circle.wait-for8 — sh.griffin/wait-for8 1.0.6

catch-dispatch clj

(catch-dispatch options throwable)

catch? clj multimethod

decides whether this exception should be caught

duration->millis clj

(duration->millis d)

exception-class? clj

(exception-class? x)

exponential-backoff-fn clj

(exponential-backoff-fn)

(exponential-backoff-fn
  {:keys [base mult jitter seed]
   :or {base (time/millis 900) mult 1.25 jitter (time/millis 100)}})

Returns an impure function, suitable for passing as a sleep argument to wait-for, that implements an exponential back-off with optional jitter.

With no-args the delay will be ~1s initially, grow 1.25 with each retry and have 100ms of jitter

algorithm is: max(0, base * mult^n +/- (jitter/2))

n is the retry number base and jitter specified as java duration

fail clj

(fail {:keys [sleep] :as options})

stuff to do when an iteration fails. Returns new options

parse-args clj

(parse-args args)

retry? clj

(retry? options)

success? clj

(success? options result)

wait-for clj

(wait-for fn)

(wait-for options fn)

Higher Order Function that controls retry behavior. By default, call f, and retry (by calling again), if f returns falsey.

• f - a fn of no arguments.

Options:

• sleep: how long to sleep between retries, either as a java8 duration or as a no-arg function returning a long millis value. The function will be called after each failure to retrieve a new value. A call to (exponential-backoff-fn) will create a suitable fn to implement exponential backoff with jitter strategy.

  Defaults to 1s.

• tries: number of times to retry before throwing. An integer, or :unlimited. Defaults to 3 (or unlimited if :timeout is given, and :tries is not)

• timeout: a java8 duration. Stop retrying when period has elapsed, regardless of how many tries are left.

• catch: By default, wait-for does not catch exceptions. Pass this to specify which exceptions should be caught and retried Can be one of several things:

  • a seq of exception classes to catch and retry on
  • an fn of one argument, the thrown exception. Retry if it returns truthy.
  • if the exception is a slingshot throwing a map, can be a keyword, or a vector of a key and value, destructuring slingshot-style. Retry if the value obtained by destrutcturing is truthy

  If the exception matches the catch clause, wait-for retries. Otherwise the exception is thrown.

• success-fn: a fn of one argument, the return value of f. Stop retrying if success-fn returns truthy. If not specified, wait-for returns when f returns truthy. May pass :no-throw here, which will return truthy when f doesn't throw.

• error-hook: a fn of one argument, an exception. Called every time fn throws, before the catch clause decides what to do with the exception. This is useful for e.g. logging.

wait-for* clj

(wait-for* {:keys [options f]})