Telegram notification support

src/riemann/telegram.clj

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+(ns ^{:doc "Send events to Telegram"}
+  riemann.telegram
+  (:require [clj-http.client :as client]
+            [clojure.string :refer [join]]))
+
+(def ^:private api-url "https://api.telegram.org/bot%s/%s")
+
+(defn- format-message [ev]
+  "Formats a message, accepts a single
+  event or a sequence of events."
+  (join "\n\n"
+        (map
+          (fn [e]
+            (str
+              "<strong>Host:</strong> " (or (:host e) "-") "\n"
+              "<strong>Service:</strong> " (or (:service e) "-") "\n"
+              "<strong>State:</strong> " (or (:state e) "-") "\n"
+              "<strong>Metric:</strong> " (or (:metric e) "-") "\n"
+              "<strong>Description:</strong> "
+                (escape (or (:description e) "-") {\< "&lt;", \> "&gt;", \& "&amp;"}))) 
+          (flatten [ev]))))
+
+(defn- post
+  "POST to the Telegram API."
+  [token chat_id event]
+  (client/post (format api-url token "sendMessage")
+               {:form-params {:chat_id chat_id 
+                              :parse_mode "HTML"
+                              :text (format-message event)}
+		:throw-entire-message? true}))
+
+(defn telegram
+  "Send events to Telegram chat. Uses your bot token and returns a function,
+  which send message through API to specified chat.
+
+  Format event (or events) to string with markdown syntax.
+
+  Telegram bots API documentation: https://core.telegram.org/bots/api
+
+  Usage:
+
+  (def token \"define_your_token\")
+  (def chat_id \"0123456\")
+
+  (streams
+    (rollup 5 3600 (telegram {:token token :chat_id chat_id})))"
+  [{:keys [token chat_id]}]
+  (fn [e] (post token chat_id e)))

test/riemann/telegram_test.clj

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+(ns riemann.telegram-test
+  (:use riemann.telegram
+        clojure.test)
+  (:require [riemann.logging :as logging]))
+
+(def api-token (System/getenv "TELEGRAM_API_TOKEN"))
+(def chat-id (System/getenv "TELEGRAM_CHAT_ID"))
+
+(when-not api-token
+  (println "export TELEGRAM_API_TOKEN=\"...\" to run these tests."))
+
+(when-not chat-id
+  (println "export TELEGRAM_CHAT_ID=\"...\" to run these tests."))
+
+(logging/init)
+
+(deftest ^:telegram ^:integration single_event
+  (let [tg (telegram {:token api-token :chat_id chat-id})]
+    (tg {:host "localhost"
+         :service "telegram single"
+         :description "Testing single event"
+         :metric 42
+         :state "ok"})))
+
+(deftest ^:telegram ^:integration multiple_events
+  (let [tg (telegram {:token api-token :chat_id chat-id})]
+    (tg [{:host "localhost"
+          :service "telegram multiple"
+          :description "Testing multiple events"
+          :metric 43
+          :state "ok"}
+         {:host "localhost"
+          :service "telegram multiple"
+          :description "Still testing multiple events"
+          :metric 44
+          :state "ok"}])))