From 70b33965065f0e93eaba68e371896149c9405f51 Mon Sep 17 00:00:00 2001 From: Eric Eastwood Date: Wed, 19 Oct 2022 15:39:43 -0500 Subject: [PATCH] Explain `SynapseError` and `FederationError` better (#14191) Explain `SynapseError` and `FederationError` better Spawning from https://github.com/matrix-org/synapse/pull/13816#discussion_r993262622 --- changelog.d/14191.doc | 1 + synapse/api/errors.py | 24 +++++++++++++++++++++--- synapse/federation/federation_server.py | 8 ++++++++ 3 files changed, 30 insertions(+), 3 deletions(-) create mode 100644 changelog.d/14191.doc diff --git a/changelog.d/14191.doc b/changelog.d/14191.doc new file mode 100644 index 000000000..6b0eeb1ae --- /dev/null +++ b/changelog.d/14191.doc @@ -0,0 +1 @@ +Update docstrings of `SynapseError` and `FederationError` to bettter describe what they are used for and the effects of using them are. diff --git a/synapse/api/errors.py b/synapse/api/errors.py index e0873b191..400dd12ab 100644 --- a/synapse/api/errors.py +++ b/synapse/api/errors.py @@ -155,7 +155,13 @@ class RedirectException(CodeMessageException): class SynapseError(CodeMessageException): """A base exception type for matrix errors which have an errcode and error - message (as well as an HTTP status code). + message (as well as an HTTP status code). These often bubble all the way up to the + client API response so the error code and status often reach the client directly as + defined here. If the error doesn't make sense to present to a client, then it + probably shouldn't be a `SynapseError`. For example, if we contact another + homeserver over federation, we shouldn't automatically ferry response errors back to + the client on our end (a 500 from a remote server does not make sense to a client + when our server did not experience a 500). Attributes: errcode: Matrix error code e.g 'M_FORBIDDEN' @@ -600,8 +606,20 @@ def cs_error(msg: str, code: str = Codes.UNKNOWN, **kwargs: Any) -> "JsonDict": class FederationError(RuntimeError): - """This class is used to inform remote homeservers about erroneous - PDUs they sent us. + """ + Raised when we process an erroneous PDU. + + There are two kinds of scenarios where this exception can be raised: + + 1. We may pull an invalid PDU from a remote homeserver (e.g. during backfill). We + raise this exception to signal an error to the rest of the application. + 2. We may be pushed an invalid PDU as part of a `/send` transaction from a remote + homeserver. We raise so that we can respond to the transaction and include the + error string in the "PDU Processing Result". The message which will likely be + ignored by the remote homeserver and is not machine parse-able since it's just a + string. + + TODO: In the future, we should split these usage scenarios into their own error types. FATAL: The remote server could not interpret the source event. (e.g., it was missing a required field) diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py index 28097664b..59e351595 100644 --- a/synapse/federation/federation_server.py +++ b/synapse/federation/federation_server.py @@ -481,6 +481,14 @@ class FederationServer(FederationBase): pdu_results[pdu.event_id] = await process_pdu(pdu) async def process_pdu(pdu: EventBase) -> JsonDict: + """ + Processes a pushed PDU sent to us via a `/send` transaction + + Returns: + JsonDict representing a "PDU Processing Result" that will be bundled up + with the other processed PDU's in the `/send` transaction and sent back + to remote homeserver. + """ event_id = pdu.event_id with nested_logging_context(event_id): try: