Policies

Configure resiliency policies for timeouts, retries and circuit breakers

Policies

You define timeouts, retries and circuit breaker policies under policies. Each policy is given a name so you can refer to them from the targets section in the resiliency spec.

Timeouts

Timeouts can be used to early-terminate long-running operations. If you’ve exceeded a timeout duration:

  • The operation in progress is terminated (if possible).
  • An error is returned.

Valid values are of the form 15s, 2m, 1h30m, etc.

Example:

  1. spec:
  2.   policies:
  3.     # Timeouts are simple named durations.
  4.     timeouts:
  5.       general: 5s
  6.       important: 60s
  7.       largeResponse: 10s

Retries

With retries, you can define a retry strategy for failed operations, including requests failed due to triggering a defined timeout or circuit breaker policy. The following retry options are configurable:

Retry optionDescription
policyDetermines the back-off and retry interval strategy. Valid values are constant and exponential. Defaults to constant.
durationDetermines the time interval between retries. Default: 5s. Only applies to the constant policy. Valid values are of the form 200ms, 15s, 2m, etc.
maxIntervalDetermines the maximum interval between retries to which the exponential back-off policy can grow. Additional retries always occur after a duration of maxInterval. Defaults to 60s. Valid values are of the form 5s, 1m, 1m30s, etc
maxRetriesThe maximum number of retries to attempt. -1 denotes an indefinite number of retries. Defaults to -1.

The exponential back-off window uses the following formula:

  1. BackOffDuration = PreviousBackOffDuration * (Random value from 0.5 to 1.5) * 1.5
  2. if BackOffDuration > maxInterval {
  3.   BackoffDuration = maxInterval
  4. }

Example:

  1. spec:
  2.   policies:
  3.     # Retries are named templates for retry configurations and are instantiated for life of the operation.
  4.     retries:
  5.       pubsubRetry:
  6.         policy: constant
  7.         duration: 5s
  8.         maxRetries: 10
  10.       retryForever:
  11.         policy: exponential
  12.         maxInterval: 15s
  13.         maxRetries: -1 # Retry indefinitely
Circuit breakers

Circuit breakers (CBs) policies are used when other applications/services/components are experiencing elevated failure rates. CBs monitor the requests and shut off all traffic to the impacted service when a certain criteria is met. By doing this, CBs give the service time to recover from their outage instead of flooding them with events. The CB can also allow partial traffic through to see if the system has healed (half-open state). Once successful requests start to occur, the CB can close and allow traffic to resume.

Retry optionDescription
maxRequestsThe maximum number of requests allowed to pass through when the CB is half-open (recovering from failure). Defaults to 1.
intervalThe cyclical period of time used by the CB to clear its internal counts. If set to 0 seconds, this never clears. Defaults to 0s.
timeoutThe period of the open state (directly after failure) until the CB switches to half-open. Defaults to 60s.
tripA Common Expression Language (CEL) statement that is evaluated by the CB. When the statement evaluates to true, the CB trips and becomes open. Default is consecutiveFailures > 5.
circuitBreakerScopeSpecify whether circuit breaking state should be scoped to an individual actor ID, all actors across the actor type, or both. Possible values include id, type, or both
circuitBreakerCacheSizeSpecify a cache size for the number of CBs to keep in memory. The value should be larger than the expected number of active actor instances. Provide an integer value, for example 5000.

Example:

  1. spec:
  2.   policies:
  3.     circuitBreakers:
  4.       pubsubCB:
  5.         maxRequests: 1
  6.         interval: 8s
  7.         timeout: 45s
  8.         trip: consecutiveFailures > 8

Last modified June 23, 2022: Merge pull request #2550 from ItalyPaleAle/cosmosdb-harcoded-dapr-version (cf03237)