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

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.

Features

• Blastly fast and efficient, Gohalt has minimal performance overhead, it was design with performance as the primary goal.

• Flexible and powerful, Gohalt supports numbers of different throttling strategies and conditions that could be easily combined and customized to match your needs link.

• Easy to integrate, Gohalt provides numbers of built in middlewares for simple (couple lines of code) integrations with stdlib and other libraries, among which are: io, rpc/grpc, http, sql, gin, etc.

• Metrics awareness, Gohalt could use Prometheus metrics as a conditions for throttling.

• Queueing and delayed processing, Gohalt supports throttling queueing which means you can easily save throttled query to rabbitmq/kafka stream to process it later.

• Durable storage, Gohalt has embedded k/v storage to provide thtottling persistence and durability.

• Meta awareness, Gohalt provides easy way to access inner throttlers state in form of meta that can be later exposed to logging, headers, etc.

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, 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
// WithKey adds the provided key to the provided context
// to add additional call identifier to context.
// Resulted context is used by: `pattern` throtttler.
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`
// - `WithKey`
// - `WithMessage`
// - `WithMarshaler`
func WithParams(ctx context.Context, ts time.Time, priority uint8, 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 chanel 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)),
	)

Throttlers

Throttler	Definition	Description
echo	func NewThrottlerEcho(err error) Throttler	Always throttles with the specified error back.
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 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.
context	func NewThrottlerContext() Throttler	Always throttless on done context.
panic	func NewThrottlerPanic() Throttler	Always panics.
each	func NewThrottlerEach(threshold uint64) Throttler	Throttles each periodic i-th call defined by the specified threshold.
before	func NewThrottlerBefore(threshold uint64) Throttler	Throttles each call below the i-th call defined by the specified threshold.
after	func NewThrottlerAfter(threshold uint64) Throttler	Throttles each call after the i-th call defined by the specified threshold.
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 math/rand as PRNG function and expects rand seeding by a client.
running	func NewThrottlerRunning(threshold uint64) Throttler	Throttles each call which exeeds the running quota acquired - release q defined by the specified threshold.
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.
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.
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.
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.
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.
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.
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.
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.
ring	func NewThrottlerRing(thrs ...Throttler) Throttler	Throttles if the i-th call throttler from provided list throttle.
all	func NewThrottlerAll(thrs ...Throttler) Throttler	Throttles call if all provided throttlers throttle.
any	func NewThrottlerAny(thrs ...Throttler) Throttler	Throttles call if any of provided throttlers throttle.
not	func NewThrottlerNot(thr Throttler) Throttler	Throttles call if provided throttler doesn't throttle.
suppress	func NewThrottlerSuppress(thr Throttler) Throttler	Suppresses provided throttler to never throttle.

Integrations

Library	Adapter
gin	func NewMiddlewareGin(thr Throttler, with GinWith, on GinOn) gin.HandlerFunc
stdlib http handler	func NewMiddlewareStd(h http.Handler, thr Throttler, with StdWith, on StdOn) http.Handler
echo	func NewMiddlewareEcho(thr Throttler, with EchoWith, on EchoOn) echo.MiddlewareFunc
beego	func NewMiddlewareBeego(thr Throttler, with BeegoWith, on BeegoOn) beego.FilterFunc
kit	func NewMiddlewareKit(thr Throttler, with KitWith, on KitOn) endpoint.Middleware
mux	func NewMiddlewareMux(h http.Handler, thr Throttler, with MuxWith, on MuxOn) http.Handler
httprouter	func NewMiddlewareRouter(h http.Handler, thr Throttler, with RouterWith, on RouterOn) http.Handler
reveal	func NewMiddlewareRevel(thr Throttler, with RevealWith, on RevealOn) revel.Filter
iris	func NewMiddlewareIris(thr Throttler, with IrisWith, on IrisOn) iris.Handler
fasthttp	func NewMiddlewareFast(h fasthttp.RequestHandler, thr Throttler, with FastWith, on FastOn) fasthttp.RequestHandler
stdlib rt	func NewRoundTripperStd(rt http.RoundTripper, thr Throttler, with RoundTripperStdWith, on RoundTripperStdOn) http.RoundTripper
fasthttp rt	func NewRoundTripperFast(rt RoundTripperFast, thr Throttler, with RoundTripperFastWith, on RoundTripperFastOn) RoundTripperFast
stdlib rpc client coded	func NewRPCClientCodec(cc rpc.ClientCodec, thr Throttler, with RPCCodecWith, on RPCCodecOn) rpc.ClientCodec
stdlib rpc server coded	func NewRPCServerCodec(sc rpc.ServerCodec, thr Throttler, with RPCCodecWith, on RPCCodecOn) rpc.ServerCodec
grpc client stream	func NewGRPCClientStream(cs grpc.ClientStream, thr Throttler, with GRPCStreamWith, on GRPCStreamOn) grpc.ClientStream
grpc server stream	func NewGrpServerStream(ss grpc.ServerStream, thr Throttler, with GRPCStreamWith, on GRPCStreamOn) grpc.ServerStream
go-micro client	func NewMicroClient(thr Throttler, with MicroClientWith, on MicroOn) client.Wrapper
go-micro server	func NewMicroHandler(thr Throttler, with MicroServerWith, on MicroOn) server.HandlerWrapper
stdlib net conn	func NewNetConn(conn net.Conn, thr Throttler, with NetConnWith, on NetConnOn, mode NetConnMode) net.Conn
stdlib sql	func NewSQLClient(cli SQLClient, thr Throttler, with SQLClientWith, on SQLClientOn) SQLClient
stdlib io reader	func NewReader(r io.Reader, thr Throttler, with RWWith, on RWOn) io.Reader
stdlib io writer	func NewWriter(w io.Writer, thr Throttler, with RWWith, on RWOn) io.Writer

Licence

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