Improvements to repmgr cluster show

Add documentation; show recovery status in --csv mode.

README.md

@@ -23,10 +23,12 @@ Simply:
 Ensure `pg_config` for the target PostgreSQL version is in `$PATH`.
 
 
-Commands
---------
+Reference
+---------
 
-Currently available:
+### repmgr commands
+
+The following commands are available:
 
     repmgr primary register
     repmgr primary unregister
@@ -38,10 +40,64 @@ Currently available:
     repmgr standby follow
 
     repmgr bdr register
+    repmgr bdr unregister
 
+    repmgr cluster show
     repmgr cluster event [--all] [--node-id] [--node-name] [--event] [--event-matching]
 
 
+* `primary register`
+
+    Registers a primary in a streaming replication cluster, and configures
+    it for use with repmgr.  This command needs to be executed before any
+    standby nodes are registered.
+
+    `master register` can be used as an alias for `primary register`.
+
+* `cluster show`
+
+    Displays information about each active node in the replication cluster. This
+    command polls each registered server and shows its role (`master` / `standby` /
+    `bdr`) and status. It polls each server directly and can be run on any node
+    in the cluster; this is also useful when analyzing connectivity from a particular
+    node.
+
+    This command requires either a valid `repmgr.conf` file or a database connection
+    string to one of the registered nodes; no  additional arguments are needed.
+
+    Example:
+
+        $ repmgr -f /etc/repmgr.conf cluster show
+
+         ID | Name  | Role    | Status    | Upstream | Connection string
+        ----+-------+---------+-----------+----------+-----------------------------------------
+         1  | node1 | primary | * running |          | host=db_node1 dbname=repmgr user=repmgr
+         2  | node2 | standby |   running | node1    | host=db_node2 dbname=repmgr user=repmgr
+         3  | node3 | standby |   running | node1    | host=db_node3 dbname=repmgr user=repmgr
+
+    To show database connection errors when polling nodes, run the command in
+    `--verbose` mode.
+
+    The `cluster show` command accepts an optional parameter `--csv`, which
+    outputs the replication cluster's status in a simple CSV format, suitable for
+    parsing by scripts:
+
+        $ repmgr -f /etc/repmgr.conf cluster show --csv
+        1,-1,-1
+        2,0,0
+        3,0,1
+
+    The columns have following meanings:
+
+        - node ID
+        - availability (0 = available, -1 = unavailable)
+        - recovery state (0 = not in recovery, 1 = in recovery, -1 = unknown)
+
+    Note that the availability is tested by connecting from the node where
+    `repmgr cluster show` is executed, and does not necessarily imply the node
+    is down.
+
+
 Backwards compatibility
 -----------------------
 

dbutils.c

@@ -1303,6 +1303,7 @@ _populate_node_record(PGresult *res, t_node_info *node_info, int row)
 
 	/* Set remaining struct fields with default values */
 	node_info->node_status = NODE_STATUS_UNKNOWN;
+	node_info->recovery_type = RECTYPE_UNKNOWN;
 	node_info->last_wal_receive_lsn = InvalidXLogRecPtr;
 	node_info->monitoring_state = MS_NORMAL;
 	node_info->conn = NULL;

dbutils.h

@@ -32,7 +32,7 @@ typedef enum {
 } ExtensionStatus;
 
 typedef enum {
-	RECTYPE_UNKNOWN = 0,
+	RECTYPE_UNKNOWN = -1,
 	RECTYPE_PRIMARY,
 	RECTYPE_STANDBY
 } RecoveryType;
@@ -79,6 +79,7 @@ typedef struct s_node_info
 	/* used during failover to track node status */
 	XLogRecPtr	  last_wal_receive_lsn;
 	NodeStatus	  node_status;
+	RecoveryType  recovery_type;
 	MonitoringState monitoring_state;
 	PGconn		 *conn;
 	/* for ad-hoc use e.g. when working with a list of nodes */
@@ -100,6 +101,7 @@ typedef struct s_node_info
 	"", \
 	InvalidXLogRecPtr, \
 	NODE_STATUS_UNKNOWN, \
+	RECTYPE_UNKNOWN,  \
 	MS_NORMAL, \
 	NULL, \
 	"" \

doc/changes-in-repmgr4.md

@@ -1,4 +1,12 @@
 
+Standardisation on `primary`
+----------------------------
+
+To standardise terminolgy, `primary` is used to denote the read/write
+node in a streaming replication cluster. `master` is still accepted
+as a synonym (e.g. `repmgr master register`).
+
+
 New command line options
 ------------------------
 
@@ -29,6 +37,18 @@ Changed command line options
   configuration file option `monitoring_history`. This enables the
   setting to be changed without having to modify system service files.
 
+Changes to repmgr commands
+--------------------------
+
+
+### `repmgr cluster show`
+
+This now displays the role of each node (e.g. `primary`, `standby`)
+and its status in separate columns.
+
+The `--csv` option now emits a third column indicating the recovery
+status of the node.
+
 
 Removed configuration file options
 ----------------------------------

repmgr-action-cluster.c

@@ -88,7 +88,6 @@ do_cluster_show(void)
 
 	for (cell = nodes.head; cell; cell = cell->next)
 	{
-		RecoveryType rec_type = RECTYPE_UNKNOWN;
 		PQExpBufferData details;
 
 		cell->node_info->conn = establish_db_connection_quiet(cell->node_info->conninfo);
@@ -97,14 +96,12 @@ do_cluster_show(void)
 		{
 			cell->node_info->node_status = NODE_STATUS_UP;
 
-			if (cell->node_info->type != BDR)
-			{
-				rec_type = get_recovery_type(cell->node_info->conn);
-			}
+			cell->node_info->recovery_type = get_recovery_type(cell->node_info->conn);
 		}
 		else
 		{
 			cell->node_info->node_status = NODE_STATUS_DOWN;
+			cell->node_info->recovery_type = RECTYPE_UNKNOWN;
 		}
 
 		initPQExpBuffer(&details);
@@ -122,7 +119,7 @@ do_cluster_show(void)
 				{
 					if (cell->node_info->active == true)
 					{
-						switch (rec_type)
+						switch (cell->node_info->recovery_type)
 						{
 							case RECTYPE_PRIMARY:
 								appendPQExpBuffer(&details, "* running");
@@ -137,7 +134,7 @@ do_cluster_show(void)
 					}
 					else
 					{
-						if (rec_type == RECTYPE_PRIMARY)
+						if (cell->node_info->recovery_type == RECTYPE_PRIMARY)
 							appendPQExpBuffer(&details, "! running");
 						else
 							appendPQExpBuffer(&details, "! running as standby");
@@ -162,7 +159,7 @@ do_cluster_show(void)
 				{
 					if (cell->node_info->active == true)
 					{
-						switch (rec_type)
+						switch (cell->node_info->recovery_type)
 						{
 							case RECTYPE_STANDBY:
 								appendPQExpBuffer(&details, "  running");
@@ -177,7 +174,7 @@ do_cluster_show(void)
 					}
 					else
 					{
-						if (rec_type == RECTYPE_STANDBY)
+						if (cell->node_info->recovery_type == RECTYPE_STANDBY)
 							appendPQExpBuffer(&details, "! running");
 						else
 							appendPQExpBuffer(&details, "! running as primary");
@@ -216,6 +213,8 @@ do_cluster_show(void)
 			break;
 			case UNKNOWN:
 			{
+				/* this should never happen */
+				appendPQExpBuffer(&details, "? unknown node type");
 			}
 			break;
 		}
@@ -277,8 +276,29 @@ do_cluster_show(void)
 		if (runtime_options.csv)
 		{
 			int connection_status =	(PQstatus(conn) == CONNECTION_OK) ? 0 : -1;
+			int recovery_type = RECTYPE_UNKNOWN;
 
-			printf("%i,%d\n", cell->node_info->node_id, connection_status);
+			/*
+			 * here we explicitly convert the RecoveryType to integer values to
+			 * avoid implicit dependency on the values in the enum
+			 */
+			switch (cell->node_info->recovery_type)
+			{
+				case RECTYPE_UNKNOWN:
+					recovery_type = -1;
+					break;
+				case RECTYPE_PRIMARY:
+					recovery_type = 0;
+					break;
+				case RECTYPE_STANDBY:
+					recovery_type = 1;
+					break;
+			}
+
+			printf("%i,%i,%i\n",
+				   cell->node_info->node_id,
+				   connection_status,
+				   recovery_type);
 		}
 		else
 		{

repmgr-client.c

@@ -1048,6 +1048,10 @@ check_cli_parameters(const int action)
 			}
 
 		}
+		case CLUSTER_SHOW:
+			if (runtime_options.connection_param_provided)
+				config_file_required = false;
+			break;
 		case CLUSTER_EVENT:
 			/* no required parameters */
 			break;
@@ -1066,6 +1070,7 @@ check_cli_parameters(const int action)
 		{
 			case STANDBY_CLONE:
 			case STANDBY_FOLLOW:
+			case CLUSTER_SHOW:
 				break;
 			default:
 				item_list_append_format(&cli_warnings,