def is_cacheable_msg(msg: ForwardMsg) -> bool:
"""True if the given message qualifies for caching."""
if msg.WhichOneof("type") in {"ref_hash", "initialize"}:
# Some message types never get cached
return False
return msg.ByteSize() >= int(
config.get_option("global.minCachedMessageSize"))
def _send_message(self, session_info: SessionInfo, msg: ForwardMsg) -> None:
"""Send a message to a client.
If the client is likely to have already cached the message, we may
instead send a "reference" message that contains only the hash of the
message.
Parameters
----------
session_info : SessionInfo
The SessionInfo associated with websocket
msg : ForwardMsg
The message to send to the client
"""
msg.metadata.cacheable = is_cacheable_msg(msg)
msg_to_send = msg
if msg.metadata.cacheable:
populate_hash_if_needed(msg)
if self._message_cache.has_message_reference(
msg, session_info.session, session_info.report_run_count
):
# This session has probably cached this message. Send
# a reference instead.
LOGGER.debug("Sending cached message ref (hash=%s)" % msg.hash)
msg_to_send = create_reference_msg(msg)
# Cache the message so it can be referenced in the future.
# If the message is already cached, this will reset its
# age.
LOGGER.debug("Caching message (hash=%s)" % msg.hash)
self._message_cache.add_message(
msg, session_info.session, session_info.report_run_count
)
# If this was a `report_finished` message, we increment the
# report_run_count for this session, and update the cache
if (
msg.WhichOneof("type") == "report_finished"
and msg.report_finished == ForwardMsg.FINISHED_SUCCESSFULLY
):
LOGGER.debug(
"Report finished successfully; "
"removing expired entries from MessageCache "
"(max_age=%s)",
config.get_option("global.maxCachedMessageAge"),
)
session_info.report_run_count += 1
self._message_cache.remove_expired_session_entries(
session_info.session, session_info.report_run_count
)
# Ship it off!
if session_info.ws is not None:
session_info.ws.write_message(
serialize_forward_msg(msg_to_send), binary=True
)
