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* Outdated comment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

2 files changed, 30 insertions, 5 deletions

diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py
index dee3710f68..e60334547e 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -36,6 +36,7 @@ from twisted.internet.task import _EPSILON, Cooperator
 from twisted.web._newclient import ResponseDone
 from twisted.web.http_headers import Headers
 
+import synapse.logging.opentracing as opentracing
 import synapse.metrics
 import synapse.util.retryutils
 from synapse.api.errors import (
@@ -339,9 +340,25 @@ class MatrixFederationHttpClient(object):
         else:
             query_bytes = b""
 
-        headers_dict = {b"User-Agent": [self.version_string_bytes]}
+        # Retreive current span
+        scope = opentracing.start_active_span(
+            "outgoing-federation-request",
+            tags={
+                opentracing.tags.SPAN_KIND: opentracing.tags.SPAN_KIND_RPC_CLIENT,
+                opentracing.tags.PEER_ADDRESS: request.destination,
+                opentracing.tags.HTTP_METHOD: request.method,
+                opentracing.tags.HTTP_URL: request.path,
+            },
+            finish_on_close=True,
+        )
+
+        # Inject the span into the headers
+        headers_dict = {}
+        opentracing.inject_active_span_byte_dict(headers_dict, request.destination)
 
-        with limiter:
+        headers_dict[b"User-Agent"] = [self.version_string_bytes]
+
+        with limiter, scope:
             # XXX: Would be much nicer to retry only at the transaction-layer
             # (once we have reliable transactions in place)
             if long_retries:
@@ -419,6 +436,10 @@ class MatrixFederationHttpClient(object):
                         response.phrase.decode("ascii", errors="replace"),
                     )
 
+                    opentracing.set_tag(
+                        opentracing.tags.HTTP_STATUS_CODE, response.code
+                    )
+
                     if 200 <= response.code < 300:
                         pass
                     else:
@@ -499,8 +520,7 @@ class MatrixFederationHttpClient(object):
                         _flatten_response_never_received(e),
                     )
                     raise
-
-            defer.returnValue(response)
+        defer.returnValue(response)
 
     def build_auth_headers(
         self, destination, method, url_bytes, content=None, destination_is=None
diff --git a/synapse/http/servlet.py b/synapse/http/servlet.py
index cd8415acd5..889038ff25 100644
--- a/synapse/http/servlet.py
+++ b/synapse/http/servlet.py
@@ -20,6 +20,7 @@ import logging
 from canonicaljson import json
 
 from synapse.api.errors import Codes, SynapseError
+from synapse.logging.opentracing import trace_servlet
 
 logger = logging.getLogger(__name__)
 
@@ -290,7 +291,11 @@ class RestServlet(object):
             for method in ("GET", "PUT", "POST", "OPTIONS", "DELETE"):
                 if hasattr(self, "on_%s" % (method,)):
                     method_handler = getattr(self, "on_%s" % (method,))
-                    http_server.register_paths(method, patterns, method_handler)
+                    http_server.register_paths(
+                        method,
+                        patterns,
+                        trace_servlet(self.__class__.__name__, method_handler),
+                    )
 
         else:
             raise NotImplementedError("RestServlet must register something.")