From 15099131addbb3c605cd362caf589c1bc48749fb Mon Sep 17 00:00:00 2001
From: Adam Vialpando <adamvialpando@gmail.com>
Date: Tue, 21 Apr 2026 11:23:32 -0700
Subject: [PATCH] feat: Expose ConnectionPool customization on
 FlagsmithConfig.Builder

Add connectionPool(ConnectionPool) to FlagsmithConfig.Builder so users
can tune how long OkHttp keeps idle connections alive and how many it
retains. This addresses stale connection reuse when running behind
intermediaries (AWS ALB, nginx) that close idle sockets sooner than
OkHttp's default of 5 minutes.

Passing null, or not calling the method, preserves OkHttp's defaults.
Existing users see no behavior change.

Closes #207
---
 .../com/flagsmith/config/FlagsmithConfig.java | 17 ++++++++
 .../flagsmith/config/FlagsmithConfigTest.java | 40 +++++++++++++++++++
 2 files changed, 57 insertions(+)

diff --git a/src/main/java/com/flagsmith/config/FlagsmithConfig.java b/src/main/java/com/flagsmith/config/FlagsmithConfig.java
index ffb7357f..33d8cd1f 100644
--- a/src/main/java/com/flagsmith/config/FlagsmithConfig.java
+++ b/src/main/java/com/flagsmith/config/FlagsmithConfig.java
@@ -11,6 +11,7 @@
 import javax.net.ssl.SSLSocketFactory;
 import javax.net.ssl.X509TrustManager;
 import lombok.Getter;
+import okhttp3.ConnectionPool;
 import okhttp3.HttpUrl;
 import okhttp3.Interceptor;
 import okhttp3.OkHttpClient;
@@ -64,6 +65,9 @@ protected FlagsmithConfig(Builder builder) {
     if (builder.proxy != null) {
       httpBuilder.proxy(builder.proxy);
     }
+    if (builder.connectionPool != null) {
+      httpBuilder.connectionPool(builder.connectionPool);
+    }
     if (!builder.supportedProtocols.isEmpty()) {
       httpBuilder.protocols(
           builder.supportedProtocols.stream()
@@ -110,6 +114,7 @@ public static class Builder {
     private X509TrustManager trustManager;
     private FlagsmithFlagDefaults flagsmithFlagDefaults;
     private AnalyticsProcessor analyticsProcessor;
+    private ConnectionPool connectionPool;
 
     private Boolean enableLocalEvaluation = Boolean.FALSE;
     private Integer environmentRefreshIntervalSeconds = DEFAULT_ENVIRONMENT_REFRESH_SECONDS;
@@ -203,6 +208,18 @@ public Builder withProxy(Proxy proxy) {
       return this;
     }
 
+    /**
+     * Provide a custom OkHttp ConnectionPool to tune keep-alive duration and maximum idle
+     * connections. When not set, OkHttp's defaults are used.
+     *
+     * @param connectionPool the ConnectionPool to use for the HTTP client
+     * @return the Builder
+     */
+    public Builder connectionPool(ConnectionPool connectionPool) {
+      this.connectionPool = connectionPool;
+      return this;
+    }
+
     /**
      * Add retries for HTTP request to the builder.
      *
diff --git a/src/test/java/com/flagsmith/config/FlagsmithConfigTest.java b/src/test/java/com/flagsmith/config/FlagsmithConfigTest.java
index 12c4a7d3..a2524964 100644
--- a/src/test/java/com/flagsmith/config/FlagsmithConfigTest.java
+++ b/src/test/java/com/flagsmith/config/FlagsmithConfigTest.java
@@ -2,12 +2,15 @@
 
 import static org.junit.Assert.assertNull;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import com.flagsmith.config.FlagsmithConfig.Protocol;
 import java.net.InetSocketAddress;
 import java.net.Proxy;
 import java.util.Collections;
+import java.util.concurrent.TimeUnit;
+import okhttp3.ConnectionPool;
 import okhttp3.mock.MockInterceptor;
 import org.junit.jupiter.api.Test;
 
@@ -53,6 +56,29 @@ public void configTest_multipleInterceptors() {
     assertEquals(2, flagsmithConfig.getHttpClient().interceptors().size());
   }
 
+  @Test
+  public void configTest_customConnectionPool_respectsKeepAliveAndMaxIdle() throws Exception {
+    final ConnectionPool pool = new ConnectionPool(7, 42, TimeUnit.SECONDS);
+
+    final FlagsmithConfig flagsmithConfig = FlagsmithConfig.newBuilder()
+        .connectionPool(pool)
+        .build();
+
+    final ConnectionPool wired = flagsmithConfig.getHttpClient().connectionPool();
+    final Object delegate = readField(wired, "delegate");
+    assertEquals(7, readInt(delegate, "maxIdleConnections"));
+    assertEquals(TimeUnit.SECONDS.toNanos(42), readLong(delegate, "keepAliveDurationNs"));
+  }
+
+  @Test
+  public void configTest_nullConnectionPool_isSafeAndUsesDefault() {
+    final FlagsmithConfig flagsmithConfig = FlagsmithConfig.newBuilder()
+        .connectionPool(null)
+        .build();
+
+    assertNotNull(flagsmithConfig.getHttpClient().connectionPool());
+  }
+
   @Test
   public void configTest_supportedProtocols() {
     final FlagsmithConfig defaultFlagsmithConfig = FlagsmithConfig.newBuilder().build();
@@ -65,4 +91,18 @@ public void configTest_supportedProtocols() {
     assertEquals(1, customFlagsmithConfig.getHttpClient().protocols().size());
     assertEquals(okhttp3.Protocol.HTTP_1_1, customFlagsmithConfig.getHttpClient().protocols().get(0));
   }
+
+  private static Object readField(Object target, String fieldName) throws Exception {
+    java.lang.reflect.Field field = target.getClass().getDeclaredField(fieldName);
+    field.setAccessible(true);
+    return field.get(target);
+  }
+
+  private static int readInt(Object target, String fieldName) throws Exception {
+    return (int) readField(target, fieldName);
+  }
+
+  private static long readLong(Object target, String fieldName) throws Exception {
+    return (long) readField(target, fieldName);
+  }
 }