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Autotest Test API

This is a review of the available autotest test API.

Control files

A control file is just python code, and therefore should follow the Autotest python style. The control file ultimately defines the test. In fact the entire test can be coded in the control file. However if this leads to a very complicated control file, it is generally recommended that most of the test code logic be placed in a python module that the control file runs (via the job object).

A control file should define at the very top a set of variables. These are:

  • AUTHOR
  • TIME
  • NAME
  • TEST_CATEGORY
  • TEST_CLASS
  • TEST_TYPE
  • SYNC_COUNT
  • DOC

All except SYNC_COUNT are set to a string. SYNC_COUNT is a number which has relevance for the scheduling of multi-machine server side jobs. In addition you can define the variable EXPERIMENTAL (either True or False). By default it is False, but when set to True, will control whether the job shows up in the web frontend by default.

Unlike python test code, it is not imported, but rather is executed directly with the exec() method in the context of certain global and local symbols. One of the symbols that your control file can assume exists is job. The job object has a number of methods that you will most probably use in your control file. The most common are

  • job.run_test(test_object, tag, iterations, constraints, **dargs)******
  • job.parallel_simple(run_method, machine_list)
  • job.record(status_code, subdir, operation, status)

In addition, the control file has access to machines which is a list of the machines that were passed to the autoserv executable.

Client side tests

A client side test runs entirely on the client (or host machine). Essentially the entire client subdirectory of Autotest is installed on the host machine at the beginning of the test. And so the client control file through the job.run_test() method can execute code contained in a test class. A test class is code that is generally located in either a subdirectory of client/tests/ or client/site_tests/. A test class always is a subclass of autotest_lib.client.bin.test.test. You then must provide an override for the run_once() method in your class. You must also define the class variable version. The run_once method can accept any arguments you desire. These are passed in as the *dargs*****in the *job.run_test()* method in the control file.

In addition to run_once() you may optionally override the following methods

  • initialize()
  • setup()
  • warmup()
  • run_once()
  • postprocess()

The initialize is called first every time the test is run. The setup method is called once if the test version changed. Then the warmup is called once. After this run_once is called iterations times. Finally postprocess is called. The arguments that each method take are arbitrary. The *dargs*****from *run_test()* are simply passed through. The exception being *postprocess* which takes no arguments (other than self of course).

The autotest_lib.client.bin.test.test class also defines various useful variables. These are

  • job: the job object from the control file
  • autodir: the autotest directory
  • outputdir: the output directory
  • resultsdir: the results directory
  • profdir: the profiling directory
  • debugdir: the debugging directory
  • bindir: The bin directory
  • srcdir: the src directory
  • tmpdir: the tmp directory

In addition the test object has a handful of very useful methods

  • write_test_keyval(attr_dict)
  • write_perf_keyval(perf_dict)
  • write_attr_keyval(attr_dict)
  • write_iteration_keyval(attr_dict, perf_dict)

The test keyvals are key/attribute pairs that are associated with the test. You supply a dictionary, and these will be recorded in a test level keyvals file as well as in the results (tko) database. The iteration keyvals can be either performance metrics (a number) or an attribute (a string). They can be recorded for each iteration, and you can either record one, the other, or both with the latter three methods above.

In addition the test class at the end of each iteration will evaluate any constraints that have been passed into the test via the job.run_test() command. The constraints variable is a list of strings, where each string makes an assertion regarding an iteration keyval. These are evaluated, and failures are recorded. An example constraints might be: constraints = ['throughput > 6500', 'test_version == 2']

Generally a typical client side test will make use of code contained in the standard python libraries, as well as the various utilities located in autotest_lib.client.bin.utils.

Server side tests

In a typical server side test, the autotest client is not installed on the host machines. Rather the server keeps host objects that represent an ssh connection to the host machine, and through which the server can execute code on the clients. A host object is generally created in the following way

host = hosts.create_host(machine)

The hosts module is one of those symbols that you can safely assume is present in your server control file. The machine is a machine name, and is generally one of the list machines which is also assumed to be accessible from your control file.

A typical server control file might look like

def run(machine):
    host = hosts.create_host(machine)
    ...

job.parallel_simple(run, machines)

In the above code, the job.parallel_simple() takes the list of machines and a method, and executes that method for each member of machines. The first line of the run method creates a host object that the server can use to execute commands (via ssh) on the client. A host object has various member variables:

  • hostname
  • autodir
  • ip
  • user
  • port
  • password
  • env
  • serverdir

Running code on a client can be done via the host object. Typical methods of a host object are:

  • run(cmd)
  • run_output(cmd, *args, **dargs)******
  • reboot()
  • sysrq_reboot()
  • get_file(src, dest, delete_dest=False)
  • send_file(src, dest, delete_dest=False)
  • get_tmp_dir()
  • is_up()
  • is_shutting_down()
  • wait_up(timeout=None)
  • wait_down(timeout=None)
  • ssh_ping(timeout=60)

A large number of other methods are available and are scattered throughout the code in server/hosts/. The host object that is created by the hosts.create_host() method is a mix-in of various host behaviours that are defined in the server/hosts directory. However the most common are defined above.

In addition to methods on host, we can run client code via our server control file using an Autotest object. In order to use the autotest module you must import if from autotest_lib.server. A typical usage is

from autotest_lib.server import autotest

control_file = """job.run_test('sleeptest')"""

def run(machine):
    host = hosts.create_host(machine)
    at = autotest.Autotest(host)
    at.run(control_file, machine)


job.parallel_simple(run, machines)

The autotest object will (as part of its instantiation) install the autotest client on the host. Then we can use the run method to run code on the client. The first argument is a string. We could have just as easily written

at.run(open("some control file").read(), machine))

as well.

Multi-machine server side tests

The power of server side tests, is their ability to run different code on multiple machines simultaneously, and to control their interactions. The easiest way to describe a multi-machine test is to look at a real example of one. The following control file is located in server/tests/netperf2/control.srv

AUTHOR = "mbligh@google.com (Martin Bligh) and bboe@google.com (Bryce Boe)"
TIME = "SHORT"
NAME = "Netperf Multi-machine"
TEST_CATEGORY = "Stress"
TEST_CLASS = 'Hardware'
TEST_TYPE = "Server"
SYNC_COUNT = 2
DOC = """
...
"""

from autotest_lib.server import utils, autotest

def run(pair):
    server = hosts.create_host(pair[0])
    client = hosts.create_host(pair[1])

    server_at = autotest.Autotest(server)
    client_at = autotest.Autotest(client)

    template = ''.join(["job.run_test('netperf2', server_ip='%s', client_ip=",
                        "'%s', role='%s', test='TCP_STREAM', test_time=10,",
                        "stream_list=[1,10])"])

    server_control_file = template % (server.ip, client.ip, 'server')
    client_control_file = template % (server.ip, client.ip, 'client')

    server_command = subcommand(server_at.run,
                                [server_control_file, server.hostname])
    client_command = subcommand(client_at.run,
                                [client_control_file, client.hostname])

    parallel([server_command, client_command])


# grab the pairs (and failures)
(pairs, failures) = utils.form_ntuples_from_machines(machines, 2)

for failure in failures:
    job.record("FAIL", failure[0], "netperf2", failure[1])

# now run through each pair and run
job.parallel_simple(run, pairs, log=False)

The top of the file contains the usual control variables. The most important one is SYNC_COUNT. This test is a 2 machine test. The first code that runs, is the line

(pairs, failures) = utils.form_ntuples_from_machines(machines, 2)

This code uses a method from autotest_lib.server.utils which given the full collection of machines, forms a list of pairs of machines, and a list of 'failures'. These failures will ,in this case, be at most a single machine (odd man out). The next line merely uses the job object to record a failure for each of the failures. After this, we call job.parallel_simple() passing in the run function and the list of pairs.

The run function defined above takes a pair (recall the function referenced in job.parallel_simple() takes a single element from the list that is passed in. In this case it is a single pair). We then create a host object for each of the machines in the pair. Then we create an autotest object for each host. A control file string is then constructed for each of the machines. In this test one host acts as a client, while the other acts as a server in a network test between the two hosts. So in this test server does not refer to the autotest server, but rather to one of the autotest clients running this two machine test.

The next three lines are new. The subcommand class, and the parallel method are defined in autotest_lib.server and are assumed to be part of the control files namespace. The constructor to subcommand requires a method, and list of args to pass to that method

server_command = subcommand(server_at.run, [server_control_file, server.hostname])

Here the method is the run method of one of the autotest objects created earlier, and we are passing that method the server_control_file, and the hostname. We form the two subcommands (one for the netperf test server and the other for the netperf test client). We pass these both to the parallel() method as a list. This method executes both subcommands simultaneously.

The server netperf2 test whose control file is described above, makes use of the client side netperf2.py test file. This is located in client/tests/netperf2/netperf2.py. This code is resident on the host machines by virtue of the creation of the autotest objects. If you take a look at the run_once method of the netperf2 class, you will see how it is that we synchronize the running of the client and server sides of the netperf2 test. The relevant code is

...
server_tag = server_ip + '#netperf-server'
client_tag = client_ip + '#netperf-client'
all = [server_tag, client_tag]
...
if role == 'server':
    ...
    self.job.barrier(server_tag, 'start_%d' % num_streams, 600).rendevous(*all)
    ...
else if role == 'client':
    ...
    self.job.barrier(client_tag, 'start_%d' % num_streams, 600).rendevous(*all)
    ...

The above demonstrates how we can synchronize clients. In the above we register two tags (one for each of two roles). Recall that one of the hosts is running as the client, while the other is running as the server. We then form a list of the two tags. The next code segment is important. If we are the server, we employ the job object that every test has a reference to, and use it to construct a barrier object using the server_tag. This says we are registering at the barrier using the server_tag as our tag, and additionally we pass in 600 seconds as our timeout. The second argument is a logging string. We then call the rendevous method of the barrier object (yes it is mis-spelled in the code) and pass in *all. This says that we will wait until all the tags in the all list register. The client side of the code does the complementary thing. The rendevous method blocks until both the server_tag and the client_tag register. Using these barriers, we can sync the client and server.

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