pg_log_debug("using for rewind restore_command = \'%s\'",
restore_command);
destroyPQExpBuffer(postgres_cmd);
}
@ -1080,7 +1091,7 @@ ensureCleanShutdown(const char *argv0)
int ret;
#define MAXCMDLEN (2 * MAXPGPATH)
char exec_path[MAXPGPATH];
char cmd[MAXCMDLEN];
PQExpBuffer postgres_cmd;
/* locate postgres binary */
if ((ret = find_other_exec(argv0, "postgres",
@ -1119,14 +1130,26 @@ ensureCleanShutdown(const char *argv0)
* fsync here. This makes the recovery faster, and the target data folder
* is synced at the end anyway.
*/
snprintf(cmd, MAXCMDLEN, "\"%s\" --single -F -D \"%s\" template1 < \"%s\"",
exec_path, datadir_target, DEVNULL);
postgres_cmd = createPQExpBuffer();
if (system(cmd) != 0)
/* path to postgres, properly quoted */
appendShellString(postgres_cmd, exec_path);
/* add set of options with properly quoted data directory */
appendPQExpBufferStr(postgres_cmd, " --single -F -D ");
appendShellString(postgres_cmd, datadir_target);
/* finish with the database name, and a properly quoted redirection */
appendPQExpBufferStr(postgres_cmd, " template1 < ");
appendShellString(postgres_cmd, DEVNULL);
if (system(postgres_cmd->data) != 0)
{
pg_log_error("postgres single-user mode in target cluster failed");
pg_fatal("Command was: %s", cmd);
pg_fatal("Command was: %s", postgres_cmd->data);
}
destroyPQExpBuffer(postgres_cmd);
}
static void