[+] add Etcd usage example

Author: pashagolub

samples/Etcd.sql

@@ -0,0 +1,134 @@
+-- This sample demonstrates how to read multiple key-value pairs from an etcd cluster
+-- based on a prefix and reflect them in a database table.
+--
+-- It assumes that:
+-- 1. etcdctl is installed and available in the system's PATH.
+-- 2. The etcd cluster is accessible. The default endpoint is http://127.0.0.1:2379.
+-- 3. The user running pg_timetable has sufficient permissions to execute the etcdctl command.
+
+-- The chain will perform the following steps:
+-- 1. Define one task to write to etcd and provide multiple parameter rows to it.
+--    The task will be executed for each parameter row.
+-- 2. Read all key-values under that prefix from etcd as a single JSON object.
+-- 3. Parse the JSON, decode the base64 keys and values, and store them in a table.
+-- 4. Log the number of keys retrieved.
+-- 5. Delete all keys under the prefix from etcd using a single parameterized task.
+
+-- Setup: A table to store the keys and values from etcd
+CREATE TABLE IF NOT EXISTS etcd_test_data (
+    key TEXT,
+    value TEXT
+);
+TRUNCATE public.etcd_test_data;
+
+-- Setup: A temporary table to store raw JSON output from etcd
+CREATE TABLE IF NOT EXISTS etcd_json_raw (
+    data JSONB
+);
+TRUNCATE etcd_json_raw;
+
+-- The chain definition
+-- It runs once and then removes itself (self_destruct).
+INSERT INTO timetable.chain (
+    chain_name,
+    run_at,
+    max_instances,
+    live,
+    self_destruct
+)
+VALUES (
+    'ETCD Prefix-Read-Clean',
+    '* * * * *', -- Run every minute, but self_destruct will make it run once
+    1,
+    TRUE,
+    TRUE
+)
+RETURNING chain_id;
+
+-- Task 1: A single task to write key-value pairs to etcd.
+-- This task will be executed 3 times, once for each parameter row below.
+WITH task AS (
+    INSERT INTO timetable.task (chain_id, task_order, task_name, kind, command, ignore_error)
+    SELECT currval('timetable.chain_chain_id_seq'), 10, 'Write keys to etcd', 'PROGRAM', 'etcdctl', FALSE
+    RETURNING task_id
+)
+INSERT INTO timetable.parameter (task_id, order_id, value)
+SELECT task_id, 1, '["--endpoints=http://127.0.0.1:2379", "put", "/pg_timetable/multi/key1", "value1"]'::jsonb FROM task UNION ALL
+SELECT task_id, 2, '["--endpoints=http://127.0.0.1:2379", "put", "/pg_timetable/multi/key2", "value2"]'::jsonb FROM task UNION ALL
+SELECT task_id, 3, '["--endpoints=http://127.0.0.1:2379", "put", "/pg_timetable/multi/key3", "value3"]'::jsonb FROM task;
+
+-- Task 2: Read all keys under the prefix from etcd as JSON
+INSERT INTO timetable.task (
+    chain_id,
+    task_order,
+    task_name,
+    kind,
+    command,
+    ignore_error
+)
+SELECT
+    currval('timetable.chain_chain_id_seq'),
+    20,
+    'Read from etcd with prefix',
+    'SQL',
+    $$COPY etcd_json_raw (data) FROM PROGRAM 'etcdctl --endpoints=http://127.0.0.1:2379 get --prefix /pg_timetable/multi/ --write-out=json'$$,
+    FALSE;
+
+-- Task 3: Parse JSON array and store the key-value pairs
+INSERT INTO timetable.task (
+    chain_id,
+    task_order,
+    task_name,
+    kind,
+    command,
+    ignore_error
+)
+SELECT
+    currval('timetable.chain_chain_id_seq'),
+    30,
+    'Parse etcd output and store',
+    'SQL',
+    $$INSERT INTO public.etcd_test_data (key, value)
+      SELECT
+          convert_from(decode(kv->>'key', 'base64'), 'UTF8'),
+          convert_from(decode(kv->>'value', 'base64'), 'UTF8')
+      FROM
+          etcd_json_raw,
+          jsonb_array_elements(data->'kvs') AS kv$$,
+    FALSE;
+
+-- Task 4: Log the result
+INSERT INTO timetable.task (
+    chain_id,
+    task_order,
+    task_name,
+    kind,
+    command,
+    ignore_error
+)
+SELECT
+    currval('timetable.chain_chain_id_seq'),
+    40,
+    'Log etcd output',
+    'SQL',
+    $task$
+    DO
+        $$
+            DECLARE
+            msg integer;
+            BEGIN
+                SELECT count(*) FROM public.etcd_test_data INTO msg;
+                RAISE notice 'Loaded keys from etcd: %', msg; 
+            END;
+        $$
+    $task$,
+    FALSE;
+
+-- Task 5: Clean up the keys in etcd
+WITH task AS (
+    INSERT INTO timetable.task (chain_id, task_order, task_name, kind, command, ignore_error)
+    SELECT currval('timetable.chain_chain_id_seq'), 50, 'Clean up etcd', 'PROGRAM', 'etcdctl', FALSE
+    RETURNING task_id
+)
+INSERT INTO timetable.parameter (task_id, order_id, value)
+SELECT task_id, 1, '["--endpoints=http://127.0.0.1:2379", "del", "--prefix", "/pg_timetable/multi/"]'::jsonb FROM task;