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Improve opentracing for federation requests (#11870)

The idea here is to set the parent span for incoming federation requests to the
*outgoing* span on the other end. That means that you can see (most of) the
full end-to-end flow when you have a process that includes federation requests.

However, in order not to lose information, we still want a link to the
`incoming-federation-request` span from the servlet, so we have to create
another span to do exactly that.
This commit is contained in:
Richard van der Hoff 2022-02-03 12:29:16 +00:00 committed by GitHub
parent 31b554c297
commit 964f5b9324
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3 changed files with 61 additions and 19 deletions

1
changelog.d/11870.misc Normal file
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@ -0,0 +1 @@
Improve opentracing for incoming federation requests.

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@ -15,6 +15,7 @@
import functools
import logging
import re
import time
from typing import TYPE_CHECKING, Any, Awaitable, Callable, Optional, Tuple, cast
from synapse.api.errors import Codes, FederationDeniedError, SynapseError
@ -24,8 +25,10 @@ from synapse.http.servlet import parse_json_object_from_request
from synapse.http.site import SynapseRequest
from synapse.logging.context import run_in_background
from synapse.logging.opentracing import (
active_span,
set_tag,
span_context_from_request,
start_active_span,
start_active_span_follows_from,
whitelisted_homeserver,
)
@ -265,6 +268,7 @@ class BaseFederationServlet:
content = parse_json_object_from_request(request)
try:
with start_active_span("authenticate_request"):
origin: Optional[str] = await authenticator.authenticate_request(
request, content
)
@ -282,15 +286,30 @@ class BaseFederationServlet:
# update the active opentracing span with the authenticated entity
set_tag("authenticated_entity", origin)
# if the origin is authenticated and whitelisted, link to its span context
# if the origin is authenticated and whitelisted, use its span context
# as the parent.
context = None
if origin and whitelisted_homeserver(origin):
context = span_context_from_request(request)
if context:
servlet_span = active_span()
# a scope which uses the origin's context as a parent
processing_start_time = time.time()
scope = start_active_span_follows_from(
"incoming-federation-request", contexts=(context,) if context else ()
"incoming-federation-request",
child_of=context,
contexts=(servlet_span,),
start_time=processing_start_time,
)
else:
# just use our context as a parent
scope = start_active_span(
"incoming-federation-request",
)
try:
with scope:
if origin and self.RATELIMIT:
with ratelimiter.ratelimit(origin) as d:
@ -308,6 +327,16 @@ class BaseFederationServlet:
response = await func(
origin, content, request.args, *args, **kwargs
)
finally:
# if we used the origin's context as the parent, add a new span using
# the servlet span as a parent, so that we have a link
if context:
scope2 = start_active_span_follows_from(
"process-federation_request",
contexts=(scope.span,),
start_time=processing_start_time,
)
scope2.close()
return response

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@ -478,6 +478,8 @@ def start_active_span(
def start_active_span_follows_from(
operation_name: str,
contexts: Collection,
child_of=None,
start_time: Optional[float] = None,
*,
inherit_force_tracing=False,
tracer=None,
@ -487,6 +489,14 @@ def start_active_span_follows_from(
Args:
operation_name: name of the operation represented by the new span
contexts: the previous spans to inherit from
child_of: optionally override the parent span. If unset, the currently active
span will be the parent. (If there is no currently active span, the first
span in `contexts` will be the parent.)
start_time: optional override for the start time of the created span. Seconds
since the epoch.
inherit_force_tracing: if set, and any of the previous contexts have had tracing
forced, the new span will also have tracing forced.
tracer: override the opentracing tracer. By default the global tracer is used.
@ -497,7 +507,9 @@ def start_active_span_follows_from(
references = [opentracing.follows_from(context) for context in contexts]
scope = start_active_span(
operation_name,
child_of=child_of,
references=references,
start_time=start_time,
tracer=tracer,
)