⚙️ Only consider physical replicas as replicas

Co-authored-by: Russell McQueeney <rmcq@utexas.edu>

Author: RTLS

docker/replica-cdc-dev/init-primary.sh

@@ -27,12 +27,17 @@ psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-E
     CREATE PUBLICATION sequin_pub FOR TABLE test_table;
     
     -- Drop existing replication slot if it exists
-    SELECT pg_drop_replication_slot('sequin_slot') WHERE EXISTS (SELECT 1 FROM pg_replication_slots WHERE slot_name = 'sequin_slot');
+    SELECT pg_drop_replication_slot(slot_name)
+    FROM pg_replication_slots
+    WHERE slot_name LIKE 'pg_%_sync_%' OR slot_name = 'sequin_slot';
     
-    -- Create replication slot
+    -- Create primary replication slot
     SELECT pg_create_logical_replication_slot('sequin_slot', 'pgoutput');
 EOSQL
 
 # Configure pg_hba.conf to allow replication connections
 echo "host replication replicator all md5" >> "$PGDATA/pg_hba.conf"
-echo "host all replicator all md5" >> "$PGDATA/pg_hba.conf" 
+echo "host all replicator all md5" >> "$PGDATA/pg_hba.conf"
+
+# Set synchronous_commit to local to improve performance
+echo "synchronous_commit = local" >> "$PGDATA/postgresql.conf"

docker/replica-cdc-dev/init-replica.sh

@@ -26,7 +26,17 @@ psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-E
     CREATE SUBSCRIPTION sequin_sub
     CONNECTION 'host=postgres-primary port=5432 user=replicator password=replicator_password dbname=postgres'
     PUBLICATION sequin_pub
-    WITH (copy_data = true);
+    WITH (copy_data = true, create_slot = true, enabled = true, connect = true, slot_name = 'sequin_sub', disable_on_error = false);
+EOSQL
+
+# Allow time for the subscription to be established
+sleep 5
+
+# Restart subscription if needed
+psql -v ON_ERROR_STOP=0 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
+    -- Restart subscription if not active
+    ALTER SUBSCRIPTION sequin_sub DISABLE;
+    ALTER SUBSCRIPTION sequin_sub ENABLE;
 EOSQL
 
 # Wait for initial data copy to complete

lib/sequin/databases/databases.ex

@@ -433,7 +433,7 @@ defmodule Sequin.Databases do
 
   def test_maybe_replica(%PostgresDatabase{} = db, db_primary) do
     cond do
-      not replica?(db) ->
+      not is_physical_replica?(db) ->
         :ok
 
       is_nil(db_primary) ->
@@ -627,18 +627,16 @@ defmodule Sequin.Databases do
     end
   end
 
-  @spec replica?(%PostgresDatabase{}) :: boolean()
-  def replica?(%PostgresDatabase{} = db) do
+  @spec is_physical_replica?(%PostgresDatabase{}) :: boolean()
+  def is_physical_replica?(%PostgresDatabase{} = db) do
     with_uncached_connection(db, fn conn ->
       query = """
-        SELECT
-          pg_is_in_recovery() AS is_physical_replica,
-          EXISTS (SELECT 1 FROM pg_subscription) AS has_logical_replication
+        SELECT pg_is_in_recovery() AS is_physical_replica
       """
 
       case Postgres.query(conn, query, []) do
-        {:ok, %{rows: [[is_physical, has_logical]]}} ->
-          is_physical or has_logical
+        {:ok, %{rows: [[is_physical]]}} ->
+          is_physical
 
         _ ->
           false