Propagate opentracing contexts through EDUs (#5852)

Propagate opentracing contexts through EDUs
Co-Authored-By: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

changelog.d/5852.feature

@@ -0,0 +1 @@
+Pass opentracing contexts between servers when transmitting EDUs.

docs/opentracing.rst

@@ -32,7 +32,7 @@ It is up to the remote server to decide what it does with the spans
 it creates. This is called the sampling policy and it can be configured
 through Jaeger's settings.
 
-For OpenTracing concepts see 
+For OpenTracing concepts see
 https://opentracing.io/docs/overview/what-is-tracing/.
 
 For more information about Jaeger's implementation see
@@ -79,7 +79,7 @@ Homeserver whitelisting
 
 The homeserver whitelist is configured using regular expressions. A list of regular
 expressions can be given and their union will be compared when propagating any
-spans contexts to another homeserver. 
+spans contexts to another homeserver.
 
 Though it's mostly safe to send and receive span contexts to and from
 untrusted users since span contexts are usually opaque ids it can lead to
@@ -92,6 +92,29 @@ two problems, namely:
   but that doesn't prevent another server sending you baggage which will be logged
   to OpenTracing's logs.
 
+==========
+EDU FORMAT
+==========
+
+EDUs can contain tracing data in their content. This is not specced but
+it could be of interest for other homeservers.
+
+EDU format (if you're using jaeger):
+
+.. code-block:: json
+
+   {
+     "edu_type": "type",
+     "content": {
+       "org.matrix.opentracing_context": {
+         "uber-trace-id": "fe57cf3e65083289"
+       }
+     }
+   }
+
+Though you don't have to use jaeger you must inject the span context into
+`org.matrix.opentracing_context` using the opentracing `Format.TEXT_MAP` inject method.
+
 ==================
 Configuring Jaeger
 ==================

synapse/federation/federation_server.py

@@ -43,7 +43,7 @@
 from synapse.federation.units import Edu, Transaction
 from synapse.http.endpoint import parse_server_name
 from synapse.logging.context import nested_logging_context
-from synapse.logging.opentracing import log_kv, trace
+from synapse.logging.opentracing import log_kv, start_active_span_from_edu, trace
 from synapse.logging.utils import log_function
 from synapse.replication.http.federation import (
     ReplicationFederationSendEduRestServlet,
@@ -811,12 +811,13 @@ def on_edu(self, edu_type, origin, content):
         if not handler:
             logger.warn("No handler registered for EDU type %s", edu_type)
 
-        try:
-            yield handler(origin, content)
-        except SynapseError as e:
-            logger.info("Failed to handle edu %r: %r", edu_type, e)
-        except Exception:
-            logger.exception("Failed to handle edu %r", edu_type)
+        with start_active_span_from_edu(content, "handle_edu"):
+            try:
+                yield handler(origin, content)
+            except SynapseError as e:
+                logger.info("Failed to handle edu %r: %r", edu_type, e)
+            except Exception:
+                logger.exception("Failed to handle edu %r", edu_type)
 
     def on_query(self, query_type, args):
         handler = self.query_handlers.get(query_type)

synapse/federation/sender/transaction_manager.py

@@ -14,11 +14,19 @@
 # limitations under the License.
 import logging
 
+from canonicaljson import json
+
 from twisted.internet import defer
 
 from synapse.api.errors import HttpResponseException
 from synapse.federation.persistence import TransactionActions
 from synapse.federation.units import Transaction
+from synapse.logging.opentracing import (
+    extract_text_map,
+    set_tag,
+    start_active_span_follows_from,
+    tags,
+)
 from synapse.util.metrics import measure_func
 
 logger = logging.getLogger(__name__)
@@ -44,93 +52,109 @@ def __init__(self, hs):
     @defer.inlineCallbacks
     def send_new_transaction(self, destination, pending_pdus, pending_edus):
 
-        # Sort based on the order field
-        pending_pdus.sort(key=lambda t: t[1])
-        pdus = [x[0] for x in pending_pdus]
-        edus = pending_edus
+        # Make a transaction-sending opentracing span. This span follows on from
+        # all the edus in that transaction. This needs to be done since there is
+        # no active span here, so if the edus were not received by the remote the
+        # span would have no causality and it would be forgotten.
+        # The span_contexts is a generator so that it won't be evaluated if
+        # opentracing is disabled. (Yay speed!)
 
-        success = True
+        span_contexts = (
+            extract_text_map(json.loads(edu.get_context())) for edu in pending_edus
+        )
 
-        logger.debug("TX [%s] _attempt_new_transaction", destination)
+        with start_active_span_follows_from("send_transaction", span_contexts):
 
-        txn_id = str(self._next_txn_id)
+            # Sort based on the order field
+            pending_pdus.sort(key=lambda t: t[1])
+            pdus = [x[0] for x in pending_pdus]
+            edus = pending_edus
 
-        logger.debug(
-            "TX [%s] {%s} Attempting new transaction" " (pdus: %d, edus: %d)",
-            destination,
-            txn_id,
-            len(pdus),
-            len(edus),
-        )
+            success = True
 
-        transaction = Transaction.create_new(
-            origin_server_ts=int(self.clock.time_msec()),
-            transaction_id=txn_id,
-            origin=self._server_name,
-            destination=destination,
-            pdus=pdus,
-            edus=edus,
-        )
+            logger.debug("TX [%s] _attempt_new_transaction", destination)
 
-        self._next_txn_id += 1
+            txn_id = str(self._next_txn_id)
 
-        logger.info(
-            "TX [%s] {%s} Sending transaction [%s]," " (PDUs: %d, EDUs: %d)",
-            destination,
-            txn_id,
-            transaction.transaction_id,
-            len(pdus),
-            len(edus),
-        )
+            logger.debug(
+                "TX [%s] {%s} Attempting new transaction" " (pdus: %d, edus: %d)",
+                destination,
+                txn_id,
+                len(pdus),
+                len(edus),
+            )
 
-        # Actually send the transaction
-
-        # FIXME (erikj): This is a bit of a hack to make the Pdu age
-        # keys work
-        def json_data_cb():
-            data = transaction.get_dict()
-            now = int(self.clock.time_msec())
-            if "pdus" in data:
-                for p in data["pdus"]:
-                    if "age_ts" in p:
-                        unsigned = p.setdefault("unsigned", {})
-                        unsigned["age"] = now - int(p["age_ts"])
-                        del p["age_ts"]
-            return data
-
-        try:
-            response = yield self._transport_layer.send_transaction(
-                transaction, json_data_cb
+            transaction = Transaction.create_new(
+                origin_server_ts=int(self.clock.time_msec()),
+                transaction_id=txn_id,
+                origin=self._server_name,
+                destination=destination,
+                pdus=pdus,
+                edus=edus,
             )
-            code = 200
-        except HttpResponseException as e:
-            code = e.code
-            response = e.response
 
-            if e.code in (401, 404, 429) or 500 <= e.code:
-                logger.info("TX [%s] {%s} got %d response", destination, txn_id, code)
-                raise e
+            self._next_txn_id += 1
 
-        logger.info("TX [%s] {%s} got %d response", destination, txn_id, code)
+            logger.info(
+                "TX [%s] {%s} Sending transaction [%s]," " (PDUs: %d, EDUs: %d)",
+                destination,
+                txn_id,
+                transaction.transaction_id,
+                len(pdus),
+                len(edus),
+            )
 
-        if code == 200:
-            for e_id, r in response.get("pdus", {}).items():
-                if "error" in r:
+            # Actually send the transaction
+
+            # FIXME (erikj): This is a bit of a hack to make the Pdu age
+            # keys work
+            def json_data_cb():
+                data = transaction.get_dict()
+                now = int(self.clock.time_msec())
+                if "pdus" in data:
+                    for p in data["pdus"]:
+                        if "age_ts" in p:
+                            unsigned = p.setdefault("unsigned", {})
+                            unsigned["age"] = now - int(p["age_ts"])
+                            del p["age_ts"]
+                return data
+
+            try:
+                response = yield self._transport_layer.send_transaction(
+                    transaction, json_data_cb
+                )
+                code = 200
+            except HttpResponseException as e:
+                code = e.code
+                response = e.response
+
+                if e.code in (401, 404, 429) or 500 <= e.code:
+                    logger.info(
+                        "TX [%s] {%s} got %d response", destination, txn_id, code
+                    )
+                    raise e
+
+            logger.info("TX [%s] {%s} got %d response", destination, txn_id, code)
+
+            if code == 200:
+                for e_id, r in response.get("pdus", {}).items():
+                    if "error" in r:
+                        logger.warn(
+                            "TX [%s] {%s} Remote returned error for %s: %s",
+                            destination,
+                            txn_id,
+                            e_id,
+                            r,
+                        )
+            else:
+                for p in pdus:
                     logger.warn(
-                        "TX [%s] {%s} Remote returned error for %s: %s",
+                        "TX [%s] {%s} Failed to send event %s",
                         destination,
                         txn_id,
-                        e_id,
-                        r,
+                        p.event_id,
                     )
-        else:
-            for p in pdus:
-                logger.warn(
-                    "TX [%s] {%s} Failed to send event %s",
-                    destination,
-                    txn_id,
-                    p.event_id,
-                )
-            success = False
+                success = False
 
-        return success
+            set_tag(tags.ERROR, not success)
+            return success

synapse/federation/units.py

@@ -38,6 +38,9 @@ class Edu(JsonEncodedObject):
 
     internal_keys = ["origin", "destination"]
 
+    def get_context(self):
+        return getattr(self, "content", {}).get("org.matrix.opentracing_context", "{}")
+
 
 class Transaction(JsonEncodedObject):
     """ A transaction is a list of Pdus and Edus to be sent to a remote home

synapse/handlers/devicemessage.py

@@ -15,9 +15,17 @@
 
 import logging
 
+from canonicaljson import json
+
 from twisted.internet import defer
 
 from synapse.api.errors import SynapseError
+from synapse.logging.opentracing import (
+    get_active_span_text_map,
+    set_tag,
+    start_active_span,
+    whitelisted_homeserver,
+)
 from synapse.types import UserID, get_domain_from_id
 from synapse.util.stringutils import random_string
 
@@ -100,14 +108,21 @@ def send_device_message(self, sender_user_id, message_type, messages):
 
         message_id = random_string(16)
 
+        context = get_active_span_text_map()
+
         remote_edu_contents = {}
         for destination, messages in remote_messages.items():
-            remote_edu_contents[destination] = {
-                "messages": messages,
-                "sender": sender_user_id,
-                "type": message_type,
-                "message_id": message_id,
-            }
+            with start_active_span("to_device_for_user"):
+                set_tag("destination", destination)
+                remote_edu_contents[destination] = {
+                    "messages": messages,
+                    "sender": sender_user_id,
+                    "type": message_type,
+                    "message_id": message_id,
+                    "org.matrix.opentracing_context": json.dumps(context)
+                    if whitelisted_homeserver(destination)
+                    else None,
+                }
 
         stream_id = yield self.store.add_messages_to_device_inbox(
             local_messages, remote_edu_contents

synapse/logging/opentracing.py

@@ -149,6 +149,9 @@ def set_fates(clotho, lachesis, atropos, father="Zues", mother="Themis"):
 ``logging/opentracing.py`` has a ``whitelisted_homeserver`` method which takes
 in a destination and compares it to the whitelist.
 
+Most injection methods take a 'destination' arg. The context will only be injected
+if the destination matches the whitelist or the destination is None.
+
 =======
 Gotchas
 =======
@@ -576,6 +579,29 @@ def inject_active_span_text_map(carrier, destination, check_destination=True):
     )
 
 
+def get_active_span_text_map(destination=None):
+    """
+    Gets a span context as a dict. This can be used instead of manually
+    injecting a span into an empty carrier.
+
+    Args:
+        destination (str): the name of the remote server.
+
+    Returns:
+        dict: the active span's context if opentracing is enabled, otherwise empty.
+    """
+
+    if not opentracing or (destination and not whitelisted_homeserver(destination)):
+        return {}
+
+    carrier = {}
+    opentracing.tracer.inject(
+        opentracing.tracer.active_span, opentracing.Format.TEXT_MAP, carrier
+    )
+
+    return carrier
+
+
 def active_span_context_as_string():
     """
     Returns: