Allow for timeout if featurehub is unreachable, so we don't block indefinitely

client-java-core/src/main/java/io/featurehub/client/EdgeFeatureHubConfig.java

@@ -8,6 +8,7 @@
 
 import java.util.ServiceLoader;
 import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
 import java.util.function.Supplier;
 
 public class EdgeFeatureHubConfig implements FeatureHubConfig {
@@ -81,6 +82,16 @@ public void init() {
     }
   }
 
+  @Override
+  public void init(long timeout, TimeUnit unit) {
+    try {
+      final Future<ClientContext> futureContext = newContext().build();
+      futureContext.get(timeout, unit);
+    } catch (Exception e) {
+      log.error("Failed to initialize FeatureHub client", e);
+    }
+  }
+
   @Override
   public boolean isServerEvaluation() {
     return serverEvaluation;

client-java-core/src/main/java/io/featurehub/client/FeatureHubConfig.java

@@ -2,6 +2,7 @@
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 
+import java.util.concurrent.TimeUnit;
 import java.util.function.Supplier;
 
 public interface FeatureHubConfig {
@@ -21,6 +22,13 @@ public interface FeatureHubConfig {
    */
   void init();
 
+  /**
+   * If you are using a client evaluated feature context, this will initialise the service and block until
+   * the provided timeout or until you have received your first set of features. Server Evaluated contexts
+   * should not use it because it needs to re-request data from the server each time you change your context.
+   */
+  void init(long timeout, TimeUnit unit);
+
   /**
    * The API Key indicates this is going to be server based evaluation
    */

client-java-core/src/test/groovy/io/featurehub/client/EdgeFeatureHubConfigSpec.groovy

@@ -143,4 +143,41 @@ class EdgeFeatureHubConfigSpec extends Specification {
       1 * mockRequest.get() >> Readyness.Ready
       0 * _
   }
+
+  def "init completes successfully if future resolves within the given time"() {
+    given: "A client eval feature config"
+      def config = new EdgeFeatureHubConfig("http://localhost/", "123*abc")
+    and: "A mock future that completes successfully"
+      def futureContext = Mock(Future<ClientContext>)
+      def mockContext = Mock(ClientContext)
+    and: "I mock the context and future"
+      def clientContext = Mock(ClientContext)
+      clientContext.build() >> futureContext
+      config = Spy(config) {
+        newContext() >> clientContext
+      }
+    when: "init is called with a reasonable timeout"
+      config.init(100, TimeUnit.MILLISECONDS)
+    then: "The get method on the future should be called with timeout"
+      1 * futureContext.get(100, TimeUnit.MILLISECONDS) >> mockContext
+      0 * _
+  }
+
+  def "init should timeout if future does not complete within the given time"() {
+    given: "A client eval feature config"
+      def config = new EdgeFeatureHubConfig("http://localhost/", "123*abc")
+    and: "A mock future that does not complete in time"
+      def futureContext = Mock(Future<ClientContext>)
+    and: "I mock the context and future"
+      def clientContext = Mock(ClientContext)
+      clientContext.build() >> futureContext
+      config = Spy(config) {
+        newContext() >> clientContext
+      }
+    when: "init is called with a very short timeout"
+      config.init(1, TimeUnit.MILLISECONDS)
+    then: "The get method on the future should be called with timeout"
+      1 * futureContext.get(1, TimeUnit.MILLISECONDS) >> { throw new java.util.concurrent.TimeoutException() }
+      0 * _
+  }
 }