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net.modulolotus.truegrit.circuit-breaker
Implements circuit breakers, which keep track of fn failures and temporarily disable a fn when it fails too often.
Implements circuit breakers, which keep track of fn failures and temporarily disable a fn when it fails too often. See https://resilience4j.readme.io/docs/circuitbreaker
*default-config*clj
Set this to override the R4j defaults with your own
Set this to override the R4j defaults with your own
add-listenersclj
(add-listeners cb
{:keys [on-event on-success on-error on-state-transition on-reset
on-ignored-error on-call-not-permitted
on-failure-rate-exceeded on-slow-call-rate-exceeded]})Add event handlers for CircuitBreaker lifecycle events. Note that a call that succeeds on the first try will generate no events.
Config map options
:on-event- a handler that runs for all events:on-success- a handler that runs after every successful call - receives a CircuitBreakerOnSuccessEvent:on-error- a handler that runs after every failed call - receives a CircuitBreakerOnErrorEvent:on-state-transition - a handler that runs after a state changed (OPEN, CLOSED, HALF_OPEN) - receives a CircuitBreakerOnStateTransitionEvent - breakers start in CLOSED:on-reset- a handler that runs after a manual reset - receives a CircuitBreakerOnResetEvent:on-ignored-error- a handler that runs after an error was ignored - receives a CircuitBreakerOnIgnoredErrorEvent:on-call-not-permitted- a handler that runs after a call was attempted, but the breaker forbid it - receives a CircuitBreakerOnCallNotPermittedEvent - NB: this can trigger on health checks, seecall-allowed?for more:on-failure-rate-exceeded- a handler that runs after the failure rate is exceeded - receives a CircuitBreakerOnFailureRateExceededEvent:on-slow-call-rate-exceeded- a handler that runs after the slow call rate is exceeded - receives a CircuitBreakerOnSlowCallRateExceededEvent - NB: this can trigger on health checks, seecall-allowed?for more
Add event handlers for CircuitBreaker lifecycle events. Note that a call that succeeds on the first try will generate no events. Config map options - `:on-event` - a handler that runs for all events - `:on-success` - a handler that runs after every successful call - receives a CircuitBreakerOnSuccessEvent - `:on-error` - a handler that runs after every failed call - receives a CircuitBreakerOnErrorEvent - `:on-state`-transition - a handler that runs after a state changed (OPEN, CLOSED, HALF_OPEN) - receives a CircuitBreakerOnStateTransitionEvent - breakers start in CLOSED - `:on-reset` - a handler that runs after a manual reset - receives a CircuitBreakerOnResetEvent - `:on-ignored-error` - a handler that runs after an error was ignored - receives a CircuitBreakerOnIgnoredErrorEvent - `:on-call-not-permitted` - a handler that runs after a call was attempted, but the breaker forbid it - receives a CircuitBreakerOnCallNotPermittedEvent - NB: this can trigger on health checks, see [[call-allowed?]] for more - `:on-failure-rate-exceeded` - a handler that runs after the failure rate is exceeded - receives a CircuitBreakerOnFailureRateExceededEvent - `:on-slow-call-rate-exceeded` - a handler that runs after the slow call rate is exceeded - receives a CircuitBreakerOnSlowCallRateExceededEvent - NB: this can trigger on health checks, see [[call-allowed?]] for more
call-allowed?clj
(call-allowed? cb)Is the circuit breaker healthy enough to allow a call?
Does not rely on the CB state (OPEN, CLOSED, etc), because state alone is insufficient to determine if a call is permitted.
E.g., HALF-OPEN has an internal counter of test calls, so it may or may not allow the next one. And,
when :automatic-transition-from-open-to-half-open-enabled? is false (the default), the breaker will
remain in the OPEN state past the waiting period until a call is made or permission is checked/requested,
which can be misleading.
NB: r4j does not currently distinguish between checking and acquiring permissions. Therefore, calling this when it's not currently allowed will trigger a call-not-permitted event, even if you're not invoking the wrapped fn.
Is the circuit breaker healthy enough to allow a call? Does not rely on the CB state (OPEN, CLOSED, etc), because state alone is insufficient to determine if a call is permitted. E.g., HALF-OPEN has an internal counter of test calls, so it may or may not allow the next one. And, when `:automatic-transition-from-open-to-half-open-enabled?` is false (the default), the breaker will remain in the OPEN state past the waiting period until a call is made or permission is checked/requested, which can be misleading. NB: r4j does not currently distinguish between checking and acquiring permissions. Therefore, calling this when it's *not* currently allowed will trigger a call-not-permitted event, even if you're not invoking the wrapped fn.
circuit-breakerclj
(circuit-breaker cb-name config)Creates a CircuitBreaker with the given name and config.
Creates a CircuitBreaker with the given name and config.
circuit-breaker-configclj
(circuit-breaker-config config)Creates a Resilience4j CircuitBreakerConfig.
Config map options
:failure-rate-threshold- Percentage from 1 to 100 - if more than this percentage of calls have failed, go to OPEN - defaults to 50%:slow-call-rate-threshold- Percentage from 1 to 100 - if more than this percentage of calls are too slow, go to OPEN - defaults to 100%:slow-call-duration-threshold- How slow is too slow, even if the call succeeds? All calls exceeding this duration are treated as failures - defaults to 60000 ms - accepts number of ms or java.time.Duration:permitted-number-of-calls-in-half-open-state- # of calls to track when HALF-OPEN - defaults to 10:minimum-number-of-calls- # of calls to keep track of - will not go to OPEN unless at least this many calls have been made - defaults to 100:sliding-window-type- How the CB considers statistics. Either:countor:time. When count-based, examines the last n number of calls; when time-based, examines all calls from the last n seconds. (Time-based mimics Hystrix's behavior.) - defaults to:count:sliding-window-size- The meaning depends on :sliding-window-type. When count-based, it's the number of calls to record; when time-based, it's the number of seconds. - defaults to 100:max-wait-duration-in-half-open-state- How long to wait in HALF_OPEN before automatically switching to OPEN - 0 means wait until all calls have been completed - defaults to 0 ms - accepts number of ms or java.time.Duration:wait-duration-in-open-state- How long to wait in OPEN before allowing a call again - defaults to 60000 ms - accepts number of ms or java.time.Duration
Less common config map options
:automatic-transition-from-open-to-half-open-enabled?- Should it automatically transition to HALF-OPEN after the wait duration, or only after a call or check is made? - NB: when false, an OPEN state may actually allow calls if the wait duration has passed and nobody has tried yet, so don't rely on state, usecall-allowed?- defaults to false:record-exceptions- A coll of Throwables to record failure for - defaults to empty, which means all exceptions are recorded -:ignore-exceptionstakes precedence over this:ignore-exceptions- A coll of Throwables to ignore - e.g.,[IrrelevantException IgnoreThisException]- are not counted as either successes or failures - defaults to empty:record-exception- A 1-arg fn that tests a Throwable and returns true if it should be recorded as a failure, false if not -:ignore-exceptionpredicate takes precedence:ignore-exception- A 1-arg fn that tests a Throwable and returns true if it should be ignored, false if not
Creates a Resilience4j CircuitBreakerConfig. Config map options - `:failure-rate-threshold` - Percentage from 1 to 100 - if more than this percentage of calls have failed, go to OPEN - defaults to 50% - `:slow-call-rate-threshold` - Percentage from 1 to 100 - if more than this percentage of calls are too slow, go to OPEN - defaults to 100% - `:slow-call-duration-threshold` - How slow is too slow, *even if* the call succeeds? All calls exceeding this duration are treated as failures - defaults to 60000 ms - accepts number of ms or java.time.Duration - `:permitted-number-of-calls-in-half-open-state` - # of calls to track when HALF-OPEN - defaults to 10 - `:minimum-number-of-calls` - # of calls to keep track of - will not go to OPEN unless at least this many calls have been made - defaults to 100 - `:sliding-window-type` - How the CB considers statistics. Either `:count` or `:time`. When count-based, examines the last n number of calls; when time-based, examines all calls from the last n seconds. (Time-based mimics Hystrix's behavior.) - defaults to `:count` - `:sliding-window-size` - The meaning depends on :sliding-window-type. When count-based, it's the number of calls to record; when time-based, it's the number of seconds. - defaults to 100 - `:max-wait-duration-in-half-open-state` - How long to wait in HALF_OPEN before automatically switching to OPEN - 0 means wait until all calls have been completed - defaults to 0 ms - accepts number of ms or java.time.Duration - `:wait-duration-in-open-state` - How long to wait in OPEN before allowing a call again - defaults to 60000 ms - accepts number of ms or java.time.Duration Less common config map options - `:automatic-transition-from-open-to-half-open-enabled?` - Should it automatically transition to HALF-OPEN after the wait duration, or only after a call or check is made? - NB: when false, an OPEN state may actually allow calls if the wait duration has passed and nobody has tried yet, so don't rely on state, use [[call-allowed?]] - defaults to false - `:record-exceptions` - A coll of Throwables to record failure for - defaults to empty, which means all exceptions are recorded - `:ignore-exceptions` takes precedence over this - `:ignore-exceptions` - A coll of Throwables to ignore - e.g., `[IrrelevantException IgnoreThisException]` - are not counted as either successes *or* failures - defaults to empty - `:record-exception` - A 1-arg fn that tests a Throwable and returns true if it should be recorded as a failure, false if not - `:ignore-exception` predicate takes precedence - `:ignore-exception` - A 1-arg fn that tests a Throwable and returns true if it should be ignored, false if not
metricsclj
(metrics cb)Returns metrics for the given circuit breaker.
Failure rate is a percentage, unless insufficient calls have been made (i.e.,
below :minimum-number-of-calls), in which case it's -1.
Slow calls refer to calls that take a long time, but do not actually fail.
Returns metrics for the given circuit breaker. Failure rate is a percentage, unless insufficient calls have been made (i.e., below `:minimum-number-of-calls`), in which case it's -1. Slow calls refer to calls that take a long time, but do not actually fail.
retrieveclj
(retrieve f)Retrieves a circuit breaker from a wrapped fn
Retrieves a circuit breaker from a wrapped fn
state-nameclj
(state-name cb)Returns a keyword of the current state of the CircuitBreaker.
One of: :closed, :open, :half-open, :forced-open, or :disabled
NB: Do not rely on the state to determine if a call can be made. Use call-allowed? instead.
Returns a keyword of the current state of the CircuitBreaker. One of: `:closed`, `:open`, `:half-open`, `:forced-open`, or `:disabled` NB: Do not rely on the state to determine if a call can be made. Use [[call-allowed?]] instead.
wrapclj
(wrap f cb)Wraps a function in a CircuitBreaker.
Attaches the circuit breaker as metadata on the wrapped fn at :truegrit/circuit-breaker
Wraps a function in a CircuitBreaker. Attaches the circuit breaker as metadata on the wrapped fn at :truegrit/circuit-breaker
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