Files
2020-04-08 10:39:44 -07:00

217 lines
8.5 KiB
Python

import logging
import threading
from .constants import HOSTNAME_KEY, SAMPLING_PRIORITY_KEY, ORIGIN_KEY
from .internal.logger import get_logger
from .internal import hostname
from .settings import config
from .utils.formats import asbool, get_env
log = get_logger(__name__)
class Context(object):
"""
Context is used to keep track of a hierarchy of spans for the current
execution flow. During each logical execution, the same ``Context`` is
used to represent a single logical trace, even if the trace is built
asynchronously.
A single code execution may use multiple ``Context`` if part of the execution
must not be related to the current tracing. As example, a delayed job may
compose a standalone trace instead of being related to the same trace that
generates the job itself. On the other hand, if it's part of the same
``Context``, it will be related to the original trace.
This data structure is thread-safe.
"""
_partial_flush_enabled = asbool(get_env('tracer', 'partial_flush_enabled', 'false'))
_partial_flush_min_spans = int(get_env('tracer', 'partial_flush_min_spans', 500))
def __init__(self, trace_id=None, span_id=None, sampling_priority=None, _dd_origin=None):
"""
Initialize a new thread-safe ``Context``.
:param int trace_id: trace_id of parent span
:param int span_id: span_id of parent span
"""
self._trace = []
self._finished_spans = 0
self._current_span = None
self._lock = threading.Lock()
self._parent_trace_id = trace_id
self._parent_span_id = span_id
self._sampling_priority = sampling_priority
self._dd_origin = _dd_origin
@property
def trace_id(self):
"""Return current context trace_id."""
with self._lock:
return self._parent_trace_id
@property
def span_id(self):
"""Return current context span_id."""
with self._lock:
return self._parent_span_id
@property
def sampling_priority(self):
"""Return current context sampling priority."""
with self._lock:
return self._sampling_priority
@sampling_priority.setter
def sampling_priority(self, value):
"""Set sampling priority."""
with self._lock:
self._sampling_priority = value
def clone(self):
"""
Partially clones the current context.
It copies everything EXCEPT the registered and finished spans.
"""
with self._lock:
new_ctx = Context(
trace_id=self._parent_trace_id,
span_id=self._parent_span_id,
sampling_priority=self._sampling_priority,
)
new_ctx._current_span = self._current_span
return new_ctx
def get_current_root_span(self):
"""
Return the root span of the context or None if it does not exist.
"""
return self._trace[0] if len(self._trace) > 0 else None
def get_current_span(self):
"""
Return the last active span that corresponds to the last inserted
item in the trace list. This cannot be considered as the current active
span in asynchronous environments, because some spans can be closed
earlier while child spans still need to finish their traced execution.
"""
with self._lock:
return self._current_span
def _set_current_span(self, span):
"""
Set current span internally.
Non-safe if not used with a lock. For internal Context usage only.
"""
self._current_span = span
if span:
self._parent_trace_id = span.trace_id
self._parent_span_id = span.span_id
else:
self._parent_span_id = None
def add_span(self, span):
"""
Add a span to the context trace list, keeping it as the last active span.
"""
with self._lock:
self._set_current_span(span)
self._trace.append(span)
span._context = self
def close_span(self, span):
"""
Mark a span as a finished, increasing the internal counter to prevent
cycles inside _trace list.
"""
with self._lock:
self._finished_spans += 1
self._set_current_span(span._parent)
# notify if the trace is not closed properly; this check is executed only
# if the debug logging is enabled and when the root span is closed
# for an unfinished trace. This logging is meant to be used for debugging
# reasons, and it doesn't mean that the trace is wrongly generated.
# In asynchronous environments, it's legit to close the root span before
# some children. On the other hand, asynchronous web frameworks still expect
# to close the root span after all the children.
if span.tracer and span.tracer.log.isEnabledFor(logging.DEBUG) and span._parent is None:
unfinished_spans = [x for x in self._trace if not x.finished]
if unfinished_spans:
log.debug('Root span "%s" closed, but the trace has %d unfinished spans:',
span.name, len(unfinished_spans))
for wrong_span in unfinished_spans:
log.debug('\n%s', wrong_span.pprint())
def _is_sampled(self):
return any(span.sampled for span in self._trace)
def get(self):
"""
Returns a tuple containing the trace list generated in the current context and
if the context is sampled or not. It returns (None, None) if the ``Context`` is
not finished. If a trace is returned, the ``Context`` will be reset so that it
can be re-used immediately.
This operation is thread-safe.
"""
with self._lock:
# All spans are finished?
if self._finished_spans == len(self._trace):
# get the trace
trace = self._trace
sampled = self._is_sampled()
sampling_priority = self._sampling_priority
# attach the sampling priority to the context root span
if sampled and sampling_priority is not None and trace:
trace[0].set_metric(SAMPLING_PRIORITY_KEY, sampling_priority)
origin = self._dd_origin
# attach the origin to the root span tag
if sampled and origin is not None and trace:
trace[0].set_tag(ORIGIN_KEY, origin)
# Set hostname tag if they requested it
if config.report_hostname:
# DEV: `get_hostname()` value is cached
trace[0].set_tag(HOSTNAME_KEY, hostname.get_hostname())
# clean the current state
self._trace = []
self._finished_spans = 0
self._parent_trace_id = None
self._parent_span_id = None
self._sampling_priority = None
return trace, sampled
elif self._partial_flush_enabled:
finished_spans = [t for t in self._trace if t.finished]
if len(finished_spans) >= self._partial_flush_min_spans:
# partial flush when enabled and we have more than the minimal required spans
trace = self._trace
sampled = self._is_sampled()
sampling_priority = self._sampling_priority
# attach the sampling priority to the context root span
if sampled and sampling_priority is not None and trace:
trace[0].set_metric(SAMPLING_PRIORITY_KEY, sampling_priority)
origin = self._dd_origin
# attach the origin to the root span tag
if sampled and origin is not None and trace:
trace[0].set_tag(ORIGIN_KEY, origin)
# Set hostname tag if they requested it
if config.report_hostname:
# DEV: `get_hostname()` value is cached
trace[0].set_tag(HOSTNAME_KEY, hostname.get_hostname())
self._finished_spans = 0
# Any open spans will remain as `self._trace`
# Any finished spans will get returned to be flushed
self._trace = [t for t in self._trace if not t.finished]
return finished_spans, sampled
return None, None