Documentation
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Overview ¶
Package admit contains utilities for admission control.
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func Do ¶
Do calls f after being admitted by the controller. f's bool return value is passed on to the underlying policy upon Release, and the error is simply returned back to the caller as a convenience. If policy is nil, then this will simply call f.
func EnableVarExport ¶
EnableVarExport enables the export of relevant vars useful for debugging/monitoring.
func Retry ¶
func Retry(ctx context.Context, policy RetryPolicy, tokens int, f func() (CapacityStatus, error)) error
Retry calls f after being admitted by the Policy (implied by the given RetryPolicy). If f returns Within, true is passed to the underlying policy upon Release and false otherwise. If f returns OverNeedRetry, f will be retried as per the RetryPolicy (and the error returned by f is ignored), and if f can no longer be retried, the error returned by retry.Policy will be returned.
Types ¶
type CapacityStatus ¶ added in v0.0.7
type CapacityStatus int
CapacityStatus is the feedback provided by the user to Retry about the underlying resource being managed by Policy.
const ( // Within means that the underlying resource is within capacity. Within CapacityStatus = iota // OverNoRetry means that the underlying resource is over capacity but no retry is needed. // This is useful in situations where a request using the resource succeeded, but there are // signs of congestion (for example, in the form of high latency). OverNoRetry // OverNeedRetry means that the underlying resource is over capacity and a retry is needed. // This is useful in situations where requests failed due to the underlying resource hitting capacity limits. OverNeedRetry )
type Policy ¶
type Policy interface {
// Acquire acquires a number of tokens from the admission controller.
// Returns on success, or if the context was canceled.
// Acquire can also return with an error if the number of requested tokens
// exceeds the upper limit of available tokens.
Acquire(ctx context.Context, need int) error
// Release a number of tokens to the admission controller,
// reporting whether the request was within the capacity limits.
Release(tokens int, ok bool)
}
Policy implements the low level details of an admission control policy. Users typically use a utility function such as admit.Do or admit.Retry.
func AIMD ¶ added in v0.0.7
AIMD returns a Policy which uses the Additive increase/multiplicative decrease algorithm for computing the amount of the concurrency to allow. AIMD is not fair: tokens are not granted in FIFO order; rather, waiters are picked randomly to be granted new tokens.
func Controller ¶
Controller returns a Policy which starts with a concurrency limit of 'start' and can grow upto a maximum of 'limit' as long as errors aren't observed. A controller is not fair: tokens are not granted in FIFO order; rather, waiters are picked randomly to be granted new tokens.
type RetryPolicy ¶
RetryPolicy combines an admission controller with a retry policy.
func AIMDWithRetry ¶ added in v0.0.7
func AIMDWithRetry(min int, decfactor float32, retryPolicy retry.Policy) RetryPolicy
AIMDWithRetry returns a RetryPolicy which uses the Additive increase/multiplicative decrease algorithm for computing the amount of the concurrency to allow. AIMDWithRetry is not fair: tokens are not granted in FIFO order; rather, waiters are picked randomly to be granted new tokens.
func ControllerWithRetry ¶
func ControllerWithRetry(start, limit int, retryPolicy retry.Policy) RetryPolicy
ControllerWithRetry returns a RetryPolicy which starts with a concurrency limit of 'start' and can grow upto a maximum of 'limit' if no errors are seen. A controller is not fair: tokens are not granted in FIFO order; rather, waiters are picked randomly to be granted new tokens.
Source Files