TL;DR

Langohr is a Clojure RabbitMQ client that embraces AMQP 0.9.1 Model.

3.0.0 is a major release that introduces breaking API changes, JDK 8 compatibility, minor new features and major internal revamp.

Options as Maps

Functions that take options now require a proper Clojure map instead of pseudo keyword arguments:

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;; in Langohr 2.x

(lq/declare ch q :durable true)
(lhcons/subscribe ch q (fn [_ _ _])
                        :consumer-tag ctag :handle-cancel-ok (fn [_]))
(lb/publish ch "" q "a message" :mandatory true)

;; in Langohr 3.x
(lq/declare ch q {:durable true})
(lhcons/subscribe ch q (fn [_ _ _])
                        {:consumer-tag ctag :handle-cancel-ok (fn [_])})
(lb/publish ch "" q "a message" {:mandatory true})

JDK 8 Compatibility

Langohr test suite now passes on JDK 8 (previously there was 1 failure in recovery test).

GH issue: #54.

Connection Recovery Performed by Java Client

Langohr no longer implements automatic connection recovery of its own. The feature is still there and there should be no behaviour changes but the functionality has now been pushed “upstream” in the Java client, so Langohr now relies on it to do all the work.

There is two public API changes:

• com.novemberain.langohr.Recoverable is gone, langohr.core/on-recovery now uses com.rabbitmq.client.Recoverable instead in its signature.

• Server-named queues will change after recovery. Use langohr.core/on-queue-recovery to register a listener for queue name change.

GH issue: #58.

RabbitMQ Java Client Upgrade

RabbitMQ Java client dependency has been updated to 3.4.2.

Custom Exception Handlers

langohr.core/exception-handler is a function that customizes default exception handler RabbitMQ Java client uses:

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(require '[langohr.core :as rmq])

(let [(rmq/exception-handler :handle-consumer-exception-fn (fn [ch ex consumer
                                                               consumer-tag method-name]
                                                             ))]
  )

Valid keys are:

• :handle-connection-exception-fn
• :handle-return-listener-exception-fn
• :handle-flow-listener-exception-fn
• :handle-confirm-listener-exception-fn
• :handle-blocked-listener-exception-fn
• :handle-consumer-exception-fn
• :handle-connection-recovery-exception-fn
• :handle-channel-recovery-exception-fn
• :handle-topology-recovery-exception-fn

GH issue: #47.

Clojure 1.7 Support

Clojure 1.7-specific compilation issues and warnings were eliminated.

clj-http Upgrade

clj-http dependency has been updated to 1.0.0.

ClojureWerkz Support Upgrade

clojurewerkz/support dependency has been updated to 1.1.0.

langohr.core/version is Removed

langohr.core/version was removed.

Change Log

Langohr change log is available on GitHub.

Langohr is a ClojureWerkz Project

Langohr is part of the group of libraries known as ClojureWerkz, together with

• Elastisch, a minimalistic well documented Clojure client for ElasticSearch
• Cassaforte, a Clojure Cassandra client built around CQL 3.0
• Monger, a Clojure MongoDB client for a more civilized age
• Neocons, a client for the Neo4J REST API
• Quartzite, a powerful scheduling library

and several others. If you like Langohr, you may also like our other projects.

Let us know what you think on Twitter or on the Clojure mailing list.

About the Author

Michael on behalf of the ClojureWerkz Team