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repmgr/repmgr-action-daemon.c
Ian Barwick 2491b8ae52 Add functionality to "pause" repmgrd 
In some circumstances, e.g. while performing a switchover, it is essential
that repmgrd does not take any kind of failover action, as this will put
the cluster into an incorrect state.

Previously it was necessary to stop repmgrd on all nodes (or at least
those nodes which repmgrd would consider as promotion candidates), however
this is a cumbersome and potentially risk-prone operation, particularly if the
replication cluster contains more than a couple of servers.

To prevent this issue from occurring, this patch introduces the ability
to "pause" repmgrd on all nodes wth a single command ("repmgr daemon pause")
which notifies repmgrd not to take any failover action until the node
is "unpaused" ("repmgr daemon unpause").

"repmgr daemon status" provides an overview of each node and whether repmgrd
is running, and if so whether it is paused.

"repmgr standby switchover" has been modified to automatically pause repmgrd
while carrying out the switchover.

See documentation for further details.
2018-09-27 16:42:10 +09:00

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/*
* repmgr-action-daemon.c
*
* Implements repmgrd actions for the repmgr command line utility
* Copyright (c) 2ndQuadrant, 2010-2018
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "repmgr.h"
#include "repmgr-client-global.h"
#include "repmgr-action-daemon.h"
/*
* Possibly also show:
* - repmgrd start time?
* - repmgrd mode
* - priority
* - whether promotion candidate (due to zero priority/different location)
*/
typedef enum
{
STATUS_ID = 0,
STATUS_NAME,
STATUS_ROLE,
STATUS_PG,
STATUS_RUNNING,
STATUS_PID,
STATUS_PAUSED
} StatusHeader;
#define STATUS_HEADER_COUNT 7
struct ColHeader headers_status[STATUS_HEADER_COUNT];
static void fetch_node_records(PGconn *conn, NodeInfoList *node_list);
static void _do_repmgr_pause(bool pause);
void
do_daemon_status(void)
{
PGconn *conn = NULL;
NodeInfoList nodes = T_NODE_INFO_LIST_INITIALIZER;
NodeInfoListCell *cell = NULL;
int i;
RepmgrdInfo **repmgrd_info;
ItemList warnings = {NULL, NULL};
/* Connect to local database to obtain cluster connection data */
log_verbose(LOG_INFO, _("connecting to database"));
if (strlen(config_file_options.conninfo))
conn = establish_db_connection(config_file_options.conninfo, true);
else
conn = establish_db_connection_by_params(&source_conninfo, true);
fetch_node_records(conn, &nodes);
repmgrd_info = (RepmgrdInfo **) pg_malloc0(sizeof(RepmgrdInfo *) * nodes.node_count);
if (repmgrd_info == NULL)
{
log_error(_("unable to allocate memory"));
exit(ERR_OUT_OF_MEMORY);
}
strncpy(headers_status[STATUS_ID].title, _("ID"), MAXLEN);
strncpy(headers_status[STATUS_NAME].title, _("Name"), MAXLEN);
strncpy(headers_status[STATUS_ROLE].title, _("Role"), MAXLEN);
strncpy(headers_status[STATUS_PG].title, _("Status"), MAXLEN);
strncpy(headers_status[STATUS_RUNNING].title, _("repmgrd"), MAXLEN);
strncpy(headers_status[STATUS_PID].title, _("PID"), MAXLEN);
strncpy(headers_status[STATUS_PAUSED].title, _("Paused?"), MAXLEN);
for (i = 0; i < STATUS_HEADER_COUNT; i++)
{
headers_status[i].max_length = strlen(headers_status[i].title);
}
i = 0;
for (cell = nodes.head; cell; cell = cell->next)
{
int j;
repmgrd_info[i] = pg_malloc0(sizeof(RepmgrdInfo));
repmgrd_info[i]->node_id = cell->node_info->node_id;
repmgrd_info[i]->pid = UNKNOWN_PID;
repmgrd_info[i]->paused = false;
repmgrd_info[i]->running = false;
repmgrd_info[i]->pg_running = true;
cell->node_info->conn = establish_db_connection_quiet(cell->node_info->conninfo);
if (PQstatus(cell->node_info->conn) != CONNECTION_OK)
{
if (runtime_options.verbose)
{
char error[MAXLEN];
strncpy(error, PQerrorMessage(cell->node_info->conn), MAXLEN);
item_list_append_format(&warnings,
"when attempting to connect to node \"%s\" (ID: %i), following error encountered :\n\"%s\"",
cell->node_info->node_name, cell->node_info->node_id, trim(error));
}
else
{
item_list_append_format(&warnings,
"unable to connect to node \"%s\" (ID: %i)",
cell->node_info->node_name, cell->node_info->node_id);
}
repmgrd_info[i]->pg_running = false;
maxlen_snprintf(repmgrd_info[i]->pg_running_text, "%s", _("not running"));
maxlen_snprintf(repmgrd_info[i]->repmgrd_running, "%s", _("n/a"));
maxlen_snprintf(repmgrd_info[i]->pid_text, "%s", _("n/a"));
}
else
{
maxlen_snprintf(repmgrd_info[i]->pg_running_text, "%s", _("running"));
repmgrd_info[i]->pid = repmgrd_get_pid(cell->node_info->conn);
repmgrd_info[i]->running = repmgrd_is_running(cell->node_info->conn);
if (repmgrd_info[i]->running == true)
{
maxlen_snprintf(repmgrd_info[i]->repmgrd_running, "%s", _("running"));
}
else
{
maxlen_snprintf(repmgrd_info[i]->repmgrd_running, "%s", _("not running"));
}
if (repmgrd_info[i]->pid == UNKNOWN_PID)
{
maxlen_snprintf(repmgrd_info[i]->pid_text, "%s", _("n/a"));
}
else
{
maxlen_snprintf(repmgrd_info[i]->pid_text, "%i", repmgrd_info[i]->pid);
}
repmgrd_info[i]->paused = repmgrd_is_paused(cell->node_info->conn);
PQfinish(cell->node_info->conn);
}
headers_status[STATUS_NAME].cur_length = strlen(cell->node_info->node_name);
headers_status[STATUS_ROLE].cur_length = strlen(get_node_type_string(cell->node_info->type));
headers_status[STATUS_PID].cur_length = strlen(repmgrd_info[i]->pid_text);
headers_status[STATUS_RUNNING].cur_length = strlen(repmgrd_info[i]->repmgrd_running);
headers_status[STATUS_PG].cur_length = strlen(repmgrd_info[i]->pg_running_text);
for (j = 0; j < STATUS_HEADER_COUNT; j++)
{
if (headers_status[j].cur_length > headers_status[j].max_length)
{
headers_status[j].max_length = headers_status[j].cur_length;
}
}
i++;
}
/* Print column header row (text mode only) */
if (runtime_options.output_mode == OM_TEXT)
{
print_status_header(STATUS_HEADER_COUNT, headers_status);
}
i = 0;
for (cell = nodes.head; cell; cell = cell->next)
{
if (runtime_options.output_mode == OM_CSV)
{
printf("%i,%s,%s,%i,%i,%i,%i\n",
cell->node_info->node_id,
cell->node_info->node_name,
get_node_type_string(cell->node_info->type),
repmgrd_info[i]->pg_running ? 1 : 0,
repmgrd_info[i]->running ? 1 : 0,
repmgrd_info[i]->pid,
repmgrd_info[i]->paused ? 1 : 0);
}
else
{
printf(" %-*i ", headers_status[STATUS_ID].max_length, cell->node_info->node_id);
printf("| %-*s ", headers_status[STATUS_NAME].max_length, cell->node_info->node_name);
printf("| %-*s ", headers_status[STATUS_ROLE].max_length, get_node_type_string(cell->node_info->type));
printf("| %-*s ", headers_status[STATUS_PG].max_length, repmgrd_info[i]->pg_running_text);
printf("| %-*s ", headers_status[STATUS_RUNNING].max_length, repmgrd_info[i]->repmgrd_running);
printf("| %-*s ", headers_status[STATUS_PID].max_length, repmgrd_info[i]->pid_text);
if (repmgrd_info[i]->pid == UNKNOWN_PID)
printf("| %-*s ", headers_status[STATUS_PAUSED].max_length, "n/a");
else
printf("| %-*s ", headers_status[STATUS_PAUSED].max_length, repmgrd_info[i]->paused ? "yes" : "no");
printf("\n");
}
free(repmgrd_info[i]);
i++;
}
free(repmgrd_info);
/* emit any warnings */
if (warnings.head != NULL && runtime_options.terse == false && runtime_options.output_mode != OM_CSV)
{
ItemListCell *cell = NULL;
printf(_("\nWARNING: following issues were detected\n"));
for (cell = warnings.head; cell; cell = cell->next)
{
printf(_(" - %s\n"), cell->string);
}
if (runtime_options.verbose == false)
{
log_hint(_("execute with --verbose option to see connection error messages"));
}
}
}
void
do_daemon_pause(void)
{
_do_repmgr_pause(true);
}
void
do_daemon_unpause(void)
{
_do_repmgr_pause(false);
}
static void
_do_repmgr_pause(bool pause)
{
PGconn *conn = NULL;
NodeInfoList nodes = T_NODE_INFO_LIST_INITIALIZER;
NodeInfoListCell *cell = NULL;
RepmgrdInfo **repmgrd_info;
int i;
int error_nodes = 0;
repmgrd_info = (RepmgrdInfo **) pg_malloc0(sizeof(RepmgrdInfo *) * nodes.node_count);
if (repmgrd_info == NULL)
{
log_error(_("unable to allocate memory"));
exit(ERR_OUT_OF_MEMORY);
}
/* Connect to local database to obtain cluster connection data */
log_verbose(LOG_INFO, _("connecting to database"));
if (strlen(config_file_options.conninfo))
conn = establish_db_connection(config_file_options.conninfo, true);
else
conn = establish_db_connection_by_params(&source_conninfo, true);
fetch_node_records(conn, &nodes);
i = 0;
for (cell = nodes.head; cell; cell = cell->next)
{
repmgrd_info[i] = pg_malloc0(sizeof(RepmgrdInfo));
repmgrd_info[i]->node_id = cell->node_info->node_id;
log_verbose(LOG_DEBUG, "pausing node %i (%s)",
cell->node_info->node_id,
cell->node_info->node_name);
cell->node_info->conn = establish_db_connection_quiet(cell->node_info->conninfo);
if (PQstatus(cell->node_info->conn) != CONNECTION_OK)
{
log_warning(_("unable to connect to node %i"),
cell->node_info->node_id);
error_nodes++;
}
else
{
if (runtime_options.dry_run == true)
{
if (pause == true)
{
log_info(_("would pause node %i (%s) "),
cell->node_info->node_id,
cell->node_info->node_name);
}
else
{
log_info(_("would unpause node %i (%s) "),
cell->node_info->node_id,
cell->node_info->node_name);
}
}
else
{
bool success = repmgrd_pause(cell->node_info->conn, pause);
if (success == false)
error_nodes++;
log_notice(_("node %i (%s) %s"),
cell->node_info->node_id,
cell->node_info->node_name,
success == true
? pause == true ? "paused" : "unpaused"
: pause == true ? "not paused" : "not unpaused");
}
PQfinish(cell->node_info->conn);
}
i++;
}
if (error_nodes > 0)
{
if (pause == true)
{
log_error(_("unable to pause %i node(s)"), error_nodes);
}
else
{
log_error(_("unable to unpause %i node(s)"), error_nodes);
}
log_hint(_("execute \"repmgr daemon status\" to view current status"));
exit(ERR_REPMGRD_PAUSE);
}
exit(SUCCESS);
}
void
fetch_node_records(PGconn *conn, NodeInfoList *node_list)
{
bool success = get_all_node_records(conn, node_list);
if (success == false)
{
/* get_all_node_records() will display any error message */
PQfinish(conn);
exit(ERR_BAD_CONFIG);
}
if (node_list->node_count == 0)
{
log_error(_("no node records were found"));
log_hint(_("ensure at least one node is registered"));
PQfinish(conn);
exit(ERR_BAD_CONFIG);
}
}
void do_daemon_help(void)
{
print_help_header();
printf(_("Usage:\n"));
printf(_(" %s [OPTIONS] daemon status\n"), progname());
printf(_(" %s [OPTIONS] daemon pause\n"), progname());
printf(_(" %s [OPTIONS] daemon unpause\n"), progname());
puts("");
printf(_("DAEMON STATUS\n"));
puts("");
printf(_(" \"daemon status\" shows the status of repmgrd on each node in the cluster\n"));
puts("");
printf(_(" --csv emit output as CSV\n"));
printf(_(" --verbose show text of database connection error messages\n"));
puts("");
printf(_("DAEMON PAUSE\n"));
puts("");
printf(_(" \"daemon pause\" instructs repmgrd on each node to pause failover detection\n"));
puts("");
printf(_(" --dry-run check if nodes are reachable but don't pause repmgrd\n"));
puts("");
printf(_("DAEMON PAUSE\n"));
puts("");
printf(_(" \"daemon unpause\" instructs repmgrd on each node to resume failover detection\n"));
puts("");
printf(_(" --dry-run check if nodes are reachable but don't unpause repmgrd\n"));
puts("");
puts("");
}
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