Re: Perform streaming logical transactions by background workers and parallel apply
Amit Kapila <amit.kapila16@gmail.com>
On Fri, Nov 11, 2022 at 2:12 PM houzj.fnst@fujitsu.com
<houzj.fnst@fujitsu.com> wrote:
>
Few comments on v46-0001:
======================
1.
+static void
+apply_handle_stream_abort(StringInfo s)
{
...
+ /* Send STREAM ABORT message to the parallel apply worker. */
+ parallel_apply_send_data(winfo, s->len, s->data);
+
+ if (abort_toplevel_transaction)
+ {
+ parallel_apply_unlock_stream(xid, AccessExclusiveLock);
Shouldn't we need to release this lock before sending the message as
we are doing for streap_prepare and stream_commit? If there is a
reason for doing it differently here then let's add some comments for
the same.
2. It seems once the patch makes the file state as busy
(LEADER_FILESET_BUSY), it will only be accessible after the leader
apply worker receives a transaction end message like stream_commit. Is
my understanding correct? If yes, then why can't we make it accessible
after the stream_stop message? Are you worried about the concurrency
handling for reading and writing the file? If so, we can probably deal
with it via some lock for reading and writing to file for each change.
I think after this we may not need additional stream level lock/unlock
in parallel_apply_spooled_messages. I understand that you probably
want to keep the code simple so I am not suggesting changing it
immediately but just wanted to know whether you have considered
alternatives here.
3. Don't we need to release the transaction lock at stream_abort in
parallel apply worker? I understand that we are not waiting for it in
the leader worker but still parallel apply worker should release it if
acquired at stream_start by it.
4. A minor comment change as below:
diff --git a/src/backend/replication/logical/worker.c
b/src/backend/replication/logical/worker.c
index 43f09b7e9a..c771851d1f 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -1851,6 +1851,9 @@ apply_handle_stream_abort(StringInfo s)
parallel_apply_stream_abort(&abort_data);
/*
+ * We need to wait after processing rollback
to savepoint for the next set
+ * of changes.
+ *
* By the time parallel apply worker is
processing the changes in
* the current streaming block, the leader
apply worker may have
* sent multiple streaming blocks. So, try to
lock only if there
--
With Regards,
Amit Kapila.
Commits
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the thread's linked commits as JSON, with link sources.
API reference →
-
Fix invalid memory access during the shutdown of the parallel apply worker.
- 3d144c6c8602 16.0 landed
-
Fix assertion failure in apply worker.
- de63f8dadee4 16.0 landed
-
Use elog to report unexpected action in handle_streamed_transaction().
- 781ac42d43ab 16.0 landed
-
Use appropriate wait event when sending data in the apply worker.
- d9d7fe68d35e 16.0 landed
-
Allow the logical_replication_mode to be used on the subscriber.
- 9f2213a7c575 16.0 landed
-
Rename GUC logical_decoding_mode to logical_replication_mode.
- 1e8b61735cfb 16.0 landed
-
Display the leader apply worker's PID for parallel apply workers.
- d540a02a724b 16.0 landed
-
Improve the code to decide and process the apply action.
- c981d9145dea 16.0 landed
-
Document the newly added wait events added by commit 216a784829.
- cd06ccd78fcf 16.0 landed
-
Perform apply of large transactions by parallel workers.
- 216a784829c2 16.0 landed
-
Wake up a subscription's replication worker processes after DDL.
- c6e1f62e2cee 16.0 cited
-
Add copyright notices to meson files
- 8284cf5f746f 16.0 cited
-
Better document logical replication parameters
- a8500750ca0a 16.0 cited
-
Add a common function to generate the origin name.
- 776e1c8a5d14 16.0 cited
-
Harmonize parameter names in storage and AM code.
- bfcf1b34805f 16.0 cited
-
Avoid using list_length() to test for empty list.
- efd0c16becbf 16.0 cited
-
Improve two comments related to a boolean DefElem's value
- 8445f5a21d40 16.0 cited
-
Fix partition table's REPLICA IDENTITY checking on the subscriber.
- 26b3455afaa9 15.0 cited
-
Fix data inconsistency between publisher and subscriber.
- b7658c24c7c1 15.0 cited
-
Fix cache look-up failures while applying changes in logical replication.
- 5a97b1325453 15.0 cited