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repmgr: only require 'wal_keep_segments' to be set in certain corner cases

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Now that repmgr uses pg_basebackup's `--xlog-method=stream` setting by
default, and enables provision of `restore_command`, there's no reason
to require `wal_keep_segments` to be set in the default use-case.

`repmgr standby clone` will now only fail with an error if `wal_keep_segments`
is zero and one of the following cases applies:

* `--rsync-only` clone with no `restore_command` set
* clone with pg_basebackup and `--xlog-method=fetch`
* -w/--wal-keep-segments specified on the command line

If, for whatever reason, it's necessary to perform a standby clone
with `wal_keep_segments=0` in one of the above cases, specifying
`-w/--wal-keep-segments=0` on the command line will effectively
override the check.

GitHub #204
This commit is contained in:
Ian Barwick
2016-09-21 16:42:14 +09:00
parent 5090b8cab1
commit 114c1bddcb
3 changed files with 72 additions and 37 deletions
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17
README.md
View File

@@ -287,7 +287,7 @@ both servers.
### PostgreSQL configuration
On the master server, a PostgreSQL instance must be initialised and running.
The following replication settings must be included in `postgresql.conf`:
The following replication settings may need to be adjusted:
# Enable replication connections; set this figure to at least one more
@@ -302,13 +302,6 @@ The following replication settings must be included in `postgresql.conf`:
wal_level = 'hot_standby'
# How much WAL to retain on the master to allow a temporarily
# disconnected standby to catch up again. The larger this is, the
# longer the standby can be disconnected. This is needed only in
# 9.3; from 9.4, replication slots can be used instead (see below).
wal_keep_segments = 5000
# Enable read-only queries on a standby
# (Note: this will be ignored on a master but we recommend including
# it anyway)
@@ -323,6 +316,14 @@ The following replication settings must be included in `postgresql.conf`:
# ignores archiving. Use something more sensible.
archive_command = '/bin/true'
# If cloning using rsync, or you have configured `pg_basebackup_options`
# in `repmgr.conf` to include the setting `--xlog-method=fetch`, *and*
# you have not set `restore_command` in `repmgr.conf`to fetch WAL files
# from another source such as Barman, you'll need to set `wal_keep_segments`
# to a high enough value to ensure that all WAL files generated while
# the standby is being cloned are retained until the standby starts up.
# wal_keep_segments = 5000
* * *

90
repmgr.c
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@@ -6478,7 +6478,17 @@ check_upstream_config(PGconn *conn, int server_version_num, bool exit_on_error)
int i;
bool config_ok = true;
char *wal_error_message = NULL;
t_basebackup_options backup_options = T_BASEBACKUP_OPTIONS_INITIALIZER;
bool xlog_stream = true;
/*
* Parse `pg_basebackup_options`, if set, to detect whether --xlog-method
* has been set to something other than `stream` (i.e. `fetch`), as
* this will influence some checks
*/
parse_pg_basebackup_options(options.pg_basebackup_options, &backup_options);
if (strlen(backup_options.xlog_method) && strcmp(backup_options.xlog_method, "stream") != 0)
xlog_stream = false;
/* Check that WAL level is set correctly */
if (server_version_num < 90400)
{
@@ -6582,35 +6592,66 @@ check_upstream_config(PGconn *conn, int server_version_num, bool exit_on_error)
}
/*
* physical replication slots not available or not requested, and Barman mode not used -
* ensure some reasonably high value set for `wal_keep_segments`
* physical replication slots not available or not requested - check if
* there are any circumstances where `wal_keep_segments` should be set
*/
else if (! runtime_options.without_barman && strcmp(options.barman_server, "") == 0)
{
i = guc_set_typed(conn, "wal_keep_segments", ">=",
runtime_options.wal_keep_segments, "integer");
if (i == 0 || i == -1)
bool check_wal_keep_segments = false;
char min_wal_keep_segments[MAXLEN] = "1";
/*
* -w/--wal-keep-segments was supplied - check against that value
*/
if (wal_keep_segments_used == true)
{
if (i == 0)
check_wal_keep_segments = true;
strncpy(min_wal_keep_segments, runtime_options.wal_keep_segments, MAXLEN);
}
/*
* A non-zero `wal_keep_segments` value will almost certainly be required
* if rsync mode is being used, or pg_basebackup with --xlog-method=fetch,
* *and* no restore command has been specified
*/
else if ( (runtime_options.rsync_only == true || xlog_stream == false)
&& strcmp(options.restore_command, "") == 0)
{
check_wal_keep_segments = true;
}
if (check_wal_keep_segments == true)
{
i = guc_set_typed(conn, "wal_keep_segments", ">=", min_wal_keep_segments, "integer");
if (i == 0 || i == -1)
{
log_err(_("parameter 'wal_keep_segments' must be be set to %s or greater (see the '-w' option or edit the postgresql.conf of the upstream server.)\n"),
runtime_options.wal_keep_segments);
if (server_version_num >= 90400)
if (i == 0)
{
log_hint(_("in PostgreSQL 9.4 and later, replication slots can be used, which "
"do not require 'wal_keep_segments' to be set to a high value "
"(set parameter 'use_replication_slots' in the configuration file to enable)\n"
log_err(_("parameter 'wal_keep_segments' on the upstream server must be be set to %s or greater\n"),
min_wal_keep_segments);
log_hint(_("Choose a value sufficiently high enough to retain enough WAL "
"until the standby has been cloned and started.\n "
"Alternatively set up WAL archiving using e.g. PgBarman and configure "
"'restore_command' in repmgr.conf to fetch WALs from there.\n"
));
if (server_version_num >= 90400)
{
log_hint(_("In PostgreSQL 9.4 and later, replication slots can be used, which "
"do not require 'wal_keep_segments' to be set "
"(set parameter 'use_replication_slots' in repmgr.conf to enable)\n"
));
}
}
}
if (exit_on_error == true)
{
PQfinish(conn);
exit(ERR_BAD_CONFIG);
}
if (exit_on_error == true)
{
PQfinish(conn);
exit(ERR_BAD_CONFIG);
}
config_ok = false;
config_ok = false;
}
}
}
@@ -6687,18 +6728,14 @@ check_upstream_config(PGconn *conn, int server_version_num, bool exit_on_error)
if (!runtime_options.rsync_only)
{
t_basebackup_options backup_options = T_BASEBACKUP_OPTIONS_INITIALIZER;
PGconn **connections;
bool xlog_stream = true;
int i;
PGconn **connections;
int i;
int min_replication_connections = 1,
possible_replication_connections = 0;
t_conninfo_param_list repl_conninfo;
parse_pg_basebackup_options(options.pg_basebackup_options, &backup_options);
/* Make a copy of the connection parameter arrays, and append "replication" */
initialize_conninfo_params(&repl_conninfo, false);
@@ -6715,8 +6752,6 @@ check_upstream_config(PGconn *conn, int server_version_num, bool exit_on_error)
* --xlog-method set by user to something other than "stream" (should be "fetch",
* but we're just checking it's not "stream")
*/
if (strlen(backup_options.xlog_method) && strcmp(backup_options.xlog_method, "stream") != 0)
xlog_stream = false;
if (xlog_stream == true)
min_replication_connections += 1;
@@ -6751,7 +6786,6 @@ check_upstream_config(PGconn *conn, int server_version_num, bool exit_on_error)
log_err(_("unable to establish necessary replication connections\n"));
log_hint(_("increase 'max_wal_senders' by at least %i\n"), min_replication_connections - possible_replication_connections);
if (exit_on_error == true)
{
PQfinish(conn);

2
repmgr.h
View File

@@ -36,7 +36,7 @@
#define ERRBUFF_SIZE 512
#define DEFAULT_WAL_KEEP_SEGMENTS "5000"
#define DEFAULT_WAL_KEEP_SEGMENTS "0"
#define DEFAULT_DEST_DIR "."
#define DEFAULT_REPMGR_SCHEMA_PREFIX "repmgr_"
#define DEFAULT_PRIORITY 100