Module io.helidon.discovery.providers.eureka

Package io.helidon.discovery.providers.eureka

Interface EurekaDiscovery

All Superinterfaces:

AutoCloseable, Discovery, RuntimeType.Api<EurekaDiscoveryConfig>

public interface EurekaDiscovery
extends RuntimeType.Api<EurekaDiscoveryConfig>, Discovery

A Discovery implementation that communicates with Netflix's Eureka server version 2.

Please see the Discovery documentation for important contractual obligations that must be fulfilled by any implementation of this interface.

Configuration

Configuration for EurekaDiscoveryConfig instances is normally found under the top-level Helidon configuration key named discovery, under a sub-key named eureka. Please see the configuration reference for more details.

Configuration for connecting to a Eureka server hosted on localhost, port 8761 (the port used by Eureka by default), looks like this (in YAML format, often in an application.yaml classpath resource):

discovery:
  eureka:
    client:
      base-uri: "http://localhost:8761/eureka"
    enabled: true # true by default; made explicit here for example purposes

Acquisition ("Declarative" Usage)

To acquire a Discovery instance, inject it, using the Service.Inject annotation. Alternatively, use the static Services.get(Class) method, supplying Discovery.class as its sole argument.

Creation ("Imperative" Usage)

Users of the Helidon Builder API may create instances of this interface via the create(EurekaDiscoveryConfig) method. Instances created in this manner are guaranteed to implement all of the contractual requirements of this interface and its (transitive) supertypes.

(Users of the Helidon Builder API may indirectly create instances of the EurekaDiscoveryConfig interface, if required, via the builder() method, which is a Helidon Builder API-mandated convenience method that, by specification, simply delegates to the EurekaDiscoveryConfig.builder() method. See EurekaDiscoveryConfig.builder() for contractual details related to the creation of EurekaDiscoveryConfig.Builder instances. See EurekaDiscoveryConfig for contractual details related to EurekaDiscoveryConfig instances built using EurekaDiscoveryConfig.Builder instances. These contracts do not affect the requirements this interface imposes on its implementations.)

Any other means of implementing this interface is permitted, so long as it results in an implementation that implements the contractual requirements of this interface's (transitive and reflexive) supertypes.

Logging

Implementations created via the create(EurekaDiscoveryConfig) method (which includes instances available via dependency injection), and any internal supporting classes, will use Loggers whose names begin with io.helidon.discovery.providers.eureka..

Logging output is particularly important to monitor because as a general rule Discovery implementations must strive to be resilient in the presence of failures.

Design note: This interface extends Api<EurekaDiscoveryConfig> to conform to the requirements of the Helidon Builder API. Implementations of this interface must therefore also abide by its contract.

See Also:

• uris(String, URI)
• close()
• create(EurekaDiscoveryConfig)
• builder()
• EurekaDiscoveryConfig.builder()
• EurekaDiscoveryConfig.Builder.build()
• EurekaDiscoveryConfig
• RuntimeType.Api
• Helidon Builder API
• Helidon Configuration Reference

Method Summary

Modifier and Type	Method	Description
static EurekaDiscoveryConfig.Builder	builder()	A convenience method required by, and complying with the requirements of, the Helidon Builder API that, per contract, invokes the EurekaDiscoveryConfig.builder() method and returns its result.
void	close()	Closes any resources used by this EurekaDiscovery implementation.
static EurekaDiscovery	create(EurekaDiscoveryConfig prototype)	Required by, and complying with the requirements of, the Helidon Builder API, creates a new EurekaDiscovery implementation whose state is derived from the supplied EurekaDiscoveryConfig and returns it.
static EurekaDiscovery	create(Consumer<EurekaDiscoveryConfig.Builder> consumer)	A convenience method required by, and complying with the requirements of, the Helidon Builder API that, per contract, builds a new EurekaDiscovery implementation and returns it.
EurekaDiscoveryConfig	prototype()	Returns a non-null, determinate EurekaDiscoveryConfig object representing the prototypical state of this EurekaDiscovery implementation.
SequencedSet<DiscoveredUri>	uris(String discoveryName, URI defaultValue)	Returns a non-null, immutable, non-empty, SequencedSet of DiscoveredUri instances suitable for the supplied discovery name.

Method Details

close

void close()

Closes any resources used by this EurekaDiscovery implementation.

Eureka is a server. Its existence implies network communication. Consequently EurekaDiscovery implementations are required to implement this method, as appropriate, such that it cleans up network-related resources (such as HTTP connections).

The behavior of any given EurekaDiscovery implementation is undefined, unless otherwise documented by the specific implementation, after an invocation of its close() method has taken place. For maximum portability, callers should assume that closing a EurekaDiscovery instance transitions it into a terminal state.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Discovery

Throws:

RuntimeException - if an error occurs

See Also:

• Discovery.close()

prototype

EurekaDiscoveryConfig prototype()

Returns a non-null, determinate EurekaDiscoveryConfig object representing the prototypical state of this EurekaDiscovery implementation.

Specified by:

prototype in interface RuntimeType.Api<EurekaDiscoveryConfig>

Returns:

a non-null, determinate EurekaDiscoveryConfig object representing the prototypical state of this EurekaDiscovery implementation

See Also:

• EurekaDiscoveryConfig

uris

SequencedSet<DiscoveredUri> uris(String discoveryName,
 URI defaultValue)

Returns a non-null, immutable, non-empty, SequencedSet of DiscoveredUri instances suitable for the supplied discovery name.

See the documentation for the Discovery.uris(String, URI) method for more contractual information. Documentation that follows is specific to all EurekaDiscovery implementations. Any given EurekaDiscovery implementation may further refine these requirements.

Implementations of this method often serve cached information. The cache is typically refreshed by a background thread on a regular interval. See EurekaDiscoveryConfig.cache() and EurekaDiscoveryConfig.registryFetchInterval() and their related methods.

Implementations of this method must treat discovery names in a case-insensitive manner.

Implementations of this method must order elements in the returned SequencedSet with elements that are known at invocation time to be UP or STARTING preceding other elements. All other ordering is undefined.

Specified by:

uris in interface Discovery

Parameters:

discoveryName - a discovery name; must not be null; will be handled in a case-insensitive manner; must comply with any requirements that might exist pertaining to a Eureka application name

defaultValue - a URI that will be represented as a DiscoveredUri with no metdata if any kind of error occurs that prevents a normal invocation, or if the return value of an invocation of this method would otherwise be empty; must not be null; will always be represented as a DiscoveredUri and included as the last element in the returned SequencedSet

Returns:

a non-null, immutable, non-empty, SequencedSet of DiscoveredUri instances

Throws:

NullPointerException - if any argument is null

IllegalArgumentException - if any argument is unsuitable in any way

See Also:

• Discovery.uris(String, URI)
• close()
• EurekaDiscoveryConfig.cache()
• DiscoveredUri

builder

static EurekaDiscoveryConfig.Builder builder()

A convenience method required by, and complying with the requirements of, the Helidon Builder API that, per contract, invokes the EurekaDiscoveryConfig.builder() method and returns its result.

Returns:

a non-null EurekaDiscoveryConfig.Builder of EurekaDiscoveryConfig instances

See Also:

• EurekaDiscoveryConfig.builder()
• EurekaDiscoveryConfig
• EurekaDiscoveryConfig.Builder
• Helidon Builder API

create

static EurekaDiscovery create(EurekaDiscoveryConfig prototype)

Required by, and complying with the requirements of, the Helidon Builder API, creates a new EurekaDiscovery implementation whose state is derived from the supplied EurekaDiscoveryConfig and returns it.

Parameters:

prototype - the EurekaDiscoveryConfig from which the implementation will be created; must not be null

Returns:

a new, non-null EurekaDiscovery implementation

Throws:

NullPointerException - if prototype is null

See Also:

• prototype()
• Helidon Builder API

create

static EurekaDiscovery create(Consumer<EurekaDiscoveryConfig.Builder> consumer)

A convenience method required by, and complying with the requirements of, the Helidon Builder API that, per contract, builds a new EurekaDiscovery implementation and returns it.

Parameters:

consumer - a Consumer of EurekaDiscoveryConfig.Builder instances that typically mutates its supplied EurekaDiscoveryConfig.Builder; must not be null

Returns:

a new, non-null EurekaDiscovery implementation as returned by the EurekaDiscoveryConfig.Builder.build() method

Throws:

NullPointerException - if consumer is null

See Also:

• Builder.update(Consumer)
• EurekaDiscoveryConfig.Builder.build()
• Helidon Builder API