Github user dhutchis commented on a diff in the pull request:
https://github.com/apache/accumulo/pull/96#discussion_r61037738
--- Diff:
core/src/main/java/org/apache/accumulo/core/client/impl/SyncingTabletLocator.java
---
@@ -0,0 +1,108 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.accumulo.core.client.impl;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.accumulo.core.client.AccumuloException;
+import org.apache.accumulo.core.client.AccumuloSecurityException;
+import org.apache.accumulo.core.client.TableNotFoundException;
+import org.apache.accumulo.core.data.KeyExtent;
+import org.apache.accumulo.core.data.Mutation;
+import org.apache.accumulo.core.data.Range;
+import org.apache.accumulo.core.security.Credentials;
+import org.apache.hadoop.io.Text;
+
+/**
+ * Syncs itself with the static collection of TabletLocators, so that when
the server clears it, it will automatically get the most up-to-date version.
Caching
+ * TabletLocators locally is safe when using SyncingTabletLocator.
+ */
+public class SyncingTabletLocator extends TabletLocator {
+ /*
+ * Implementation: the invalidateCache calls do not need to call
syncLocator because it is okay if an outdated locator is invalidated. In this
case, on the
+ * next call to a meaningful function like binRanges, the new locator
will replace the current one and be used instead. The new locator is fresh; it
has no
+ * cache at all when created.
+ */
+
+ /**
+ * Used to tell SyncingTabletLocator how to fetch a new locator when the
current one is outdated. For example,
+ * <code>TabletLocator.getLocator(instance, tableId);</code>
+ */
+ public interface GetLocatorFunction {
--- End diff --
Actually now that I look more closely, there really is just one getLocators
method in TabletLocator. I must have seen something that doesn't exist.
Nevertheless, I imagine a use case where a client wants to modify a locator
after obtaining one. It might wrap the locator inside an anonymous class or
something like a TImeoutTabletLocator. If I had not changed
TimeoutTabletLocator to subclass SyncingTabletLocator, then I would have done
something like this.
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