| Title: Apache Accumulo Isolation Example |
| Notice: 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. |
| |
| |
| Accumulo has an isolated scanner that ensures partial changes to rows are not |
| seen. Isolation is documented in ../docs/isolation.html and the user manual. |
| |
| InterferenceTest is a simple example that shows the effects of scanning with |
| and without isolation. This program starts two threads. One threads |
| continually upates all of the values in a row to be the same thing, but |
| different from what it used to be. The other thread continually scans the |
| table and checks that all values in a row are the same. Without isolation the |
| scanning thread will sometimes see different values, which is the result of |
| reading the row at the same time a mutation is changing the row. |
| |
| Below, Interference Test is run without isolation enabled for 5000 iterations |
| and it reports problems. |
| |
| $ ./bin/accumulo org.apache.accumulo.examples.simple.isolation.InterferenceTest -i instance -z zookeepers -u username -p password -t isotest --iterations 5000 |
| ERROR Columns in row 053 had multiple values [53, 4553] |
| ERROR Columns in row 061 had multiple values [561, 61] |
| ERROR Columns in row 070 had multiple values [570, 1070] |
| ERROR Columns in row 079 had multiple values [1079, 1579] |
| ERROR Columns in row 088 had multiple values [2588, 1588] |
| ERROR Columns in row 106 had multiple values [2606, 3106] |
| ERROR Columns in row 115 had multiple values [4615, 3115] |
| finished |
| |
| Below, Interference Test is run with isolation enabled for 5000 iterations and |
| it reports no problems. |
| |
| $ ./bin/accumulo org.apache.accumulo.examples.simple.isolation.InterferenceTest -i instance -z zookeepers -u username -p password -t isotest --iterations 5000 --isolated |
| finished |
| |
| |