Prior to this change, the publish API returns 200 in most of
the cases.
This change provides more insights to the publish result.
For single message publish endpoint (`publish/`):
HTTP error codes are:
200: Everything is OK
202: No subscriber for the topic
400: When mesage is invalid message.
e.g. bad topic name or QoS out of range.
503: Failed to dispatch the message. e.g. during EMQX restart.
The response body is a JSON object with two fields
`message_id`, and `publish_result`.
The `message_id` is a globally unique ID for tracing.
`publish_result` is `"OK"` when the message is delivered
to at least one subscriber.
Otherwise `"no_subscriber"`.
`publish_result` may also be some other informative
message to hint the failure result, the content of which
may change in the future.
For `publish/bulk` endpoint:
200: When all message in the bulk are published OK
202: If at least one message in the bulk had `"no_subscriber"` result
400: When mesage is invalid message. e.g. bad topic name or
QoS out of range.
503: When there is at least one message failed at dispatch.
The reply body is a list of JSON objects having the same layout
as for hte `publish` endpoint.
For takeover, there should be no message re-dispatch because
the messages will be retried by the new session.
For kick, messages should not be re-dispatched for security reason.
i.e. if admin has identified that there are malicious messages
stored in persisted sessions, killing the session should not
cause messages to be re-dispatched
1. The unit of `deliver_begin_at` is incorrectly used the `seconds`, the resulting is incorrect when `stats_type` is `internal` or `response`
2. The config update doesn't actually take effect, the `load` function always used the old config
This commit adds a rule engine configuration option for changing the
implementation module used for the rule engine function jq. The two
options are `jq_port` (uses Erlang port programs to interact with jq)
and `jq_nif` (uses an Erlang NIF library to interact with jq).
Thanks to @terry-xiaoyu (Xinyu Liu <506895667@qq.com>) for Chinese
translations
