Hystrix-clj

hystrix.txt

  Functions for defining and executing Hystrix dependency commands and collapers.

  The definition of commands and collapers is separated from their instantiation and execution.
  They are represented as plain Clojure maps (see below) which are later instantiated into
  functional HystrixCommand or HystrixCollapser instances.

  A command definition map can be passed to the execute, and queue functions
  to invoke the command.

  HystrixCommand

  A command is defined as a map with the following keys:

    :type            Always :command. Required.
    :group-key       A HystrixCommandGroupKey, string, or keyword. Required.
    :command-key     A HystrixCommandKey, string, or keyword. Required.
    :thread-pool-key A HystrixThreadPoolKey, string, or keyword. Required.
    :run-fn          The function to run for the command. The function may have any number of
                     arguments. Required.
    :fallback-fn     A function with the same args as :run-fn that calculates a fallback
                     result when the command fails. Optional, defaults to a function that throws
                     UnsupportedOperationException.
    :cache-key-fn    A function which the same args as :run-fn that calculates a cache
                     key for the given args. Optional, defaults to nil, i.e. no caching.

  For example, here's a definition for an addition command:

    ; Define the command
    (def plus-command
      {:type        :command
       :group-key   :MyMathGroup
       :command-key :plus
       :run-fn      +})

    ; Execute the command
    (hystrix/execute plus-command 1 2 3 4 5)
    ;=> 15

    ; Queue the command
    (def f (hystrix/queue plus-command 4 5))
    ;=> java.util.concurrent.Future/clojure.lang.IDeref

    ; Now you can deref the future as usual
    @f   ; or (.get f)
    ;=> 9