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Try to return earlier in idempotent master_add_node

pull/4767/head
Marco Slot 2021-03-01 15:45:16 +01:00
parent 6c409b5d3e
commit f25de6a0e3
1 changed files with 21 additions and 3 deletions
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24
src/backend/distributed/metadata/node_metadata.c
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@ -1384,16 +1384,34 @@ AddNodeMetadata(char *nodeName, int32 nodePort,
*nodeAlreadyExists = false;
/*
* Take an exclusive lock on pg_dist_node to serialize node changes.
* Prevent / wait for concurrent modification before checking whether
* the worker already exists in pg_dist_node.
*/
LockRelationOid(DistNodeRelationId(), RowShareLock);
WorkerNode *workerNode = FindWorkerNodeAnyCluster(nodeName, nodePort);
if (workerNode != NULL)
{
/* return early without holding locks when the node already exists */
*nodeAlreadyExists = true;
return workerNode->nodeId;
}
/*
* We are going to change pg_dist_node, prevent any concurrent reads that
* are not tolerant to concurrent node addition by taking an exclusive
* lock (conflicts with all but AccessShareLock).
*
* We may want to relax or have more fine-grained locking in the future
* to allow users to add multiple nodes concurrently.
*/
LockRelationOid(DistNodeRelationId(), ExclusiveLock);
WorkerNode *workerNode = FindWorkerNodeAnyCluster(nodeName, nodePort);
/* recheck in case 2 node additions pass the first check concurrently */
workerNode = FindWorkerNodeAnyCluster(nodeName, nodePort);
if (workerNode != NULL)
{
/* fill return data and return */
*nodeAlreadyExists = true;
return workerNode->nodeId;