Gohalt 👮‍♀🛑: Fast; Simple; Powerful; Go Throttler library

go get -u github.com/1pkg/gohalt

Introduction

Gohalt is simple and convenient yet powerful and efficient throttling go library. Gohalt provides various throttlers and surronding tools to build throttling pipelines and rate limiters of any complexity adjusted to your specific needs. Gohalt provides an easy way to integrate throttling and rate limiting with your infrastructure through built in middlewares.

Concepts

Gohalt uses Throttler as the core interface for all derived throttlers and surronding tools.

// Throttler defines core gohalt throttler abstraction and exposes pair of counterpart methods: `Acquire` and `Release`.
type Throttler interface {
	// Acquire takes a part of throttling quota or returns error if throttling quota is drained
	// it needs to be called right before shared resource acquire.
	Acquire(context.Context) error
	// Release puts a part of throttling quota back or returns error if this is not possible
	// it needs to be called just after shared resource release.
	Release(context.Context) error
}

Throttler interface exposes pair of counterpart methods: Acquire takes a part of throttling quota or returns error if throttling quota is drained and needs to be called right before shared resource acquire; Release puts a part of throttling quota back or returns error if this is not possible and needs to be called just after shared resource release; Note: all derived throttler implementations are thread safe, so they could be used concurrently without additional locking. Note: all acquired throttlers should be released exatly the same amount of times they have been acquired. Note: despite throttler Release method has the same signature as Acquire has, Release implementations should try to handle any internal error gracefully and return error back rarely, nevertheless all errors returned by Release should be handeled by client.

In Gohalt throtllers could be easily combined with each other to build complex pipelines. There are multiple composite throttlers (all, any, ring, pattern, not, generator, etc) as well as leaf throttlers (timed, latency, monitor, metric, percentile, etc) to work with in Gohalt. If you don't find in existing throttlers the one that fits your needs you can create custom throttler by implementing Throttler interface. Such custom throttler should work with existing Gohalt throttlers and tools out of box.

Gohalt includes multiple supporting surrounding tools to make throttling more sugary.

// Runnable defined by typical abstract async func signature.
// Runnable is used by `Runner` as a subject for execution.
type Runnable func(context.Context) error
// Runner defines abstraction to execute a set of `Runnable`
// and return possible execution error back.
// Runner is designed to simplify work with throttlers
// by managing `Acquire`/`Release` loop.
type Runner interface {
	// Run executes single prodived `Runnable` instance.
	Run(Runnable)
	// Result returns possible execution error back.
	Result() error
}

Runnable and Runner define slim abstraction for executable and executor in Gohalt. Runner insterface aims to provide similar interface as errgroup.Group does. So to run a single executable use Run to wait and get result use Result. There are two runners implementations in Gohalt:

• sync func NewRunnerSync(ctx context.Context, thr Throttler) Runner
• async func NewRunnerAsync(ctx context.Context, thr Throttler) Runner Both implementation accept throttler and context as input arguments and handle all throttling cycle internaly. This way client donesn't need to call neither Acquire nor Release manually, all this is done by the runner. This way the only thing that needs to be done to add throttling to existing code wrap existing executable by Runnable. The only difference between sync and async runner is that the async runner starts each new Runnable inside new goroutine and uses locks for its imternal state. Note: You can't use sync runner in async fashion with go syncr.Run(func(context.Context) error{}) this will cause data race, use async runner instead async.Run(func(context.Context) error{}).

Last but not least Gohalt uses context heavily inside and there are multiple helpers to provide data via context for throttles, see throttles list to know when to use them.

// WithTimestamp adds the provided timestamp to the provided context
// to determine latency between `Acquire` and `Release`.
// Resulted context is used by: `latency` and `percentile` throtttlers.
func WithTimestamp(ctx context.Context, ts time.Time) context.Context
// WithPriority adds the provided priority to the provided context
// to differ `Acquire` priority levels.
// Resulted context is used by: `priority` throtttler.
func WithPriority(ctx context.Context, priority uint8) context.Context
// WithWeight adds the provided weight to the provided context
// to differ `Acquire` weight levels.
// Resulted context is used by: `semaphore` and `cellrate` throtttlers.
func WithWeight(ctx context.Context, weight int64) context.Context
// WithKey adds the provided key to the provided context
// to add additional call identifier to context.
// Resulted context is used by: `before`, `after`, `timed`, `adaptive`, `semaphore`, `cellrate` and `bucket` throtttlers.
func WithKey(ctx context.Context, key string) context.Context
// WithMessage adds the provided message to the provided context
// to add additional message that need to be used to context.
// Resulted context is used by: `enqueue` throtttler.
func WithMessage(ctx context.Context, message interface{}) context.Context
// WithMarshaler adds the provided marshaler to the provided context
// to add additional message marshaler that need to be used to context.
// Resulted context is used by: `enqueue` throtttler.
// Used in pair with `WithMessage`.
func WithMarshaler(ctx context.Context, mrsh Marshaler) context.Context
// WithParams facade call that respectively calls:
// - `WithTimestamp`
// - `WithPriority`
// - `WithWeight`
// - `WithKey`
// - `WithMessage`
// - `WithMarshaler`
func WithParams(ctx context.Context, ts time.Time, priority uint8, weight int64, key string, message interface{}, marshaler Marshaler) context.Context

Also there is yet another throttling sugar func WithThrottler(ctx context.Context, thr Throttler, freq time.Duration) context.Context related to context. Which defines context implementation that uses parrent context plus throttler internally. Using it you can keep typical context patterns for cancelation handling and apply and combine it with throttling.

select {
	case <-ctx.Done():
		return ctx.Error()
	default:
}

If internal context throttler is throttling context done channel will be closed respectively. Note such behavior is implemented by throttler long pooling with the specified frequency, so efficiently there will be additional throttling user in form of long pooling goroutine.

// complex throttler example
thr := NewThrottlerAll( // throttles only if all children throttle
	NewThrottlerPattern(
		Pattern{ // use throttler only if provided key matches `192.*.*.*` submask
			Pattern: regexp.MustCompile(`192\.[0-9]+\.[0-9]+\.[0-9]+`),
			Throttler: NewThrottlerAny( // throttles if any children throttles
				// throttles only if latency is above 50 millisecond
				NewThrottlerLatency(50*time.Millisecond, 5*time.Second),
				// throttles only if cpu usage is above 70%
				NewThrottlerMonitor(NewMonitorSystem(time.Minute), Stats{CPUUsage: 0.7}),
			),
		},
	),
	// throttles each not 3rd call
	NewThrottlerNot(NewThrottlerEach(3)),
	// enqueues provided message to queue
	NewThrottlerEnqueue(NewEnqueuerRabbit("amqp://user:pass@localhost:5672/vhost", "queue", time.Minute)),
)

In gohalt v0.4.0 breaking change is introduced to replace all untyped errors with two major error types:

• ErrorThreshold which defines error type that occurs if throttler reaches specified threshold.
• ErrorInternal which defines error type that occurs if throttler internal error happens. You can find list of returning error types for all existing throttlers in throttlers table bellow or in documentation.
  Note: not every gohalt throttler must return error; some throttlers might cause different side effects like logging or call to time.Sleep instead.

Throttlers

Throttler	Definition	Description
echo	func NewThrottlerEcho(err error) Throttler	Always throttles with the specified error back. - could return any specified error;
wait	func NewThrottlerWait(duration time.Duration) Throttler	Always waits for the specified duration.
square	func NewThrottlerSquare(duration time.Duration, limit time.Duration, reset bool) Throttler	Always waits for square growing [1, 4, 9, 16, ...] multiplier on the specified initial duration, up until the specified duration limit is reached. If reset is set then after throttler riches the specified duration limit next multiplier value will be reseted.
jitter	func NewThrottlerJitter(initial time.Duration, limit time.Duration, reset bool, jitter float64) Throttler	Waits accordingly to undelying square throttler but also adds the provided jitter delta distribution on top. Jitter value is normalized to [0.0, 1.0] range and defines which part of square delay could be randomized in percents. Implementation uses secure crypto/rand as PRNG function.
context	func NewThrottlerContext() Throttler	Always throttless on done context. - could return ErrorInternal;
panic	func NewThrottlerPanic() Throttler	Always panics with ErrorInternal.
each	func NewThrottlerEach(threshold uint64) Throttler	Throttles each periodic i-th call defined by the specified threshold. - could return ErrorThreshold;
before	func NewThrottlerBefore(threshold uint64) Throttler	Throttles each call below the i-th call defined by the specified threshold. Use WithWeight to override context call qunatity, 1 by default. - could return ErrorThreshold;
after	func NewThrottlerAfter(threshold uint64) Throttler	Throttles each call after the i-th call defined by the specified threshold. Use WithWeight to override context call qunatity, 1 by default. - could return ErrorThreshold;
past	func NewThrottlerPast(threshold time.Time) Throttler	Throttles each call befor timestamp defined by the specified UTC time threshold. - could return ErrorThreshold;
future	func NewThrottlerFuture(threshold time.Time) Throttler	Throttles each call after timestamp defined by the specified UTC time threshold. - could return ErrorThreshold;
chance	func NewThrottlerChance(threshold float64) Throttler	Throttles each call with the chance p defined by the specified threshold. Chance value is normalized to [0.0, 1.0] range. Implementation uses secure crypto/rand as PRNG function. - could return ErrorThreshold;
running	func NewThrottlerRunning(threshold uint64) Throttler	Throttles each call which exeeds the running quota acquired - release q defined by the specified threshold. - could return ErrorThreshold;
buffered	func NewThrottlerBuffered(threshold uint64) Throttler	Waits on call which exeeds the running quota acquired - release q defined by the specified threshold until the running quota is available again.
priority	func NewThrottlerPriority(threshold uint64, levels uint8) Throttler	Waits on call which exeeds the running quota acquired - release q defined by the specified threshold until the running quota is available again. Running quota is not equally distributed between n levels of priority defined by the specified levels. Use func WithPriority(ctx context.Context, priority uint8) context.Context to override context call priority, 1 by default.
timed	func NewThrottlerTimed(threshold uint64, interval time.Duration, quantum time.Duration) Throttler	Throttles each call which exeeds the running quota acquired - release q defined by the specified threshold in the specified interval. Periodically each specified interval the running quota number is reseted. If quantum is set then quantum will be used instead of interval to provide the running quota delta updates. Use WithWeight to override context call qunatity, 1 by default. - could return ErrorThreshold;
latency	func NewThrottlerLatency(threshold time.Duration, retention time.Duration) Throttler	Throttles each call after the call latency l defined by the specified threshold was exeeded once. If retention is set then throttler state will be reseted after retention duration. Use func WithTimestamp(ctx context.Context, ts time.Time) context.Context to specify running duration between throttler acquire and release. - could return ErrorThreshold;
percentile	func NewThrottlerPercentile(threshold time.Duration, capacity uint8, percentile float64, retention time.Duration) Throttler	Throttles each call after the call latency l defined by the specified threshold was exeeded once considering the specified percentile. Percentile values are kept in bounded buffer with capacity c defined by the specified capacity. If retention is set then throttler state will be reseted after retention duration. Use func WithTimestamp(ctx context.Context, ts time.Time) context.Context to specify running duration between throttler acquire and release. - could return ErrorThreshold;
monitor	func NewThrottlerMonitor(mnt Monitor, threshold Stats) Throttler	Throttles call if any of the stats returned by provided monitor exceeds any of the stats defined by the specified threshold or if any internal error occurred. Builtin Monitor implementations come with stats caching by default. Use builtin NewMonitorSystem to create go system monitor instance. - could return ErrorInternal; - could return ErrorThreshold;
metric	func NewThrottlerMetric(mtc Metric) Throttler	Throttles call if boolean metric defined by the specified boolean metric is reached or if any internal error occurred. Builtin Metric implementations come with boolean metric caching by default. Use builtin NewMetricPrometheus to create Prometheus metric instance. - could return ErrorInternal; - could return ErrorThreshold;
enqueuer	func NewThrottlerEnqueue(enq Enqueuer) Throttler	Always enqueues message to the specified queue throttles only if any internal error occurred. Use func WithMessage(ctx context.Context, message interface{}) context.Context to specify context message for enqueued message and func WithMarshaler(ctx context.Context, mrsh Marshaler) context.Context to specify context message marshaler. Builtin Enqueuer implementations come with connection reuse and retries by default. Use builtin func NewEnqueuerRabbit(url string, queue string, retries uint64) Enqueuer to create RabbitMQ enqueuer instance or func NewEnqueuerKafka(net string, url string, topic string, retries uint64) Enqueuer to create Kafka enqueuer instance. - could return ErrorInternal;
adaptive	func NewThrottlerAdaptive(threshold uint64, interval time.Duration, quantum time.Duration, step uint64, thr Throttler) Throttler	Throttles each call which exeeds the running quota acquired - release q defined by the specified threshold in the specified interval. Periodically each specified interval the running quota number is reseted. If quantum is set then quantum will be used instead of interval to provide the running quota delta updates. Provided adapted throttler adjusts the running quota of adapter throttler by changing the value by d defined by the specified step, it subtracts d^2 from the running quota if adapted throttler throttles or adds d to the running quota if it doesn't. Use WithWeight to override context call qunatity, 1 by default. - could return ErrorThreshold;
pattern	func NewThrottlerPattern(patterns ...Pattern) Throttler	Throttles if matching throttler from provided patterns throttles. Use func WithKey(ctx context.Context, key string) context.Context to specify key for regexp pattern throttler matching. Pattern defines a pair of regexp and related throttler. - could return ErrorInternal; - could return any underlying throttler error;
ring	func NewThrottlerRing(thrs ...Throttler) Throttler	Throttles if the i-th call throttler from provided list throttle. - could return ErrorInternal; - could return any underlying throttler error;
all	func NewThrottlerAll(thrs ...Throttler) Throttler	Throttles call if all provided throttlers throttle. - could return ErrorInternal;
any	func NewThrottlerAny(thrs ...Throttler) Throttler	Throttles call if any of provided throttlers throttle. - could return ErrorInternal;
not	func NewThrottlerNot(thr Throttler) Throttler	Throttles call if provided throttler doesn't throttle. - could return ErrorInternal;
suppress	func NewThrottlerSuppress(thr Throttler) Throttler	Suppresses provided throttler to never throttle.
retry	func NewThrottlerRetry(thr Throttler, retries uint64) Throttler	Retries provided throttler error up until the provided retries threshold. If provided onthreshold flag is set even ErrorThreshold errors will be retried. Internally retry uses square throttler with DefaultRetriedDuration initial duration. - could return any underlying throttler error;
cache	func NewThrottlerCache(thr Throttler, cache time.Duration) Throttler	Caches provided throttler calls for the provided cache duration, throttler release resulting resets cache. Only non throttling calls are cached for the provided cache duration. - could return any underlying throttler error;
generator	func NewThrottlerGenerator(gen Generator, capacity uint64, eviction float64) Throttler	Creates new throttler instance that throttles if found key matching throttler throttles. If no key matching throttler has been found generator used insted to provide new throttler that will be added to existing throttlers map. Generated throttlers are kept in bounded map with capacity c defined by the specified capacity and eviction rate e defined by specified eviction value is normalized to [0.0, 1.0], where eviction rate affects number of throttlers that will be removed from the map after bounds overflow. Use WithKey to specify key for throttler matching and generation. - could return ErrorInternal; - could return any underlying throttler error;
semaphore	func NewThrottlerSemaphore(weight int64) Throttler	Creates new throttler instance that throttles call if underlying semaphore throttles. Use WithWeight to override context call weight, 1 by default. - could return ErrorThreshold;
cellrate	func NewThrottlerCellRate(threshold uint64, interval time.Duration, monotone bool) Throttler	Creates new throttler instance that uses generic cell rate algorithm to throttles call within provided interval and threshold. If provided monotone flag is set class to release will have no effect on throttler. Use WithWeight to override context call qunatity, 1 by default. - could return ErrorThreshold;
bucket	func NewThrottlerBucket(threshold uint64, interval time.Duration, monotone bool) Throttler	Creates new throttler instance that leaky bucket algorithm to throttles call within provided interval and threshold. If provided monotone flag is set class to release will have no effect on throttler. Use WithWeight to override context call qunatity, 1 by default. - could return ErrorThreshold;

Licence

Gohalt is licensed under the MIT License.
See LICENSE for the full license text.