Add citus_nodes view (#7968)

DESCRIPTION: Adds `citus_nodes` view that displays the node name, port,
role, and "active" for nodes in the cluster.

This PR adds `citus_nodes` view to the `pg_catalog` schema. The
`citus_nodes` view is created in the `citus` schema and is used to
display the node name, port, role, and active status of each node in the
`pg_dist_node` table.

The view is granted `SELECT` permission to the `PUBLIC` role and is set
to the `pg_catalog` schema.

Test cases was added to `multi_cluster_management` tests. 

structs.py was modified to add white spaces as `citus_indent` required.

---------

Co-authored-by: Alper Kocatas <alperkocatas@microsoft.com>

src/backend/distributed/sql/citus--13.0-1--13.1-1.sql

@@ -50,3 +50,4 @@ DROP VIEW IF EXISTS pg_catalog.citus_lock_waits;
 #include "udfs/citus_is_primary_node/13.1-1.sql"
 #include "udfs/citus_stat_counters/13.1-1.sql"
 #include "udfs/citus_stat_counters_reset/13.1-1.sql"
+#include "udfs/citus_nodes/13.1-1.sql"

src/backend/distributed/sql/downgrades/citus--13.1-1--13.0-1.sql

@@ -45,3 +45,4 @@ DROP FUNCTION citus_internal.is_replication_origin_tracking_active();
 DROP VIEW pg_catalog.citus_stat_counters;
 DROP FUNCTION pg_catalog.citus_stat_counters(oid);
 DROP FUNCTION pg_catalog.citus_stat_counters_reset(oid);
+DROP VIEW IF EXISTS pg_catalog.citus_nodes;

src/backend/distributed/sql/udfs/citus_nodes/13.1-1.sql

@@ -0,0 +1,18 @@
+SET search_path = 'pg_catalog';
+DROP VIEW IF EXISTS pg_catalog.citus_nodes;
+
+CREATE OR REPLACE VIEW citus.citus_nodes AS
+SELECT
+    nodename,
+    nodeport,
+    CASE
+        WHEN groupid = 0 THEN 'coordinator'
+        ELSE 'worker'
+    END AS role,
+    isactive AS active
+FROM pg_dist_node;
+
+ALTER VIEW citus.citus_nodes SET SCHEMA pg_catalog;
+GRANT SELECT ON pg_catalog.citus_nodes TO PUBLIC;
+
+RESET search_path;

src/backend/distributed/sql/udfs/citus_nodes/latest.sql

@@ -0,0 +1,18 @@
+SET search_path = 'pg_catalog';
+DROP VIEW IF EXISTS pg_catalog.citus_nodes;
+
+CREATE OR REPLACE VIEW citus.citus_nodes AS
+SELECT
+    nodename,
+    nodeport,
+    CASE
+        WHEN groupid = 0 THEN 'coordinator'
+        ELSE 'worker'
+    END AS role,
+    isactive AS active
+FROM pg_dist_node;
+
+ALTER VIEW citus.citus_nodes SET SCHEMA pg_catalog;
+GRANT SELECT ON pg_catalog.citus_nodes TO PUBLIC;
+
+RESET search_path;

src/test/regress/expected/multi_cluster_management.out

@@ -72,6 +72,45 @@ SELECT master_get_active_worker_nodes();
  (localhost,57637)
 (2 rows)
 
+-- get all nodes
+SELECT * from citus_nodes;
+ nodename  | nodeport |    role     | active
+---------------------------------------------------------------------
+ localhost |    57637 | worker      | t
+ localhost |    57638 | worker      | t
+ localhost |    57636 | coordinator | t
+(3 rows)
+
+-- get get active nodes
+SELECT * from citus_nodes where active = 't';
+ nodename  | nodeport |    role     | active
+---------------------------------------------------------------------
+ localhost |    57637 | worker      | t
+ localhost |    57638 | worker      | t
+ localhost |    57636 | coordinator | t
+(3 rows)
+
+-- get coordinator nodes
+SELECT * from citus_nodes where role = 'coordinator';
+ nodename  | nodeport |    role     | active
+---------------------------------------------------------------------
+ localhost |    57636 | coordinator | t
+(1 row)
+
+-- get worker nodes
+SELECT * from citus_nodes where role = 'worker';
+ nodename  | nodeport |  role  | active
+---------------------------------------------------------------------
+ localhost |    57637 | worker | t
+ localhost |    57638 | worker | t
+(2 rows)
+
+-- get nodes with unknown role
+SELECT * from citus_nodes where role = 'foo';
+ nodename | nodeport | role | active
+---------------------------------------------------------------------
+(0 rows)
+
 -- try to add a node that is already in the cluster
 SELECT * FROM master_add_node('localhost', :worker_1_port);
  master_add_node
@@ -126,6 +165,34 @@ SELECT master_get_active_worker_nodes();
  (localhost,57637)
 (1 row)
 
+-- get get active nodes
+SELECT * from citus_nodes where active = 't';
+ nodename  | nodeport |    role     | active
+---------------------------------------------------------------------
+ localhost |    57636 | coordinator | t
+ localhost |    57637 | worker      | t
+(2 rows)
+
+-- get get inactive nodes
+SELECT * from citus_nodes where active = 'f';
+ nodename  | nodeport |  role  | active
+---------------------------------------------------------------------
+ localhost |    57638 | worker | f
+(1 row)
+
+-- make sure non-superusers can access the view
+CREATE ROLE normaluser;
+SET ROLE normaluser;
+SELECT * FROM citus_nodes;
+ nodename  | nodeport |    role     | active
+---------------------------------------------------------------------
+ localhost |    57636 | coordinator | t
+ localhost |    57638 | worker      | f
+ localhost |    57637 | worker      | t
+(3 rows)
+
+SET ROLE postgres;
+DROP ROLE normaluser;
 -- add some shard placements to the cluster
 SET citus.shard_count TO 16;
 SET citus.shard_replication_factor TO 1;

src/test/regress/expected/multi_extension.out

@@ -1483,8 +1483,9 @@ SELECT * FROM multi_extension.print_extension_changes();
                                                                 | function citus_stat_counters(oid) SETOF record
                                                                 | function citus_stat_counters_reset(oid) void
                                                                 | function citus_unmark_object_distributed(oid,oid,integer,boolean) void
+                                                                | view citus_nodes
                                                                 | view citus_stat_counters
-(30 rows)
+(31 rows)
 
 DROP TABLE multi_extension.prev_objects, multi_extension.extension_diff;
 -- show running version

src/test/regress/expected/upgrade_list_citus_objects.out

@@ -380,6 +380,7 @@ ORDER BY 1;
  view citus_dist_stat_activity
  view citus_lock_waits
  view citus_locks
+ view citus_nodes
  view citus_schema.citus_schemas
  view citus_schema.citus_tables
  view citus_shard_indexes_on_worker
@@ -392,6 +393,6 @@ ORDER BY 1;
  view citus_stat_tenants_local
  view pg_dist_shard_placement
  view time_partitions
-(361 rows)
+(362 rows)
 
 DROP TABLE extension_basic_types;

src/test/regress/mitmscripts/structs.py

@@ -137,18 +137,21 @@ class Message:
 
 class SharedMessage(Message, metaclass=MessageMeta):
     "A message which could be sent by either the frontend or the backend"
+
     _msgtypes = dict()
     _classes = dict()
 
 
 class FrontendMessage(Message, metaclass=MessageMeta):
     "A message which will only be sent be a backend"
+
     _msgtypes = dict()
     _classes = dict()
 
 
 class BackendMessage(Message, metaclass=MessageMeta):
     "A message which will only be sent be a frontend"
+
     _msgtypes = dict()
     _classes = dict()
 

src/test/regress/sql/multi_cluster_management.sql

@@ -32,6 +32,21 @@ SELECT result FROM run_command_on_workers('SELECT citus_is_primary_node()');
 -- get the active nodes
 SELECT master_get_active_worker_nodes();
 
+-- get all nodes
+SELECT * from citus_nodes;
+
+-- get get active nodes
+SELECT * from citus_nodes where active = 't';
+
+-- get coordinator nodes
+SELECT * from citus_nodes where role = 'coordinator';
+
+-- get worker nodes
+SELECT * from citus_nodes where role = 'worker';
+
+-- get nodes with unknown role
+SELECT * from citus_nodes where role = 'foo';
+
 -- try to add a node that is already in the cluster
 SELECT * FROM master_add_node('localhost', :worker_1_port);
 
@@ -51,6 +66,20 @@ SELECT citus_disable_node('localhost', :worker_2_port);
 SELECT public.wait_until_metadata_sync(20000);
 SELECT master_get_active_worker_nodes();
 
+-- get get active nodes
+SELECT * from citus_nodes where active = 't';
+
+-- get get inactive nodes
+SELECT * from citus_nodes where active = 'f';
+
+-- make sure non-superusers can access the view
+CREATE ROLE normaluser;
+SET ROLE normaluser;
+SELECT * FROM citus_nodes;
+
+SET ROLE postgres;
+DROP ROLE normaluser;
+
 -- add some shard placements to the cluster
 SET citus.shard_count TO 16;
 SET citus.shard_replication_factor TO 1;