Refactor out creation of server TRIDs so they can be tested

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=152837185

java/google/registry/flows/EppController.java

@@ -50,6 +50,7 @@ public final class EppController {
   @Inject EppMetric.Builder eppMetricBuilder;
   @Inject EppMetrics eppMetrics;
   @Inject BigQueryMetricsEnqueuer bigQueryMetricsEnqueuer;
+  @Inject ServerTridProvider serverTridProvider;
   @Inject EppController() {}
 
   /** Reads EPP XML, executes the matching flow, and returns an {@link EppOutput}. */
@@ -83,7 +84,8 @@ public final class EppController {
             Strings.repeat("=", 40));
         // Return early by sending an error message, with no clTRID since we couldn't unmarshal it.
         eppMetricBuilder.setStatus(e.getResult().getCode());
-        return getErrorResponse(e.getResult(), Trid.create(null));
+        return getErrorResponse(
+            e.getResult(), Trid.create(null, serverTridProvider.createServerTrid()));
       }
       if (!eppInput.getTargetIds().isEmpty()) {
         eppMetricBuilder.setEppTarget(Joiner.on(',').join(eppInput.getTargetIds()));

java/google/registry/flows/FlowModule.java

@@ -152,6 +152,13 @@ public class FlowModule {
     return credentials;
   }
 
+  @Provides
+  @FlowScope
+  Trid provideTrid(EppInput eppInput, ServerTridProvider serverTridProvider) {
+    return Trid.create(
+        eppInput.getCommandWrapper().getClTrid(), serverTridProvider.createServerTrid());
+  }
+
   @Provides
   @FlowScope
   @ClientId
@@ -161,12 +168,6 @@ public class FlowModule {
     return Strings.nullToEmpty(sessionMetadata.getClientId());
   }
 
-  @Provides
-  @FlowScope
-  static Trid provideTrid(EppInput eppInput) {
-    return Trid.create(eppInput.getCommandWrapper().getClTrid());
-  }
-
   @Provides
   @FlowScope
   static Class<? extends Flow> provideFlowClass(EppInput eppInput) {

java/google/registry/flows/ServerTridProvider.java

@@ -0,0 +1,28 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.flows;
+
+import google.registry.model.eppcommon.Trid;
+
+/**
+ * An interface that provides server Trids.
+ *
+ * @see Trid
+ */
+public interface ServerTridProvider {
+
+  /** Creates a new server Trid. */
+  public String createServerTrid();
+}

java/google/registry/flows/ServerTridProviderImpl.java

@@ -0,0 +1,50 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.flows;
+
+import static com.google.common.primitives.Longs.BYTES;
+
+import com.google.common.io.BaseEncoding;
+import java.nio.ByteBuffer;
+import java.util.UUID;
+import java.util.concurrent.atomic.AtomicLong;
+import javax.inject.Inject;
+
+/** A server Trid provider that generates globally incrementing UUIDs. */
+public class ServerTridProviderImpl implements ServerTridProvider {
+
+  private static final String SERVER_ID = getServerId();
+  private static final AtomicLong idCounter = new AtomicLong();
+
+  @Inject public ServerTridProviderImpl() {}
+
+  /** Creates a unique id for this server instance, as a base64 encoded UUID. */
+  private static String getServerId() {
+    UUID uuid = UUID.randomUUID();
+    ByteBuffer buffer =
+        ByteBuffer.allocate(BYTES * 2)
+            .putLong(uuid.getMostSignificantBits())
+            .putLong(uuid.getLeastSignificantBits());
+    return BaseEncoding.base64().encode(buffer.array());
+  }
+
+  @Override
+  public String createServerTrid() {
+    // The server id can be at most 64 characters. The SERVER_ID is at most 22 characters (128
+    // bits in base64), plus the dash. That leaves 41 characters, so we just append the counter in
+    // hex.
+    return String.format("%s-%x", SERVER_ID, idCounter.incrementAndGet());
+  }
+}

java/google/registry/flows/ServerTridProviderModule.java

@@ -0,0 +1,28 @@
+// Copyright 2017 The Nomulus Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package google.registry.flows;
+
+import dagger.Module;
+import dagger.Provides;
+
+/** Dagger module for the server Trid provider. */
+@Module
+public class ServerTridProviderModule {
+
+  @Provides
+  static ServerTridProvider provideServerTridProvider(ServerTridProviderImpl defaultProvider) {
+    return defaultProvider;
+  }
+}