Spring Boot Apache HTTP Client Performance Tuning

How do you optimize pooled connections to downstream services using Apache HttpClient?

Here is an experiment.

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 https://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.3.4.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <groupId>com.efeyopixel</groupId>

    <artifactId>myclient</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <name>myclient</name>

    <description>Demo project for Spring Boot</description>

    <properties>

        <java.version>1.8</java.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

    <!-- https://mvnrepository.com/artifact/org.apache.httpcomponents/httpclient -->

    <dependency>

        <groupId>org.apache.httpcomponents</groupId>

        <artifactId>httpclient</artifactId>

        <version>4.5.12</version>

    </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-devtools</artifactId>

            <scope>runtime</scope>

            <optional>true</optional>

        </dependency>

        <dependency>

            <groupId>org.projectlombok</groupId>

            <artifactId>lombok</artifactId>

            <optional>true</optional>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-test</artifactId>

            <scope>test</scope>

            <exclusions>

                <exclusion>

                    <groupId>org.junit.vintage</groupId>

                    <artifactId>junit-vintage-engine</artifactId>

                </exclusion>

            </exclusions>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

Java Code;

package com.efeyopixel.myclient;

import java.io.IOException;

import org.apache.http.HttpHost;

import org.apache.http.client.methods.CloseableHttpResponse;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.conn.routing.HttpRoute;

import org.apache.http.impl.client.CloseableHttpClient;

import org.apache.http.impl.client.HttpClients;

import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;

import org.apache.http.util.EntityUtils;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.context.annotation.Bean;

import org.springframework.http.ResponseEntity;

import org.springframework.stereotype.Service;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RestController;

import lombok.AllArgsConstructor;

import lombok.extern.slf4j.Slf4j;

@SpringBootApplication

public class IwsclientApplication {

    public static void main(final String[] args) {

        SpringApplication.run(IwsclientApplication.class, args);

    }

    @Bean

    public CloseableHttpClient connectionManager() {

        final PoolingHttpClientConnectionManager connManager = new PoolingHttpClientConnectionManager();

        connManager.setMaxTotal(100);

        connManager.setDefaultMaxPerRoute(10);

        final HttpHost host = new HttpHost("localhost", 8083);

        connManager.setMaxPerRoute(new HttpRoute(host), 8);

        final CloseableHttpClient client = 

        HttpClients.custom().setConnectionManager(connManager).build();

        return client;

    }

}

@Slf4j

@RestController

@AllArgsConstructor

class IndexController {

    private final DownstreamService dService;

    @GetMapping("/pass")

    public ResponseEntity<?> name() {

        log.info("pass endpoint");

        return ResponseEntity.ok(dService.name());

    }

}

@Slf4j

@Service

@AllArgsConstructor

class DownstreamService {

    

    final CloseableHttpClient client;

    

    public String name() {

        String response = null;

        CloseableHttpResponse execute = null;

        try {

            execute = client.execute(new HttpGet("http://localhost:8083/apage"));

            response = EntityUtils.toString(execute.getEntity());

        } catch (final IOException e) {

            log.error(e.getMessage(), e);

        } finally {

            if (response != null) {

                log.debug("closing response");

                EntityUtils.consumeQuietly(execute.getEntity());

            }

        }   

        return response;

    }

}