Add metric for lock contention

Also - remove logging from TransactNew, to prevent double logging on transient
failures (TransactNew retries on failure)

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=172500772

java/google/registry/model/server/LockMetrics.java

@@ -0,0 +1,45 @@
+// 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.model.server;
+
+import com.google.common.collect.ImmutableSet;
+import google.registry.model.server.Lock.LockState;
+import google.registry.monitoring.metrics.IncrementableMetric;
+import google.registry.monitoring.metrics.LabelDescriptor;
+import google.registry.monitoring.metrics.MetricRegistryImpl;
+import javax.annotation.Nullable;
+
+/** Metrics for lock contention. */
+class LockMetrics {
+
+  private static final ImmutableSet<LabelDescriptor> LABEL_DESCRIPTORS =
+      ImmutableSet.of(
+          LabelDescriptor.create("tld", "TLD"),
+          LabelDescriptor.create("resource", "resource name"),
+          LabelDescriptor.create(
+              "state", "The existing lock state (before attempting to acquire)."));
+
+  private static final IncrementableMetric lockRequestsMetric =
+      MetricRegistryImpl.getDefault()
+          .newIncrementableMetric(
+              "/lock/acquire_lock_requests",
+              "Count of lock acquisition attempts",
+              "count",
+              LABEL_DESCRIPTORS);
+
+  void record(String resourceName, @Nullable String tld, LockState state) {
+    lockRequestsMetric.increment(String.valueOf(tld), resourceName, state.name());
+  }
+}