Overview
--------

The stress script is designed to perform testing of the MySQL server in 
a multi-threaded environment. 

All functionality regarding stress testing is implemented in the
mariadb-stress-test.pl script.

The stress script allows:
 
 - To stress test the mariadb-test binary test engine.
 - To stress test the regular test suite.
 - To specify files with lists of tests both for initialization of
   stress db and for further testing itself.
 - To define the number of threads to be concurrently used in testing.
 - To define limitations for the test run. such as the number of tests or
   loops for execution or duration of testing, delay between test
   executions, and so forth.
 - To get a readable log file that can be used for identification of
   errors that occur during testing.

There are two ways to run the mariadb-stress-test.pl script:

 - For most cases, it is enough to use the options below for starting
   the stress test from the mariadb-test-run wrapper. In this case, the
   server is run automatically, all preparation steps are performed,
   and after that the stress test is started.

 - In advanced case, you can run the mariadb-stress-test.pl script directly.
   But this requires that you perform some preparation steps and to specify
   a bunch of options as well, so this invocation method may be a bit
   complicated.

Usage
-----

The following mysql-test-run options are specific to stress-testing:

--stress 
  Enable stress mode

--stress-suite=<suite name>
  Test suite name to use in stress testing.  We assume that all suites
  are located in the mysql-test/suite directory.
  There is one special suite name - <main|default> that corresponds
  to the regular test suite located in the mysql-test directory. 
  
--stress-threads=<number of threads>
  The number of threads to use in stress testing.
  
--stress-tests-file=<filename with list of tests>
  The file that contains the list of tests (without .test suffix) to use in 
  stress testing. The default filename is stress_tests.txt and the default 
  location of this file is suite/<suite name>/stress_tests.txt

--stress-init-file=<filename with list of tests>
  The file that contains list of tests (without .test suffix) to use in 
  stress testing for initialization of the stress db. These tests will be 
  executed only once before starting the test itself. The default filename 
  is stress_init.txt and the default location of this file is 
  suite/<suite name>/stress_init.txt

--stress-mode=<method which will be used for choosing tests from the list>
  Possible values are: random(default), seq 

  There are two possible modes that affect the order of test selection
  from the list:
    - In random mode, tests are selected in random order
    - In seq mode, each thread executes tests in a loop one by one in
	  the order specified in the list file.

--stress-test-count=<number>
  Total number of tests that will be executed concurrently by all threads

--stress-loop-count=<number>
  Total number of loops in seq mode that will be executed concurrently 
  by all threads

--stress-test-duration=<number>
  Duration of stress testing in seconds

Examples
-------- 

1. Example of a simple command line to start a stress test:

 mariadb-test-run --stress alias

Runs a stress test with default values for number of threads and number
of tests, with test 'alias' from suite 'main'.

2. Using in stress testing tests from other suites:

 - mariadb-test-run --stress --stress-threads=10 --stress-test-count=1000 \
                 --stress-suite=example  --stress-tests-file=testslist.txt

   Runs a stress test with 10 threads, executes 1000 tests by all 
   threads, tests are used from suite 'example', the list of tests is
   taken from file 'testslist.txt'

 - mariadb-test-run --stress --stress-threads=10 --stress-test-count=1000 \
                  --stress-suite=example sum_distinct

   Runs stress test with 10 threads, executes 1000 tests by all 
   threads, tests are used from suite 'example', the list of tests
   contains only one test 'sum_distinct'

3. Debugging of issues found with stress test

 Right now, the stress test is not fully integrated in mariadb-test-run
 and does not support the --gdb option. To debug issues found with the
 stress test, you must start the MariaDB server separately under a debugger
 and then run the stress test like this:
 
 - mariadb-test-run --extern --stress --stress-threads=10 \
                  --stress-test-count=1000 --stress-suite=example \
                  sum_distinct