Package com.linecorp.armeria.client.endpoint

Interface EndpointSelectionStrategy

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface EndpointSelectionStrategy

Endpoint selection strategy that creates a EndpointSelector.

Method Summary

Modifier and Type	Method	Description
static WeightRampingUpStrategyBuilder	builderForRampingUp()	Returns a new WeightRampingUpStrategyBuilder that builds a weight ramping up EndpointSelectionStrategy which ramps the weight of newly added Endpoints.
EndpointSelector	newSelector(EndpointGroup endpointGroup)	Creates a new EndpointSelector that selects an Endpoint from the specified EndpointGroup.
static EndpointSelectionStrategy	rampingUp()	Returns a weight ramping up EndpointSelectionStrategy which ramps the weight of newly added Endpoints using EndpointWeightTransition.linear().
static EndpointSelectionStrategy	roundRobin()	Returns a round-robin strategy, which ignores Endpoint.weight().
static EndpointSelectionStrategy	sticky(ToLongFunction<? super ClientRequestContext> requestContextHasher)	Returns a sticky strategy which uses a user passed ToLongFunction to compute hashes for consistent hashing.
static EndpointSelectionStrategy	weightedRoundRobin()	Returns a weighted round-robin strategy.

Method Details

weightedRoundRobin

static EndpointSelectionStrategy weightedRoundRobin()

Returns a weighted round-robin strategy. The endpoint is selected using Interleaved WRR algorithm.

See Also:

• roundRobin()
• sticky(ToLongFunction)

roundRobin

static EndpointSelectionStrategy roundRobin()

Returns a round-robin strategy, which ignores Endpoint.weight().

See Also:

• weightedRoundRobin()
• sticky(ToLongFunction)

rampingUp

@UnstableApi
static EndpointSelectionStrategy rampingUp()

Returns a weight ramping up EndpointSelectionStrategy which ramps the weight of newly added Endpoints using EndpointWeightTransition.linear(). The Endpoint is selected using weighted random distribution. The weights of Endpoints are ramped up by 10 percent every 2 seconds up to 100 percent by default. If you want to customize the parameters, use builderForRampingUp().

builderForRampingUp

@UnstableApi
static WeightRampingUpStrategyBuilder builderForRampingUp()

Returns a new WeightRampingUpStrategyBuilder that builds a weight ramping up EndpointSelectionStrategy which ramps the weight of newly added Endpoints. The Endpoint is selected using weighted random distribution.

sticky

static EndpointSelectionStrategy sticky(ToLongFunction<? super ClientRequestContext> requestContextHasher)

Returns a sticky strategy which uses a user passed ToLongFunction to compute hashes for consistent hashing.

This strategy can be useful when all requests that qualify some given criteria must be sent to the same backend server. A common use case is to send all requests for the same logged-in user to the same backend, which could have a local cache keyed by user id.

In below example, created strategy will route all HttpRequest which have the same value for key "cookie" of its header to the same server:

 ToLongFunction<ClientRequestContext> hasher = (ClientRequestContext ctx) -> {
     return ((HttpRequest) ctx.request()).headers().get(HttpHeaderNames.COOKIE).hashCode();
 };
 EndpointSelectionStrategy strategy = EndpointSelectionStrategy.sticky(hasher);
 

See Also:

• roundRobin()
• weightedRoundRobin()

newSelector

EndpointSelector newSelector(EndpointGroup endpointGroup)

Creates a new EndpointSelector that selects an Endpoint from the specified EndpointGroup.