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项目作者： nokia

项目描述 ：
Moler – library to help in building automated tests
高级语言： Python
项目地址: git://github.com/nokia/moler.git
创建时间： 2018-01-31T08:08:52Z
项目社区：https://github.com/nokia/moler
开源协议：BSD 3-Clause "New" or "Revised" License
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Table of Contents

  1. Changelog
  2. Moler info
  3. Moler usage examples
  4. API design reasoning
  5. Designed API

Changelog

View our chronological list of user-facing changes, large and small, made to the Moler project.

moler logo

Moler

Moler (name origin) is a Python library
that provides “bricks” for building automated tests.
All these “bricks” have clearly defined responsibilities, have similar API,
follow same construction pattern (so new ones are easy to create).

Here they are:

  • Commands as self-reliant object
    • to allow for command triggering and parsing encapsulated in single object (lower maintenance cost)
  • Event observers & callbacks (alarms are events example)
    • to allow for online reaction (not offline postprocessing)
  • Run observers/commands in the background
    • to allow for test logic decomposition into multiple commands running in parallel
    • to allow for handling unexpected system behavior (reboots, alarms)
  • State machines -> automatic auto-connecting after dropped connection
    • to increase framework auto-recovery and help in troubleshooting “what went wrong”
  • Automatic logging of all connections towards devices used by tests
    • to decrease investigation time by having logs focused on different parts of system under test

Moler usage examples

Let’s see Moler in action. Here is hypothetical use case: “find PIDs of all python processes”:

  2. from moler.config import load_config
  3. from moler.device import DeviceFactory
  5. load_config(config='my_devices.yml')                    # description of available devices
  6. my_unix = DeviceFactory.get_device(name='MyMachine')    # take specific device out of available ones
  7. ps_cmd = my_unix.get_cmd(cmd_name="ps",                 # take command of that device
  8.                          cmd_params={"options": "-ef"})
  10. processes_info = ps_cmd()                               # run the command, it returns result
  11. for proc_info in processes_info:
  12.     if 'python' in proc_info['CMD']:
  13.         print("PID: {info[PID]} CMD: {info[CMD]}".format(info=proc_info))
  • To have command we ask device “give me such command”.
  • To run command we just call it as function (command object is callable)
  • What command returns is usually dict or list of dicts - easy to process

Above code displays:

  2.     PID: 1817 CMD: /usr/bin/python /usr/share/system-config-printer/applet.py
  3.     PID: 21825 CMD: /usr/bin/python /home/gl/moler/examples/command/unix_ps.py

How does it know what 'MyMachine' means? Code loads definition from my_devices.yml configuration file:

  2.     DEVICES:
  4.       MyMachine:
  5.         DEVICE_CLASS: moler.device.unixlocal.UnixLocal
  7.       RebexTestMachine:
  8.         DEVICE_CLASS: moler.device.unixremote.UnixRemote
  9.         CONNECTION_HOPS:
  10.           UNIX_LOCAL:                # from state
  11.             UNIX_REMOTE:             # to state
  12.               execute_command: ssh   # via command
  13.               command_params:        # with params
  14.                 expected_prompt: demo@
  15.                 host: test.rebex.net
  16.                 login: demo
  17.                 password: password
  18.                 set_timeout: None   # remote doesn't support: export TMOUT

We have remote machine in our config. Let’s check if there is ‘readme.txt’ file
on that machine (and some info about the file):

  1. from moler.device import DeviceFactory
  2. remote_unix = DeviceFactory.get_device(name='RebexTestMachine')  # it starts in local shell
  3. remote_unix.goto_state(state="UNIX_REMOTE")                      # make it go to remote shell
  5. ls_cmd = remote_unix.get_cmd(cmd_name="ls", cmd_params={"options": "-l"})
  7. remote_files = ls_cmd()
  9. if 'readme.txt' in remote_files['files']:
  10.     print("readme.txt file:")
  11.     readme_file_info = remote_files['files']['readme.txt']
  12.     for attr in readme_file_info:
  13.         print("  {:<18}: {}".format(attr, readme_file_info[attr]))

As you may noticed device is state machine. State transitions are defined inside
configuration file under CONNECTION_HOPS. Please note, that it is only config file who
knows “I need to use ssh to be on remote” - client code just says “go to remote”.
Thanks to that you can exchange “how to reach remote” without any change in main code.

Above code displays:

  2.     readme.txt file:
  3.       permissions       : -rw-------
  4.       hard_links_count  : 1
  5.       owner             : demo
  6.       group             : users
  7.       size_raw          : 403
  8.       size_bytes        : 403
  9.       date              : Apr 08  2014
  10.       name              : readme.txt

How about doing multiple things in parallel. Let’s ping google
while asking test.rebex.net about readme.txt file:

  1. from moler.device import DeviceFactory
  2. my_unix = DeviceFactory.get_device(name='MyMachine')
  3. host = 'www.google.com'
  4. ping_cmd = my_unix.get_cmd(cmd_name="ping", cmd_params={"destination": host, "options": "-w 6"})
  6. remote_unix = DeviceFactory.get_device(name='RebexTestMachine')
  7. remote_unix.goto_state(state="UNIX_REMOTE")
  8. ls_cmd = remote_unix.get_cmd(cmd_name="ls", cmd_params={"options": "-l"})
  10. print("Start pinging {} ...".format(host))
  11. ping_cmd.start()                                # run command in background
  12. print("Let's check readme.txt at {} while pinging {} ...".format(remote_unix.name, host))
  14. remote_files = ls_cmd()                         # foreground "run in the meantime"
  15. file_info = remote_files['files']['readme.txt']
  16. print("readme.txt file: owner={fi[owner]}, size={fi[size_bytes]}".format(fi=file_info))
  18. ping_stats = ping_cmd.await_done(timeout=6)     # await background command
  19. print("ping {}: {}={}, {}={} [{}]".format(host,'packet_loss',
  20.                                           ping_stats['packet_loss'],
  21.                                           'time_avg',
  22.                                           ping_stats['time_avg'],
  23.                                           ping_stats['time_unit']))
  1. Start pinging www.google.com ...
  2. Let's check readme.txt at RebexTestMachine while pinging www.google.com ...
  3. readme.txt file: owner=demo, size=403
  4. ping www.google.com: packet_loss=0, time_avg=35.251 [ms]

Besides being callable command-object works as “Future” (result promise).
You can start it in background and later await till it is done to grab result.

If we enhance our configuration with logging related info:

  1.     LOGGER:
  2.       PATH: ./logs
  3.       DATE_FORMAT: "%H:%M:%S"

then above code will automatically create Molers’ main log (moler.log)
which shows activity on all devices:

  1. 22:30:19.723 INFO       moler               |More logs in: ./logs
  2. 22:30:19.747 INFO       MyMachine           |Connection to: 'MyMachine' has been opened.
  3. 22:30:19.748 INFO       MyMachine           |Changed state from 'NOT_CONNECTED' into 'UNIX_LOCAL'
  4. 22:30:19.866 INFO       MyMachine           |Event 'moler.events.unix.wait4prompt.Wait4prompt':'[re.compile('^moler_bash#')]' started.
  5. 22:30:19.901 INFO       RebexTestMachine    |Connection to: 'RebexTestMachine' has been opened.
  6. 22:30:19.901 INFO       RebexTestMachine    |Changed state from 'NOT_CONNECTED' into 'UNIX_LOCAL'
  7. 22:30:19.919 INFO       RebexTestMachine    |Event 'moler.events.unix.wait4prompt.Wait4prompt':'[re.compile('demo@')]' started.
  8. 22:30:19.920 INFO       RebexTestMachine    |Event 'moler.events.unix.wait4prompt.Wait4prompt':'[re.compile('^moler_bash#')]' started.
  9. 22:30:19.921 INFO       RebexTestMachine    |Command 'moler.cmd.unix.ssh.Ssh':'TERM=xterm-mono ssh -l demo test.rebex.net' started.
  10. 22:30:19.921 INFO       RebexTestMachine    |TERM=xterm-mono ssh -l demo test.rebex.net
  11. 22:30:20.763 INFO       RebexTestMachine    |*********
  12. 22:30:20.909 INFO       RebexTestMachine    |Changed state from 'UNIX_LOCAL' into 'UNIX_REMOTE'
  13. 22:30:20.917 INFO       RebexTestMachine    |Command 'moler.cmd.unix.ssh.Ssh' finished.
  14. 22:30:20.919 INFO       MyMachine           |Command 'moler.cmd.unix.ping.Ping':'ping www.google.com -w 6' started.
  15. 22:30:20.920 INFO       MyMachine           |ping www.google.com -w 6
  16. 22:30:20.920 INFO       RebexTestMachine    |Command 'moler.cmd.unix.ls.Ls':'ls -l' started.
  17. 22:30:20.922 INFO       RebexTestMachine    |ls -l
  18. 22:30:20.985 INFO       RebexTestMachine    |Command 'moler.cmd.unix.ls.Ls' finished.
  19. 22:30:26.968 INFO       MyMachine           |Command 'moler.cmd.unix.ping.Ping' finished.
  20. 22:30:26.992 INFO       RebexTestMachine    |Event 'moler.events.unix.wait4prompt.Wait4prompt': '[re.compile('^moler_bash#')]' finished.
  21. 22:30:27.011 INFO       RebexTestMachine    |Event 'moler.events.unix.wait4prompt.Wait4prompt': '[re.compile('demo@')]' finished.
  22. 22:30:27.032 INFO       MyMachine           |Event 'moler.events.unix.wait4prompt.Wait4prompt': '[re.compile('^moler_bash#')]' finished.

As you may noticed main log shows code progress from high-level view - data
on connections are not visible, just activity of commands running on devices.

If you want to see in details what has happened on each device - you have it in device logs.
Moler creates log per each device
moler.RebexTestMachine.log:

  1. 22:30:19.901  |Changed state from 'NOT_CONNECTED' into 'UNIX_LOCAL'
  2. 22:30:19.902 <|
  3. 22:30:19.919  |Event 'moler.events.unix.wait4prompt.Wait4prompt':'[re.compile('demo@')]' started.
  4. 22:30:19.920  |Event 'moler.events.unix.wait4prompt.Wait4prompt':'[re.compile('^moler_bash#')]' started.
  5. 22:30:19.921  |Command 'moler.cmd.unix.ssh.Ssh':'TERM=xterm-mono ssh -l demo test.rebex.net' started.
  6. 22:30:19.921 >|TERM=xterm-mono ssh -l demo test.rebex.net
  8. 22:30:19.924 <|TERM=xterm-mono ssh -l demo test.rebex.net
  10. 22:30:20.762 <|Password:
  11. 22:30:20.763 >|*********
  12. 22:30:20.763 <|
  14. 22:30:20.908 <|Welcome to Rebex Virtual Shell!
  15.               |For a list of supported commands, type 'help'.
  16.               |demo@ETNA:/$
  17. 22:30:20.909  |Changed state from 'UNIX_LOCAL' into 'UNIX_REMOTE'
  18. 22:30:20.917  |Command 'moler.cmd.unix.ssh.Ssh' finished.
  19. 22:30:20.920  |Command 'moler.cmd.unix.ls.Ls':'ls -l' started.
  20. 22:30:20.922 >|ls -l
  22. 22:30:20.974 <|ls -l
  24. 22:30:20.978 <|drwx------ 2 demo users          0 Jul 26  2017 .
  26. 22:30:20.979 <|drwx------ 2 demo users          0 Jul 26  2017 ..
  27.               |drwx------ 2 demo users          0 Dec 03  2015 aspnet_client
  28.               |drwx------ 2 demo users          0 Oct 27  2015 pub
  29.               |-rw------- 1 demo users        403 Apr 08  2014 readme.txt
  30.               |demo@ETNA:/$
  31. 22:30:20.985  |Command 'moler.cmd.unix.ls.Ls' finished.
  32. 22:30:26.992  |Event 'moler.events.unix.wait4prompt.Wait4prompt': '[re.compile('^moler_bash#')]' finished.
  33. 22:30:27.011  |Event 'moler.events.unix.wait4prompt.Wait4prompt': '[re.compile('demo@')]' finished.

and moler.MyMachine.log:

  1. 22:30:19.748  |Changed state from 'NOT_CONNECTED' into 'UNIX_LOCAL'
  2. 22:30:19.748 <|
  3. 22:30:19.866  |Event 'moler.events.unix.wait4prompt.Wait4prompt':'[re.compile('^moler_bash#')]' started.
  4. 22:30:20.919  |Command 'moler.cmd.unix.ping.Ping':'ping www.google.com -w 6' started.
  5. 22:30:20.920 >|ping www.google.com -w 6
  7. 22:30:20.921 <|ping www.google.com -w 6
  9. 22:30:20.959 <|PING www.google.com (216.58.215.68) 56(84) bytes of data.
  10. 22:30:20.960 <|
  12. 22:30:21.000 <|64 bytes from waw02s16-in-f4.1e100.net (216.58.215.68): icmp_seq=1 ttl=51 time=40.1 ms
  13. 22:30:21.001 <|
  15. 22:30:21.992 <|64 bytes from waw02s16-in-f4.1e100.net (216.58.215.68): icmp_seq=2 ttl=51 time=31.0 ms
  17. 22:30:22.999 <|64 bytes from waw02s16-in-f4.1e100.net (216.58.215.68): icmp_seq=3 ttl=51 time=36.5 ms
  19. 22:30:23.996 <|64 bytes from waw02s16-in-f4.1e100.net (216.58.215.68): icmp_seq=4 ttl=51 time=31.4 ms
  21. 22:30:24.996 <|64 bytes from waw02s16-in-f4.1e100.net (216.58.215.68): icmp_seq=5 ttl=51 time=29.8 ms
  23. 22:30:26.010 <|64 bytes from waw02s16-in-f4.1e100.net (216.58.215.68): icmp_seq=6 ttl=51 time=42.4 ms
  25. 22:30:26.960 <|
  26.               |--- www.google.com ping statistics ---
  27.               |6 packets transmitted, 6 received, 0% packet loss, time 5007ms
  28.               |rtt min/avg/max/mdev = 29.888/35.251/42.405/4.786 ms
  29.               |moler_bash#
  30. 22:30:26.968  |Command 'moler.cmd.unix.ping.Ping' finished.
  31. 22:30:27.032  |Event 'moler.events.unix.wait4prompt.Wait4prompt': '[re.compile('^moler_bash#')]' finished.

If the log files are too large you can split files.

The log files can be split by size. For example let’s assume we want split log files by 5 MB (5242880 bytes) and we want
to keep maximum 999 files:

  1.     LOGGER:
  2.       PATH: ./logs
  3.       DATE_FORMAT: "%H:%M:%S"
  4.       LOG_ROTATION:
  5.         KIND: size
  6.         INTERVAL: 5242880
  7.         BACKUP_COUNT: 999  # Default value

The log files can be split by time. For example let’s assume we want split log files every 30 minutes (1800 seconds)
and we want to keep maximum 999 files (default value):

  1.     LOGGER:
  2.       PATH: ./logs
  3.       DATE_FORMAT: "%H:%M:%S"
  4.       LOG_ROTATION:
  5.         KIND: time
  6.         INTERVAL: 1800
  7.         BACKUP_COUNT: 999  # Default value

For space saving Moler can compress the logs after rotation. The external tool is used. Let’s use the above examples
to show how to compress logs:

  1.     LOGGER:
  2.       PATH: ./logs
  3.       DATE_FORMAT: "%H:%M:%S"
  4.       LOG_ROTATION:
  5.         KIND: size
  6.         INTERVAL: 5242880
  7.         BACKUP_COUNT: 999  # Default value
  8.         COMPRESS_AFTER_ROTATION: True  # Default is False
  9.         COMPRESS_COMMAND: "zip -9mq {compressed} {log_input}"  # Default value
  10.         COMPRESSED_FILE_EXTENSION: ".zip"  # Default value
  1.     LOGGER:
  2.       PATH: ./logs
  3.       DATE_FORMAT: "%H:%M:%S"
  4.       LOG_ROTATION:
  5.         KIND: time
  6.         INTERVAL: 1800
  7.         BACKUP_COUNT: 999  # Default value
  8.         COMPRESS_COMMAND: "zip -9mq {compressed} {log_input}"  # Default value
  9.         COMPRESSED_FILE_EXTENSION: ".zip"  # Default value

In a script we can also disable logging from device. Please use it very carefully. Investigation any issue may be
impossible if we don’t have full logs.

  1. from moler.device import DeviceFactory
  2. my_unix = DeviceFactory.get_device(name='MyMachine')
  4. my_unix.disbale_logging()  # to disable logging on device
  6. my_unix.enable_logging()  # to enable logging on device

In a script you can add suffix to all log files or only to files for specific devices. with disable logging from device.

  1. from moler.device import DeviceFactory
  2. from moler.config.loggers import change_logging_suffix
  3. change_logging_suffix(".suffix1")  # all log files with suffix
  4. change_logging_suffix(None)  # all log files without suffx
  6. my_unix = DeviceFactory.get_device(name='MyMachine')
  8. my_unix.set_logging_suffix("device_suffix")  # to add suffix to filename with logs
  10. my_unix.set_logging_suffix(None)  # to remove suffix from filename with logs

Previous examples ask device to create command. We can also create command ourselves
giving it connection to operate on:

  2. import time
  3. from moler.cmd.unix.ping import Ping
  4. from moler.connection_factory import get_connection
  6. host = 'www.google.com'
  7. terminal = get_connection(io_type='terminal', variant='threaded')  # take connection
  8. with terminal.open():
  9.     ping_cmd = Ping(connection=terminal.moler_connection,
  10.                     destination=host, options="-w 6")
  11.     print("Start pinging {} ...".format(host))
  12.     ping_cmd.start()
  13.     print("Doing other stuff while pinging {} ...".format(host))
  14.     time.sleep(3)
  15.     ping_stats = ping_cmd.await_done(timeout=4)
  16.     print("ping {}: {}={}, {}={} [{}]".format(host,'packet_loss',
  17.                                               ping_stats['packet_loss'],
  18.                                               'time_avg',
  19.                                               ping_stats['time_avg'],
  20.                                               ping_stats['time_unit']))

Please note also that connection is context manager doing open/close actions.

  2.     Start pinging www.google.com ...
  3.     Doing other stuff while pinging www.google.com ...
  4.     ping www.google.com: packet_loss=0, time_avg=50.000 [ms]

Reuse freedom

Library gives you freedom which part you want to reuse. We are fans of “take what you need only”.

  • You may use configuration files or configure things by Python calls.

    1.  from moler.config import load_config
    2.  load_config(config={'DEVICES': {'MyMachine': {'DEVICE_CLASS': 'moler.device.unixlocal.UnixLocal'}}})
  • You may use devices or create commands manually

  • You can take connection or build it yourself:

    1.  from moler.threaded_moler_connection import ThreadedMolerConnection
    2.  from moler.io.raw.terminal import ThreadedTerminal
    4.  terminal_connection = ThreadedTerminal(moler_connection=ThreadedMolerConnection())
  • You can even install your own implementation in place of default implementation per connection type

API design reasoning

The main goal of command is its usage simplicity: just run it and give me back its result.

Command hides from its caller:

  • a way how it realizes “runs”
  • how it gets data of output to be parsed
  • how it parses that data

Command shows to its caller:

  • API to start/stop it or await for its completion
  • API to query for its result or result readiness

Command works as Futures and promises

After starting, we await for its result which is parsed out command output provided usually as dict.
Running that command and parsing its output may take some time, so till that point result computation is yet incomplete.

Command as future

  • it starts some command on device/shell over connection
    (as future-function starts its execution)
  • it parses data incoming over such connection
    (as future-function does its processing)
  • it stores result of that parsing
    (as future-function concludes in calculation result)
  • it provides means to return that result
    (as future-function does via ‘return’ or ‘yield’ statement)
  • its result is not ready “just-after” calling command
    (as it is with future in contrast to function)

So command should have future API.

Quote from “Professional Python” by Luke Sneeringer:

The Future is a standalone object. It is independent of the actual function that is running.
It does nothing but store the state and result information.

Command differs in that it is both:

  • function-like object performing computation
  • future-like object storing result of that computation.

Command vs. Connection-observer

Command is just “active version” of connection observer.

Connection observer is passive since it just observes connection for some data;
data that may just asynchronously appear (alarms, reboots or anything you want).
Intention here is split of responsibility: one observer is looking for alarms,
another one for reboots.

Command is active since it actively triggers some output on connection
by sending command-string over that connection. So, it activates some action
on device-behind-connection. That action is “command” in device terminology.
Like ping on bash console/device. And it produces that “command” output.
That output is what Moler’s Command as connection-observer is looking for.

Most well known Python’s futures

API concurrent.futures.Future asyncio.Future
storing result :white_check_mark: set_result() :white_check_mark: set_result()
result retrieval :white_check_mark: result() :white_check_mark: result()
storing failure cause :white_check_mark: set_exception() :white_check_mark: set_exception()
failure cause retrieval :white_check_mark: exception() :white_check_mark: exception()
stopping :white_check_mark: cancel() :white_check_mark: cancel()
check if stopped :white_check_mark: cancelled() :white_check_mark: cancelled()
check if running :white_check_mark: running() :no_entry_sign: (but AbstractEventLoop.running())
check if completed :white_check_mark: done() :white_check_mark: done()
subscribe completion :white_check_mark: add_done_callback() :white_check_mark: add_done_callback()
unsubscribe completion :no_entry_sign: :white_check_mark: remove_done_callback()

Starting callable to be run “as future” is done by entities external to future-object

API concurrent.futures
start via Executor objects (thread/proc)		 asyncio
start via module-lvl functions or ev-loop
start callable submit(fn, args, **kwargs)
Schedules callable to be executed as
fn(args **kwargs) -> Future		 ensure_future(coro_or_future) -> Task
future = run_coroutine_threadsafe(coro, loop)
start same callable
on data iterator		 map(fn, *iterables, timeout) -> iterator join_future = asyncio.gather(*map(f, iterable))
loop.run_until_complete(join_future)

Awaiting completion of future is done by entities external to future-object

API concurrent.futures
awaiting by module level functions		 asyncio
awaiting by module-lvl functions or ev-loop
await completion done, not_done = wait(futures, timeout) -> futures done, not_done = await wait(futures)
results = await gather(futures)
result = await future
result = yield from future
result = await coroutine
result = yield from coroutine
result = yield from wait_for(future, timeout)
loop.run_until_complete(future) -> blocking run
process as they
complete		 for done in as_completed(futures, timeout) -> futures for done in as_completed(futures, timeout) -> futures

Fundamental difference of command

Contrary to concurrent.futures and asyncio we don’t want command to be run by some external entity.
We want it to be self-executable for usage simplicity.
We want to take command and just say to it:

  • “run” or “run in background”
  • and not “Hi, external runner, would you run/run-background that command for me”

Designed API

  1. create command object

    1. command = Command()

  2. run it synchronously/blocking and get result in one shot behaves like function call since Command is callable.

Run-as-callable gives big advantage since it fits well in python ecosystem.

  1. result = command()

function example:

  1. map(ping_cmd, all_machines_to_validate_reachability)

  1. run it asynchronously/nonblocking

    1. command_as_future = command.start()

  2. shift from background to foreground

asyncio: variant looks like:

  1. result = await future
  2. done_futures, pending = yield from asyncio.wait(futures)
  3. result = yield from asyncio.wait_for(future, 60.0)

and concurrent.futures variant looks like:

  1. done_futures, pending = wait(futures)

Moler’s API maps to above well-known API

  1. result = command.await_done(timeout)
  • it is “internal” to command “Hi command, that is what I want from you” (above APIs say “Hi you there, that is what I want you to do with command”)
  • it directly (Zen of Python) shows what we are awaiting for
  • timeout is required parameter (not as in concurrent.futures) since we don’t expect endless execution of command (user must know what is worst case timeout to await command completion)

Video introduction

You can watch videos how to use Moler on YouTube.