| --- |
| title: Isolation Example |
| --- |
| |
| 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 |
| |
| |
