NsqClient

A basic but reliable .NET Standard 2.0 library for publishing and subscribing to NSQ.

It's currently used in production to handle hundreds of thousands of messages per week.

Features

• Support for NSQ 1.2.0
• Publishing of string or byte[] messages to topics
• Subscribing with callbacks (with Finish, Touch and Requeue operations)
• Settings: MaxInFlight (RDY) and MsgTimeout
• Automatic reconnection when the connection is lost
• Async API

Currently not supported

These features are not supported, but might be in the future.

• Discovery
• Backoff
• TLS
• Snappy
• AUTH

Installation

Install from NuGet.

PM> Install-Package NsqClient

or

> dotnet add package NsqClient

Usage

Publishing

Create an instance of INsqProducer, connect (by default to localhost:4150) and then call PublishAsync:

INsqProducer producer = new NsqProducer();
await producer.ConnectAsync();

string topicName = "mytopic";
string message = "mymessage";
await producer.PublishAsync(topicName, message);

You can also specify the connection parameters explicitly:

INsqProducer producer = new NsqProducer(new NsqProducerOptions("hostname", 4150));

And publish messages as byte[] instead of string:

byte[] msg = Encoding.UTF8.GetBytes("my_message");
await producer.PublishAsync("topic_name", msg);

Subscribing

Create an INsqConsumer instance and register the OnMessage event.

string topicName = "mytopic";
string channelName = "mychannel";
INsqConsumer consumer = new NsqConsumer(new NsqConsumerOptions(topicName, channelName));

connection.OnMessage += OnMessage;

await connection.ConnectAsync();

Then handle the message in the callback:

private async void OnMessage(object sender, NsqMessageEventArgs msg)
{
    Console.WriteLine("Received new message");
    Console.WriteLine("Processing attempt number: {0}", msg.Attempt);
    Console.WriteLine("Raw payload length: {0}", msg.Body.Length)
    Console.WriteLine("Payload string:\n{0}", msg.BodyString);

    await msg.Finish();
}

The available operations on a message are:

• msg.Finish() to complete the message
• msg.Requeue() to requeue with a 1 second delay
• msg.Requeue(TimeSpan) to requeue with a custom delay
• msg.Touch() to touch the message so that it's not delivered again

The NsqConsumerOptions class has many constructors that allow to set:

• hostname and port of nsqd
• the topic name
• the channel name
• the maxInFlight value: maximum number of messages that will be processed by this consumer at a given time
• the msgTimeout for this client, after which the message will be delivered again by the server

The maxInFlight value can also be adjusted at any given time with the SetMaxInFlight(int) method.

Error handling

INsqProducer and INsqConsumer both provide a way to handle and log connection errors and reconnections.

Connection errors

The OnError event is raised when there's an internal exception while reading from the stream, or when an error frame is received from NSQ.

connection.OnError += OnError;

private static void OnError(object sender, NsqErrorEventArgs eventArgs)
{
    Console.WriteLine("OnError: {0}", eventArgs.Exception);
}

Disconnections

The OnDisconnected event is raised when the client disconnects from the NSQ instance. A property WillReconnect tells whether the client will attempt to reconnect (true except when shutting down).

connection.OnDisconnected += OnDisconnected;

private static void OnDisconnected(object sender, NsqDisconnectionEventArgs e)
{
    Console.WriteLine("OnDisconnected: Disconnected. Will reconnect? " + e.WillReconnect);
}

Reconnections

The OnReconnected event is raised after the client has successfully reconnected to the NSQ server.

connection.OnReconnected += OnReconnected;

private static void OnReconnected(object sender, NsqReconnectionEventArgs e)
{
    Console.WriteLine($"OnReconnected: Reconnected after {e.Attempts} attempts");
    Console.WriteLine($"In {e.ReconnectedAfter.TotalSeconds} seconds");
}