Support parameterized metrics

Metrics like Counter1 and Timer1 can now be given a field to
dynamically allocate submetrics for specific values.

Rename the versions with no field Counter0 and Timer0 to
indicate they do allocate submetrics.

Support Counter1-3 and Timer1-3 for up to 3 dimensional
submetrics of either kind.

Description.setFieldOrdering() can be used to control how
the submetrics are named in DropWizard. The default appends
field values to create a new submetric. Another option is
offered to insert field values before the last '/', allowing
things to be broken down by a slightly different layout.

Change-Id: Id2b4f59eb603eb8c8690753650a5720fc26d617b

gerrit-server/src/main/java/com/google/gerrit/metrics/Counter1.java

@@ -0,0 +1,44 @@
+// Copyright (C) 2015 The Android Open Source Project
+//
+// 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 com.google.gerrit.metrics;
+
+import com.google.gerrit.extensions.registration.RegistrationHandle;
+
+/**
+ * Metric whose value increments during the life of the process.
+ * <p>
+ * Suitable uses are "total requests handled", "bytes sent", etc.
+ * Use {@link Description#setRate()} to suggest the monitoring system
+ * should also track the rate of increments if this is of interest.
+ * <p>
+ * For an instantaneous read of a value that can change over time
+ * (e.g. "memory in use") use a {@link CallbackMetric}.
+ *
+ * @param <F1> type of the field.
+ */
+public abstract class Counter1<F1> implements RegistrationHandle {
+  /** Increment the counter by one event. */
+  public void increment(F1 field1) {
+    incrementBy(field1, 1);
+  }
+
+  /**
+   * Increment the counter by a specified amount.
+   *
+   * @param field1 bucket to increment.
+   * @param value value to increment by, must be >= 0.
+   */
+  public abstract void incrementBy(F1 field1, long value);
+}