Short example how to avoid problem with infinite amount of ConnectionPools created by OkHttpClient 3.6.0.

readme.md

Problem description can be found here:

• square/okhttp#3160
• https://github.com/couchbase/couchbase-lite-java-core/issues/1489

App.java

package com.github.hubertwo.okhttptest;


import okhttp3.*;

import java.io.IOException;
import java.util.concurrent.TimeUnit;

/**
 * This is a short example how to avoid problem
 * with infinite amount of ConnectionPools created by OkHttpClient 3.6.0.
 */
public class App {

    public static void main(String[] args) throws IOException, InterruptedException {

        // Create you own ConnectionPool and use it whenever
        // you are creating OkHttpClient.
        final ConnectionPool connectionPool = new ConnectionPool(2, 10, TimeUnit.SECONDS);

        for (int i = 0; i < 10; i++) {
            // Create new client with previously created connection pool.
            OkHttpClient client = new OkHttpClient.Builder()
                    .connectionPool(connectionPool) // If you want to reproduce problem comment this line.
                    .build();

            // Executing request.
            Request request = new Request.Builder()
                    .url("https://github.com/HubertWo")
                    .build();
            try (Response response = client.newCall(request).execute()) {
                System.out.println(response.code());
            }

            // Close OkHttpClient according to: 
            // https://square.github.io/okhttp/3.x/okhttp/okhttp3/OkHttpClient.html
            client.dispatcher().executorService().shutdown();
            client.connectionPool().evictAll();
            
            // For better visualization.
            TimeUnit.SECONDS.sleep(2);
        }
    }
}

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>OkHttpTest</groupId>
    <artifactId>OkHttpTest</artifactId>
    <version>1.0-SNAPSHOT</version>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>


    <dependencies>
        <dependency>
            <groupId>com.squareup.okhttp3</groupId>
            <artifactId>okhttp</artifactId>
            <version>3.6.0</version>
        </dependency>
    </dependencies>

</project>