It is often useful to be able to sync the metadata in parallel
across nodes.
Also citus_finalize_upgrade_to_citus11() uses
start_metadata_sync_to_primary_nodes() after this commit.
Note that this commit does not parallelize all pieces of node
activation or metadata syncing. Instead, it tries to parallelize
potenially large parts of metadata, which is the objects and
distributed tables (in general Citus tables).
In the future, it would be nice to sync the reference tables
in parallel across nodes.
Create ~720 distributed tables / ~23450 shards
```SQL
-- declaratively partitioned table
CREATE TABLE github_events_looooooooooooooong_name (
event_id bigint,
event_type text,
event_public boolean,
repo_id bigint,
payload jsonb,
repo jsonb,
actor jsonb,
org jsonb,
created_at timestamp
) PARTITION BY RANGE (created_at);
SELECT create_time_partitions(
table_name := 'github_events_looooooooooooooong_name',
partition_interval := '1 day',
end_at := now() + '24 months'
);
CREATE INDEX ON github_events_looooooooooooooong_name USING btree (event_id, event_type, event_public, repo_id);
SELECT create_distributed_table('github_events_looooooooooooooong_name', 'repo_id');
SET client_min_messages TO ERROR;
```
across 1 node: almost same as expected
```SQL
SELECT start_metadata_sync_to_primary_nodes();
Time: 15664.418 ms (00:15.664)
select start_metadata_sync_to_node(nodename,nodeport) from pg_dist_node;
Time: 14284.069 ms (00:14.284)
```
across 7 nodes: ~3.5x improvement
```SQL
SELECT start_metadata_sync_to_primary_nodes();
┌──────────────────────────────────────┐
│ start_metadata_sync_to_primary_nodes │
├──────────────────────────────────────┤
│ t │
└──────────────────────────────────────┘
(1 row)
Time: 25711.192 ms (00:25.711)
-- across 7 nodes
select start_metadata_sync_to_node(nodename,nodeport) from pg_dist_node;
Time: 82126.075 ms (01:22.126)
```
Before this commit, we had:
```SQL
SELECT citus_disable_node(nodename, nodeport, force boolean DEFAULT false)
```
Where, we allow forcing to disable first worker node with
`force:=true`. However, it entails the risk for losing
data / diverging placement data etc.
With `force` flag, we control disabling the first worker node,
and with `async` flag we control whether the changes are done
via bg worker or immediately.
```SQL
SELECT citus_disable_node(nodename, nodeport, force boolean DEFAULT false, sync boolean DEFAULT false)
```
Where we can achieve all the following:
| Mode | Data loss possibility | Can run in 2PC | Handle multiple node failures | Immediately effective |
| --- |--- |--- |--- |--- |
| force:false, sync: false | false | true | true | false |
| force:false, sync: true | false | false | false | true |
| force:true, sync: false | true | true | true | false |
| force:true, sync: true | false | false | false | true |
Marco Slot
Onder Kalaci