Jaffle 0.2¶

Jaffle is an automation tool for Python software development, which has the following features:

Instantiate Python applications in a Jupyter kernel and allows them to interact each other
Launch external processes
Combine all log messages and allows filtering and reformatting by regular expressions and functions
Built-in WatchdogApp watches filesystem events and triggers another app, arbitrary code, and functions, which make it possible to setup various automations.

Screenshot¶

Developing a single-page web app using Tornado and React

Warning

Jaffle is intended to be a development tool and does not care much about security. Arbitrary Python code can be executed in jaffle.hcl and you should not use it as a part of production environment. jaffle.hcl is like a Makefile or a shell script included in a source code repository.

Installation¶

Prerequisite¶

UNIX-like OS
- Windows is not supported
Python >= 3.4
Jupyter Notebook >= 5.0
Tornado >= 4.5, < 5

Jupyter Notebook and Tornado will be installed automatically if they do not exist in your environment. Tornado 5 is not yet supported.

Installation¶

$ pip install jaffle

You will also probably need pytest:

$ pip install pytest

Commands¶

Jaffle consists of the following commands:

jaffle start¶

Starts Jaffle.

Type ctrl-c to stop it.

Usage¶

jaffle start [options] [conf_file, ...]

The default value for conf_file is "jaffle.hcl".

If multiple config files are provided, they will be merged into one configuration.

Options¶

–debug

Set log level to logging.DEBUG (maximize logging output)
-y

Answer yes to any questions instead of prompting.
–disable-color

Disable color output.
–log-level=<Enum> (Application.log_level)

Default: 30

Choices: (0, 10, 20, 30, 40, 50, ‘DEBUG’, ‘INFO’, ‘WARN’, ‘ERROR’, ‘CRITICAL’) Set the log level by value or name.
–log-datefmt=<Unicode> (Application.log_datefmt)

Default: ‘%Y-%m-%d %H:%M:%S’

The date format used by logging formatters for %(asctime)s
–log-format=<Unicode> (Application.log_format)

Default: ‘%(time_color)s%(asctime)s.%(msecs).03d%(time_color_end)s %(name_color)s%(name)14s%(name_color_end)s %(level_color)s %(levelname)1.1s %(level_color_end)s %(message)s’

The Logging format template
–runtime-dir=<Unicode> (BaseJaffleCommand.runtime_dir)

Default: ‘.jaffle’

Runtime directory path.
–variables=<List> (JaffleStartCommand.variables)

Default: []

Value assignments to the variables.

Merging Multiple Configurations¶

If you provide multiple configuration files, Jaffle read the first file and then merges the rest one by one. Maps are merged deeply and other elements are overwritten.

Given that we have the following three configurations.

a.hcl:

process "server" {
  command = "start_server"
  env = {
    FOO = 1
  }
}

b.hcl:

process "server" {
  command = "start_server"
  env = {
    BAR = 2
  }
}

c.hcl:

process "server" {
  command = "start_server"
  env = {
    FOO = 4
    BAZ = 3
  }
}

When we start Jaffle by typing jaffle start a.hcl b.hcl c.hcl, the configuration will be as below:

process "server" {
  command = "start_server"
  env = {
    FOO = 4
    BAR = 2
    BAZ = 3
  }
}

Resolved variables are passed to the later configurations. Given that we have the following two configurations and use them as jaffle start a.hcl b.hcl.

a.hcl:

variable "server_command" {
  default = "start_server"
}

variable "disable_server" {
  default = false
}

process "server" {
  command  = "${var.server_command}"
  disabled = "${var.disable_server}"
}

b.hcl:

variable "disable_server" {
  default = true # switch the default value to true
}

process "server" {
  command  = "${var.server_command} --debug"
}

The configurations will be merged as follows:

variable "server_command" {
  default = "start_server"
}

variable "disable_server" {
  default = true
}

process "server" {
  command  = "${var.server_command} --debug"
  disabled = "${var.disable_server}"
}

Tip

The configuration merging is useful when you have a default configuration in your repository and you want to overwrite some part of it.

Example:

$ jaffle start jaffle.hcl debug.hcl log_filter.hcl

jaffle stop¶

Stops the running Jaffle process. If it is not running, removes runtime files if they exist.

Usage¶

jaffle stop [options]

Options¶

–runtime-dir=<Unicode> (BaseJaffleCommand.runtime_dir)

Default: ‘.jaffle’

Runtime directory path.

jaffle console¶

Opens an interactive shell and attaches to the specified kernel instance.

Type ctrl-c or ctrl-d to stop it.

Usage¶

jaffle console <kernel_instance_name> [options]

The default value for conf_file is "jaffle.hcl".

Options¶

–debug

Set log level to logging.DEBUG (maximize logging output)
-y

Answer yes to any questions instead of prompting.
–disable-color

Disable color output.
–log-level=<Enum> (Application.log_level)

Default: 30

Choices: (0, 10, 20, 30, 40, 50, ‘DEBUG’, ‘INFO’, ‘WARN’, ‘ERROR’, ‘CRITICAL’) Set the log level by value or name.
–log-datefmt=<Unicode> (Application.log_datefmt)

Default: ‘%Y-%m-%d %H:%M:%S’

The date format used by logging formatters for %(asctime)s
–log-format=<Unicode> (Application.log_format)

Default: ‘%(time_color)s%(asctime)s.%(msecs).03d%(time_color_end)s %(name_color)s%(name)14s%(name_color_end)s %(level_color)s %(levelname)1.1s %(level_color_end)s %(message)s’

The Logging format template
–runtime-dir=<Unicode> (BaseJaffleCommand.runtime_dir)

Default: ‘.jaffle’

Runtime directory path.

jaffle attach¶

Opens an interactive shell and attaches to the specified app. The app must support attaching. Only PyTestRunnerApp supports this.

Type ctrl-c or ctrl-d to stop it.

Usage¶

jaffle attach <app> [options]

Options¶

–debug

Set log level to logging.DEBUG (maximize logging output)
-y

Answer yes to any questions instead of prompting.
–disable-color

Disable color output.
–log-level=<Enum> (Application.log_level)

Default: 30

Choices: (0, 10, 20, 30, 40, 50, ‘DEBUG’, ‘INFO’, ‘WARN’, ‘ERROR’, ‘CRITICAL’) Set the log level by value or name.
–log-datefmt=<Unicode> (Application.log_datefmt)

Default: ‘%Y-%m-%d %H:%M:%S’

The date format used by logging formatters for %(asctime)s
–log-format=<Unicode> (Application.log_format)

Default: ‘%(time_color)s%(asctime)s.%(msecs).03d%(time_color_end)s %(name_color)s%(name)14s%(name_color_end)s %(level_color)s %(levelname)1.1s %(level_color_end)s %(message)s’

The Logging format template
–runtime-dir=<Unicode> (BaseJaffleCommand.runtime_dir)

Default: ‘.jaffle’

Runtime directory path.

Configuration¶

Note

Currently Jaffle does not check the configuration file syntax. If Jaffle does not work as you expect, please check the configuration carefully. Jaffle will have the configuration validation in the future release.

Syntax¶

Configuration Syntax¶

The configuration language of jaffle.hcl is HCL (HashiCorp Configuration Language).

The top-level of the configuration can have the following items:

Example¶

kernel "py_kernel" {}

app "watchdog" {
  class  = "jaffle.app.watchdog.WatchdogApp"
  kernel = "py_kernel"

  logger {
    level = "info"
  }

  options {
    handlers = [{
      watch_path         = "my_module"
      patterns           = ["*.py"]
      ignore_directories = true
      functions          = ["pytest.handle_watchdog_event({event})"]
    }]
  }
}

app "pytest" {
  class  = "jaffle.app.pytest.PyTestRunnerApp"
  kernel = "py_kernel"

  logger {
    level = "info"
  }

  options {
    args = ["-s", "-v", "--color=yes"]

    auto_test = [
      "my_module/tests/test_*.py",
    ]

    auto_test_map {
      "my_module/**/*.py" = "my_module/tests/{}/test_{}.py"
    }
  }
}

JSON¶

Since JSON is a valid HCL, you can also write the configuration file as JSON. The previous HCL example is same as the following JSON.

{
  "kernel": {
    "py_kernel": {}
  },
  "app": {
    "watchdog": {
      "class": "jaffle.app.watchdog.WatchdogApp",
      "kernel": "py_kernel",
      "logger": {
        "level": "info"
      },
      "options": {
        "handlers": [
          {
            "watch_path": "my_module",
            "patterns": [
              "*.py"
            ],
            "ignore_directories": true,
            "functions": [
              "pytest.handle_watchdog_event({event})"
            ]
          }
        ]
      }
    },
    "pytest": {
      "class": "jaffle.app.pytest.PyTestRunnerApp",
      "kernel": "py_kernel",
      "logger": {
        "level": "info"
      },
      "options": {
        "args": [
          "-s",
          "-v",
          "--color=yes"
        ],
        "auto_test": [
          "my_module/tests/test_*.py"
        ],
        "auto_test_map": {
          "my_module/**/*.py": "my_module/tests/{}/test_{}.py"
        }
      }
    }
  }
}

Interpolation Syntax¶

Jaffle configuration supports interpolation syntax wrapped by ${}. You can get environment varialbes, call functions, and execute Python code in it:

Example:

${'hello'.upper()}

The above produces 'HELLO'.

Environment Variables¶

All environment variables consist of alphanumeric uppercase characters are available in the interpolation syntax.

Example:

${HOME}/etc

The above produces /home/your_account/etc if your HOME is '/home/your_account'.

If you need a default value for an environment variable, use env() function instead.

Variables¶

Defined variables can be embedded with ${var.name} syntax in arbitrary HCL value part.

Example:

disabled = "${var.enable_debug}"

See variable section for details.

Functions¶

env()¶

env(name, default='')[source]¶

Gets an environment variable.

Parameters:	name (str) – Environment variable name. default (str) – Default value.
Returns:	env – Value of the environment variable.
Return type:	str

exec()¶

exec(command)[source]¶

Executes a command and returns the result of it.

Parameters:	command (str) – Command name and arguments separated by whitespaces.
Returns:	result – Result of the command.
Return type:	str

fg()¶

fg(color)[source]¶

Inserts the escape sequence of the foreground color.

Available colors are ‘black’, ‘red’, ‘green’, ‘yellow’, ‘blue’, ‘magenta’, ‘cyan’, ‘white’, ‘bright_black’, ‘bright_red’, ‘bright_green’, ‘bright_yellow’, ‘bright_blue’ , ‘bright_magenta’, ‘bright_cyan’ and ‘bright_white’.

Parameters:	color (str) – Foreground color in str (e.g. ‘red’).
Returns:	seq – Escape sequence of the foreground color.
Return type:	str
Raises:	`ValueError` – Invalid color name.

bg()¶

bg(color)[source]¶

Inserts the escape sequence of the background color.

Available colors are ‘black’, ‘red’, ‘green’, ‘yellow’, ‘blue’, ‘magenta’, ‘cyan’, ‘white’, ‘bright_black’, ‘bright_red’, ‘bright_green’, ‘bright_yellow’, ‘bright_blue’ , ‘bright_magenta’, ‘bright_cyan’ and ‘bright_white’.

Parameters:	color (str) – Background color in str (e.g. ‘red’).
Returns:	seq – Escape sequence of the background color.
Return type:	str
Raises:	`ValueError` – Invalid color name.

reset()¶

reset()[source]¶

Inserts the escape sequence of display reeet.

Returns:	seq – Escape sequence of display reeet.
Return type:	str

jq_all()¶

jq_all(query, data_str, *args, **kwargs)[source]¶

Queries the nested data and returns all results as a list.

Parameters:	data_str (str) – Nested data in Python dict’s representation format. If must be loadable by `yaml.safe_load()`.
Returns:	result – String representation of the result list.
Return type:	str

pyjq processes the query. jq() is an alias to jq_all().

jq_first()¶

jq_first(query, data_str, *args, **kwargs)[source]¶

Queries the nested data and returns the first result.

Parameters:	data_str (str) – Nested data in Python dict’s representation format. If must be loadable by `yaml.safe_load()`.
Returns:	result – String representation of the result object.
Return type:	str

pyjq processes the query. jqf() is an alias to jq_first().

Filters¶

The | operator can be used in a ${} expression to apply filters.

Example:

${'hello world' | u}

The u filter applies URL escaping to the string, and produces 'hello+world'.

To apply more than one filter, separate them by a comma:

${'  hello world  ' | trim,u}

The above produces 'hello+world'.

Available Filters¶

u

URL escaping.

${"hello world" | x} => 'hello+world'

h

HTML escaping.

${"hello world" | x} => 'hello world'

x

XML escaping.

${"hello world" | x} => 'hello world'

trim

Whitespace trimming.

${" hello world " | x} => 'hello world'

entity

Produces HTML entity references for applicable strings.

${"→" | entit} => '→'

Configuration Blocks¶

kernel¶

Example¶

The kernel block defines a kernel instance name and configures the kernel.

kernel "py_kernel" {
  kernel_name = "python3"
  pass_env = ["PATH", "HOME"]
}

Description¶

kernel_name (str | optional | default: "")

kernel_name is a Jupyter kernel name. You can install multiple kernels and switch them by specifying kernel_name. If it is not specified, the default kernel will be launched. The kernel must be IPython kernel and the Python version must be greater than or equal to 3.4. See also Installing the IPython kernel in the IPython document.

pass_env ([str] | optional | default: [])

pass_env defines environment variables which will be passed to the kernel. Jaffle itself has the environment variables defined in your environment, but the kernel will be launched as an independent process and the environment variables are not passed by default.

Tip

If the kernel executes a Python console script in a virtualenv, you will have to pass PATH environment variable to the kernel.

app¶

The app block configures a Jaffle app which will be launched in a kernel. The name next to app keyword will be the variable name in the kernel and will be accessed from other configuration blocks. The name must be valid in an IPython kernel.

Example¶

app "pytest" {
  class  = "jaffle.app.pytest.PyTestRunnerApp"
  kernel = "py_kernel"

  options {
    args = ["-s", "-v", "--color=yes"]

    auto_test = [
      "my_module/tests/test_*.py",
    ]

    auto_test_map {
      "my_module/**/*.py" = "my_module/tests/{}/test_{}.py"
    }
  }
}

Description¶

class (str | required)

The class name of the Jaffle app. It must begin with the top-level module name. e.g.: "jaffle.app.pytest.PyTestRunnerApp".
kernel (str | required)

The kernel in which the app is instantiated. The specified kernel must be defined in a kernel block.
start (str | optional | default: null)

Python code to be executed just after the app is instanticated in a kernel.
logger (logger | optional | default: {})

The app logger configuration.

options (map | optional | default: {})

options will be passed to the app initializer (__init__() method) as keyword arguments. The format of options depends on each app.

process¶

The process block configures an external process. The output to stdout and stderr are redirected to the logger with level info and warning respectively.

Example¶

process "webdev" {
  command = "yarn start"
  tty     = true

  env {
    BROWSER = "none"
  }
}

Description¶

command (str | required)

The command and arguments separated by whitespaces.
tty (bool | optional | default: false)

Whether to enable special care for a TTY application. Some applications require a foreground TTY access and/or send escape sequences aggressively. When tty is true, Jaffle runs the process via Pexpect and filters the output. Font style sequences are still available but all other escape sequences will be dropped. Try this option if your command does not work or makes the log output collapse.
env (map | optional | default: {})

The environment variables to be passed to the process.
logger (logger | optional | default: {})

The process logger configuration.

job¶

The job block configures a job which can be executed from a Jaffle app.

Example¶

job "sphinx" {
  command = "sphinx-build -M html docs docs/_build"
}

Here is an WatchdogApp configuration which executes the job:

app "watchdog" {
  class  = "jaffle.app.watchdog.WatchdogApp"
  kernel = "py_kernel"

  options {
    handlers = [
      {
        patterns           = ["*/my_module/*.py", "*/docs/*.*"]
        ignore_patterns    = ["*/_build/*"]
        ignore_directories = true
        jobs               = ["sphinx"]
      },
    ]
  }
}

Description¶

command (str | required)

The command and arguments separated by whitespaces.
logger (logger | optional | default: {})

The job logger configuration.

Jaffle Apps¶

Only WatchdogApp supports executing jobs.

logger¶

The logger block configures log suppressing and replacing rules by regular expressions. logger is available in the root, app and process blocks. The root logger configures the global rules which are applied after each app- or process-level rule.

Example¶

logger {
  suppress_regex = ["^\\s*$"] # drop empty line
  replace_regex = [
    {
      from = "(some_keyword)"
      to   = "\033[31m\\1\033[0m" # red color
    },
  ]
}

Description¶

name (str | optional | default: <object name>)

The logger name. The root logger does not have this.

Note

Each logger should have a unique logger name. If multiple loggers of apps, process or jobs have the same logger name, level, suppress_regex, etc. are overwritten multiple times and the last configuration takes effect. That may not be the expected behavior.
level (str | optional | default: 'info')

The logger level. Log messages are filtered by this level. Available levels are ‘critical’, ‘error’, ‘warning’, ‘info’ and ‘debug’. See Python logging reference for more information.
suppress_regex ([str] | optional | default: [])

Regular expression patterns to suppress log messages. If one of the patterns matches the log message, the message will be omitted.
replace_regex ([{“from”: str, “to”: str}] | optional | default: [])

The matched groups can be used in to string as \\1, \\2, and so on. Note that \ (backslash) must be escaped by an extra \, such as \\n.

Tip

replace_regex is especially useful to emphasize keywords on debugging like the example below.

variable¶

The variable block defines a variable which will be used in another blocks. The variables can be set from environment variables (J_VAR_name=value) or the command argument (--variables='["name=value"]').

Example¶

variable "disable_frontend" {
  type = "bool"
  default = false
}

process "frontend" {
  command  = "yarn start"
  tty      = true
  disabled = "${var.disable_frontend}"
}

Description¶

type (str | optional | default: undefined)

The type of the variable. Available types are ‘str’, ‘bool’, ‘int’, ‘float’, ‘list’ and ‘dict’.
default (object | optional | default: undefined)

The default value of the variable. If it is not defined, the value must be provided at runtime from an environment variable or the command-line argument.

If type is not provided, it will be inferred based on default. If default is not provided, it is assumed to be str.

Embedding Variables¶

The variable embedding can be used only in a string:

disabled = "${var.disable_frontend}" # OK

It cannot be used outside of a string even though the target attribute requires bool or int because it is not a valid HCL:

disabled = ${var.disable_frontend} # NG

In Jaffle, the following strings can be treated as boolean values:

'true' and '1' => true
'false' and '0' => false

disabled = false

Setting Variables¶

Your can set values to the variables from environment variables (J_VAR_name=value) or the command argument (--variables='["name=value"]').

Example: Setting true to disable_frontend from an environment variable:

$ J_VAR_disable_frontend=true jaffle start

Example: Setting true to disable_frontend from the command-line argument:

$ jaffle start --variables='["disable_frontend=true"]'

Jaffle Apps¶

Built-in Apps¶

WatchdogApp¶

WatchdogApp launches Watchdog handlers with given patterns and callback code blocks. Since Jaffle is initially designed to be an automation tool, WatchdogApp is regarded as the central app among other Jaffle apps.

Watchdog is a Python API library and shell utilities to monitor file system events.

Example Configuration¶

app "watchdog" {
  class  = "jaffle.app.watchdog.WatchdogApp"
  kernel = "py_kernel"

  options {
    handlers = [{
      patterns           = ["*.py"]
      ignore_patterns    = ["*/tests/*.py"]
      ignore_directories = true
      functions          = ["pytest.handle_watchdog_event({event})"]
    }]
  }
}

Options¶

handlers (list[dict] | optional | default: [])

Watchdog handler definitions. The dict format is described below.

Handler dict Format¶

watch_path (str | optional | default: current_directory)

The directory to be watched by the handler. Both absolute and relative paths are available.
patterns (list[str] | optional | default: [])

The path matching patterns to execute handler code blocks and jobs. The pattern syntax is the same as Python’s fnmatch. Since the Watchdog event has an absolute file path, you will probably need * at the beginning of the pattern (e.g.: patterns = ["*/foo/*.py"]).

Note

The Watchdog pattern syntax and the PyTestRunner pattern syntax are difference from each other. They may be changed to be identical in the future release.

ignore_patterns (list[str] | optional | default: [])

The path matching patterns to be ignored. The pattern syntax is the same as patterns.
ignore_directories (bool | optional | default: false)

Whether to ignore Watchdog events of directories.
throttle (float | optional | default: 0.0)

The throttle time in seconds for event handling. When an event is handled, the event handling is disabled until the throttle time passes by. If it is 0, the throttling is disabled.
debounce (float | optional | default: 0.0)

The debounce time in seconds for event handling. The event will be handled only when the debounce time has passed without receiving any other events. If it is 0, the debouncing is disabled.

Tip

Throttling and debouncing are useful when your editor or any other app does multiple file-system operations at once. For example, when you save a file in an editor, the editor may write the file twice to do auto-formatting. In this case, two events are going to be handled each time you save a file and you might want to handle the event only once. throttle and debounce come into play in this situation.
code_blocks (list[str] | optional | default: [])

The code blocks to be executed by the handler.
jobs (list[str] optional | default: [])

The jobs to be executed by the handler. Jobs must be defined in job blocks.
clear_cache (list[str] | optional | default: <modules found under the current directory>)

The module names which will be removed from the module cache (sys.modules) before executing handler code blocks.

Integration with Other Apps¶

WatchdogApp handler executes Python code written in code_blocks, with replacing the interpolation keyword {event} with an watchdog.events.FileSystemEvent object.

Example:

code_blocks = ["pytest.handle_watchdog_event({event})"]

PyTestRunnerApp and TornadoBridgeApp has handle_watchdog_event() to handle the Watchdog event.

PyTestRunnerApp¶

PyTestRunnerApp runs pytest on receiving Watchdog events sent from WatchdogApp. That works very fast because PyTestRunnerApp runs pytest as a Python function in a Jupyter kernel process instead of executing the external py.test command, and it also keeps cache of imported modules which do not require reloading.

PyTestRunnerApp also has the interactive shell which allows you to run tests interactively.

Example Configuration¶

app "pytest" {
  class  = "jaffle.app.pytest.PyTestRunnerApp"
  kernel = "py_kernel"

  options {
    args = ["-s", "-v", "--color=yes"]

    auto_test = [
      "jaffle_tornado_spa_example/tests/test_*.py",
    ]

    auto_test_map {
      "jaffle_tornado_spa_example/**/*.py" = "jaffle_tornado_spa_example/tests/{}/test_{}.py"
    }
  }
}

Optionns¶

args (list[str] | optional | default: [])

The pytest arguments.
auto_test

The file path patterns to be executed by pytest. The pattern syntax is the same as shell glob but supports only * and **. * matches arbitrary characters except for / (slash), whereas ** matches all characters.
auto_test_map

The file path patterns map to determine test files to be executed. If the event path matches to the left-hand-side pattern, the files which match the right-hand-side will be executed. The pattern syntax is the same as auto_test. The strings matched to * or ** in the left-hand-side will be expanded into {} in the right-hand-side one by one.

Tip

It is recommended to create a Python implimentation file and a unit test file to have one-to-one correspondence to each other. That makes easy to setup auto_test_map.

If you editor supports jumping to alternative file like vim-projectionist, it also helps a lot.
clear_cache (list[str] | optional | default: <modules found under the current directory>)

The module names which will be removed from the module cache (sys.modules) before restarting the app. If it is not provided, TornadoBridgeApp searches modules by calling setuptools.find_packages(). Note that the root Python module must be in the current working directory to be found by TornadoBridgeApp. If it is included in a sub-directory, you must specify clear_cache manually.

Interactive Shell¶

You can use an interactive shell which attaches the session to PyTestRunnerApp running in a Jupyter kernel.

Example:

$ jaffle attach pytest

You can type test case names with auto-completion. The tests are executed in the Jupyter kernel.

TornadoBridgeApp¶

TornadoBridgeApp manages a Tornado application in IPython kernels running in a Jaffle.

Example Configuration¶

app "tornado_app" {
  class  = "jaffle.app.tornado.TornadoBridgeApp"
  kernel = "py_kernel"
  start  = "tornado_app.start()"

  logger {
    level = "info",
  }

  options {
    app_class          = "my_module.app.ExampleApp"
    argv               = ["--port=9999"]
    threaded           = true
    clear_cache = ["my_module"]
  }
}

Options¶

app_class (str | required | default: undefined)

The Tornado application class to be launched in a kernel. It must be a fully qualified class name which begins from the top module name joined with ., e.g. foo.bar.BazApp.
argv (list[str] | optional | default: [])

The arguments to the Tornado application. They will be passed directly to __init__() of the class.
threaded (bool | optional | default: false)

Whether to launch the app in an independent IO loop thread. Tornado applications can basically be launched in the main thread and share the IO loop with other apps and the Jaffle itself. However, some apps cannot dispose all running functions from the IO loop and that makes troubles on calling start() and stop() several times, because the remaining functions may cause errors. When threaded is true, the app uses its own IO loop which will be stopped together with the app itself.
clear_cache (list[str] | optional | default: <modules found under the current directory>)

The module names which will be removed from the module cache (sys.modules) before restarting the app. If it is not provided, TornadoBridgeApp searches modules by calling setuptools.find_packages(). Note that the root Python module must be in the current working directory to be found by TornadoBridgeApp. If it is included in a sub-directory, you must specify clear_cache manually.

Available Tornado Applications¶

TornadoBridgeApp assumes that the Tornado application has start() and stop() and they meet the following requirements:

start() gets the IOLoop by calling tornado.ioloop.IOLoop.current().
IOLoop.start() is called only from start().
IOLoop.stop() is called only from an IOLoop callback which is added by stop().

Example:

class ExampleApp(Application):

    def start(self):
        self.io_loop = ioloop.IOLoop.current()
        try:
            self.io_loop.start()
        except KeyboardInterrupt:
            self.log.info('Interrupt')

    def stop(self):
        def _stop():
            self.http_server.stop()
            self.io_loop.stop()
        self.io_loop.add_callback(_stop)

They are required because Jaffle must protect the main IOLoop not to be terminated or overwritten by the app. If your application cannot meet the requirements, you can create a custom Jaffle app inheriting TornadoBridgeApp.

Integration with WatchdogApp ¶

TornadoBridgeApp.handle_watchdog_event() handles an Watchdog event sent from WatchdogApp. It restarts the Tornado application.

Example WatchdogApp configuration:

app "watchdog" {
  class  = "jaffle.app.watchdog.WatchdogApp"
  kernel = "py_kernel"

  options {
    handlers = [
      {
        patterns           = ["*.py"]
        ignore_directories = true
        functions          = ["my_app.handle_watchdog_event({event})"]
      },
    ]
  }
}

app "my_app" {
  class  = "jaffle.app.tornado.TornadoBridgeApp"
  kernel = "py_kernel"
  start  = "tornado_app.start()"

  options {
    app_class = "my_module.app.ExampleApp"
  }
}

Custom Apps¶

You can create your own Jaffle app by inheriting BaseJaffleApp. See Developers Guide for more information.

Cookbook¶

Auto-testing with pytest¶

You can setup auto-testing by using WatchdogApp and PyTestRunnerApp.

Here is the example jaffle.hcl, which can be used by jaffle start.

kernel "py_kernel" {}

app "watchdog" {
  class  = "jaffle.app.watchdog.WatchdogApp"
  kernel = "py_kernel"

  options {
    handlers = [{
      watch_path         = "pytest_example"
      patterns           = ["*.py"]
      ignore_directories = true
      code_blocks        = ["pytest.handle_watchdog_event({event})"]
    }]
  }
}

app "pytest" {
  class  = "jaffle.app.pytest.PyTestRunnerApp"
  kernel = "py_kernel"

  options {
    args = ["-s", "-v", "--color=yes"]

    auto_test = [
      "pytest_example/tests/test_*.py",
    ]

    auto_test_map {
      "pytest_example/**/*.py" = "pytest_example/tests/{}/test_{}.py"
    }
  }
}

L1: Define the kernel py_kernel which is used by watchdog and pytest.
L3-5: Create WatchdogApp with name watchdog in the kernel py_kernel.
L9-11: Let Watchdog watch the directory pytest_example with provided patterns.
L12: When an event comes, the handler executes this code block. The variable pytest is an app created later (L17).
L17-19: Define PyTestRunnerApp with name pytest in the kernel py_kernel.
L24-26: When pytest_example/tests/test_*.py is modified, pytest executes it.
L28-30: When pytest_example/**/*.py is modified, pytest executes the file matched to the pattern pytest_example/tests/{}/test_{}.py.

Interactive Shell¶

You can also use the interactive shell which attaches the session to the running pytest instance:

$ jaffle attach pytest

When you hit t TAB /, test cases are auto-completed.

Screenshot¶

Note

The source package of Jaffle contains example projects in examples directory. You can see the latest version of them here: https://github.com/yatsu/jaffle/tree/master/examples

A pytest example is here: https://github.com/yatsu/jaffle/tree/master/examples/pytest

Automatic Sphinx Document Build¶

Here is a simple example which generates a Sphinx document on detecting *.rst update. It assumes .rst files are stored in docs directory and the result HTML will be stored in docs/_build.

jaffle.hcl:

kernel "py_kernel" {
  pass_env = ["PATH"] # required to run sphinx-build in virtualenv
}

app "watchdog" {
  class  = "jaffle.app.watchdog.WatchdogApp"
  kernel = "py_kernel"

  options {
    handlers = [{
      patterns           = ["*/docs/*.*"]
      ignore_patterns    = ["*/_build/*"]
      ignore_directories = true
      jobs               = ["sphinx"]
    }]
  }
}

job "sphinx" {
  command = "sphinx-build -M html docs docs/_build"
}

L1-3: Define the kernel py_kernel which is used by watchdog and pytest. You need to pass PATH environment variable if sphinx-build is installed in a virtualenv.
L5-7: Create WatchdogApp with name watchdog in the kernel py_kernel.
L10-13: Let Watchdog_ watch the directory pytest_example with provided patterns.
L14: When an event comes, the handler executes the job sphinx which will be defined later (L19-21)
L19-21: Define sphinx job to execute sphinx-build

Note

Ignoreing _build directory is important (L12 of the above example). If you forget that, sphinx job updates _build directory and that triggers sphinx job again. That will be an infinite loop.

Refreshing Browser¶

Here is another example on macOS which also refreshes Google Chrome’s current tab on detecting file updates.

kernel "py_kernel" {
  pass_env = ["PATH"]
}

app "watchdog" {
  class  = "jaffle.app.watchdog.WatchdogApp"
  kernel = "py_kernel"

  options {
    handlers = [{
      patterns           = ["*/docs/*.*"]
      ignore_patterns    = ["*/_build/*"]
      ignore_directories = true
      jobs = [
        "sphinx",
        "chrome_refresh",
      ]
    }]
  }
}

job "sphinx" {
  command = "sphinx-build -M html docs docs/_build"
}

job "chrome_refresh" {
  command = "osascript chrome_refresh.scpt"
}

You also need the AppleScript file chrome_refresh.scpt in the current directory as below.

tell application "Google Chrome" to tell the active tab of its first window
    reload
end tell

Tip

On Linux, maybe you can use xdotool to refresh your browser.

Note

The source package of Jaffle contains example projects in examples directory. You can see the latest version of them here: https://github.com/yatsu/jaffle/tree/master/examples

Jaffle uses the above configuration to generate this Sphinx document: https://github.com/yatsu/jaffle/tree/master/jaffle.hcl

Web Development with Tornado and React¶

This is an example Jaffle configuration for the web development which uses Tornado and React to build the back-end API and the front-end web interface respectively.

It does:

Launch the Tornado application including HTTP server
Launch the Webpack dev server as an external process by executing yarn start
Launch Jest as an external process by executing yarn test
Restart the Tornado application when a related file is updated
Execute pytest when a related file is updated

This page assumes that you have already know the basic configuration for a pytest. If not, please read the section Auto-testing with pytest.

jaffle.hcl:

kernel "py_kernel" {}

app "watchdog" {
  class  = "jaffle.app.watchdog.WatchdogApp"
  kernel = "py_kernel"

  options {
    handlers = [
      {
        watch_path         = "tornado_spa"
        patterns           = ["*.py"]
        ignore_patterns    = ["*/tests/*.py"]
        ignore_directories = true
        clear_cache        = ["tornado_spa"]

        code_blocks = [
          "tornado_app.handle_watchdog_event({event})",
          "pytest.handle_watchdog_event({event})",
        ]
      },
      {
        watch_path         = "tornado_spa/tests"
        patterns           = ["*/test_*.py"]
        ignore_directories = true
        clear_cache        = ["tornado_spa.tests"]

        code_blocks = [
          "pytest.handle_watchdog_event({event})",
        ]
      },
    ]
  }
}

app "tornado_app" {
  class  = "jaffle.app.tornado.TornadoBridgeApp"
  kernel = "py_kernel"
  start  = "tornado_app.start()"

  options {
    app_class   = "tornado_spa.app.ExampleApp"
    args        = ["--port=9999"]
    clear_cache = []
  }
}

app "pytest" {
  class  = "jaffle.app.pytest.PyTestRunnerApp"
  kernel = "py_kernel"

  options {
    args = ["-s", "-v", "--color=yes"]

    auto_test = [
      "tornado_spa/tests/test_*.py",
    ]

    auto_test_map {
      "tornado_spa/**/*.py" = "tornado_spa/tests/{}/test_{}.py"
    }

    clear_cache = []
  }
}

process "frontend" {
  command = "yarn start"
  tty     = true

  env {
    BROWSER = "none"
  }
}

process "jest" {
  command = "yarn test"
  tty     = true
}

Clearing Module Cache¶

Since two applications tornado_app and pytest run in the same Jupyter kernel and share the same Python modules in memory, you should manually configure the cache clear. By default TornadoBridgeApp and PyTestRunnerApp clear the modules found under the current directory on receiving an Watchdog event. That causes duplicated cache clear on the same module. To prevent that, the configuration above has clear_cache = [] in both tornado_app and pytest to disable cache clear and has clear_cache = ["tornado_spa"] in watchdog to let WatchdogApp clear the module cache instead.

Note

If clear_cache configuration is incorrect, TornadoBridgeApp or PyTestRunnerApp may not reload Python modules.

Screenshot¶

Note

The source package of Jaffle contains example projects in examples directory. You can see the latest version of them here: https://github.com/yatsu/jaffle/tree/master/examples

A Tornado and React example is here: https://github.com/yatsu/jaffle/tree/master/examples/tornado_spa

Jupyter Extension Development¶

This page assumes that you have already know the basic configuration for a Tornado application. If not, please read the section Web Development with Tornado and React.

To execute examples/jupyter_ext, you need to setup the Python project and install Jupyter serverextension and nbextension first.

Example setup:

$ cd example/jupyter_ext
$ pip install -e .
$ jupyter serverextension install jupyter_myext --user
$ jupyter nbextension install jupyter_myext --user

Here is the Jaffle configuration.

jaffle.hcl:

kernel "py_kernel" {}

app "watchdog" {
  class  = "jaffle.app.watchdog.WatchdogApp"
  kernel = "py_kernel"

  options {
    handlers = [
      {
        patterns           = ["*.py"]
        ignore_patterns    = ["*/tests/*.py"]
        ignore_directories = true
        clear_cache        = ["jupyter_myext"]

        code_blocks = [
          "notebook.handle_watchdog_event({event})",
          "pytest.handle_watchdog_event({event})",
        ]
      },
      {
        patterns           = ["*/tests/test_*.py"]
        ignore_directories = true
        clear_cache        = ["jupyter_myext.tests"]

        code_blocks = [
          "pytest.handle_watchdog_event({event})",
        ]
      },
      {
        patterns           = ["*.js"]
        ignore_directories = true

        code_blocks = [
          "nbext_install.handle_watchdog_event({event})",
        ]
      },
    ]
  }
}

app "notebook" {
  class  = "jaffle.app.tornado.TornadoBridgeApp"
  kernel = "py_kernel"

  options {
    app_class = "notebook.notebookapp.NotebookApp"

    args = [
      "--port=9999",
      "--NotebookApp.token=''",
    ]

    clear_cache = []
  }

  start = "notebook.start()"
}

app "pytest" {
  class  = "jaffle.app.pytest.PyTestRunnerApp"
  kernel = "py_kernel"

  options {
    args = ["-s", "--color=yes"]

    auto_test = [
      "jupyter_myext/tests/test_*.py",
    ]

    auto_test_map {
      "jupyter_myext/**/*.py" = "jupyter_myext/tests/{}/test_{}.py"
    }

    clear_cache = []
  }
}

app "nbext_install" {
  class  = "jupyter_myext._devel.NBExtensionInstaller"
  kernel = "py_kernel"
}

L10-28: The handler configuration of pytest execution and Tornado restart, same as the example: Web Development with Tornado and React.
L29-36: The handler configuration to install nbextension on detecting .js file update.
L41-57: Launch Jupyter notebook server via TornadoBridgeApp with the main IO loop of the kernel process.
L78-81: The definition of an app that installs the nbextension.

Tip

This example uses NBExtensionInstaller to install the Jupyter nbextension. You can define a job that executes jupyter nbextension install --overwrite instead. If you do so, be sure to set pass_env = ["PATH"] in the kernel section if Jupyter is installed in a virtualenv.

Note

The source package of Jaffle contains example projects in examples directory. You can see the latest version of them here: https://github.com/yatsu/jaffle/tree/master/examples

A Jupyter extension example is here: https://github.com/yatsu/jaffle/tree/master/examples/jupyter_ext

Overwriting the Configuration¶

You might want to add jaffle.hcl to your source code repository to share it within your team. At the same time, you might want to run Jaffle with your own customized log filtering. Editing the same jaffle.hcl is hard and it may cause an accidental repository commit. Jaffle provides the following two features to overwrite and customize the base configuration.

Merging multiple configurations
Setting variable from command-line

examples/tornado_spa_advanced is the example which demonstrates them.

Merging Multiple Configurations¶

You can provide multiple configuration file to jaffle start. For example:

$ jaffle start jaffle.hcl my_jaffle.hcl

Jaffle read the first file and then merges the other files one by one. Maps are merged deeply and other elements are overwritten.

Let’s say you have this jaffle.hcl.

variable "watchdog_log_level" {
  default = "info"
}

app "watchdog" {
  # ...
  logger {
    level = "${var.watchdog_log_level}"
  }
  # ...
}

And this my_jaffle.hcl.

variable "watchdog_log_level" {
  default = "debug" # overwrite "info" => "debug"
}

The configuration will be merged as follows.

variable "watchdog_log_level" {
  default = "debug"
}

app "watchdog" {
  # ...
  logger {
    level = "${var.watchdog_log_level}"
  }
  # ...
}

Please refer to the Merging Multiple Configurations section of the jaffle start Command Reference.

Setting Variable from Command-line¶

You can provide variables from command-line. The example shown in the previous section can be executed with debug log-level as follows.

$ J_VAR_watchdog_log_level=debug jaffle start

You can also set it by --variables option.

$ jaffle start --variables='["watchdog_log_level=debug"]'

Please refer to the variable document.

Note

The source package of Jaffle contains example projects in examples directory. You can see the latest version of them here: https://github.com/yatsu/jaffle/tree/master/examples

Troubleshooting¶

Debug Logging¶

--debug option enables the debug logging of Jaffle itself.

$ jaffle start --debug

Each app has its own log-level setting. You can set it in jaffle.hcl.

app "myapp" {
  # ...

  logger {
    level = "debug"
  }
}

You can also set the log-level using a variable like this.

variable "myapp_log_level" {
  default = "info"
}

app "myapp" {
  # ...

  logger {
    level = "${var.myapp_log_level}"
  }
}

You can switch the log-level by providing the value as an environment variable.

$ J_VAR_myapp_log_level=debug jaffle start

The command-line argument --variables is also avilable to do the same thing.

$ jaffle start --variables='["myapp_log_level=debug"]'

Jaffle Console¶

jaffle console allows you to open an interactive shell and attaches the session into the running kernel. You can inspect or set variables of running apps in it.

$ jaffle console my_kernel

Version History¶

0.2.2 (May 21, 2018)¶

Fix: String interpolations in logger settings are not evaluated

0.2.1 (May 20, 2018)¶

Fix: String interpolations in app options are not evaluated

0.2.0 (May 16, 2018)¶

Now String interpolations are evaluated at runtime instead of on loading the configuration
Add functions jq_all() and jq_first() and their aliases jq() and jqf()
Change environment variable prefix T_VAR_ to J_VAR_
Simplify BaseJaffleApp I/F
Improve Tornado app stability on syntax errors and exceptions raised in start()
Fix hidden Tornado log messages

0.1.2 (May 8, 2018)¶

Add fg(), bg() and reset() function
Fix errors on starting/stopping threaded Tornado app

0.1.0 (May 6, 2018)¶

Initial release

Developers Guide¶

API¶

jaffle.app.base¶

BaseJaffleApp¶

class BaseJaffleApp(app_conf_data)[source]¶

Base class for Jaffle apps.

completer_class¶: The completer class for the interactive shell. It is required only if the app supports interactive shell.

lexer_class¶: The lexer class for the interactive shell. It is required only if the app supports interactive shell.

classmethod command_to_code(app_name, command)[source]¶

Converts a command comes from jaffle attach <app> to a code to be executed.

If the app supports jaffle attach, this method must be implemented.

Parameters:	app_name (str) – App name defined in jaffle.hcl. command (str) – Command name received from the shell of `jaffle attach`.
Returns:	code – Code to be executed.
Return type:	str

execute_code(code, *args, **kwargs)[source]¶

Executes a code.

Parameters:	code (str) – Code to be executed. It will be formateed as `code.format(args, kwargs)`. args* (list) – Positional arguments to `code.format()`. kwargs (dict) – Keyward arguments to `code.formmat()`.
Returns:	future – Future which will have the execution result.
Return type:	tornado.gen.Future

execute_command(command, logger=None)[source]¶

Executes a command.

Parameters:	command (str) – Command to be executed. logger (logging.Logger) – Logger.
Returns:	future – Future which will have the execution result.
Return type:	tornado.gen.Future

execute_job(job_name)[source]¶

Executes a job.

Parameters:	job_name (str) – Job to be executed.
Returns:	future – Future which will have the execution result.
Return type:	tornado.gen.Future

Utility Functions¶

capture_method_output(method)[source]¶

Decorator for an app method to capture standard output and redirects it to the logger. stdout and stderr are logged with level INFO and WARNING respectively.

Parameters:	method (function) – Method to be wrapped.

Source Code¶

GitHub repository: yatsu/jaffle

Bugs/Requests¶

Please use the GitHub issue tracker to submit bugs or request features.

License¶

Jaffle is available under BSD 3-Clause License.

This web site and all documentation are licensed under Creative Commons 3.0.

Jaffle 0.2¶

Screenshot¶

Installation¶

Prerequisite¶

Installation¶

Commands¶

jaffle start¶

Usage¶

Options¶

Merging Multiple Configurations¶

jaffle stop¶

Usage¶

Options¶

jaffle console¶

Usage¶

Options¶

jaffle attach¶

Usage¶

Options¶

Configuration¶

Syntax¶

Configuration Syntax¶

Example¶

JSON¶

Interpolation Syntax¶

Environment Variables¶

Variables¶

Functions¶

Filters¶

Configuration Blocks¶

kernel¶

Example¶

Description¶

app¶

Example¶

Description¶

process¶

Example¶

Description¶

job¶

Example¶

Description¶

Jaffle Apps¶

logger¶

Example¶

Description¶

variable¶

Example¶

Description¶

Embedding Variables¶

Setting Variables¶

Jaffle Apps¶

Built-in Apps¶

WatchdogApp¶

Example Configuration¶

Options¶

Integration with Other Apps¶

PyTestRunnerApp¶

Example Configuration¶

Optionns¶

Interactive Shell¶

TornadoBridgeApp¶

Example Configuration¶

Options¶

Available Tornado Applications¶

Integration with WatchdogApp¶

Custom Apps¶

Cookbook¶

Auto-testing with pytest¶

Interactive Shell¶

Screenshot¶

Automatic Sphinx Document Build¶

Refreshing Browser¶

Web Development with Tornado and React¶

Clearing Module Cache¶

Screenshot¶

Jupyter Extension Development¶

Overwriting the Configuration¶

Merging Multiple Configurations¶

Setting Variable from Command-line¶

Integration with WatchdogApp ¶