Cleanly terminate deltachat-rpc-server (#4234)

Do it as per "Thread safety" section in deltachat-ffi/deltachat.h. Also terminate on ctrl-c.

CHANGELOG.md

@@ -9,7 +9,8 @@
 - Compress `mime_headers` column with HTML emails stored in database
 - Strip BIDI characters in system messages, files, group names and contact names #3479
 - maybe_add_time_based_warnings(): Use release date instead of the provider DB update one
-
+- Cleanly terminate deltachat-rpc-server.
+  Also terminate on ctrl-c.
 
 ### Fixes
 - Fix python bindings README documentation on installing the bindings from source.

Cargo.lock

@@ -1280,6 +1280,7 @@ dependencies = [
  "serde",
  "serde_json",
  "tokio",
+ "tokio-util",
  "yerpc",
 ]
 

deltachat-rpc-server/Cargo.toml

@@ -20,6 +20,7 @@ log = "0.4"
 serde_json = "1.0.95"
 serde = { version = "1.0", features = ["derive"] }
 tokio = { version = "1.27.0", features = ["io-std"] }
+tokio-util = "0.7.7"
 yerpc = { version = "0.4.0", features = ["anyhow_expose"] }
 
 [features]

deltachat-rpc-server/src/main.rs

@@ -3,6 +3,7 @@ use std::env;
 ///!
 ///! It speaks JSON Lines over stdio.
 use std::path::PathBuf;
+use std::sync::Arc;
 
 use anyhow::{anyhow, Context as _, Result};
 use deltachat::constants::DC_VERSION_STR;
@@ -10,7 +11,9 @@ use deltachat_jsonrpc::api::events::event_to_json_rpc_notification;
 use deltachat_jsonrpc::api::{Accounts, CommandApi};
 use futures_lite::stream::StreamExt;
 use tokio::io::{self, AsyncBufReadExt, BufReader};
+use tokio::sync::RwLock;
 use tokio::task::JoinHandle;
+use tokio_util::sync::CancellationToken;
 use yerpc::{RpcClient, RpcSession};
 
 #[tokio::main(flavor = "multi_thread")]
@@ -40,24 +43,38 @@ async fn main() -> Result<()> {
     let events = accounts.get_event_emitter();
 
     log::info!("Creating JSON-RPC API.");
-    let state = CommandApi::new(accounts);
+    let accounts = Arc::new(RwLock::new(accounts));
+    let state = CommandApi::from_arc(accounts.clone());
 
     let (client, mut out_receiver) = RpcClient::new();
-    let session = RpcSession::new(client.clone(), state);
+    let session = RpcSession::new(client.clone(), state.clone());
+    let canceler = CancellationToken::new();
 
     // Events task converts core events to JSON-RPC notifications.
     let events_task: JoinHandle<Result<()>> = tokio::spawn(async move {
+        let mut r = Ok(());
         while let Some(event) = events.recv().await {
-            let event = event_to_json_rpc_notification(event);
+            if r.is_err() {
-            client.send_notification("event", Some(event)).await?;
+                continue;
             }
+            let event = event_to_json_rpc_notification(event);
+            r = client.send_notification("event", Some(event)).await;
+        }
+        r?;
         Ok(())
     });
 
     // Send task prints JSON responses to stdout.
+    let cancelable = canceler.clone();
     let send_task: JoinHandle<anyhow::Result<()>> = tokio::spawn(async move {
-        while let Some(message) = out_receiver.next().await {
+        loop {
-            let message = serde_json::to_string(&message)?;
+            let message = tokio::select! {
+                _ = cancelable.cancelled() => break,
+                message = out_receiver.next() => match message {
+                    None => break,
+                    Some(message) => serde_json::to_string(&message)?,
+                }
+            };
             log::trace!("RPC send {}", message);
             println!("{message}");
         }
@@ -68,23 +85,41 @@ async fn main() -> Result<()> {
     let recv_task: JoinHandle<anyhow::Result<()>> = tokio::spawn(async move {
         let stdin = io::stdin();
         let mut lines = BufReader::new(stdin).lines();
-        while let Some(message) = lines.next_line().await? {
+        loop {
+            let message = tokio::select! {
+                _ = tokio::signal::ctrl_c() => {
+                    log::info!("got ctrl-c event");
+                    break;
+                }
+                message = lines.next_line() => match message? {
+                    None => {
+                        log::info!("EOF reached on stdin");
+                        break;
+                    }
+                    Some(message) => message,
+                }
+            };
             log::trace!("RPC recv {}", message);
             let session = session.clone();
             tokio::spawn(async move {
                 session.handle_incoming(&message).await;
             });
         }
-        log::info!("EOF reached on stdin");
         Ok(())
     });
 
-    // Wait for the end of stdin.
+    // Wait for the end of stdin / ctrl-c.
-    recv_task.await??;
+    recv_task.await?.ok();
 
-    // Shutdown the server.
+    // See "Thread safety" section in deltachat-ffi/deltachat.h for explanation.
-    send_task.abort();
+    // NB: Events are drained by events_task.
-    events_task.abort();
+    canceler.cancel();
+    accounts.read().await.stop_io().await;
+    drop(state);
+    let (r0, r1) = tokio::join!(events_task, send_task);
+    for r in [r0, r1] {
+        r??;
+    }
 
     Ok(())
 }