174 lines
4.4 KiB
Python
174 lines
4.4 KiB
Python
from __future__ import print_function
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import abc
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import collections
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import json
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import os
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import pydoc
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import re
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import sys
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import pager
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import pygments
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import six
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from dcos import constants, errors, util
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from pygments.formatters import Terminal256Formatter
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from pygments.lexers import JsonLexer
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try:
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basestring = basestring
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except NameError:
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# We are in python3 define basestring as str
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basestring = str
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logger = util.get_logger(__name__)
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class Emitter(object):
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"""Abstract class for emitting events."""
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@abc.abstractmethod
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def publish(self, event):
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"""Publishes an event.
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:param event: event to publish
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:type event: any
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"""
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raise NotImplementedError
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class FlatEmitter(Emitter):
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"""Simple emitter that sends all publish events to the provided handler.
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If no handler is provider then use :py:const:`DEFAULT_HANDLER`.
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:param handler: event handler to call when publish is called
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:type handler: func(event) where event is defined in
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:py:func:`FlatEmitter.publish`
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"""
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def __init__(self, handler=None):
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if handler is None:
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self._handler = DEFAULT_HANDLER
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else:
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self._handler = handler
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def publish(self, event):
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"""Publishes an event.
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:param event: event to publish
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:type event: any
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"""
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self._handler(event)
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def print_handler(event):
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"""Default handler for printing event to stdout.
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:param event: event to emit to stdout
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:type event: str, dict, list, or dcos.errors.Error
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"""
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pager_command = os.environ.get(constants.DCOS_PAGER_COMMAND_ENV)
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if event is None:
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# Do nothing
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pass
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elif isinstance(event, six.string_types):
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_page(event, pager_command)
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elif isinstance(event, errors.Error):
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print(event.error(), file=sys.stderr)
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elif (isinstance(event, collections.Mapping) or
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isinstance(event, collections.Sequence) or isinstance(event, bool) or
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isinstance(event, six.integer_types) or isinstance(event, float)):
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# These are all valid JSON types let's treat them different
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processed_json = _process_json(event, pager_command)
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_page(processed_json, pager_command)
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else:
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logger.debug('Printing unknown type: %s, %r.', type(event), event)
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_page(event, pager_command)
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def _process_json(event, pager_command):
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"""Conditionally highlights the supplied JSON value.
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:param event: event to emit to stdout
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:type event: str, dict, list, or dcos.errors.Error
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:returns: String representation of the supplied JSON value,
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possibly syntax-highlighted.
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:rtype: str
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"""
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json_output = json.dumps(event, sort_keys=True, indent=2)
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# Strip trailing whitespace
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json_output = re.sub(r'\s+$', '', json_output, 0, re.M)
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force_colors = False # TODO(CD): Introduce a --colors flag
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if not sys.stdout.isatty():
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if force_colors:
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return _highlight_json(json_output)
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else:
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return json_output
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supports_colors = not util.is_windows_platform()
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pager_is_set = pager_command is not None
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should_highlight = force_colors or supports_colors and not pager_is_set
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if should_highlight:
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json_output = _highlight_json(json_output)
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return json_output
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def _page(output, pager_command=None):
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"""Conditionally pipes the supplied output through a pager.
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:param output:
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:type output: object
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:param pager_command:
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:type pager_command: str
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"""
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output = str(output)
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if pager_command is None:
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pager_command = 'less -R'
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if not sys.stdout.isatty() or util.is_windows_platform():
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print(output)
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return
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num_lines = output.count('\n')
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exceeds_tty_height = pager.getheight() - 1 < num_lines
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if exceeds_tty_height:
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pydoc.pipepager(output, cmd=pager_command)
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else:
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print(output)
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def _highlight_json(json_value):
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"""
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:param json_value: JSON value to syntax-highlight
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:type json_value: dict, list, number, string, boolean, or None
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:returns: A string representation of the supplied JSON value,
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highlighted for a terminal that supports ANSI colors.
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:rtype: str
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"""
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return pygments.highlight(
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json_value, JsonLexer(), Terminal256Formatter()).strip()
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DEFAULT_HANDLER = print_handler
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"""The default handler for an emitter: :py:func:`print_handler`."""
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