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:

9ce4a3d

* 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 <[email protected]>

* Outdated comment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

Author: JorikSchellekens

changelog.d/5544.misc

@@ -0,0 +1 @@
+Added opentracing and configuration options.

docs/sample_config.yaml

@@ -1395,3 +1395,20 @@ password_config:
 #  module: "my_custom_project.SuperRulesSet"
 #  config:
 #    example_option: 'things'
+
+
+## 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:
+#    - ".*"

synapse/app/_base.py

@@ -243,6 +243,9 @@ def handle_sighup(*args, **kwargs):
         # Load the certificate from disk.
         refresh_certificate(hs)
 
+        # Start the tracer
+        synapse.logging.opentracing.init_tracer(hs.config)
+
         # It is now safe to start your Synapse.
         hs.start_listening(listeners)
         hs.get_datastore().start_profiling()

synapse/config/homeserver.py

@@ -40,6 +40,7 @@
 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

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:
+        #    - ".*"
+        """

synapse/federation/transport/server.py

@@ -21,6 +21,7 @@
 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 @@ def new_func(request, *args, **kwargs):
                 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)
 

synapse/http/matrixfederationclient.py

@@ -36,6 +36,7 @@
 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 @@ def _send_request(
         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 @@ def _send_request(
                         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 @@ def _send_request(
                         _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

synapse/http/servlet.py

@@ -20,6 +20,7 @@
 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 @@ def register(self, http_server):
             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.")

synapse/logging/context.py

@@ -186,6 +186,7 @@ class LoggingContext(object):
         "alive",
         "request",
         "tag",
+        "scope",
     ]
 
     thread_local = threading.local()
@@ -238,6 +239,7 @@ def __init__(self, name=None, parent_context=None, request=None):
         self.request = None
         self.tag = ""
         self.alive = True
+        self.scope = None
 
         self.parent_context = parent_context
 
@@ -322,10 +324,12 @@ def copy_to(self, record):
         another LoggingContext
         """
 
-        # 'request' is the only field we currently use in the logger, so that's
-        # all we need to copy
+        # we track the current request
         record.request = self.request
 
+        # we also track the current scope:
+        record.scope = self.scope
+
     def start(self):
         if get_thread_id() != self.main_thread:
             logger.warning("Started logcontext %s on different thread", self)