plugin: rescan restarts plugin on update

lightningd/plugin.c

@@ -1,4 +1,6 @@
 #include <ccan/array_size/array_size.h>
+#include <ccan/ccan/tal/grab_file/grab_file.h>
+#include <ccan/crc32c/crc32c.h>
 #include <ccan/list/list.h>
 #include <ccan/mem/mem.h>
 #include <ccan/opt/opt.h>
@@ -215,28 +217,44 @@ static void destroy_plugin(struct plugin *p)
 	}
 }
 
+static u32 file_checksum(const char* path)
+{
+	char *content = grab_file(tmpctx, path);
+	if (content == NULL) return 0;
+	return crc32c(0, content, tal_count(content));
+}
+
 struct plugin *plugin_register(struct plugins *plugins, const char* path TAKES,
 			       struct command *start_cmd, bool important,
 			       const char *parambuf STEALS,
 			       const jsmntok_t *params STEALS)
 {
 	struct plugin *p, *p_temp;
+	u32 chksum;
 
 	/* Don't register an already registered plugin */
 	list_for_each(&plugins->plugins, p_temp, list) {
 		if (streq(path, p_temp->cmd)) {
-			if (taken(path))
-				tal_free(path);
-		 	/* If added as "important", upgrade to "important".  */
+			/* If added as "important", upgrade to "important".  */
 			if (important)
 				p_temp->important = true;
+			/* stop and restart plugin on different checksum */
+			chksum = file_checksum(path);
+			if (p_temp->checksum != chksum && !p_temp->important) {
+				plugin_kill(p_temp, LOG_INFORM,
+					    "Plugin changed, needs restart.");
+				break;
+			}
+			if (taken(path))
+				tal_free(path);
 			return NULL;
 		}
 	}
 
 	p = tal(plugins, struct plugin);
 	p->plugins = plugins;
 	p->cmd = tal_strdup(p, path);
+	p->checksum = file_checksum(p->cmd);
 	p->shortname = path_basename(p, p->cmd);
 	p->start_cmd = start_cmd;
 

lightningd/plugin.h

@@ -48,6 +48,7 @@ struct plugin {
 
 	pid_t pid;
 	char *cmd;
+	u32 checksum;
 	struct io_conn *stdin_conn, *stdout_conn;
 	struct plugins *plugins;
 	const char **plugin_path;

tests/test_plugin.py

@@ -21,6 +21,7 @@
 import re
 import signal
 import sqlite3
+import stat
 import subprocess
 import time
 import unittest
@@ -2472,3 +2473,51 @@ def test_custom_notification_topics(node_factory):
     # The plugin just dist what previously was a fatal mistake (emit
     # an unknown notification), make sure we didn't kill it.
     assert 'custom_notifications.py' in [p['name'] for p in l1.rpc.listconfigs()['plugins']]
+
+
+def test_restart_on_update(node_factory):
+    """Tests if plugin rescan restarts modified plugins
+    """
+    # we need to write plugin content dynamically
+    content = """#!/usr/bin/env python3
+from pyln.client import Plugin
+import time
+plugin = Plugin()
+@plugin.init()
+def init(options, configuration, plugin):
+    plugin.log("test_restart_on_update %s")
+plugin.run()
+    """
+
+    # get a node that is not started so we can put a plugin in its lightning_dir
+    n = node_factory.get_node(start=False)
+    lndir = n.daemon.lightning_dir
+
+    # write hello world plugin to lndir/plugins
+    os.makedirs(os.path.join(lndir, 'plugins'), exist_ok=True)
+    path = os.path.join(lndir, 'plugins', 'test_restart_on_update.py')
+    file = open(path, 'w+')
+    file.write(content % "1")
+    file.close()
+    os.chmod(path, os.stat(path).st_mode | stat.S_IEXEC)
+
+    # now fire up the node and wait for the plugin to print hello
+    n.daemon.start()
+    n.daemon.logsearch_start = 0
+    n.daemon.wait_for_log(r"test_restart_on_update 1")
+
+    # a rescan should not yet reload the plugin on the same file
+    n.rpc.plugin_rescan()
+    assert not n.daemon.is_in_log(r"Plugin changed, needs restart.")
+
+    # modify the file
+    file = open(path, 'w+')
+    file.write(content % "2")
+    file.close()
+    os.chmod(path, os.stat(path).st_mode | stat.S_IEXEC)
+
+    # rescan and check
+    n.rpc.plugin_rescan()
+    n.daemon.wait_for_log(r"Plugin changed, needs restart.")
+    n.daemon.wait_for_log(r"test_restart_on_update 2")
+    n.stop()