From a1e56a8c963da1163e8baf47d44820fc9ffac922 Mon Sep 17 00:00:00 2001
From: Joris Mancini <joris.mancini_externe@rte-france.com>
Date: Thu, 19 Jun 2025 15:24:42 +0200
Subject: [PATCH] feat: make http client pool connections configurable and
 increase default values

Signed-off-by: Joris Mancini <joris.mancini_externe@rte-france.com>
---
 pom.xml                                       | 10 +++----
 .../study/server/RestTemplateConfig.java      | 27 +++++++++++++++++--
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/pom.xml b/pom.xml
index ab13dbab90..f2374a202a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -161,6 +161,10 @@
             <groupId>io.projectreactor</groupId>
             <artifactId>reactor-core</artifactId>
         </dependency>
+        <dependency>
+            <groupId>org.apache.httpcomponents.client5</groupId>
+            <artifactId>httpclient5</artifactId>
+        </dependency>
         <dependency>
             <groupId>org.projectlombok</groupId>
             <artifactId>lombok</artifactId>
@@ -196,12 +200,6 @@
         </dependency>
 
         <!-- Runtime dependencies -->
-        <dependency>
-            <!-- Used by RestTemplate -->
-            <groupId>org.apache.httpcomponents.client5</groupId>
-            <artifactId>httpclient5</artifactId>
-            <scope>runtime</scope>
-        </dependency>
         <dependency>
             <groupId>org.liquibase</groupId>
             <artifactId>liquibase-core</artifactId>
diff --git a/src/main/java/org/gridsuite/study/server/RestTemplateConfig.java b/src/main/java/org/gridsuite/study/server/RestTemplateConfig.java
index 07fcaa17de..f5bcac1ef7 100644
--- a/src/main/java/org/gridsuite/study/server/RestTemplateConfig.java
+++ b/src/main/java/org/gridsuite/study/server/RestTemplateConfig.java
@@ -20,6 +20,10 @@
 import com.powsybl.sensitivity.json.SensitivityJsonModule;
 import com.powsybl.shortcircuit.json.ShortCircuitAnalysisJsonModule;
 import com.powsybl.timeseries.json.TimeSeriesJsonModule;
+import org.apache.hc.client5.http.classic.HttpClient;
+import org.apache.hc.client5.http.impl.classic.HttpClients;
+import org.apache.hc.client5.http.impl.io.PoolingHttpClientConnectionManager;
+import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.http.client.HttpComponentsClientHttpRequestFactory;
@@ -31,9 +35,28 @@
 @Configuration
 public class RestTemplateConfig {
 
+    @Value("${http.client.pool.max-connections:500}")
+    private int httpClientPoolMaxConnections;
+
+    @Value("${http.client.pool.max-connections-per-host:200}")
+    private int httpClientPoolMaxConnectionsPerHost;
+
+    @Bean
+    public HttpClient httpClient() {
+        PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
+        // By default, it's limited to 20 connections and 5 connections per host which is very too low for study-server needs
+        connectionManager.setMaxTotal(httpClientPoolMaxConnections);
+        connectionManager.setDefaultMaxPerRoute(httpClientPoolMaxConnectionsPerHost);
+
+        return HttpClients.custom()
+            .setConnectionManager(connectionManager)
+            .build();
+    }
+
     @Bean
-    public RestTemplate restTemplate() {
-        final RestTemplate restTemplate = new RestTemplate(new HttpComponentsClientHttpRequestFactory());
+    public RestTemplate restTemplate(HttpClient httpClient) {
+        // We're using HttpComponentsClientHttpRequestFactory from apache httpclient5 to handle properly HTTP PATCH method
+        final RestTemplate restTemplate = new RestTemplate(new HttpComponentsClientHttpRequestFactory(httpClient));
 
         //find and replace Jackson message converter with our own
         for (int i = 0; i < restTemplate.getMessageConverters().size(); i++) {