This has now been implemented so that the information is provided as part of the session information.
When querying for the session data, the output will contain the following:

$ curl admin:password@127.0.0.1:8989/v1/sessions/7

{

    "links": {

        "self": "http://127.0.0.1:8989/v1/sessions/7"

    },

   "data": {

...

        "attributes": {

...

            "queries": [

                {

                    "command": "COM_QUERY",

                    "statement": "select @@version_comment limit 1",

                    "received": "2018-11-07T11:28:22.133",

                    "completed": "2018-11-07T11:28:22.133",

                    "responses": [

                        {

                            "server": "Server2",

                            "duration": 0

                        }

                    ]

                },

...

}

where

• command denotes the protocol command,
• statement is present if the command is COM_QUERY,
• received shows the timestamp when MaxScale received the packet,
• completed is present and shows the timestamp, if MaxScale has received all responses from the servers (may be just one),
• responses is an array containing the individual server notes (may be just one), where server identifies the server and duration the time, expressed in milliseconds, it took before MaxScale received the response.

This information is available if retain_last_statements has been specified, either in the MaxScale global section or specifically for the service the session relates to.

The maxctrl command show sessions shows the last statements of the sessions, but not the details.

The feature can be turned on and off at runtime using maxctrl alter service. E.g.

maxctrl -u admin -p password alter service RWS retain_last_statements 5

The command above will cause new sessions related to the service RWS to retain the last 5 statements of the session. Existing sessions are not affected.