Improve messaging during logical replication worker startup

In case the subscription is removed before the worker is fully started,
give a specific error message instead of the generic "cache lookup"
error.

Author: Petr Jelinek <petr.jelinek@2ndquadrant.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>

diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 93a42d9322cd73a043726e348ff5b3172a6a3e04..b10857550a6105ec509c607c5b38961d3006b358 100644 (file)
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -1553,14 +1553,20 @@ ApplyWorkerMain(Datum main_arg)
                                         ALLOCSET_DEFAULT_SIZES);
    StartTransactionCommand();
    oldctx = MemoryContextSwitchTo(ApplyContext);
-   MySubscription = GetSubscription(MyLogicalRepWorker->subid, false);
+
+   MySubscription = GetSubscription(MyLogicalRepWorker->subid, true);
+   if (!MySubscription)
+   {
+       ereport(LOG,
+               (errmsg("logical replication apply worker for subscription %u will not "
+                       "start because the subscription was removed during startup",
+                       MyLogicalRepWorker->subid)));
+       proc_exit(0);
+   }
+
    MySubscriptionValid = true;
    MemoryContextSwitchTo(oldctx);
 
-   /* Setup synchronous commit according to the user's wishes */
-   SetConfigOption("synchronous_commit", MySubscription->synccommit,
-                   PGC_BACKEND, PGC_S_OVERRIDE);
-
    if (!MySubscription->enabled)
    {
        ereport(LOG,
@@ -1571,6 +1577,10 @@ ApplyWorkerMain(Datum main_arg)
        proc_exit(0);
    }
 
+   /* Setup synchronous commit according to the user's wishes */
+   SetConfigOption("synchronous_commit", MySubscription->synccommit,
+                   PGC_BACKEND, PGC_S_OVERRIDE);
+
    /* Keep us informed about subscription changes. */
    CacheRegisterSyscacheCallback(SUBSCRIPTIONOID,
                                  subscription_change_cb,