Merge 6581fa2 into 951ee6c

src/ziggurat/init.clj

@@ -4,7 +4,7 @@
             [mount.core :as mount :refer [defstate]]
             [schema.core :as s]
             [ziggurat.config :refer [ziggurat-config] :as config]
-            [ziggurat.messaging.rabbitmq-wrapper :as rmqw]
+            [ziggurat.messaging.messaging :as messaging]
             [ziggurat.messaging.consumer :as messaging-consumer]
             [ziggurat.messaging.producer :as messaging-producer]
             [ziggurat.metrics :as metrics]
@@ -27,15 +27,15 @@
        (mount/with-args args)
        (mount/start))))
 
-(defn- start-rabbitmq-connection [args]
-  (start* #{#'rmqw/connection} args))
+(defn- start-messaging [args]
+  (messaging/start-connection config/config (:stream-routes args)))
 
-(defn- start-rabbitmq-consumers [args]
-  (start-rabbitmq-connection args)
+(defn- start-messaging-consumers [args]
+  (start-messaging args)
   (messaging-consumer/start-subscribers (get args :stream-routes) (ziggurat-config)))
 
-(defn- start-rabbitmq-producers [args]
-  (start-rabbitmq-connection args)
+(defn- start-messaging-producers [args]
+  (start-messaging args)
   (messaging-producer/make-queues (get args :stream-routes)))
 
 (defn start-kafka-producers []
@@ -46,24 +46,24 @@
 
 (defn start-stream [args]
   (start-kafka-producers)
-  (start-rabbitmq-producers args)
+  (start-messaging-producers args)
   (start-kafka-streams args))
 
 (defn start-management-apis [args]
-  (start-rabbitmq-connection args)
+  (start-messaging args)
   (start* #{#'server/server} (dissoc args :actor-routes)))
 
 (defn start-server [args]
-  (start-rabbitmq-connection args)
+  (start-messaging args)
   (start* #{#'server/server} args))
 
 (defn start-workers [args]
   (start-kafka-producers)
-  (start-rabbitmq-producers args)
-  (start-rabbitmq-consumers args))
+  (start-messaging-producers args)
+  (start-messaging-consumers args))
 
-(defn- stop-rabbitmq-connection []
-  (mount/stop #'rmqw/connection))
+(defn- stop-messaging []
+  (messaging/stop-connection config/config (:stream-routes mount/args)))
 
 (defn stop-kafka-producers []
   (mount/stop #'kafka-producers))
@@ -72,21 +72,21 @@
   (mount/stop #'streams/stream))
 
 (defn stop-workers []
-  (stop-rabbitmq-connection)
+  (stop-messaging)
   (stop-kafka-producers))
 
 (defn stop-server []
   (mount/stop #'server/server)
-  (stop-rabbitmq-connection))
+  (stop-messaging))
 
 (defn stop-stream []
   (stop-kafka-streams)
-  (stop-rabbitmq-connection)
+  (stop-messaging)
   (stop-kafka-producers))
 
 (defn stop-management-apis []
   (mount/stop #'server/server)
-  (stop-rabbitmq-connection))
+  (stop-messaging))
 
 (def valid-modes-fns
   {:api-server     {:start-fn start-server :stop-fn stop-server}
@@ -115,7 +115,6 @@
 (defn stop-common-states []
   (mount/stop #'config/config
               #'metrics/statsd-reporter
-              #'rmqw/connection
               #'nrepl-server/server
               #'tracer/tracer))
 

src/ziggurat/messaging/messaging.clj

@@ -0,0 +1,65 @@
+(ns ziggurat.messaging.messaging
+  (:require [ziggurat.config :refer [ziggurat-config]]
+            [ziggurat.messaging.rabbitmq-wrapper :as rmqw]
+            [ziggurat.messaging.messaging-interface :as messaging-interface]
+            [clojure.tools.logging :as log]))
+
+(def messaging-impl (atom nil))
+
+(defn get-implementation []
+  (if (nil? @messaging-impl)
+    (throw (Exception. "Messaging Library is not initialized"))
+    @messaging-impl))
+
+(defn- get-messaging-implementor-constructor []
+  (if-let [configured-metrics-class-constructor (get-in (ziggurat-config) [:messaging :constructor])]
+    (let [configured-constructor-symbol (symbol configured-metrics-class-constructor)
+          constructor-namespace         (namespace configured-constructor-symbol)
+          _                             (require [(symbol constructor-namespace)])
+          metric-constructor            (resolve configured-constructor-symbol)]
+
+      (if (nil? metric-constructor)
+        (throw (ex-info "Incorrect messaging_interface implementation constructor configured. Please fix it." {:constructor-configured configured-constructor-symbol}))
+        metric-constructor))
+    rmqw/->RabbitMQMessaging))
+
+(defn initialise-messaging-library []
+  (let [messaging-impl-constructor (get-messaging-implementor-constructor)]
+    (reset! messaging-impl (messaging-impl-constructor))))
+
+(defn start-connection [config stream-routes]
+  (do (initialise-messaging-library)
+      (log/info "Initializing Messaging Library")
+      (messaging-interface/start-connection (get-implementation) config stream-routes)))
+
+(defn stop-connection [config stream-routes]
+  (do (log/info "Stopping Messaging Library")
+      (messaging-interface/stop-connection (get-implementation) config stream-routes)))
+
+(defn create-and-bind-queue
+  ([queue-name exchange-name]
+   (create-and-bind-queue queue-name exchange-name nil))
+  ([queue-name exchange-name dead-letter-exchange]
+   (messaging-interface/create-and-bind-queue (get-implementation) queue-name exchange-name dead-letter-exchange)))
+
+(defn publish
+  ([exchange message-payload]
+   (messaging-interface/publish (get-implementation) exchange message-payload))
+  ([exchange message-payload expiration]
+   (messaging-interface/publish (get-implementation) exchange message-payload expiration)))
+
+(defn get-messages-from-queue
+  ([queue-name ack?]
+   (messaging-interface/get-messages-from-queue (get-implementation) queue-name ack?))
+  ([queue-name ack? count]
+   (messaging-interface/get-messages-from-queue (get-implementation) queue-name ack? count)))
+
+(defn process-messages-from-queue [queue-name count processing-fn]
+  (messaging-interface/process-messages-from-queue (get-implementation) queue-name count processing-fn))
+
+(defn start-subscriber [prefetch-count wrapped-mapper-fn queue-name]
+  (messaging-interface/start-subscriber (get-implementation) prefetch-count wrapped-mapper-fn queue-name))
+
+(defn consume-message [ch meta payload ack?]
+  (messaging-interface/consume-message (get-implementation) ch meta payload ack?))
+

src/ziggurat/messaging/messaging_interface.clj

@@ -0,0 +1,79 @@
+(ns ziggurat.messaging.messaging-interface)
+
+(defprotocol MessagingProtocol
+  "A protocol that defines the interface for queue-based retry implementation libraries. Any type or class that implements this protocol can be passed to the messaging namespace to be used for retrying messages.
+ Example implementations for this protocol:
+
+ start-connection [config stream-routes]
+ This is used to initialize the messaging library so that it push messages to the retry backend.
+ Args:
+    - impl: the class object that implements this protocol, i.e. an instance of the deftype for example
+    - config: It is the config map defined in the `config.edn` file. It includes the entire config map
+    - stream-routes: It is a map containing topic entities and their handler functions, channels and their handler functions
+
+ stop-connection [impl connection config stream-routes]
+ This is used to stop the messaging library and cleanup resources.
+ Args:
+    - impl: the class object that implements this protocol, i.e. an instance of the deftype for example
+    - connection: The connection object that is used which can be used to close and cleanup network connections to the retry backend
+    - config: It is the config map defined in the `config.edn` file. It includes the entire config map
+    - stream-routes: It is a map containing topic entities and their handler functions, channels and their handler functions
+
+ create-and-bind-queue [impl queue-name exchange-name dead-letter-exchange]
+ This is used to create a queue and bind it to an exchange.
+ Args:
+    - impl: the class object that implements this protocol, i.e. an instance of the deftype for example
+    - queue-name: The name of the queue which will be bound the exchange
+    - exchange-name: The name of the exchange to bind the queue to, Example if `test_application_queue` is bound to `test_application_exchange` then all messages which need to be sent to `test_application_queue`
+    will have to be sent to the `test_application_exchange` which will route it to the bound queue.
+    - dead-letter-exchange: The name of the dead-letter-exchange if specified will be bound the queue which will in turn route all messages which have exceeded the max retries to the specified dead-letter-exchange
+
+ get-messages-from-queue [impl queue-name ack? count]
+ This is used to fetch and deserialize them messages from the queue.
+ Args:
+    - impl: the class object that implements this protocol, i.e. an instance of the deftype for example
+    - queue-name: this is the name of the queue from where to fetch messages
+    - ack?: a boolean flag which indicates if the message will be acknowledged upon consumption, ack-ing the message should discard it from the queue preventing a re-consumption.
+    - count: `count` number of messages will be fetched from the queue. If not provided it will default to an arbitrary value, ideally `1`.
+
+ process-messages-from-queue [impl queue-name count processing-fn]
+ This is used to process messages from the queue. This method does not return the messages unlike `get-messages-from-queue`, instead it runs the `processing-fn` against every message consumed from the queue
+ Args:
+    - impl: the class object that implements this protocol, i.e. an instance of the deftype for example
+    - queue-name: the name of the queue to consume messages from
+    - ack?: a boolean flag which indicates if the message will be acknowledged upon consumption, ack-ing the message should discard it from the queue preventing a re-consumption.
+    - count: `count` number of messages will be consumed from the queue. If not provided it will default to an arbitrary value, ideally `1`.
+
+ start-subscriber [impl prefetch-count wrapped-mapper-fn queue-name]
+ This method is used to start subscribers for a specific queue
+ Args:
+    - impl: the class object that implements this protocol, i.e. an instance of the deftype for example
+    - prefetch-count: The maximum number of unacknowledged messages that a consumer can receive at once
+    - wrapped-mapper-fn: This is the processing-fn which will run against every messaged consumed from the queue
+    - queue-name: This is the name of the queue to which a subscriber will subscribe to
+
+ consume-message [impl ch meta payload ack?]
+ ; Todo should be removed as it is only being used for testing
+ This method deserializes the message consumed from the queue
+ Args:
+    - impl: the class object that implements this protocol, i.e. an instance of the deftype for example
+    - ch: A Channel object
+    - meta: metadata containing information about the message payload
+    - payload: the message payload in byte-array format as fetched from the queue
+    - ack?: a boolean flag which indicates if the message will be acknowledged upon consumption, ack-ing the message should discard it from the queue preventing a re-consumption.
+ "
+
+  (start-connection [impl config stream-routes])
+  (stop-connection [impl config stream-routes])
+  (publish
+    [impl exchange message-payload]
+    [impl exchange message-payload expiration])
+  (create-and-bind-queue
+    [impl queue-name exchange-name]
+    [impl queue-name exchange-name dead-letter-exchange])
+  (get-messages-from-queue
+    [impl queue-name ack?]
+    [impl queue-name ack? count])
+  (process-messages-from-queue [impl queue-name count processing-fn])
+  (start-subscriber [impl prefetch-count wrapped-mapper-fn queue-name])
+  (consume-message [impl ch meta payload ack?]))