queue

Documentation

Overview

Package queue provides components for the queue-proxy binary.

Index

• Constants
• Variables
• func ForwardedShimHandler(h http.Handler) http.Handler
• func NewRequestMetricHandler(h http.Handler, r stats.StatsReporter, b *Breaker) (http.Handler, error)
• func TimeToFirstByteTimeoutHandler(h http.Handler, dt time.Duration, msg string) http.Handler
• type Breaker
  • func NewBreaker(params BreakerParams) *Breaker
  • func (b *Breaker) Capacity() int
  • func (b *Breaker) InFlight() int
  • func (b *Breaker) Maybe(ctx context.Context, thunk func()) error
  • func (b *Breaker) UpdateConcurrency(size int) error
• type BreakerParams
• type Channels
• type PrometheusStatsReporter
  • func NewPrometheusStatsReporter(namespace, config, revision, pod string, reportingPeriod time.Duration) (*PrometheusStatsReporter, error)
  • func (r *PrometheusStatsReporter) Handler() http.Handler
  • func (r *PrometheusStatsReporter) Report(stat autoscaler.Stat)
• type ReqEvent
• type ReqEventType
• type Stats
  • func NewStats(podName string, channels Channels, startedAt time.Time) *Stats

Constants

const (
	// Name is the name of the component.
	Name = "queue"

	// RequestQueueDrainPath specifies the path to wait until the proxy
	// server is shut down. Any subsequent calls to this endpoint after
	// the server has finished shutting down it will return immediately.
	// Main usage is to delay the termination of user-container until all
	// accepted requests have been processed.
	RequestQueueDrainPath = "/wait-for-drain"
)

Variables

var (
	// ErrUpdateCapacity indicates that the capacity could not be updated as wished.
	ErrUpdateCapacity = errors.New("failed to add all capacity to the breaker")
	// ErrRelease indicates that release was called more often than acquire.
	ErrRelease = errors.New("semaphore release error: returned tokens must be <= acquired tokens")
	// ErrRequestQueueFull indicates the breaker queue depth was exceeded.
	ErrRequestQueueFull = errors.New("pending request queue full")
)

Functions

func ForwardedShimHandler

func ForwardedShimHandler(h http.Handler) http.Handler

ForwardedShimHandler attempts to shim a `forwarded` HTTP header from the information available in the `x-forwarded-*` headers. When available, each node in the `x-forwarded-for` header is combined with the `x-forwarded-proto` and `x-forwarded-host` fields to construct a `forwarded` header. The `x-forwarded-by` header is ignored entirely, since it cannot be reliably combined with `x-forwarded-for`. No-op if a `forwarded` header is already present.

func NewRequestMetricHandler

func NewRequestMetricHandler(h http.Handler, r stats.StatsReporter, b *Breaker) (http.Handler, error)

NewRequestMetricHandler creates an http.Handler that emits request metrics.

func TimeToFirstByteTimeoutHandler

func TimeToFirstByteTimeoutHandler(h http.Handler, dt time.Duration, msg string) http.Handler

TimeToFirstByteTimeoutHandler returns a Handler that runs `h` with the given time limit in which the first byte of the response must be written.

The new Handler calls h.ServeHTTP to handle each request, but if a call runs for longer than its time limit, the handler responds with a 503 Service Unavailable error and the given message in its body. (If msg is empty, a suitable default message will be sent.) After such a timeout, writes by h to its ResponseWriter will return ErrHandlerTimeout.

A panic from the underlying handler is propagated as-is to be able to make use of custom panic behavior by HTTP handlers. See https://golang.org/pkg/net/http/#Handler.

The implementation is largely inspired by http.TimeoutHandler.

Types

type Breaker

type Breaker struct {
	// contains filtered or unexported fields
}

Breaker is a component that enforces a concurrency limit on the execution of a function. It also maintains a queue of function executions in excess of the concurrency limit. Function call attempts beyond the limit of the queue are failed immediately.

func NewBreaker

func NewBreaker(params BreakerParams) *Breaker

NewBreaker creates a Breaker with the desired queue depth, concurrency limit and initial capacity.

func (*Breaker) Capacity

func (b *Breaker) Capacity() int

Capacity returns the number of allowed in-flight requests on this breaker.

func (*Breaker) InFlight

func (b *Breaker) InFlight() int

InFlight returns the number of requests currently in flight in this breaker.

func (*Breaker) Maybe

func (b *Breaker) Maybe(ctx context.Context, thunk func()) error

Maybe conditionally executes thunk based on the Breaker concurrency and queue parameters. If the concurrency limit and queue capacity are already consumed, Maybe returns immediately without calling thunk. If the thunk was executed, Maybe returns true, else false.

func (*Breaker) UpdateConcurrency

func (b *Breaker) UpdateConcurrency(size int) error

UpdateConcurrency updates the maximum number of in-flight requests.

type BreakerParams

type BreakerParams struct {
	QueueDepth      int
	MaxConcurrency  int
	InitialCapacity int
}

BreakerParams defines the parameters of the breaker.

type Channels

type Channels struct {
	// Ticks with every request arrived/completed respectively
	ReqChan chan ReqEvent
	// Ticks with every stat report request
	ReportChan <-chan time.Time
	// Stat reporting channel
	StatChan chan autoscaler.Stat
}

Channels is a structure for holding the channels for driving Stats. It's just to make the NewStats signature easier to read.

type PrometheusStatsReporter

type PrometheusStatsReporter struct {
	// contains filtered or unexported fields
}

PrometheusStatsReporter structure represents a prometheus stats reporter.

func NewPrometheusStatsReporter

func NewPrometheusStatsReporter(namespace, config, revision, pod string, reportingPeriod time.Duration) (*PrometheusStatsReporter, error)

NewPrometheusStatsReporter creates a reporter that collects and reports queue metrics.

func (*PrometheusStatsReporter) Handler

func (r *PrometheusStatsReporter) Handler() http.Handler

Handler returns an uninstrumented http.Handler used to serve stats registered by this PrometheusStatsReporter.

func (*PrometheusStatsReporter) Report

func (r *PrometheusStatsReporter) Report(stat autoscaler.Stat)

Report captures request metrics.

type ReqEvent

type ReqEvent struct {
	Time      time.Time
	EventType ReqEventType
}

ReqEvent represents either an incoming or closed request.

type ReqEventType

type ReqEventType int

ReqEventType denotes the type (incoming/closed) of a ReqEvent.

const (
	// ReqIn represents an incoming request
	ReqIn ReqEventType = iota
	// ReqOut represents a finished request
	ReqOut
	// ProxiedIn represents an incoming request through a proxy.
	ProxiedIn
	// ProxiedOut represents a finished proxied request.
	ProxiedOut
)

type Stats

type Stats struct {
	// contains filtered or unexported fields
}

Stats is a structure for holding channels per pod.

func NewStats

func NewStats(podName string, channels Channels, startedAt time.Time) *Stats

NewStats instantiates a new instance of Stats.