Our MongoDB driver creates a new temporary connection, for every active
connection, to just do a single heartbeat test. There is configurable
delay between every heartbeat test. When the user has an EMQX cluster
with a MongoDB bridge (to a MongoDB replica set), there will be a lot of
connections. Furthermore, as MongoDB creates a log entry every time a
new connection is created, the log will be flooded with info about new
connection. One user have reported more than 1MB of log data in a 10
minute period.
This commit tries to fix this by increasing the default delay between
heartbeats. A better fix would be to change the MongoDB driver so that
it does not create a new connection just to do a heartbeat check, but
this is more complicated so we leave this to the future. We might also
swap out the current MongoDB driver to something better.
Fixes:
https://github.com/emqx/emqx/issues/9851
Also hexencode non-utf8 binaries. This is essentially an heuristic.
We don't know column types in runtime, and there's no simple way
to find them out. Since we're already doing full binary scan during
escaping it should be cheap to bail out on non-utf8 strings and
hexencode them instead.
Also introduce separate function to highlight that this escaping
is MySQL-specific.
So that mysql client won't attempt to prepare them automatically, thus
trashing the server's prepared statements table and making interaction
overall heavier.
This fixes a crash with an error in the log file (see below) that
happened when the MongoDB authorization module queried the database. The
reason is that the collection name that was sent to the mongodb
connection was an atom. This is fixed by making sure it is not an atom.
2023-03-08T17:16:34.215523+01:00 [error] msg: query_mongo_error, mfa:
emqx_authz_mongodb:authorize/4, line: 95, peername: 127.0.0.1:53212,
clientid: client123, collection: mqtt_acl, filter: #{username =>
<<"emqx_u">>}, reason: {resource_error,#{msg => #{error =>
{error,{error_cannot_parse_response,{op_msg_response,#{<<"code">> =>
73,<<"codeName">> => <<"InvalidNamespace">>,<<"errmsg">> => <<"Failed to
parse namespace element">>,<<"ok">> => 0.0}}}},id =>
<<"emqx_authz_mongodb:3">>,name => call_query,request =>
{find,mqtt_acl,#{username => <<"emqx_u">>},#{}},stacktrace =>
[{mc_connection_man,reply,1,[{file,"mc_connection_man.erl"},{line,123}],
...]}, reason => exception}}, resource_id: <<"emqx_authz_mongodb:3">>
Fixes: https://github.com/emqx/emqx/issues/9783
