riemann_redis_persistence.md

Persist specific events into Redis datastore:

1. Clone the Riemann Git repository (clones into directory riemann):
   $ git clone https://github.com/aphyr/riemann.git

2. Checkout the last stable version (0.2.2 in our case):
   $ cd riemann
$ git checkout tags/0.2.2

3. Add Carmine dependency to riemann/project.clj:
   [com.taoensso/carmine "1.12.0"]

4. Add the Redis persistence functionality to Riemann's config file riemann/config.riemann:

(ns riemann.config
  (:require [taoensso.carmine :as car]))

    ; Assuming a locally running Redis server listening on port 6379.
    (def pool         (car/make-conn-pool))
    (def spec-server1 (car/make-conn-spec))

    (defmacro wcar [& body] `(car/with-conn pool spec-server1 ~@body))

    (defn persist-event [& children]
      (fn [event]
        ; Persist event to a Redis list with name '<SERVICE>.new-events'.
        (try
          (wcar (car/lpush (str (:service event) ".new-events") event))
          (catch Exception e
            (error "Redis datastore not available.")))
        (call-rescue event children))
      )

It's then used this way in riemann/config.riemann:

; Persist events to Redis where service equals 'foo'.
    ; Exclude those 'foo' events where state 'expired'.
    ; Additionally add events to 'index'.
    (where
      (and
        (service "foo")
        (not (state "expired"))
        )
      (persist-event index))

5. Try it out with a locally running Redis server:
   $ lein run
   Now it's time to generate some events containing :service "foo" so the where filter from above matches.
   If the events of service foo were successfully persisted into Redis, there should be a length greater than zero (3 in our case) in foo.new-events (check with Redis shell):
   $ redis-cli
redis 127.0.0.1:6379> LLEN foo.new-events
(integer) 3

If this modified version of Riemann should be deployed with the help of lein tar, then it's necessary to copy riemann/riemann.config into riemann/pkg first. This way the config file is then located in the etc sub directory after extracting the .tar.bz2 archive (created by lein tar) on the production machine.