1.7. Tests

Developers, at a minimum, should familiarize themselves with the unit test detail; unit tests in HBase have a character not usually seen in other projects.

1.7.1. Apache HBase Modules

As of 0.96, Apache HBase is split into multiple modules which creates "interesting" rules for how and where tests are written. If you are writting code for hbase-server, see Section 1.7.2, “Unit Tests” for how to write your tests; these tests can spin up a minicluster and will need to be categorized. For any other module, for example hbase-common, the tests must be strict unit tests and just test the class under test - no use of the HBaseTestingUtility or minicluster is allowed (or even possible given the dependency tree). Running Tests in other Modules

If the module you are developing in has no other dependencies on other HBase modules, then you can cd into that module and just run:
mvn test
which will just run the tests IN THAT MODULE. If there are other dependencies on other modules, then you will have run the command from the ROOT HBASE DIRECTORY. This will run the tests in the other modules, unless you specify to skip the tests in that module. For instance, to skip the tests in the hbase-server module, you would run:
mvn clean test -PskipServerTests
from the top level directory to run all the tests in modules other than hbase-server. Note that you can specify to skip tests in multiple modules as well as just for a single module. For example, to skip the tests in hbase-server and hbase-common, you would run:
mvn clean test -PskipServerTests -PskipCommonTests

Also, keep in mind that if you are running tests in the hbase-server module you will need to apply the maven profiles discussed in Section 1.7.3, “Running tests” to get the tests to run properly.

1.7.2. Unit Tests

Apache HBase unit tests are subdivided into four categories: small, medium, large, and integration with corresponding JUnit categories: SmallTests, MediumTests, LargeTests, IntegrationTests. JUnit categories are denoted using java annotations and look like this in your unit test code.

public class TestHRegionInfo {
  public void testCreateHRegionInfoName() throws Exception {
    // ...

The above example shows how to mark a unit test as belonging to the small category. All unit tests in HBase have a categorization.

The first three categories, small, medium, and large are for tests run when you type $ mvn test; i.e. these three categorizations are for HBase unit tests. The integration category is for not for unit tests but for integration tests. These are run when you invoke $ mvn verify. Integration tests are described in Section 1.7.5, “Integration Tests” and will not be discussed further in this section on HBase unit tests.

Apache HBase uses a patched maven surefire plugin and maven profiles to implement its unit test characterizations.

Read the below to figure which annotation of the set small, medium, and large to put on your new HBase unit test. Small Tests

Small tests are executed in a shared JVM. We put in this category all the tests that can be executed quickly in a shared JVM. The maximum execution time for a small test is 15 seconds, and small tests should not use a (mini)cluster. Medium Tests

Medium tests represent tests that must be executed before proposing a patch. They are designed to run in less than 30 minutes altogether, and are quite stable in their results. They are designed to last less than 50 seconds individually. They can use a cluster, and each of them is executed in a separate JVM. Large Tests

Large tests are everything else. They are typically large-scale tests, regression tests for specific bugs, timeout tests, performance tests. They are executed before a commit on the pre-integration machines. They can be run on the developer machine as well. Integration Tests

Integration tests are system level tests. See Section 1.7.5, “Integration Tests” for more info.

1.7.3. Running tests

Below we describe how to run the Apache HBase junit categories. Default: small and medium category tests


mvn test

will execute all small tests in a single JVM (no fork) and then medium tests in a separate JVM for each test instance. Medium tests are NOT executed if there is an error in a small test. Large tests are NOT executed. There is one report for small tests, and one report for medium tests if they are executed. Running all tests


mvn test -P runAllTests

will execute small tests in a single JVM then medium and large tests in a separate JVM for each test. Medium and large tests are NOT executed if there is an error in a small test. Large tests are NOT executed if there is an error in a small or medium test. There is one report for small tests, and one report for medium and large tests if they are executed. Running a single test or all tests in a package

To run an individual test, e.g. MyTest, do

mvn test -Dtest=MyTest

You can also pass multiple, individual tests as a comma-delimited list:

mvn test -Dtest=MyTest1,MyTest2,MyTest3

You can also pass a package, which will run all tests under the package:

mvn test -Dtest=org.apache.hadoop.hbase.client.*

When -Dtest is specified, localTests profile will be used. It will use the official release of maven surefire, rather than our custom surefire plugin, and the old connector (The HBase build uses a patched version of the maven surefire plugin). Each junit tests is executed in a separate JVM (A fork per test class). There is no parallelization when tests are running in this mode. You will see a new message at the end of the -report: "[INFO] Tests are skipped". It's harmless. While you need to make sure the sum of Tests run: in the Results : section of test reports matching the number of tests you specified because no error will be reported when a non-existent test case is specified. Other test invocation permutations


mvn test -P runSmallTests

will execute "small" tests only, using a single JVM.


mvn test -P runMediumTests

will execute "medium" tests only, launching a new JVM for each test-class.


mvn test -P runLargeTests

will execute "large" tests only, launching a new JVM for each test-class.

For convenience, you can run

mvn test -P runDevTests

to execute both small and medium tests, using a single JVM. Running tests faster

By default, $ mvn test -P runAllTests runs 5 tests in parallel. It can be increased on a developer's machine. Allowing that you can have 2 tests in parallel per core, and you need about 2Gb of memory per test (at the extreme), if you have an 8 core, 24Gb box, you can have 16 tests in parallel. but the memory available limits it to 12 (24/2), To run all tests with 12 tests in parallell, do this: mvn test -P runAllTests -Dsurefire.secondPartThreadCount=12. To increase the speed, you can as well use a ramdisk. You will need 2Gb of memory to run all tests. You will also need to delete the files between two test run. The typical way to configure a ramdisk on Linux is:

$ sudo mkdir /ram2G
sudo mount -t tmpfs -o size=2048M tmpfs /ram2G

You can then use it to run all HBase tests with the command: mvn test -P runAllTests -Dsurefire.secondPartThreadCount=12 -Dtest.build.data.basedirectory=/ram2G hbasetests.sh

It's also possible to use the script hbasetests.sh. This script runs the medium and large tests in parallel with two maven instances, and provides a single report. This script does not use the hbase version of surefire so no parallelization is being done other than the two maven instances the script sets up. It must be executed from the directory which contains the pom.xml.

For example running


will execute small and medium tests. Running

./dev-support/hbasetests.sh runAllTests

will execute all tests. Running

./dev-support/hbasetests.sh replayFailed

will rerun the failed tests a second time, in a separate jvm and without parallelisation. Test Resource Checker

A custom Maven SureFire plugin listener checks a number of resources before and after each HBase unit test runs and logs its findings at the end of the test output files which can be found in target/surefire-reports per Maven module (Tests write test reports named for the test class into this directory. Check the *-out.txt files). The resources counted are the number of threads, the number of file descriptors, etc. If the number has increased, it adds a LEAK? comment in the logs. As you can have an HBase instance running in the background, some threads can be deleted/created without any specific action in the test. However, if the test does not work as expected, or if the test should not impact these resources, it's worth checking these log lines ...hbase.ResourceChecker(157): before... and ...hbase.ResourceChecker(157): after.... For example: 2012-09-26 09:22:15,315 INFO [pool-1-thread-1] hbase.ResourceChecker(157): after: regionserver.TestColumnSeeking#testReseeking Thread=65 (was 65), OpenFileDescriptor=107 (was 107), MaxFileDescriptor=10240 (was 10240), ConnectionCount=1 (was 1)

1.7.4. Writing Tests General rules

  • As much as possible, tests should be written as category small tests.
  • All tests must be written to support parallel execution on the same machine, hence they should not use shared resources as fixed ports or fixed file names.
  • Tests should not overlog. More than 100 lines/second makes the logs complex to read and use i/o that are hence not available for the other tests.
  • Tests can be written with HBaseTestingUtility. This class offers helper functions to create a temp directory and do the cleanup, or to start a cluster. Categories and execution time

  • All tests must be categorized, if not they could be skipped.
  • All tests should be written to be as fast as possible.
  • Small category tests should last less than 15 seconds, and must not have any side effect.
  • Medium category tests should last less than 50 seconds.
  • Large category tests should last less than 3 minutes. This should ensure a good parallelization for people using it, and ease the analysis when the test fails. Sleeps in tests

Whenever possible, tests should not use Thread.sleep, but rather waiting for the real event they need. This is faster and clearer for the reader. Tests should not do a Thread.sleep without testing an ending condition. This allows understanding what the test is waiting for. Moreover, the test will work whatever the machine performance is. Sleep should be minimal to be as fast as possible. Waiting for a variable should be done in a 40ms sleep loop. Waiting for a socket operation should be done in a 200 ms sleep loop. Tests using a cluster

Tests using a HRegion do not have to start a cluster: A region can use the local file system. Start/stopping a cluster cost around 10 seconds. They should not be started per test method but per test class. Started cluster must be shutdown using HBaseTestingUtility#shutdownMiniCluster, which cleans the directories. As most as possible, tests should use the default settings for the cluster. When they don't, they should document it. This will allow to share the cluster later.

1.7.5. Integration Tests

HBase integration/system tests are tests that are beyond HBase unit tests. They are generally long-lasting, sizeable (the test can be asked to 1M rows or 1B rows), targetable (they can take configuration that will point them at the ready-made cluster they are to run against; integration tests do not include cluster start/stop code), and verifying success, integration tests rely on public APIs only; they do not attempt to examine server internals asserting success/fail. Integration tests are what you would run when you need to more elaborate proofing of a release candidate beyond what unit tests can do. They are not generally run on the Apache Continuous Integration build server, however, some sites opt to run integration tests as a part of their continuous testing on an actual cluster.

Integration tests currently live under the src/test directory in the hbase-it submodule and will match the regex: **/IntegrationTest*.java. All integration tests are also annotated with @Category(IntegrationTests.class).

Integration tests can be run in two modes: using a mini cluster, or against an actual distributed cluster. Maven failsafe is used to run the tests using the mini cluster. IntegrationTestsDriver class is used for executing the tests against a distributed cluster. Integration tests SHOULD NOT assume that they are running against a mini cluster, and SHOULD NOT use private API's to access cluster state. To interact with the distributed or mini cluster uniformly, IntegrationTestingUtility, and HBaseCluster classes, and public client API's can be used.

On a distributed cluster, integration tests that use ChaosMonkey or otherwise manipulate services thru cluster manager (e.g. restart regionservers) use SSH to do it. To run these, test process should be able to run commands on remote end, so ssh should be configured accordingly (for example, if HBase runs under hbase user in your cluster, you can set up passwordless ssh for that user and run the test also under it). To facilitate that, hbase.it.clustermanager.ssh.user, hbase.it.clustermanager.ssh.opts and hbase.it.clustermanager.ssh.cmd configuration settings can be used. "User" is the remote user that cluster manager should use to perform ssh commands. "Opts" contains additional options that are passed to SSH (for example, "-i /tmp/my-key"). Finally, if you have some custom environment setup, "cmd" is the override format for the entire tunnel (ssh) command. The default string is {/usr/bin/ssh %1$s %2$s%3$s%4$s "%5$s"} and is a good starting point. This is a standard Java format string with 5 arguments that is used to execute the remote command. The argument 1 (%1$s) is SSH options set the via opts setting or via environment variable, 2 is SSH user name, 3 is "@" if username is set or "" otherwise, 4 is the target host name, and 5 is the logical command to execute (that may include single quotes, so don't use them). For example, if you run the tests under non-hbase user and want to ssh as that user and change to hbase on remote machine, you can use {/usr/bin/ssh %1$s %2$s%3$s%4$s "su hbase - -c \"%5$s\""}. That way, to kill RS (for example) integration tests may run {/usr/bin/ssh some-hostname "su hbase - -c \"ps aux | ... | kill ...\""}. The command is logged in the test logs, so you can verify it is correct for your environment. Running integration tests against mini cluster

HBase 0.92 added a verify maven target. Invoking it, for example by doing mvn verify, will run all the phases up to and including the verify phase via the maven failsafe plugin, running all the above mentioned HBase unit tests as well as tests that are in the HBase integration test group. After you have completed

mvn install -DskipTests

You can run just the integration tests by invoking:

cd hbase-it
mvn verify

If you just want to run the integration tests in top-level, you need to run two commands. First:

mvn failsafe:integration-test

This actually runs ALL the integration tests.


This command will always output BUILD SUCCESS even if there are test failures.

At this point, you could grep the output by hand looking for failed tests. However, maven will do this for us; just use:

mvn failsafe:verify

The above command basically looks at all the test results (so don't remove the 'target' directory) for test failures and reports the results. Running a subset of Integration tests

This is very similar to how you specify running a subset of unit tests (see above), but use the property it.test instead of test. To just run IntegrationTestClassXYZ.java, use:

mvn failsafe:integration-test -Dit.test=IntegrationTestClassXYZ

The next thing you might want to do is run groups of integration tests, say all integration tests that are named IntegrationTestClassX*.java:

mvn failsafe:integration-test -Dit.test=*ClassX*

This runs everything that is an integration test that matches *ClassX*. This means anything matching: "**/IntegrationTest*ClassX*". You can also run multiple groups of integration tests using comma-delimited lists (similar to unit tests). Using a list of matches still supports full regex matching for each of the groups.This would look something like:

mvn failsafe:integration-test -Dit.test=*ClassX*, *ClassY Running integration tests against distributed cluster

If you have an already-setup HBase cluster, you can launch the integration tests by invoking the class IntegrationTestsDriver. You may have to run test-compile first. The configuration will be picked by the bin/hbase script.

mvn test-compile

Then launch the tests with:

bin/hbase [--config config_dir] org.apache.hadoop.hbase.IntegrationTestsDriver

Pass -h to get usage on this sweet tool. Running the IntegrationTestsDriver without any argument will launch tests found under hbase-it/src/test, having @Category(IntegrationTests.class) annotation, and a name starting with IntegrationTests. See the usage, by passing -h, to see how to filter test classes. You can pass a regex which is checked against the full class name; so, part of class name can be used. IntegrationTestsDriver uses Junit to run the tests. Currently there is no support for running integration tests against a distributed cluster using maven (see HBASE-6201).

The tests interact with the distributed cluster by using the methods in the DistributedHBaseCluster (implementing HBaseCluster) class, which in turn uses a pluggable ClusterManager. Concrete implementations provide actual functionality for carrying out deployment-specific and environment-dependent tasks (SSH, etc). The default ClusterManager is HBaseClusterManager, which uses SSH to remotely execute start/stop/kill/signal commands, and assumes some posix commands (ps, etc). Also assumes the user running the test has enough "power" to start/stop servers on the remote machines. By default, it picks up HBASE_SSH_OPTS, HBASE_HOME, HBASE_CONF_DIR from the env, and uses bin/hbase-daemon.sh to carry out the actions. Currently tarball deployments, deployments which uses hbase-daemons.sh, and Apache Ambari deployments are supported. /etc/init.d/ scripts are not supported for now, but it can be easily added. For other deployment options, a ClusterManager can be implemented and plugged in. Destructive integration / system tests

In 0.96, a tool named ChaosMonkey has been introduced. It is modeled after the same-named tool by Netflix. Some of the tests use ChaosMonkey to simulate faults in the running cluster in the way of killing random servers, disconnecting servers, etc. ChaosMonkey can also be used as a stand-alone tool to run a (misbehaving) policy while you are running other tests.

ChaosMonkey defines Action's and Policy's. Actions are sequences of events. We have at least the following actions:

  • Restart active master (sleep 5 sec)
  • Restart random regionserver (sleep 5 sec)
  • Restart random regionserver (sleep 60 sec)
  • Restart META regionserver (sleep 5 sec)
  • Restart ROOT regionserver (sleep 5 sec)
  • Batch restart of 50% of regionservers (sleep 5 sec)
  • Rolling restart of 100% of regionservers (sleep 5 sec)

Policies on the other hand are responsible for executing the actions based on a strategy. The default policy is to execute a random action every minute based on predefined action weights. ChaosMonkey executes predefined named policies until it is stopped. More than one policy can be active at any time.

To run ChaosMonkey as a standalone tool deploy your HBase cluster as usual. ChaosMonkey uses the configuration from the bin/hbase script, thus no extra configuration needs to be done. You can invoke the ChaosMonkey by running:

bin/hbase org.apache.hadoop.hbase.util.ChaosMonkey

This will output smt like:

12/11/19 23:21:57 INFO util.ChaosMonkey: Using ChaosMonkey Policy: class org.apache.hadoop.hbase.util.ChaosMonkey$PeriodicRandomActionPolicy, period:60000
12/11/19 23:21:57 INFO util.ChaosMonkey: Sleeping for 26953 to add jitter
12/11/19 23:22:24 INFO util.ChaosMonkey: Performing action: Restart active master
12/11/19 23:22:24 INFO util.ChaosMonkey: Killing master:master.example.com,60000,1353367210440
12/11/19 23:22:24 INFO hbase.HBaseCluster: Aborting Master: master.example.com,60000,1353367210440
12/11/19 23:22:24 INFO hbase.ClusterManager: Executing remote command: ps aux | grep master | grep -v grep | tr -s ' ' | cut -d ' ' -f2 | xargs kill -s SIGKILL , hostname:master.example.com
12/11/19 23:22:25 INFO hbase.ClusterManager: Executed remote command, exit code:0 , output:
12/11/19 23:22:25 INFO hbase.HBaseCluster: Waiting service:master to stop: master.example.com,60000,1353367210440
12/11/19 23:22:25 INFO hbase.ClusterManager: Executing remote command: ps aux | grep master | grep -v grep | tr -s ' ' | cut -d ' ' -f2 , hostname:master.example.com
12/11/19 23:22:25 INFO hbase.ClusterManager: Executed remote command, exit code:0 , output:
12/11/19 23:22:25 INFO util.ChaosMonkey: Killed master server:master.example.com,60000,1353367210440
12/11/19 23:22:25 INFO util.ChaosMonkey: Sleeping for:5000
12/11/19 23:22:30 INFO util.ChaosMonkey: Starting master:master.example.com
12/11/19 23:22:30 INFO hbase.HBaseCluster: Starting Master on: master.example.com
12/11/19 23:22:30 INFO hbase.ClusterManager: Executing remote command: /homes/enis/code/hbase-0.94/bin/../bin/hbase-daemon.sh --config /homes/enis/code/hbase-0.94/bin/../conf start master , hostname:master.example.com
12/11/19 23:22:31 INFO hbase.ClusterManager: Executed remote command, exit code:0 , output:starting master, logging to /homes/enis/code/hbase-0.94/bin/../logs/hbase-enis-master-master.example.com.out
12/11/19 23:22:33 INFO util.ChaosMonkey: Started master: master.example.com,60000,1353367210440
12/11/19 23:22:33 INFO util.ChaosMonkey: Sleeping for:51321
12/11/19 23:23:24 INFO util.ChaosMonkey: Performing action: Restart random region server
12/11/19 23:23:24 INFO util.ChaosMonkey: Killing region server:rs3.example.com,60020,1353367027826
12/11/19 23:23:24 INFO hbase.HBaseCluster: Aborting RS: rs3.example.com,60020,1353367027826
12/11/19 23:23:24 INFO hbase.ClusterManager: Executing remote command: ps aux | grep regionserver | grep -v grep | tr -s ' ' | cut -d ' ' -f2 | xargs kill -s SIGKILL , hostname:rs3.example.com
12/11/19 23:23:25 INFO hbase.ClusterManager: Executed remote command, exit code:0 , output:
12/11/19 23:23:25 INFO hbase.HBaseCluster: Waiting service:regionserver to stop: rs3.example.com,60020,1353367027826
12/11/19 23:23:25 INFO hbase.ClusterManager: Executing remote command: ps aux | grep regionserver | grep -v grep | tr -s ' ' | cut -d ' ' -f2 , hostname:rs3.example.com
12/11/19 23:23:25 INFO hbase.ClusterManager: Executed remote command, exit code:0 , output:
12/11/19 23:23:25 INFO util.ChaosMonkey: Killed region server:rs3.example.com,60020,1353367027826. Reported num of rs:6
12/11/19 23:23:25 INFO util.ChaosMonkey: Sleeping for:60000
12/11/19 23:24:25 INFO util.ChaosMonkey: Starting region server:rs3.example.com
12/11/19 23:24:25 INFO hbase.HBaseCluster: Starting RS on: rs3.example.com
12/11/19 23:24:25 INFO hbase.ClusterManager: Executing remote command: /homes/enis/code/hbase-0.94/bin/../bin/hbase-daemon.sh --config /homes/enis/code/hbase-0.94/bin/../conf start regionserver , hostname:rs3.example.com
12/11/19 23:24:26 INFO hbase.ClusterManager: Executed remote command, exit code:0 , output:starting regionserver, logging to /homes/enis/code/hbase-0.94/bin/../logs/hbase-enis-regionserver-rs3.example.com.out

12/11/19 23:24:27 INFO util.ChaosMonkey: Started region server:rs3.example.com,60020,1353367027826. Reported num of rs:6

As you can see from the log, ChaosMonkey started the default PeriodicRandomActionPolicy, which is configured with all the available actions, and ran RestartActiveMaster and RestartRandomRs actions. ChaosMonkey tool, if run from command line, will keep on running until the process is killed.

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