index overview

Added in v0.1.0

Table of contents

• utils
  • Monoid
  • RetryPolicy (interface)
  • RetryStatus (interface)
  • applyPolicy
  • capDelay
  • constantDelay
  • defaultRetryStatus
  • exponentialBackoff
  • limitRetries
  • limitRetriesByDelay
  • monoidRetryPolicy

utils

Monoid

‘RetryPolicy’ is a ‘Monoid’. You can collapse multiple strategies into one using ‘concat’. The semantics of this combination are as follows:

1. If either policy returns ‘None’, the combined policy returns ‘None’. This can be used to inhibit after a number of retries, for example.

2. If both policies return a delay, the larger delay will be used. This is quite natural when combining multiple policies to achieve a certain effect.

Signature

export declare const Monoid: M.Monoid<RetryPolicy>

Example

import { monoidRetryPolicy, exponentialBackoff, limitRetries } from 'retry-ts'

// One can easily define an exponential backoff policy with a limited
// number of retries:
export const limitedBackoff = monoidRetryPolicy.concat(exponentialBackoff(50), limitRetries(5))

Added in v0.1.3

RetryPolicy (interface)

A RetryPolicy is a function that takes an RetryStatus and possibly returns a delay in milliseconds. Iteration numbers start at zero and increase by one on each retry. A None return value from the function implies we have reached the retry limit.

Signature

export interface RetryPolicy {
  (status: RetryStatus): O.Option<number>
}

Added in v0.1.0

RetryStatus (interface)

Signature

export interface RetryStatus {
  /** Iteration number, where `0` is the first try */
  iterNumber: number
  /** Delay incurred so far from retries */
  cumulativeDelay: number
  /** Latest attempt's delay. Will always be `none` on first run. */
  previousDelay: O.Option<number>
}

Added in v0.1.0

applyPolicy

Apply policy on status to see what the decision would be.

Signature

export declare function applyPolicy(policy: RetryPolicy, status: RetryStatus): RetryStatus

Added in v0.1.0

capDelay

Set a time-upperbound for any delays that may be directed by the given policy. This function does not terminate the retrying. The policy capDelay(maxDelay, exponentialBackoff(n))will never stop retrying. It will reach a state where it retries forever with a delay ofmaxDelay` between each one. To get termination you need to use one of the ‘limitRetries’ function variants.

Signature

export declare function capDelay(maxDelay: number, policy: RetryPolicy): RetryPolicy

Added in v0.1.0

constantDelay

Constant delay with unlimited retries

Signature

export declare function constantDelay(delay: number): RetryPolicy

Added in v0.1.0

defaultRetryStatus

Initial, default retry status. Exported mostly to allow user code to test their handlers and retry policies.

Signature

export declare const defaultRetryStatus: RetryStatus

Added in v0.1.0

exponentialBackoff

Grow delay exponentially each iteration. Each delay will increase by a factor of two.

Signature

export declare function exponentialBackoff(delay: number): RetryPolicy

Added in v0.1.0

limitRetries

Retry immediately, but only up to i times.

Signature

export declare function limitRetries(i: number): RetryPolicy

Added in v0.1.0

limitRetriesByDelay

Add an upperbound to a policy such that once the given time-delay amount per try has been reached or exceeded, the policy will stop retrying and fail.

Signature

export declare function limitRetriesByDelay(maxDelay: number, policy: RetryPolicy): RetryPolicy

Added in v0.1.0

monoidRetryPolicy

Use Monoid instead.

Signature

export declare const monoidRetryPolicy: M.Monoid<RetryPolicy>

Added in v0.1.0