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* Outdated comment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, 52 insertions, 0 deletions

diff --git a/synapse/config/homeserver.py b/synapse/config/homeserver.py
index acadef4fd3..72acad4f18 100644
--- a/synapse/config/homeserver.py
+++ b/synapse/config/homeserver.py
@@ -40,6 +40,7 @@ from .spam_checker import SpamCheckerConfig
 from .stats import StatsConfig
 from .third_party_event_rules import ThirdPartyRulesConfig
 from .tls import TlsConfig
+from .tracer import TracerConfig
 from .user_directory import UserDirectoryConfig
 from .voip import VoipConfig
 from .workers import WorkerConfig
@@ -75,5 +76,6 @@ class HomeServerConfig(
     ServerNoticesConfig,
     RoomDirectoryConfig,
     ThirdPartyRulesConfig,
+    TracerConfig,
 ):
     pass
diff --git a/synapse/config/tracer.py b/synapse/config/tracer.py
new file mode 100644
index 0000000000..63a637984a
--- /dev/null
+++ b/synapse/config/tracer.py
@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 The Matrix.org Foundation C.I.C.d
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from ._base import Config, ConfigError
+
+
+class TracerConfig(Config):
+    def read_config(self, config, **kwargs):
+        self.tracer_config = config.get("opentracing")
+
+        self.tracer_config = config.get("opentracing", {"tracer_enabled": False})
+
+        if self.tracer_config.get("tracer_enabled", False):
+            # The tracer is enabled so sanitize the config
+            # If no whitelists are given
+            self.tracer_config.setdefault("homeserver_whitelist", [])
+
+            if not isinstance(self.tracer_config.get("homeserver_whitelist"), list):
+                raise ConfigError("Tracer homesererver_whitelist config is malformed")
+
+    def generate_config_section(cls, **kwargs):
+        return """\
+        ## Opentracing ##
+        # These settings enable opentracing which implements distributed tracing
+        # This allows you to observe the causal chain of events across servers
+        # including requests, key lookups etc. across any server running
+        # synapse or any other other services which supports opentracing.
+        # (specifically those implemented with jaeger)
+
+        #opentracing:
+        #  # Enable / disable tracer
+        #  tracer_enabled: false
+        #  # The list of homeservers we wish to expose our current traces to.
+        #  # The list is a list of regexes which are matched against the
+        #  # servername of the homeserver
+        #  homeserver_whitelist:
+        #    - ".*"
+        """