Ensure we're not going beyond the configured limits of max_coordinators or

max_datanodes

The user can still break things by first setting a high value for max_datanodes
or max_coordinators and then lowering it again after adding nodes. So this
basic check is not enough, but better than what we've currently.

diff --git a/src/backend/pgxc/nodemgr/nodemgr.c b/src/backend/pgxc/nodemgr/nodemgr.c
index 5e3290d419fa54736638f4e5038a9a80ef7a89eb..5ae6fe5f0567ca210006a015d92f69f8ebbdd1f8 100644 (file)
--- a/src/backend/pgxc/nodemgr/nodemgr.c
+++ b/src/backend/pgxc/nodemgr/nodemgr.c
@@ -37,6 +37,7 @@
 #define MAX_TRIES_FOR_NID      200
 
 static Datum generate_node_id(const char *node_name);
+static void count_coords_datanodes(Relation rel, int *num_coord, int *num_dns);
 
 /*
  * GUC parameters.
@@ -222,7 +223,7 @@ check_node_options(const char *node_name, List *options, char **node_host,
        if (*node_type == PGXC_NODE_DATANODE && NumDataNodes >= MaxDataNodes)
                ereport(ERROR,
                                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-                                errmsg("Too many datanodes, current value of max_data_nodes is %d",
+                                errmsg("Too many datanodes, current value of max_datanodes is %d",
                                                MaxDataNodes)));
 
 #endif
@@ -314,6 +315,39 @@ cmp_nodes(const void *p1, const void *p2)
        return 1;
 }
 
+/*
+ * Count the number of coordinators and datanodes configured so far.
+ */
+static void
+count_coords_datanodes(Relation rel, int *num_coord, int *num_dns)
+{
+       int                     coordCount = 0, dnCount = 0;
+       HeapScanDesc scan;
+       HeapTuple   tuple;
+
+       scan = heap_beginscan(rel, SnapshotSelf, 0, NULL);
+       while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
+       {
+               Form_pgxc_node  nodeForm = (Form_pgxc_node) GETSTRUCT(tuple);
+
+               /* Take definition for given node type */
+               switch (nodeForm->node_type)
+               {
+                       case PGXC_NODE_COORDINATOR:
+                               coordCount++;
+                               break;
+                       case PGXC_NODE_DATANODE:
+                               dnCount++;
+                               break;
+                       default:
+                               break;
+               }
+       }
+       heap_endscan(scan);
+
+       *num_coord = coordCount;
+       *num_dns = dnCount;
+}
 
 /*
  * PgxcNodeListAndCount
@@ -692,6 +726,7 @@ PgxcNodeCreate(CreateNodeStmt *stmt)
        bool            is_primary = false;
        bool            is_preferred = false;
        Datum           node_id;
+       int                     coordCount = 0, dnCount = 0;
 
        /* Only a DB administrator can add nodes */
        if (!superuser())
@@ -763,7 +798,34 @@ PgxcNodeCreate(CreateNodeStmt *stmt)
         * There could be a relation race here if a similar Oid
         * being created before the heap is inserted.
         */
-       pgxcnodesrel = heap_open(PgxcNodeRelationId, RowExclusiveLock);
+       pgxcnodesrel = heap_open(PgxcNodeRelationId, AccessExclusiveLock);
+
+       /*
+        * Get the count of datanodes and coordinators added so far and make sure
+        * we're not exceeding the configured limits
+        *
+        * XXX This is not full proof because someone may first set
+        * max_coordinators or max_datanodes to a high value, add nodes and then
+        * lower the value again.
+        */
+       count_coords_datanodes(pgxcnodesrel, &coordCount, &dnCount);
+
+       if ((node_type == PGXC_NODE_DATANODE && dnCount >= MaxDataNodes) ||
+               (node_type == PGXC_NODE_COORDINATOR && coordCount >= MaxCoords))
+       {
+               ereport(ERROR,
+                               (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+                                errmsg("cannot add more than %d %s",
+                                        node_type == PGXC_NODE_COORDINATOR ?
+                                        MaxCoords : MaxDataNodes,
+                                        node_type == PGXC_NODE_COORDINATOR ?
+                                        "coordinators" : "datanodes"),
+                                errhint("increase the value of %s GUC and restart the cluster",
+                                        node_type == PGXC_NODE_COORDINATOR ?
+                                        "max_coordinators" : "max_datanodes"
+                                        )));
+
+       }
 
        /* Build entry tuple */
        values[Anum_pgxc_node_name - 1] = DirectFunctionCall1(namein, CStringGetDatum(node_name));
@@ -781,7 +843,7 @@ PgxcNodeCreate(CreateNodeStmt *stmt)
 
        CatalogUpdateIndexes(pgxcnodesrel, htup);
 
-       heap_close(pgxcnodesrel, RowExclusiveLock);
+       heap_close(pgxcnodesrel, AccessExclusiveLock);
 }
 
 /*
@@ -805,6 +867,7 @@ PgxcNodeAlter(AlterNodeStmt *stmt)
        bool            new_record_nulls[Natts_pgxc_node];
        bool            new_record_repl[Natts_pgxc_node];
        uint32          node_id;
+       int                     coordCount = 0, dnCount = 0;
 
        /* Only a DB administrator can alter cluster nodes */
        if (!superuser())
@@ -813,7 +876,7 @@ PgxcNodeAlter(AlterNodeStmt *stmt)
                                 errmsg("must be superuser to change cluster nodes")));
 
        /* Look at the node tuple, and take exclusive lock on it */
-       rel = heap_open(PgxcNodeRelationId, RowExclusiveLock);
+       rel = heap_open(PgxcNodeRelationId, AccessExclusiveLock);
 
        /* Check that node exists */
        if (!OidIsValid(nodeOid))
@@ -856,6 +919,29 @@ PgxcNodeAlter(AlterNodeStmt *stmt)
                                 errmsg("PGXC node %s: two nodes cannot be primary",
                                                node_name)));
 
+       /*
+        * Get the count of datanodes and coordinators added so far and make sure
+        * we're not exceeding the configured limits
+        */
+       count_coords_datanodes(rel, &coordCount, &dnCount);
+
+       if ((node_type == PGXC_NODE_DATANODE && dnCount >= MaxDataNodes) ||
+               (node_type == PGXC_NODE_COORDINATOR && coordCount >= MaxCoords))
+       {
+               ereport(ERROR,
+                               (errcode(ERRCODE_INSUFFICIENT_RESOURCES),
+                                errmsg("cannot add more than %d %s",
+                                        node_type == PGXC_NODE_COORDINATOR ?
+                                        MaxCoords : MaxDataNodes,
+                                        node_type == PGXC_NODE_COORDINATOR ?
+                                        "coordinators" : "datanodes"),
+                                errhint("increase the value of %s GUC and restart the cluster",
+                                        node_type == PGXC_NODE_COORDINATOR ?
+                                        "max_coordinators" : "max_datanodes"
+                                        )));
+
+       }
+
        /* Update values for catalog entry */
        MemSet(new_record, 0, sizeof(new_record));
        MemSet(new_record_nulls, false, sizeof(new_record_nulls));