Postgres 17 failover slot example

postgres-failover-slots/00_init.sql

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+BEGIN;
+
+create user replicator with replication encrypted password 'zufsob-kuvtum-bImxa6';
+SELECT pg_create_physical_replication_slot('replication_slot');
+
+CREATE SCHEMA inventory;
+
+-- customers
+CREATE TABLE inventory.customers (
+  id SERIAL NOT NULL PRIMARY KEY,
+  first_name VARCHAR(255) NOT NULL,
+  last_name VARCHAR(255) NOT NULL,
+  email VARCHAR(255) NOT NULL UNIQUE,
+  is_test_account BOOLEAN NOT NULL
+);
+
+ALTER SEQUENCE inventory.customers_id_seq RESTART WITH 1001;
+ALTER TABLE inventory.customers REPLICA IDENTITY FULL;
+
+INSERT INTO inventory.customers
+VALUES (default, 'Sally', 'Thomas', '[email protected]', FALSE),
+       (default, 'George', 'Bailey', '[email protected]', FALSE),
+       (default, 'Edward', 'Walker', '[email protected]', FALSE),
+       (default, 'Aidan', 'Barrett', '[email protected]', TRUE),
+       (default, 'Anne', 'Kretchmar', '[email protected]', TRUE),
+       (default, 'Melissa', 'Cole', '[email protected]', FALSE),
+       (default, 'Rosalie', 'Stewart', '[email protected]', FALSE);
+
+COMMIT;

postgres-failover-slots/README.md

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+# Failover Slots with Postgres 17
+
+This example shows the usage of Postgres 17 failover replication slots with Debezium
+(Debezium 3.0.4 or newer is required).
+
+The set-up contains a Postgres cluster with primary and read replica, fronted by pgbouncer.
+Debezium connects to the cluster via this proxy.
+When the primary goes down and the replica gets promoted to new primary,
+connecting through the proxy allows Debezium to automatically fail over from previous primary to new without requiring to be reconfigured.
+
+Start all the components:
+
+```shell
+export DEBEZIUM_VERSION=3.0
+docker compose up
+```
+
+Get a DB session on the Postgres read replica:
+
+```shell
+docker run --tty --rm -i \
+     --network failover-network \
+    quay.io/debezium/tooling:1.2 \
+    bash -c 'pgcli --prompt "\u@replica:\d> " postgresql://user:top-secret@postgres_replica:5432/inventorydb'
+```
+
+Add the database name to the connection info and reload the configuration of the read replica:
+
+```sql
+ALTER SYSTEM SET primary_conninfo = 'user=replicator password=''zufsob-kuvtum-bImxa6'' channel_binding=prefer host=postgres_primary port=5432 sslmode=prefer sslnegotiation=postgres sslcompression=0 sslcertmode=allow sslsni=1 ssl_min_protocol_version=TLSv1.2 gssencmode=prefer krbsrvname=postgres gssdelegation=0 target_session_attrs=any load_balance_hosts=disable dbname=inventorydb';
+
+SELECT pg_reload_conf();
+```
+
+Register an instance of the Postgres connector. It is going to ingest changes from the current primary server (connecting through pgbouncer):
+
+```shell
+# Start Postgres connector
+http PUT http://localhost:8083/connectors/inventory-source/config < inventory-source.json
+
+# Consume messages from a Debezium topic
+docker run --tty --rm \
+     --network failover-network \
+     quay.io/debezium/tooling:1.2 \
+     kcat -b kafka:9092 -C -o beginning -q \
+     -t dbserver1.inventory.customers | jq .payload
+
+# Modify a record in the database (current primary):
+docker run --tty --rm -i \
+     --network failover-network \
+    quay.io/debezium/tooling:1.2 \
+    bash -c 'pgcli --prompt "\u@primary:\d> " postgresql://user:top-secret@postgres_primary:5432/inventorydb'
+
+# update inventory.customers set first_name = 'Sarah' where id = 1001;
+```
+
+Next, fail over to the read replica, promoting it to new primary.
+Stop the primary instance and pgbouncer:
+
+```shell
+docker compose stop postgres_primary
+docker compose stop pgbouncer
+```
+
+The connector will lose the connection and enter a restart loop.
+Promote the read replica to new primary:
+
+```sql
+select pg_promote();
+```
+
+Reconfigure pgbouncer and restart it:
+
+```yaml
+services:
+  pgbouncer:
+    image: edoburu/pgbouncer:latest
+    environment:
+      - DB_HOST=postgres_replica
+      ...
+```
+
+```shell
+docker compose up -d
+```
+
+The connector will establish the connection again,
+now connecting to the new primary.
+Do one more change on that Postgres node (the previous replica) and observe how the change event shows up in Kafka.
+
+```sql
+update inventory.customers set first_name = 'Rudy', last_name = 'Replica' where id = 1001;
+```
+
+Shut down the cluster:
+
+```shell 
+docker compose down
+```

postgres-failover-slots/docker-compose.yaml

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+services:
+  pgbouncer:
+    image: edoburu/pgbouncer:latest
+    environment:
+      - DB_HOST=postgres_primary
+      - DB_PORT=5432
+      - DB_USER=user
+      - DB_PASSWORD=top-secret
+      - ADMIN_USERS=postgres,admin
+      - AUTH_TYPE=scram-sha-256
+    ports:
+      - 15432:5432
+    networks:
+     - my-network
+
+  # Postgres cluster set-up inspired by https://github.com/eremeykin/pg-primary-replica
+  postgres_primary:
+    image: postgres:17-alpine
+    user: postgres
+    restart: always
+    healthcheck:
+      test: 'pg_isready -U user --dbname=inventorydb'
+      interval: 10s
+      timeout: 5s
+      retries: 5
+    ports:
+      - 5432:5432
+    environment:
+      POSTGRES_USER: user
+      POSTGRES_DB: inventorydb
+      POSTGRES_PASSWORD: top-secret
+      POSTGRES_HOST_AUTH_METHOD: "scram-sha-256\nhost replication all 0.0.0.0/0 md5"
+      POSTGRES_INITDB_ARGS: "--auth-host=scram-sha-256"
+    command: |
+      postgres 
+      -c wal_level=logical 
+      -c hot_standby=on 
+      -c max_wal_senders=10 
+      -c max_replication_slots=10
+      -c synchronized_standby_slots=replication_slot
+    volumes:
+      - ./00_init.sql:/docker-entrypoint-initdb.d/00_init.sql
+    networks:
+     - my-network
+
+  postgres_replica:
+    image: postgres:17-alpine
+    user: postgres
+    restart: always
+    healthcheck:
+      test: 'pg_isready -U user --dbname=inventorydb'
+      interval: 10s
+      timeout: 5s
+      retries: 5
+    ports:
+      - 5433:5432
+    environment:
+      PGUSER: replicator
+      PGPASSWORD: zufsob-kuvtum-bImxa6
+    command: |
+      bash -c "
+      until pg_basebackup --pgdata=/var/lib/postgresql/data -R --slot=replication_slot --host=postgres_primary --port=5432
+      do
+      echo 'Waiting for primary to connect...'
+      sleep 1s
+      done
+      echo 'Backup done, starting replica...'
+      chmod 0700 /var/lib/postgresql/data
+      postgres -c wal_level=logical -c hot_standby=on -c hot_standby_feedback=1 -c sync_replication_slots=on
+      "
+    depends_on:
+      - postgres_primary
+    networks:
+     - my-network
+
+  kafka:
+    image: quay.io/debezium/kafka:${DEBEZIUM_VERSION}
+    ports:
+     - 9092:9092
+     - 9093:9093
+    environment:
+     - CLUSTER_ID=oh-sxaDRTcyAr6pFRbXyzA
+     - BROKER_ID=1
+     - KAFKA_CONTROLLER_QUORUM_VOTERS=1@kafka:9093
+    networks:
+     - my-network
+
+  connect:
+    image: quay.io/debezium/connect:${DEBEZIUM_VERSION}
+    ports:
+     - 8083:8083
+    links:
+     - kafka
+     - pgbouncer
+    environment:
+     - BOOTSTRAP_SERVERS=kafka:9092
+     - GROUP_ID=1
+     - CONFIG_STORAGE_TOPIC=my_connect_configs
+     - OFFSET_STORAGE_TOPIC=my_connect_offsets
+     - STATUS_STORAGE_TOPIC=my_connect_statuses
+# For testing newer connector versions, unpack the connector archive into this
+# directory and uncomment the lines below
+#    volumes:
+#     - ./debezium-connector-postgres:/kafka/connect/debezium-connector-postgres
+    networks:
+     - my-network
+networks:
+  my-network:
+    name: failover-network

postgres-failover-slots/inventory-source.json

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+{
+    "connector.class" : "io.debezium.connector.postgresql.PostgresConnector",
+    "tasks.max" : "1",
+    "database.hostname" : "pgbouncer",
+    "database.port" : "5432",
+    "database.user" : "user",
+    "database.password" : "top-secret",
+    "database.dbname" : "inventorydb",
+    "topic.prefix" : "dbserver1",
+    "schema.include.list" : "inventory",
+    "plugin.name" : "pgoutput",
+    "slot.failover" : "true"
+}