Implements a block form of Attempt.run/2.

Examples

iex> require Attempt
...> Attempt.execute tries: 3 do
...>   IO.puts "Welcome to Attempt"
...> end
Hi
:ok

Run a function in the context of a retry budget.

A retry budget has several compoents:

• a token bucket which acts to provide retry throttlnh for any retries

• a retry policy which determines whether to return, retry or reraise

• a backoff strategy which determines the retry backoff strategy

• a maximum number of allowable tries that are performed when in an effort to generate a non-error return

The given function will be executed until a successful return is delivered or the maximum number of tries is exceeded or if no token could be claimed.

Arguments

• fun is an anonymous function or function reference to be executed.

• options is a keyword list of options to configure the retry budget

Options

• :tries is the number of times the function will be executed if an error is returned from the function

• :token_bucket is the token bucket used to throttle the execution rate. Currently only one token bucket is implemented. See Attempt.Bucket.Token

• :retry_policy is a module that implements the Attempt.Retry behaviour to classify the return value from the fun as either :return, :retry or reraise. The default retry_policy is Attempt.Retry.DefaultPolicy.

• :backoff is a module that implements the Attempt.Retry.Backoff behaviour which is used to determine the backoff strategy for retries.

Default options

If not supplied the default options are:

• :tries is 1

• :token_bucket is Attempt.Bucket.Token.new(@default_bucket_name)

• :retry_policy is Attempt.Retry,Policy.Default

• :backoff is Attempt.Retry.Backoff.Exponential

Retry policy actions

In order to ascertain whether a function should be retried each return value needs to be classified. The classification is the responsibility of the :retry_policy module. Three classifications are available:

• :return means that the return value of the function is considered a success and it returned to the called

• :retry means that a failure return was detected but that the failure is considered transient and is therefore eligble to be retried

• :reraise means that an exception was detected and the execption is not considered transient. Therefore the exception should be re-raised.

See also Attempt.Retry.Exception which defines a protocol for determining the classification of exceptions and Attempt.Retry.DefaultPolicy which implements the default classifier.

Examples

iex#> Attempt.run fn -> "Hello World" end
"Hello World"

iex#> Attempt.run fn -> IO.puts "Reraise Failure!"; div(1,0) end, tries: 3
Reraise Failure!
** (ArithmeticError) bad argument in arithmetic expression
    :erlang.div(1, 0)
    (attempt) lib/attempt.ex:119: Attempt.execute_function/1
    (attempt) lib/attempt.ex:98: Attempt.execute/6

iex#> Attempt.run fn -> IO.puts "Try 3 times"; :error end, tries: 3
Try 3 times
Try 3 times
Try 3 times
:error

# Create a bucket that adds a new token only every 10 seconds
iex#> {:ok, bucket} = Attempt.Bucket.Token.new :test, fill_rate: 10_000

iex#> Attempt.run fn ->
        IO.puts "Try 11 times and we'll timeout claiming a token"
        :error
      end, tries: 11, token_bucket: bucket
Try 11 times and we'll timeout claiming a token
Try 11 times and we'll timeout claiming a token
Try 11 times and we'll timeout claiming a token
Try 11 times and we'll timeout claiming a token
Try 11 times and we'll timeout claiming a token
Try 11 times and we'll timeout claiming a token
Try 11 times and we'll timeout claiming a token
Try 11 times and we'll timeout claiming a token
Try 11 times and we'll timeout claiming a token
Try 11 times and we'll timeout claiming a token
{:error, {:timeout, {GenServer, :call, [:test, :claim_token, 5000]}}}