abronan / stream-client-go

Clients for the Cryptowatch public APIs

Stream Client in Golang

This library provides a Golang API to talk to the Cryptowatch Websocket Streaming API. This product is in alpha.

The Cryptowatch Websocket Streaming API is not public like our REST API. Please click here to inquire about getting access to it.

Using the library

The typical workflow is to create an instance of the connection, setup some state- and message-listeners, and then kick off the connection. As events happen, registered listeners will be called (see the note below on concurrency).

Code Sample

// Create a new stream connection instance. Note that the actual connection
// will happen later.
c, err := streamclient.NewStreamConn(&streamclient.StreamParams{
	URL: "wss://sb.cryptowat.ch",

	Reconnect:        true,
	ReconnectTimeout: 1 * time.Second,
	Backoff:          true,
	Subscriptions:    []string{
		"markets:86:trades", // Trade feed for Kraken BTCEUR
		"markets:87:trades", // Trade feed for Kraken BTCUSD
	},

	APIKey:    "myapikey",
	SecretKey: "mysecretkey",
})
if err != nil {
	log.Fatal("%s", err)
}

// Ask for the state transition updates, and present them to the user somehow
c.AddStateListener(
	streamclient.StateAny,
	func(conn *streamclient.StreamConn, oldState, state streamclient.State, cause error) {
		fmt.Printf(
		  "State updated: %s -> %s",
		  streamclient.StateNames[oldState],
		  streamclient.StateNames[state],
		)
		// If there is a non-nil cause, print it as well
		if cause != nil {
			fmt.Printf(" (%s)", cause)
		}
		fmt.Printf("\n")
	},
)

// Listen for received market messages and print them
c.AddMarketListener(
	func(conn *streamclient.StreamConn, msg *ProtobufMarkets.MarketUpdateMessage) {
		fmt.Printf("Message received: %s\n\n", proto.CompactTextString(msg))
	},
)

// Finally, connect.
c.Connect()

// NOTE: by the time Connect() returns, the connection is not yet
// established. Connect() merely starts the connection loop (which will
// handle connection, receiving data, and reconnection if requested), and
// returns.

// Wait for some external event, such as OS signal.
WaitForSomething()

// Close the connection. It will cause the reconnection to stop, and
// currently active websocket connection (if any) to close with the status
// 1000 (normal closure).
if err := c.Close(); err != nil {
	log.Fatal("Failed to close the connection: %s", err)
}

Concurrency

All methods of the StreamConn and wrappers can be called concurrently from any number of goroutines.

State listeners (registered with AddStateListener and AddStateListenerOpt) and message listeners (registered with AddMarketListener) are called by the same internal goroutine (unique to each connection); that is, they are never called concurrently with each other.

Command line tool

Use the command line tool stream-client to subscribe to live data feeds from the command line. To install the tool, run make from the root of the repo. This will create the executable bin/stream-client, which can be used as follows:

./stream-client \
    -apikey=your_api_key \
    -secretkey=your_secret_key \
    -sub subscription_key \
    -sub subscription_key2