TCPClient in json-rpc isn't thread-safe

[weissi]

swift-nio-examples/json-rpc/Sources/JsonRpc/Client.swift

Lines 20 to 60 in d36c05a

	public func connect(host: String, port: Int) -> EventLoopFuture<TCPClient> {
	assert(.initializing == self.state)
	let bootstrap = ClientBootstrap(group: self.group)
	.channelOption(ChannelOptions.socket(SocketOptionLevel(SOL_SOCKET), SO_REUSEADDR), value: 1)
	.channelInitializer { channel in
	return channel.pipeline.addTimeoutHandlers(self.config.timeout)
	.flatMap {
	channel.pipeline.addFramingHandlers(framing: self.config.framing)
	}.flatMap {
	channel.pipeline.addHandlers([
	CodableCodec<JSONResponse, JSONRequest>(),
	Handler(),
	])
	}
	}
	self.state = .connecting("\(host):\(port)")
	return bootstrap.connect(host: host, port: port).flatMap { channel in
	self.channel = channel
	self.state = .connected
	return channel.eventLoop.makeSucceededFuture(self)
	}
	}
	public func disconnect() -> EventLoopFuture<Void> {
	if .connected != self.state {
	return self.group.next().makeFailedFuture(ClientError.notReady)
	}
	guard let channel = self.channel else {
	return self.group.next().makeFailedFuture(ClientError.notReady)
	}
	self.state = .disconnecting
	channel.closeFuture.whenComplete { _ in
	self.state = .disconnected
	}
	channel.close(promise: nil)
	return channel.closeFuture
	}
	public func call(method: String, params: RPCObject) -> EventLoopFuture<Result> {

Thanks to @wlisac for the report.

At least TCPClient is very thread unsafe and really needs fixing. Without synchronisation, state is read/written to from different threads.

[Lukasa]

State is a computed property guarded by a lock.

[weissi]

oops, sorry, in this case it's only racy :). Because two connects could come it at the same time, both pass the assert(.initializing == self.state) and then weird stuff will happen from then on.