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

d96d97ad30c4a079450bc2bf02e3e2a45f7efd2d  doc: Add release note for shutdownnotify. (klementtan)
0bd73e2c453e8a88312edf43d184c33109f12ad6 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 d96d97ad30c4a079450bc2bf02e3e2a45f7efd2d
  1440000bytes:
    ACK https://github.com/bitcoin/bitcoin/pull/23395/commits/d96d97ad30c4a079450bc2bf02e3e2a45f7efd2d
  theStack:
    re-ACK d96d97ad30c4a079450bc2bf02e3e2a45f7efd2d

Tree-SHA512: 16f7406fd232e8b97aea5e58854c84755b0c35c88cb3ef9ee123b29a1475a376122b1e100da860cc336d4d657e6046a70e915fdb9b70c9fd097c6eef1b028161

1 files changed, 17 insertions, 0 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 5160718eaa..685583bcbd 100644
--- a/src/init.cpp
+++ b/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);