1.10/examples/maxmutation.md

---
title: Apache Accumulo MaxMutation Constraints Example
redirect_from:
  - /1.8/examples/maxmutation
  - /1.9/examples/maxmutation
---

This an example of how to limit the size of mutations that will be accepted into
a table. Under the default configuration, accumulo does not provide a limitation
on the size of mutations that can be ingested. Poorly behaved writers might
inadvertently create mutations so large, that they cause the tablet servers to
run out of memory. A simple contraint can be added to a table to reject very
large mutations.

    $ ./bin/accumulo shell -u username -p password

    Shell - Apache Accumulo Interactive Shell
    -
    - version: 1.5.0
    - instance name: instance
    - instance id: 00000000-0000-0000-0000-000000000000
    -
    - type 'help' for a list of available commands
    -
    username@instance> createtable test_ingest
    username@instance test_ingest> config -t test_ingest -s table.constraint.1=org.apache.accumulo.examples.simple.constraints.MaxMutationSize
    username@instance test_ingest>


Now the table will reject any mutation that is larger than 1/256th of the 
working memory of the tablet server.  The following command attempts to ingest 
a single row with 10000 columns, which exceeds the memory limit. Depending on the
amount of Java heap your tserver(s) are given, you may have to increase the number
of columns provided to see the failure.

    $ ./bin/accumulo org.apache.accumulo.test.TestIngest -i instance -z zookeepers -u username -p password --rows 1 --cols 10000 
    ERROR : Constraint violates : ConstraintViolationSummary(constrainClass:org.apache.accumulo.examples.simple.constraints.MaxMutationSize, violationCode:0, violationDescription:mutation exceeded maximum size of 188160, numberOfViolatingMutations:1)