Fix high mem usage due to many OkHttpClient instances. (#373)

sdk/src/main/java/io/dapr/client/DaprHttpBuilder.java

@@ -9,6 +9,7 @@ import io.dapr.config.Properties;
 import okhttp3.OkHttpClient;
 
 import java.time.Duration;
+import java.util.concurrent.atomic.AtomicReference;
 
 /**
  * A builder for the DaprHttp.
@@ -16,21 +17,30 @@ import java.time.Duration;
 public class DaprHttpBuilder {
 
   /**
-   * Read timeout for http calls.
+   * Singleton OkHttpClient.
    */
-  private static final Duration DEFAULT_READ_TIMEOUT = Duration.ofSeconds(60);
+  private static final AtomicReference<OkHttpClient> OK_HTTP_CLIENT = new AtomicReference<>();
+
+  /**
+   * Static lock object.
+   */
+  private static final Object LOCK = new Object();
 
   /**
    * Read timeout used to build object.
    */
-  private Duration readTimeout = DEFAULT_READ_TIMEOUT;
+  private Duration readTimeout = Duration.ofSeconds(Properties.HTTP_CLIENT_READTIMEOUTSECONDS.get());
 
   /**
    * Sets the read timeout duration for the instance to be built.
    *
+   * <p>Instead, set environment variable "DAPR_HTTP_CLIENT_READTIMEOUTSECONDS",
+   *   or system property "dapr.http.client.readtimeoutseconds".
+   *
    * @param duration Read timeout duration.
    * @return Same builder instance.
    */
+  @Deprecated
   public DaprHttpBuilder withReadTimeout(Duration duration) {
     this.readTimeout = duration;
     return this;
@@ -52,9 +62,17 @@ public class DaprHttpBuilder {
    * @return Instance of {@link DaprHttp}
    */
   private DaprHttp buildDaprHttp() {
-    OkHttpClient.Builder builder = new OkHttpClient.Builder();
-    builder.readTimeout(this.readTimeout);
-    OkHttpClient okHttpClient = builder.build();
-    return new DaprHttp(Properties.SIDECAR_IP.get(), Properties.HTTP_PORT.get(), okHttpClient);
+    if (OK_HTTP_CLIENT.get() == null) {
+      synchronized (LOCK) {
+        if (OK_HTTP_CLIENT.get() == null) {
+          OkHttpClient.Builder builder = new OkHttpClient.Builder();
+          builder.readTimeout(this.readTimeout);
+          OkHttpClient okHttpClient = builder.build();
+          OK_HTTP_CLIENT.set(okHttpClient);
+        }
+      }
+    }
+
+    return new DaprHttp(Properties.SIDECAR_IP.get(), Properties.HTTP_PORT.get(), OK_HTTP_CLIENT.get());
   }
 }

sdk/src/main/java/io/dapr/config/Properties.java

@@ -38,6 +38,11 @@ public class Properties {
    */
   private static final Charset DEFAULT_STRING_CHARSET = StandardCharsets.UTF_8;
 
+  /**
+   * Dapr's default timeout in seconds for HTTP client reads.
+   */
+  private static final Integer DEFAULT_HTTP_CLIENT_READTIMEOUTSECONDS = 60;
+
   /**
    * IP for Dapr's sidecar.
    */
@@ -86,4 +91,12 @@ public class Properties {
       "DAPR_STRING_CHARSET",
       DEFAULT_STRING_CHARSET,
       (s) -> Charset.forName(s));
+
+  /**
+   * Dapr's timeout in seconds for HTTP client reads.
+   */
+  public static final Property<Integer> HTTP_CLIENT_READTIMEOUTSECONDS = new IntegerProperty(
+      "dapr.http.client.readtimeoutseconds",
+      "DAPR_HTTP_CLIENT_READTIMEOUTSECONDS",
+      DEFAULT_HTTP_CLIENT_READTIMEOUTSECONDS);
 }

sdk/src/test/java/io/dapr/client/DaprHttpBuilderTest.java

@@ -9,37 +9,26 @@ import okhttp3.OkHttpClient;
 import org.junit.Test;
 
 import java.lang.reflect.Field;
-import java.time.Duration;
 
-import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertSame;
 
 public class DaprHttpBuilderTest {
 
   @Test
-  public void withReadTimeout() throws Exception {
-    DaprHttpBuilder daprHttpBuilder = new DaprHttpBuilder();
-    Duration duration = Duration.ofSeconds(999);
-    daprHttpBuilder.build();
-    DaprHttpBuilder dapr = daprHttpBuilder.withReadTimeout(duration);
-    assertNotNull(dapr);
+  public void singletonOkHttpClient() throws Exception {
+    DaprHttp daprHttp = new DaprHttpBuilder().build();
+    DaprHttp anotherDaprHttp = new DaprHttpBuilder().build();
 
-    DaprHttp daprHttp = daprHttpBuilder.build();
-    assertOKHttpPropertyValue(daprHttp, "readTimeoutMillis", (int)duration.toMillis());
+    assertSame(getOkHttpClient(daprHttp), getOkHttpClient(anotherDaprHttp));
   }
 
-  private static final void assertOKHttpPropertyValue(DaprHttp daprHttp, String propertyName, Object expectedValue) throws Exception {
-    // First, get okHttpClient.
+  private static OkHttpClient getOkHttpClient(DaprHttp daprHttp) throws Exception {
     Field httpClientField = DaprHttp.class.getDeclaredField("httpClient");
     httpClientField.setAccessible(true);
     OkHttpClient okHttpClient = (OkHttpClient) httpClientField.get(daprHttp);
     assertNotNull(okHttpClient);
-
-    Field propertyField = OkHttpClient.class.getDeclaredField(propertyName);
-    propertyField.setAccessible(true);
-    Object value = propertyField.get(okHttpClient);
-    assertNotNull(value);
-    assertEquals(expectedValue, value);
+    return okHttpClient;
   }
 
 }