[GitHub] [accumulo] keith-turner commented on a change in pull request #1158: Require x tservers on start

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keith-turner commented on a change in pull request #1158: Require x tservers on start
URL: https://github.com/apache/accumulo/pull/1158#discussion_r282958457
 
 

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 File path: server/master/src/main/java/org/apache/accumulo/master/util/TserverStartThreshold.java
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+/*
+ * 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 requested 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.master.util;
+
+import org.apache.accumulo.core.conf.AccumuloConfiguration;
+import org.apache.accumulo.core.conf.Property;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * User configurable guard that can block for a threshold of tservers to be registered in zookeeper
+ * and / or a max wait time is reached. The behaviour is controlled through three properties:
+ * <ul>
+ * <li>MASTER_STARTUP_TSERVER_AVAIL_MIN_COUNT - the number of tservers requested before proceeding.
+ * When set to 0 (the default) this is a noop, no blocking occurs and initial continues with
+ * original behaviour.</li>
+ * <li>MASTER_STARTUP_TSERVER_AVAIL_MAX_WAIT - the maximum time the method will block, waiting for
+ * tservers to register in zookeeper.</li>
+ * <li>MASTER_STARTUP_TSERVER_AVAIL_ABORT_ENABLED - controls the behaviour when tserver count and
+ * max wait time are set. When disabled (the default) initialization will continue with ant tservers
+ * available. When enabled, an exception is thrown to abort initialization.</li>
+ * </ul>
+ *
+ * <pre>
+ * {@code
+ *  The interactions of the properties is described in the following table:
+ *    # tservers    max wait   abort enabled            behaviour
+ *        < 1           x           x          Default. noop - no blocking, original behaviour
+ *       >= 1           0           x          Will block, potentially indefinitely until tserver
+ *                                             count reached.
+ *       >= 1         > 0         false        Will block up to max wait. Will continue if tserver
+ *                                             count not reached within max wait timeout period.
+ *       >= 1         > 0         true         Will block up to max wait. Will throw
+ *                                             IllegalStateException exception if tserver
+ *                                             count not reached within max wait timeout period.
+ * }
+ * </pre>
+ *
+ * This is a ome time guard and does not make any guarantee as to the number of tservers that remain
+ * available after this method returns.
+ *
+ * @since 1.9.4
+ */
+public class TserverStartThreshold {
 
 Review comment:
   Did you consider using Accumulo's Retry code in the implementation of this class?

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