io.servicetalk.traffic.resilience.http

Class TrafficResilienceHttpClientFilter

Object

TrafficResilienceHttpClientFilter

All Implemented Interfaces:

HttpExecutionStrategyInfluencer, StreamingHttpClientFilterFactory, ExecutionStrategyInfluencer<HttpExecutionStrategy>

public final class TrafficResilienceHttpClientFilter
extends Object
implements StreamingHttpClientFilterFactory

A StreamingHttpClientFilterFactory to enforce capacity and circuit-breaking control for a client. Requests that are not able to acquire a capacity ticket or a circuit permit, will fail with a RequestDroppedException.

Ordering of filters

Ordering of the capacity-filter is important for various reasons:

• The traffic control filter should be as early as possible in the execution chain to offer a fast-fail reaction and ideally trigger a natural back-pressure mechanism with the transport.
• The traffic control filter should not be offloaded if possible to avoid situations where continuous traffic overflows the offloading subsystem.
• The traffic control filter should be ordered after a io.servicetalk.http.netty.RetryingHttpRequesterFilter if one is used, to avail the benefit of retrying requests that failed due to (local or remote) capacity issues. RetryableRequestDroppedException are safely retry-able errors, since they occur on the outgoing side before they even touch the network. DelayedRetryRequestDroppedException errors on the other side, are remote rejections, and its up to the application logic to opt-in for them to be retryable, by configuring the relevant predicate of the io.servicetalk.http.netty.RetryingHttpRequesterFilter
• The traffic control filter should be ordered after a io.servicetalk.http.netty.RetryingHttpRequesterFilter to allow an already acquired permit to be released in case of other errors/timeouts of the operation, before retrying to re-acquire a permit. Otherwise, a permit may be held idle for as long as the operation is awaiting to be re-tried, thus, mis-utilising available resources for other requests through the same client.
• If the traffic control filter is ordered after a timeout-filter then a potential timeout will be delivered to it in the form of a cancellation. The default terminal callback for the ticket in that case, is set to dropped to avail for local throttling, since a timeout is a good indicator that a sub-process in the pipeline is not completing fast enough.
• If the traffic control filter is ordered before a timeout-filter then a potential timeout will be delivered to it in the form of a TimeoutException, which is in turn triggers the drop-event of the ticket by default. Behavior can be overridden through this TrafficResilienceHttpClientFilter.Builder.onErrorTicketTerminal(BiConsumer).

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TrafficResilienceHttpClientFilter.Builder A TrafficResilienceHttpServiceFilter instance builder.

Field Summary

Fields

Modifier and Type	Field and Description
protected static Single<StreamingHttpResponse>	DEFAULT_BREAKER_REJECTION
static Predicate<HttpResponseMetaData>	DEFAULT_BREAKER_REJECTION_PREDICATE Default rejection observer for dropped requests from an external sourced due to service unavailability.
protected static Single<StreamingHttpResponse>	DEFAULT_CAPACITY_REJECTION

Method Summary

Modifier and Type	Method and Description
StreamingHttpClientFilter	create(FilterableStreamingHttpClient client)
HttpExecutionStrategy	requiredOffloads()

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface HttpExecutionStrategyInfluencer

defaultStreamingInfluencer, influenceStrategy, requiredOffloads

Field Detail

DEFAULT_BREAKER_REJECTION_PREDICATE

public static final Predicate<HttpResponseMetaData> DEFAULT_BREAKER_REJECTION_PREDICATE

Default rejection observer for dropped requests from an external sourced due to service unavailability. see. peerBreakerRejection(HttpResponseMetaData, CircuitBreaker, Function).

The default predicate matches the following HTTP response codes:

• HttpResponseStatus.SERVICE_UNAVAILABLE

DEFAULT_CAPACITY_REJECTION

protected static final Single<StreamingHttpResponse> DEFAULT_CAPACITY_REJECTION

DEFAULT_BREAKER_REJECTION

protected static final Single<StreamingHttpResponse> DEFAULT_BREAKER_REJECTION

Method Detail

create

public StreamingHttpClientFilter create(FilterableStreamingHttpClient client)

Specified by:

create in interface StreamingHttpClientFilterFactory

requiredOffloads

public HttpExecutionStrategy requiredOffloads()

Specified by:

requiredOffloads in interface HttpExecutionStrategyInfluencer

Specified by:

requiredOffloads in interface ExecutionStrategyInfluencer<HttpExecutionStrategy>