Add basic opentracing support (#5544)

* Configure and initialise tracer

Includes config options for the tracer and sets up JaegerClient.

* Scope manager using LogContexts

We piggy-back our tracer scopes by using log context.
The current log context gives us the current scope. If new scope is
created we create a stack of scopes in the context.

* jaeger is a dependency now

* Carrier inject and extraction for Twisted Headers

* Trace federation requests on the way in and out.

The span is created in _started_processing and closed in
_finished_processing because we need a meaningful log context.

* Create logcontext for new scope.

Instead of having a stack of scopes in a logcontext we create a new
context for a new scope if the current logcontext already has a scope.

* Remove scope from logcontext if logcontext is top level

* Disable tracer if not configured

* typo

* Remove dependence on jaeger internals

* bools

* Set service name

* :Explicitely state that the tracer is disabled

* Black is the new black

* Newsfile

* Code style

* Use the new config setup.

* Generate config.

* Copyright

* Rename config to opentracing

* Remove user whitelisting

* Empty whitelist by default

* User ConfigError instead of RuntimeError

* Use isinstance

* Use tag constants for opentracing.

* Remove debug comment and no need to explicitely record error

* Two errors a "s(c)entry"

* Docstrings!

* Remove debugging brainslip

* Homeserver Whitlisting

* Better opentracing config comment

* linting

* Inclue worker name in service_name

* Make opentracing an optional dependency

* Neater config retreival

* Clean up dummy tags

* Instantiate tracing as object instead of global class

* Inlcude opentracing as a homeserver member.

* Thread opentracing to the request level

* Reference opetnracing through hs

* Instantiate dummy opentracin g for tests.

* About to revert, just keeping the unfinished changes just in case

* Revert back to global state, commit number:

9ce4a3d9067bf9889b86c360c05ac88618b85c4f

* Use class level methods in tracerutils

* Start and stop requests spans in a place where we
have access to the authenticated entity

* Seen it, isort it

* Make sure to close the active span.

* I'm getting black and blue from this.

* Logger formatting

Co-Authored-By: Erik Johnston <erik@matrix.org>

* Outdated comment

* Import opentracing at the top

* Return a contextmanager

* Start tracing client requests from the servlet

* Return noop context manager if not tracing

* Explicitely say that these are federation requests

* Include servlet name in client requests

* Use context manager

* Move opentracing to logging/

* Seen it, isort it again!

* Ignore twisted return exceptions on context exit

* Escape the scope

* Scopes should be entered to make them useful.

* Nicer decorator names

* Just one init, init?

* Don't need to close something that isn't open

* Docs make you smarter

synapse/federation/transport/server.py

@@ -21,6 +21,7 @@ import re
 from twisted.internet import defer
 
 import synapse
+import synapse.logging.opentracing as opentracing
 from synapse.api.errors import Codes, FederationDeniedError, SynapseError
 from synapse.api.room_versions import RoomVersions
 from synapse.api.urls import (
@@ -288,14 +289,29 @@ class BaseFederationServlet(object):
                 logger.warn("authenticate_request failed: %s", e)
                 raise
 
-            if origin:
-                with ratelimiter.ratelimit(origin) as d:
-                    yield d
+            # Start an opentracing span
+            with opentracing.start_active_span_from_context(
+                request.requestHeaders,
+                "incoming-federation-request",
+                tags={
+                    "request_id": request.get_request_id(),
+                    opentracing.tags.SPAN_KIND: opentracing.tags.SPAN_KIND_RPC_SERVER,
+                    opentracing.tags.HTTP_METHOD: request.get_method(),
+                    opentracing.tags.HTTP_URL: request.get_redacted_uri(),
+                    opentracing.tags.PEER_HOST_IPV6: request.getClientIP(),
+                    "authenticated_entity": origin,
+                },
+            ):
+                if origin:
+                    with ratelimiter.ratelimit(origin) as d:
+                        yield d
+                        response = yield func(
+                            origin, content, request.args, *args, **kwargs
+                        )
+                else:
                     response = yield func(
                         origin, content, request.args, *args, **kwargs
                     )
-            else:
-                response = yield func(origin, content, request.args, *args, **kwargs)
 
             defer.returnValue(response)