This is a framework to use RabbitMQ as a client/server RPC setup together with the Go amqp implementation. The framework can manage a fully functional message queue setup with reconnects, disconnects, graceful shutdown and other stability mechanisms. By providing this RabbitMQ can be used as transport and service discovery to quickly get up and running with a micro service architecture.
Since the framework handles the majority of the communication with RabbitMQ and the Go library the user does not need to know details about those systems. However, since a few interfaces exposes the Go package types and that the nomenclature is unique for RabbitMQ some prior experience is preferred.
This project has been used in production since October 2018 handling millions of requests both as server and client.
The server is inspired by the HTTP library where the user maps a RabbitMQ
binding to a handler function. A response writer is passed to the handler which
may be used as an io.Writer to write the response.
This is an example of how to get up and running with a server responding to all messages published to the given routing key.
server := NewServer("amqp://guest:guest@localhost:5672")
server.Bind(DirectBinding("routing_key", func(c context.Context, rw *ResponseWriter d *amqp.Delivery) {
// Print what the body and header was
fmt.Println(d.Body, d.Headers)
// Add a response to the publisher
fmt.Fprint(rw, "Handled")
}))
server.ListenAndServe()The example above uses a DirectBinding but all the supported bindings are
provided via an interface where the exchange type will be set to the proper
type.
server.Bind(DirectBinding("routing_key", handleFunc))
server.Bind(TopicBinding("queue-name", "routing_key.#", handleFunc))
server.Bind(HeadersBinding("queue-name", amqp.Table{"x-match": "all", "foo": "bar"}, handleFunc))If the default variables doesn't result in the desired result you can setup the binding with the type manually.
customBinding := CreateBinding("oh-sweet-queue", DefaultExchangeNameDirect, handleFunc).
WithPrefetchCount(100).
WithAutoAck(false)
server.Bind(customBinding)The server will not connect until ListenAndServe() is being called. This means
that you can configure settings for the server until that point. The settings
can be changed by calling chainable methods.
server := NewServer("amqp://guest:guest@localhost:5672").
WithDebugLogger(log.Printf).
WithErrorLogger(log.Printf).
WithTLS(&tls.Config{})QoS is by default set to a prefetch count of 10. If you want to change this
you can modify the binding by setting the PrefetchCount to something else.
The client is built around channels to be able to handle as many requests as possible without the need to setup multiple clients. All messages published get a unique correlation ID which is used to determine where a response should be passed no matter what order it's received.
The client takes a Request as input which can hold all required information
about how to route and handle the message and response.
client := NewClient("amqp://guest:guest@localhost:5672")
request := NewRequest().
WithRoutingKey("routing_key").
WithBody("This is my body)
response, err := client.Send(request)
if err != nil {
log.Fatal(err.Error())
}
log.Print(string(response.Body))The client will not connect while being created, instead this happens when the
first request is being published (while calling Send()). This allows you to
configure connection related parameters such as timeout by chaining the
methods.
// Set timeout after NewClient is invoked by chaining.
client := NewClient("amqp://guest:guest@localhost:5672").
WithTimeout(5000 * time.Milliseconds)
// Will not connect and may be changed until this call.
client.Send(NewRequest().WithRoutingKey("routing_key"))Example of available methods for chaining.
client := NewClient("amqp://guest:guest@localhost:5672").
WithDebugLogger(log.Printf).
WithErrorLogger(log.Printf).
WithDialConfig(amqp.Config{}).
WithTLS(&tls.Config{}).
WithReplyToConsumerArgs(amqp.Table{}).
WithConfirmMode(false),
WithTimeout(10 * Time.Second)Confirm mode can be set on the client and will make the client wait for Ack
from the amqp-server. This makes sending requests more reliable at the cost of
some performance as each publishing must be confirmed by the amqp-server Your
can read more here
The client is set in confirm mode by default.
You can use WithConfirmMode to control this setting. It defaults to true.
client := NewClient("amqp://guest:guest@localhost:5672").
WithConfirmMode(true)The Request type is used as input to the clients send function and holds all
the information about how to route and handle the request. All the properties
may be set with chainable methods to make it easy to construct. A Request may
be re-used as many times as desired.
request := NewRequest().
WithBody(`{"hello":"world"}`).
WithContentType("application/json").
WithContext(context.TODO()).
WithExchange("custom.exchange").
WithRoutingKey("routing_key").
WithHeaders(amqp.Headers{}).
WithTimeout(5 * time.Second).
WithMandatory(true).
WithResponse(true)By default a context.Background() will be added and WithResponse() will be
set to true.
WithTimeout will also set the Expiration on the publishing since there is no
point of handling the message after the timeout has expired. Setting
WithResponse(false) will ensure that no Expiration is set.
The Request also implements the io.Writer interface which makes it possible
to use directly like that.
request := NewRequest()
err := json.NewEncoder(request).Encode(serializableObject)
if err != nil {
panic(err)
}The client invokes a default SendFunc while calling Send() where all the
RabbitMQ communication is handled and the message is published. The sender is
attached to a public field (Sender) and may be overridden. This enables you to
handle unit testing without the need to implement an interface. This framework
comes with a package named amqprpctest which helps you create a client with
your own custom send function.
unitTestSendFunc := func(r *Request) (*amqp.Delivery, error) {
fmt.Println("will not connect or publish anything")
mockResponse := &amqp.Delivery{
Body: []byte("this is my mock response")
}
return mockResponse, nil
}
client := amqprpctest.NewTestClient(unitTestSendFunc)Both the client and the server aim to only handle the connectivity and routing within the RPC setup. This means that there's no code interacting with the request or the responses before or after a request is being published or received. To handle this in a dynamic way and allow the user to affect as much as possible for each request both the server and the client is built around middlewares.
Server middlewares can be hooked both to a specific handler or to all messages for the entire server. Middlewares can be chained to be executed in a specific order.
The middleware is inspired by the HTTP library where the middleware is defined as a function that takes a handler function as input and returns the same handler func. This makes it possible to add middlewares in any order.
The handler function HandlerFunc takes a context, a response writer and a
delivery as input not returning anything. The ServerMiddlewareFunc thus takes
this type as input and returns the same type.
type HandlerFunc func(context.Context, *ResponseWriter, amqp.Delivery)
type ServerMiddlewareFunc func(next HandlerFunc) HandlerFuncTo execute the next handler just call the received function.
server := NewServer("amqp://guest:guest@localhost:5672")
// Define a custom middleware to use for the server.
func myMiddleware(next HandlerFunc) HandlerFunc {
// Preinitialization of middleware here.
return func(ctx context.Context, rw *ResponseWriter d amqp.Delivery) {
fmt.Println("this will be executed before the actual handler")
// Execute the handler.
next(ctx, rw, d)
fmt.Println("this will be executed after the actual handler")
}
}
// Add a middleware to specific handler.
server.Bind(DirectBinding("foobar", myMiddleware(HandlerFunc)))
// Add multiple middlewares to specific handler by chainging them.
server.Bind(
DirectBinding(
"foobar",
ServerMiddlewareChain(
myHandler,
middlewareOne,
middlewareTwo,
middlewareThree,
),
)
)
// Add middleware to all handlers on the server.
server.AddMiddleware(myMiddleware)
server.ListenAndServe()Note that an example of how to handle panic recovery with a middleware if a handler would panic is located in the middleware folder in this project.
The client supports middlewares which may be executed before or after a request has been published. This is a great way to i.e enrich headers or handle errors returned.
The sender function SendFunc takes a Request as input and returns an
amqp.Delivery pointer and an error. The ClientMiddlewareFunc thus takes this
type as input and returns the same type.
type SendFunc func(r *Request) (d *amqp.Delivery, e error)
type ClientMiddlewareFunc func(next SendFunc) SendFuncA middleware can be added to the client to be executed for all requests or
attached to the Request type instead.
func myMiddleware(next SendFunc) SendFunc {
return func(r *Request) (*amqp.Delivery, error) (
r.Publishing.Headers["enriched-header"] = "yes"
r.Publishing.AppId = "my-app"
return next(r)
}
}
// Add the middleware to all request made with the client.
client := NewClient("amqp://guest:guest@localhost:5672").
AddMiddleware(myMiddleware)
// Add the middleware to a single request
reuqest := NewRequest().
WithRoutingKey("routing_key").
AddMiddleware(myMiddleware)
client.Send(request)Due to the way middlewares are added and chained the middlewares attached to the request will always be executed after the middlewares attached to the client.
For more examples of client middlewares, see examples/middleware.
You often want to know when a connection has been established and when it comes
to RabbitMQ also perform some post connection setup. This is enabled by the fact
that both the server and the client holds a list of OnStarted. The function
receives the incoming connection, outgoing connection, incoming channel and
outgoing channel.
type OnStartedFunc func(inputConn, outputConn *amqp.Connection, inputChannel, outputChannel *amqp.Channel)server := NewServer("amqp://guest:guest@localhost:5672").
OnStarted(func(inConn, outConn *amqp.Connection, inChan, outChan *amqp.Channel) {
// Do something after connection here...
})
}
server.ListenAndServe()Both the server and the client follow the recommendations for RabbitMQ connections which means separate connections for incoming and outgoing traffic and separate channels for consuming and publishing messages. Because of this the signature looks the same way for both the server and the client.
Since this frameworks main responsibility is to handle connections it's shipped
with a type named Certificates which can hold the RabbitMQ message bus CA and
the clients certificate and private key. This is just a convenient way to keep
track of certificates to use but it also implements a method named TLSConfig()
which returns a *tls.Config. This may then be used to connect with a secured
protocol (AMQPS) to the message bus.
certificates := Certificates{
CA: "/path/to/rootCA.pem",
}
// Now we can get the TLS configuration to use for the client and server.
uri := "amqps://guest:guest@localhost:5671"
server := NewServer(uri).WithTLS(certificates.TLSConfig())
client := NewClient(uri).WithTLS(certificates.TLSConfig())
server.ListenAndServe()You can specify two optional loggers for debugging and errors or unexpected behaviour. By default only error logging is turned on and is logged via the log package's standard logging.
You can provide your own logging function for both error and debug on both the client and the server.
debugLogger := log.New(os.Stdout, "DEBUG - ", log.LstdFlags)
errorLogger := log.New(os.Stdout, "ERROR - ", log.LstdFlags)
server := NewServer(url).
WithErrorLogger(errorLogger.Printf).
WithDebugLogger(debugLogger.Printf)
client := NewClient(url).
WithErrorLogger(errorLogger.Printf).
WithDebugLogger(debugLogger.Printf)This is perfect when using a logger which supports debugging as a separate
method such as the logrus logger which has Debugf and Errorf methods.
There are a few examples included in the examples folder. For more information about how to customize your setup, see the documentation.