KTOR Resilient

This repository contains a light implementation of the Ktor framework wrapped by Resilience4j, a Kotlin library for managing failures in a microservice-based system.

Expected behaviour:

The Resilience4j Aspects order is following: Retry ( CircuitBreaker ( RateLimiter ( TimeLimiter ( Bulkhead ( Function ) ) ) ) )

Requirements

• Java 17 or later

Features

• Circuit breaker pattern to prevent cascading failures
• Retry pattern to automatically retry failed requests
• Bulkhead pattern to limit the number of concurrent requests
• KTOR Client Plugins
• For more information on Resilience4j, please see the official documentation: https://resilience4j.readme.io/
• For more information on Ktor, please see the official documentation: https://ktor.io/

Installation

Add only one dependency that contains KTOR engine and Resilience4j plugins:

<dependency>
  <groupId>ua.com.lavi.ktor-resilient</groupId>
  <artifactId>ktor-resilient-client-cio-jackson</artifactId>
  <version>$version</version>
</dependency>

Usage

Create a client

ObjectMapperFactory is already configured to use KotlinModule and JavaTimeModule.

Using plugins is optional, but recommended.

  val httpClient = ResilientClient(httpClient = HttpClient(CIO) {
        install(ContentNegotiation) {
            register(ContentType.Application.Json, JacksonConverter(objectMapper = ObjectMapperFactory.objectMapper))
        }
        install(RetryPlugin) {
            retry = Retry.of("test", RetryConfig.custom<HttpClientCall>()
            .maxAttempts(5)
            .intervalFunction(IntervalFunction.of(Duration.ofMillis(500)))
            .retryOnResult { httpClientCall: HttpClientCall -> httpClientCall.response.status.value == 500 }
            .failAfterMaxAttempts(true)
            .build())
        }
    })

Plugin examples:

Can be found here: ktor-resilient-client/src/test/kotlin/PluginHttpTests.kt

Development

GPG key should be placed in ~/.gradle/gradle.properties and has the following format:

signing.gnupg.keyName=
signing.gnupg.passphrase=

Sonatype keys in the ~/.gradle/gradle.properties should have the following format:

sonatypeUsername=
sonatypePassword=

How to build and publish to sonatype? Run the following command in the console:

./gradlew clean build publishToMavenLocal
or
./gradlew clean build publishToSonatype

Contributing

To contribute to this project, simply fork the repository and submit a pull request with your changes.

License

This project is licensed under the Apache 2.0 license. See the LICENSE file for details.