Let's make a logger.

CREATE TABLE ddl_history (
    id BIGSERIAL PRIMARY KEY,
    event_time TIMESTAMPTZ DEFAULT now(),
    command TEXT,
    object_type TEXT,
    object_name TEXT
);

Create the function:

CREATE OR REPLACE FUNCTION capture_ddl()
RETURNS event_trigger
LANGUAGE plpgsql
AS $$
BEGIN
    INSERT INTO ddl_history (
        command,
        object_type,
        object_name
    )
    SELECT
        TG_TAG,
        object_type,
        object_identity
    FROM pg_event_trigger_ddl_commands();
END;
$$;

DROP TABLE

CREATE OR REPLACE FUNCTION capture_drop()
RETURNS event_trigger
LANGUAGE plpgsql
AS $$
BEGIN
    INSERT INTO ddl_log (
        event_time,
        command,
        object_type,
        object_name
    )
    SELECT
        now(),
        TG_TAG,
        object_type,
        object_identity
    FROM pg_event_trigger_dropped_objects();
END;
$$;


Create the trigger:

CREATE EVENT TRIGGER capture_ddl_trigger
ON ddl_command_end
EXECUTE FUNCTION capture_ddl();

Now test:

CREATE TABLE products (
    id INT PRIMARY KEY,
    name TEXT
);

Check:

SELECT * FROM ddl_history;



docker-compose.yml for LOGICAL REPLICATION MODE

services:
  postgres:
    image: postgres:15
    container_name: cluster1Node1

    restart: unless-stopped

    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
      POSTGRES_DB: postgres

    ports:
      - "5444:5432"

    volumes:
      - ./postgres_data:/var/lib/postgresql/data

    command:
      - postgres
      - -c
      - wal_level=logical
      - -c
      - max_replication_slots=10
      - -c
      - max_wal_senders=10


sudo docker compose down
sudo docker compose up -d


SHOW wal_level;

psql -h 172.16.10.123 -p 5444 -U postgres

SHOW max_replication_slots;
SHOW max_wal_senders;


CREATE TABLE users (
    id INT PRIMARY KEY,
    name TEXT
);


SELECT *
FROM pg_create_logical_replication_slot(
    'myslot',
    'test_decoding'
);

INSERT INTO users VALUES (1, 'Alice');

SELECT *
FROM pg_logical_slot_peek_changes(
    'myslot',
    NULL,
    NULL
);


|===================================================|
| psql -h 127.0.0.1 -p 5444 -U postgres -d postgres |
|===================================================|
command:
  - postgres
  - -c
  - wal_level=logical
  - -c
  - shared_preload_libraries=spock
  - -c
  - max_replication_slots=10
  - -c
  - max_wal_senders=10
  - -c
  - track_commit_timestamp=on
  
psql -h 127.0.0.1 -p 5444 -U postgres -d postgres

sudo nano postgres_data/pg_hba.conf

host    all    all    172.19.0.0/16    scram-sha-256
host    all    all    172.16.10.0/24    scram-sha-256

sudo docker exec -it cluster1Node1 psql -U postgres -d postgres
ALTER USER postgres WITH PASSWORD 'postgres';

sudo docker exec -it cluster1Node3 bash
psql -U postgres -c "SHOW hba_file;"
psql -U postgres -c "SELECT pg_reload_conf();"





|==========|
|LINK Nodes|
|==========|
SELECT spock.sub_create(
    subscription_name := 'node2_from_node1',
    provider_dsn := 'host=172.16.10.123 port=5444 dbname=postgres user=postgres password=postgres'
);

|=============|
|Register Node|
|=============|
psql -h localhost -p 5444 -U postgres -d postgres
CREATE EXTENSION IF NOT EXISTS spock;
SELECT extname, extversion
FROM pg_extension
WHERE extname = 'spock';
SELECT spock.node_create(
    node_name := 'node1',
    dsn := 'host=172.16.10.123 port=5444 dbname=postgres user=postgres password=postgres'
);
SELECT * FROM spock.node;

|================|
| CREATE A table |
|================|
CREATE TABLE test_replication (
    id bigint PRIMARY KEY,
    source_node text,
    message text
);

SELECT spock.repset_add_table(
    'default',
    'test_replication'
);

|===========|
|Turn On DDL|
|===========|

CREATE TABLE customers (
    id bigint PRIMARY KEY,
    name text
);
ALTER SYSTEM SET spock.enable_ddl_replication = on;
ALTER SYSTEM SET spock.include_ddl_repset = on;

SELECT pg_reload_conf();

SHOW spock.enable_ddl_replication;
SHOW spock.include_ddl_repset;

|======================================================|
| HOW TO INSERT OR PUT AUTO GEN OF ID IN EXISTING TABLE|
|======================================================|
ALTER TABLE test_replication
ALTER COLUMN id ADD GENERATED BY DEFAULT AS IDENTITY;


HOW TO UPADE A NODE CONFIG

UPDATE spock.local_node
SET node_local_interface = (
    SELECT if_id
    FROM spock.node_interface
    WHERE if_name = 'node2_local'
      AND if_nodeid = 13534
);
|========================|
|WAY TO ENTER PSQL SHELL |
|========================|
psql "postgresql://postgres_exporter:postgres@172.16.10.178:5444/postgres"

|=============================|
|ENDPONT TO DETECT A DEAD LOCK|
|=============================|
 http://172.16.10.178:9188/metrics | grep -i deadlock


|========================|
|FEATURES COMPLETED TODAY|
|========================|

| Requirement             | `postgres_exporter` | What you need                     |
| ----------------------- | ------------------: | --------------------------------- |
| Connections             |                   ✅ | postgres_exporter                 |
| Transactions            |                   ✅ | postgres_exporter                 |
| Locks                   |                ✅/⚠️ | PostgreSQL metrics/custom query   |
| Blocking sessions       |                  ⚠️ | Custom PostgreSQL query           |
| Deadlocks               |                   ✅ | postgres_exporter                 |
| Long-running queries    |                  ⚠️ | `pg_stat_activity` / custom query |
| WAL                     |                   ✅ | postgres_exporter                 |
| Database health         |                   ✅ | postgres_exporter + Prometheus    |
| PostgreSQL CPU usage    |                   ❌ | cAdvisor / process monitoring     |
| PostgreSQL memory usage |                   ❌ | cAdvisor / process monitoring     |
| Storage/disk usage      |                   ❌ | node_exporter / cAdvisor          |
| Network usage           |                   ❌ | node_exporter / cAdvisor          |


|==================|
| Whats This for?  |
|==================|

postgres=# SELECT *                       
FROM spock.replication_set_table;
  set_id   |    set_reloid    | set_att_list | set_row_filter 
-----------+------------------+--------------+----------------
 590430464 | ddl_test         |              | 
 590430464 | test_replication |              | 
 590430464 | lock_test        |              | 
(3 rows)

postgres=# 


!!!!!!!!!WHEN TESTING NEW NODES OR REFRESHING THE NODES!!!!!!!!! 
SET spock.enable_ddl_replication = off;


|=============================|
|ADD UUID IN AN EXISTING TABLE|
|=============================|

CREATE EXTENSION IF NOT EXISTS pgcrypto;
ALTER TABLE public.test_replication
ADD COLUMN uuid_id uuid DEFAULT gen_random_uuid();
Populate any existing rows that somehow got NULL:
UPDATE public.test_replication
SET uuid_id = gen_random_uuid()
WHERE uuid_id IS NULL;
Make it not null:
ALTER TABLE public.test_replication
ALTER COLUMN uuid_id SET NOT NULL;
Now remove the old primary key:
ALTER TABLE public.test_replication
DROP CONSTRAINT test_replication_pkey;
Make the UUID the new primary key:
ALTER TABLE public.test_replication
ADD PRIMARY KEY (uuid_id);

|===========================|
|!!!CAUTION AFTER LINKING!!!|
|===========================|
CHECK THIS
SELECT * FROM spock.replication_set_table;

SELECT
    slot_name,
    active,
    active_pid,
    restart_lsn,
    confirmed_flush_lsn
FROM pg_replication_slots;

postgres=# SELECT *                                                  
FROM spock.replication_set;
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
|===============================|
|CREATE A TABLE NOT USING SPROKE|
|===============================|
SELECT spock.replicate_ddl(
$$
CREATE TABLE public.vm2_ddl_test (
    uuid_id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    source_node TEXT NOT NULL,
    message TEXT,
    created_at TIMESTAMPTZ DEFAULT now()
);
$$
);

WTF IS THIS!!!
To check if provider is sending data
postgres=# SELECT
    slot_name,
    active,
    active_pid,
    restart_lsn,
    confirmed_flush_lsn
FROM pg_replication_slots;