w01fe

;; Copyright Jason Wolfe and Prismatic, 2013.
;; Licensed under the EPL, same license as Clojure

(use 'plumbing.core)
(require '[clojure.java.shell :as shell]
         '[clojure.string :as str])

(import '[java.util HashSet] '[java.io File])

(defn double-quote [s] (str "\"" s "\""))

aaronfeng

Application specific host grouping in Riemann-dash

It is generally desirable to group all the hosts for a specific service into a single dashboard view. For example, all the web servers are in single view while all the database servers are in another view.

This is usually not an issue when you are sending custom metrics using Riemann client. However, there are cases where you are using something that you do not control how the metrics are being sent. i.e., Riemann-tools.

Since Riemann-tools scripts are application agnostic, in order for the dashboard view to group hosts, we must inject some application specific information into the tags field. Tags is a collection of arbitrary strings. In the case of Riemann-tools scripts you can pass in arbitrary strings on the command line.

riemann-health --host 127.0.0.1 --tag "prod" --tag "webserver"

ndarville

Business Models

Advertising

Models	Examples
Display ads	Yahoo!
Search ads	Google

richhickey

(defmacro test->
  "Takes an expression and a set of test/form pairs. Threads expr (via ->)
  through each form for which the corresponding test expression (not threaded) is true."
  [expr
  & clauses]
  (assert (even? (count clauses)))
  (let [g (gensym)
        pstep (fn [[test step]] `(if ~test (-> ~g ~step) ~g))]
    `(let [~g ~expr
           ~@(interleave (repeat g) (map pstep (partition 2 clauses)))]

jboner

Latency Comparison Numbers (~2012)
----------------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD