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Continuous Deployment of Clojure Web Applications


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Slides from my talk at the first Clojure Conj in October, 2010. Accompanying code and a screencast may be found @

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Continuous Deployment of Clojure Web Applications

  1. 1. Continuous Deployment of Clojure Web Applications Chas Emerick @cemerick,
  2. 2. ego I am: • A Clojure programmer of > 2.5 years • Coauthor of the forthcoming “Clojure Programming” book from O’Reilly • Architect of Docuharvest • Founder of Snowtide Informatics (first (clojure-conj))
  3. 3. first principles ⚛ ☺Your Powerful Beauty Your Customers Anything that gets in the way of this happy union is the enemy. (first (clojure-conj))
  4. 4. definitional bits & minor opinions • We’re focusing on small- to medium-size deployments today. • You’re (probably) not a special snowflake. Stay close to the herd, and stick to your knitting. • Application deployment is (always?) a people and process problem, not a technology problem. (first (clojure-conj))
  5. 5. choosing a path “system administration” Unrepeatable, manual, undocumented; the high priesthoods oh god no (first (clojure-conj))
  6. 6. choosing a path (“roll your own”) Even the most clever spike is not a solution. “Emacs + SLIME + Clojure running in GNU Screen; all requests handled by Apache; mod_proxy sends them to the appropriate Jetty instance / servlet.” – Brian Carper @ clojure-websites “Feel free to say: ‘duct tape and string’ and ‘You're doing it wrong’.” – Brian Carper (private email) (first (clojure-conj))
  7. 7. obligatory yak photo (first (clojure-conj))
  8. 8. choosing a path community? standards sanity⇒ ⇒ • The Platonic ideal: vertically-integrated platforms, e.g. GAE, Heroku, Azure, VMWare/SpringSource platform • Dominant tools: Chef, Puppet, et al. • Clojure-centric tools: – jclouds: generic “cloud” API, provisioning – Pallet: declarative, composable configuration definition & management (first (clojure-conj))
  9. 9. interlude: deployment existentialism The complexity that is visited upon us when writing software is enough; in an ideal world, we shouldn’t have to develop all this extraneous expertise in how to build, package, and deploy that software as well. There are a few things in software that I know how to do really well that make me slightly unique, and I wish I could concentrate on those rather than becoming a generalist in this, yet another vector, which is fundamentally a means to an end. History and circumstance seem to be stacked against me at the moment, though. – “…wherein I feel the pain of being a generalist” (first (clojure-conj))
  10. 10. hey jclouds! • Meatspace: e.g. compute nodes, storage (local & EBS/SAN), network routing & security, IP allocation, etc • If you had an API to this infrastructurey stuff, you could make it do your bidding • Luckily: jclouds provides exactly this, for multiple cloud providers (first (clojure-conj))
  11. 11. howdy pallet! • Pallet:crates :: chef:recipes • Include recipes via chef-solo if you like • Beautiful declarative expression of provisioning and configuration operations • Simple, flexible model: lift/converge/phases/tags/prefix (first (clojure-conj))
  12. 12. pallet “Hello World” (def service (jcompute/compute-service "ec2” “AWS_ID” “AWS_SECRET_KEY” :ssh :log4j)) (pallet.core/defnode appserver {:os-family :ubuntu :os-description-matches "10.10" :min-ram 1024 :inbound-ports [22 8080]} :bootstrap (pallet.resource/phase (admin/automated-admin-user)) :configure (pallet.resource/phase ( :openjdk) (tomcat/tomcat)) :deploy (pallet.resource/phase (web-deploy warfile-path :port 8080))) (pallet.core/converge {appserver 1} :compute service :prefix “demo” :phase [:deploy]) (first (clojure-conj))
  13. 13. get thee a .war file • Allows you to deploy to any Java app server & platforms like Google App Engine and the Spring/VMWare platform • Seriously, it’s not difficult: – Maven: baked in war packaging – Leiningen/Cake: leiningen-war plugin – Gradle, Buildr, rake: Surely simple enough (first (clojure-conj))
  14. 14. app servers
  15. 15. embedded Jetty/Grizzly • Great for experimentation and throughout development, e.g. jetty directly supported in ring/compojure • In production environments: roll-your-own that buys you nothing, therefore unnecessarily evil. (first (clojure-conj))
  16. 16. Tomcat, JBoss, Glassfish et al. • Huge communities guarantee: • tool integration (e.g. profilers) • tons of experienced devs • books • monitoring and management support • resource management (e.g. DB connection pools) • clustering (e.g. Shoal) • commercial/paid support • You will eventually need these; give yourself the chance to take advantage of these resources (first (clojure-conj))
  17. 17. now for the (continuous) part (first (clojure-conj))
  18. 18. automate or die (first (clojure-conj))
  19. 19. links Resources that will eventually be available: Slides: linked from my blog @ Code: Credits: • Hugo Duncan et al. • Adrian Cole et al. • ClojureNYC and Western Mass Dev Group attendees that suffered through earlier revs of this talk (first (clojure-conj))
  20. 20. Thank You! I too am not a bit tamed—I too am untranslatable; I sound my barbaric yawp over the roofs of the world. The last scud of day holds back for me; It flings my likeness after the rest, and true as any, on the shadow’d wilds; It coaxes me to the vapor and the dusk. I depart as air—I shake my white locks at the runaway sun; I effuse my flesh in eddies, and drift it in lacy jags. I bequeathe myself to the dirt, to grow from the grass I love; If you want me again, look for me under your boot-soles. You will hardly know who I am, or what I mean; But I shall be good health to you nevertheless, And filter and fibre your blood. Failing to fetch me at first, keep encouraged; Missing me one place, search another; I stop somewhere, waiting for you. — Walt Whitman, Leaves of Grass (first (clojure-conj))