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Disable logical replication subscribers (#10249)

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Drop logical replication subscribers 
before compute starts on a non-main branch.

Add new compute_ctl spec flag: drop_subscriptions_before_start
If it is set, drop all the subscriptions from the compute node
before it starts.

To avoid race on compute start, use new GUC
neon.disable_logical_replication_subscribers
to temporarily disable logical replication workers until we drop the
subscriptions.

Ensure that we drop subscriptions exactly once when endpoint starts on a
new branch.
It is essential, because otherwise, we may drop not only inherited, but
newly created subscriptions.

We cannot rely only on spec.drop_subscriptions_before_start flag,
because if for some reason compute restarts inside VM,
it will start again with the same spec and flag value.

To handle this, we save the fact of the operation in the database
in the neon.drop_subscriptions_done table.
If the table does not exist, we assume that the operation was never
performed, so we must do it.
If table exists, we check if the operation was performed on the current
timeline.

fixes: https://github.com/neondatabase/neon/issues/8790
This commit is contained in:
Anastasia Lubennikova
2025-01-23 11:02:15 +00:00
committed by GitHub
parent 92d95b08cf
commit 8e8df1b453
17 changed files with 413 additions and 31 deletions
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11
compute_tools/src/sql/drop_subscriptions.sql Normal file
View File

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DO $$
DECLARE
subname TEXT;
BEGIN
FOR subname IN SELECT pg_subscription.subname FROM pg_subscription WHERE subdbid = (SELECT oid FROM pg_database WHERE datname = {datname_str}) LOOP
EXECUTE format('ALTER SUBSCRIPTION %I DISABLE;', subname);
EXECUTE format('ALTER SUBSCRIPTION %I SET (slot_name = NONE);', subname);
EXECUTE format('DROP SUBSCRIPTION %I;', subname);
END LOOP;
END;
$$;