add new example "interruptible sleep"

Signed-off-by: Demin Yin <deminy@deminy.net>

README.md

@@ -124,6 +124,7 @@ docker compose exec -ti client bash # Get a Bash shell in the client container.
             * [support HTTP/1, HTTP/2, and WebSocket on same port](https://github.com/deminy/swoole-by-examples/blob/master/examples/servers/mixed-protocols-1.php)
             * support multiple protocols on same server
         * [DDoS protection](https://github.com/deminy/swoole-by-examples/blob/master/examples/servers/ddos-protection.php): How to protect your Swoole-based application server from DDoS attacks.
+        * [interruptible sleep](https://github.com/deminy/swoole-by-examples/blob/master/examples/servers/interruptible-sleep.php): This example shows how to set up a cronjob in a web server, and allow the cronjob to execute at a last time when the server is shutting down.
         * multiple ports listening
 * client-side programming
     * [HTTP/1 client](https://github.com/deminy/swoole-by-examples/blob/master/examples/clients/http1.php)

docker-compose.yml

@@ -4,7 +4,7 @@ services:
   server:
     image: deminy/swoole-by-examples:server-5.1
     environment:
-      AUTORELOAD_PROGRAMS: "ddos-protection http1 http1-integrated http2 keepalive mixed-protocols-1 pool-msgqueue pool-tcp-socket pool-unix-socket redis rock-paper-scissors tcp1 tcp2 udp websocket websocket-integrated"
+      AUTORELOAD_PROGRAMS: "ddos-protection http1 http1-integrated http2 interruptible-sleep keepalive mixed-protocols-1 pool-msgqueue pool-tcp-socket pool-unix-socket redis rock-paper-scissors tcp1 tcp2 udp websocket websocket-integrated"
       DISABLE_DEFAULT_SERVER: 1
     ports:
       - 9801:9801

dockerfiles/server/rootfilesystem/etc/supervisor/service.d/interruptible-sleep.conf

@@ -0,0 +1,12 @@
+[supervisord]
+user = root
+
+[program:interruptible-sleep]
+command = /var/www/servers/interruptible-sleep.php
+user = root
+autostart = true
+autorestart = true
+stdout_logfile=/proc/self/fd/1
+stdout_logfile_maxbytes=0
+stderr_logfile=/proc/self/fd/1
+stderr_logfile_maxbytes=0

examples/servers/interruptible-sleep.php

@@ -0,0 +1,60 @@
+#!/usr/bin/env php
+<?php
+
+declare(strict_types=1);
+
+/**
+ * In this example, we start a web server with a cronjob setup to run every 19 seconds. The cron job sends a message "[INTERRUPTIBLE-SLEEP] Simulating cronjob execution.(case 1)" to the logs of the server container when executed.
+ *
+ * The problem with traditional cronjobs is that they don't get a chance to execute at a last time before the server
+ * shuts down. For example, if the cronjob is scheduled to run every 19 seconds, and the server is shutting down 15
+ * seconds after the last cronjob execution, then the cronjob will never get a chance to execute one more time before
+ * the server shuts down.
+ *
+ * In this example, we use Channel to schedule a cronjob to run every 19 seconds. The implementation allows the cronjob
+ * to execute one more time by checking if the Channel is closed when server shuts down.
+ *
+ * When running the following command to stop and restart the server, you will see the cronjob is executed one more time
+ * with message "[INTERRUPTIBLE-SLEEP] Simulating cronjob execution.(case 2)" logged in the logs of the server container:
+ *     docker compose exec -t server bash -c "supervisorctl restart interruptible-sleep"
+ */
+
+use Swoole\Coroutine;
+use Swoole\Coroutine\Channel;
+use Swoole\Http\Request;
+use Swoole\Http\Response;
+use Swoole\Http\Server;
+
+$exited = new Channel();
+$server = new Server('0.0.0.0', 9512);
+
+$server->on('workerStart', function (Server $server, int $workerId) use ($exited) {
+    if ($workerId === 0) {
+        Coroutine::create(function () use ($exited) {
+            // Here we start the second cron job that makes an HTTP request every 19 seconds.
+            while (true) {
+                echo '[INTERRUPTIBLE-SLEEP] Simulating cronjob execution. (case 1)', PHP_EOL;
+                $exited->pop(19);
+                if ($exited->errCode === SWOOLE_CHANNEL_CLOSED) {
+                    echo '[INTERRUPTIBLE-SLEEP] Simulating cronjob execution. (case 2)', PHP_EOL;
+                    break;
+                }
+            }
+            echo '[INTERRUPTIBLE-SLEEP] The cronjob has exited.', PHP_EOL;
+        });
+    }
+});
+$server->on('workerExit', function (Server $server, int $workerId) use ($exited) {
+    echo "[INTERRUPTIBLE-SLEEP] Worker #{$workerId} is exiting.", PHP_EOL;
+    if ($workerId === 0) {
+        Coroutine::create(function () use ($exited) {
+            $exited->close();
+        });
+    }
+    echo "[INTERRUPTIBLE-SLEEP] Worker #{$workerId} has exited.", PHP_EOL;
+});
+$server->on('request', function (Request $request, Response $response) {
+    $response->end('OK' . PHP_EOL);
+});
+
+$server->start();