Merge bitcoin/bitcoin#23395: util: Add -shutdownnotify option

d96d97ad30  doc: Add release note for shutdownnotify. (klementtan)
0bd73e2c45 util: Add -shutdownnotify option. (klementtan)

Pull request description:

  **Description**: Similar to `-startupnotify`, this PR adds a new option to allow users to specify a command to be executed when Bitcoin Core shuts down.

  **Note**: The `shutdownnotify` commands will not be executed if bitcoind shut down due to *unexpected* reasons (ie `killall -9 bitcoind`).

  ### Testing:
  **Normal shutdown commands**
  ```
  # start bitcoind with shutdownnotify optioin
  ./src/bitcoind -signet -shutdownnotify="touch foo.txt"

  # shutdown bitcoind
  ./src/bitcoin-cli -signet stop

  # check that foo.txt has been created
  ```

  **Final RPC call**
  Commands:
  ```
  $  ./src/bitcoind -signet -nolisten -noconnect -shutdownnotify="./src/bitcoin-cli -signet getblockchaininfo > tmp.txt"
  $ ./src/bitcoin-cli stop
  $ cat tmp.txt
  ```
  <details>
  <summary>Screen Shot</summary>

  ![image](https://user-images.githubusercontent.com/49265907/141186183-cbc6f82c-400d-4a8b-baba-27c0346c2c8a.png)
  </details>

ACKs for top commit:
  achow101:
    ACK d96d97ad30
  1440000bytes:
    ACK d96d97ad30
  theStack:
    re-ACK d96d97ad30

Tree-SHA512: 16f7406fd232e8b97aea5e58854c84755b0c35c88cb3ef9ee123b29a1475a376122b1e100da860cc336d4d657e6046a70e915fdb9b70c9fd097c6eef1b028161

doc/release-notes-23395.md

@@ -0,0 +1,8 @@
+Notable changes
+===============
+
+New settings
+------------
+
+- The `shutdownnotify` option is used to specify a command to execute synchronously
+before Bitcoin Core has begun its shutdown sequence. (#23395)

src/init.cpp

@@ -191,8 +191,24 @@ static fs::path GetPidFile(const ArgsManager& args)
 // shutdown thing.
 //
 
+#if HAVE_SYSTEM
+static void ShutdownNotify(const ArgsManager& args)
+{
+    std::vector<std::thread> threads;
+    for (const auto& cmd : args.GetArgs("-shutdownnotify")) {
+        threads.emplace_back(runCommand, cmd);
+    }
+    for (auto& t : threads) {
+        t.join();
+    }
+}
+#endif
+
 void Interrupt(NodeContext& node)
 {
+#if HAVE_SYSTEM
+    ShutdownNotify(*node.args);
+#endif
     InterruptHTTPServer();
     InterruptHTTPRPC();
     InterruptRPC();
@@ -441,6 +457,7 @@ void SetupServerArgs(ArgsManager& argsman)
     argsman.AddArg("-settings=<file>", strprintf("Specify path to dynamic settings data file. Can be disabled with -nosettings. File is written at runtime and not meant to be edited by users (use %s instead for custom settings). Relative paths will be prefixed by datadir location. (default: %s)", BITCOIN_CONF_FILENAME, BITCOIN_SETTINGS_FILENAME), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
 #if HAVE_SYSTEM
     argsman.AddArg("-startupnotify=<cmd>", "Execute command on startup.", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
+    argsman.AddArg("-shutdownnotify=<cmd>", "Execute command immediately before beginning shutdown. The need for shutdown may be urgent, so be careful not to delay it long (if the command doesn't require interaction with the server, consider having it fork into the background).", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
 #endif
 #ifndef WIN32
     argsman.AddArg("-sysperms", "Create new files with system default permissions, instead of umask 077 (only effective with disabled wallet functionality)", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);

test/functional/feature_notifications.py

@@ -31,7 +31,7 @@ class NotificationsTest(BitcoinTestFramework):
         self.num_nodes = 2
         self.setup_clean_chain = True
         # The experimental syscall sandbox feature (-sandbox) is not compatible with -alertnotify,
-        # -blocknotify or -walletnotify (which all invoke execve).
+        # -blocknotify, -walletnotify or -shutdownnotify (which all invoke execve).
         self.disable_syscall_sandbox = True
 
     def setup_network(self):
@@ -39,14 +39,18 @@ class NotificationsTest(BitcoinTestFramework):
         self.alertnotify_dir = os.path.join(self.options.tmpdir, "alertnotify")
         self.blocknotify_dir = os.path.join(self.options.tmpdir, "blocknotify")
         self.walletnotify_dir = os.path.join(self.options.tmpdir, "walletnotify")
+        self.shutdownnotify_dir = os.path.join(self.options.tmpdir, "shutdownnotify")
+        self.shutdownnotify_file = os.path.join(self.shutdownnotify_dir, "shutdownnotify.txt")
         os.mkdir(self.alertnotify_dir)
         os.mkdir(self.blocknotify_dir)
         os.mkdir(self.walletnotify_dir)
+        os.mkdir(self.shutdownnotify_dir)
 
         # -alertnotify and -blocknotify on node0, walletnotify on node1
         self.extra_args = [[
             f"-alertnotify=echo > {os.path.join(self.alertnotify_dir, '%s')}",
             f"-blocknotify=echo > {os.path.join(self.blocknotify_dir, '%s')}",
+            f"-shutdownnotify=echo > {self.shutdownnotify_file}",
         ], [
             f"-walletnotify=echo %h_%b > {os.path.join(self.walletnotify_dir, notify_outputname('%w', '%s'))}",
         ]]
@@ -162,6 +166,10 @@ class NotificationsTest(BitcoinTestFramework):
 
         # TODO: add test for `-alertnotify` large fork notifications
 
+        self.log.info("test -shutdownnotify")
+        self.stop_nodes()
+        self.wait_until(lambda: os.path.isfile(self.shutdownnotify_file), timeout=10)
+
     def expect_wallet_notify(self, tx_details):
         self.wait_until(lambda: len(os.listdir(self.walletnotify_dir)) >= len(tx_details), timeout=10)
         # Should have no more and no less files than expected