Add offset to console logs

https://blueprints.launchpad.net/nova/+spec/console-log-offset

In order to observe console logs from specified position we need to add new optional argument to console logs command that allows to list logs from specified position.

Problem description

When user triggers console-log command it gets all logs from the end. It might be not useful to get all log content when you observe your system activity and want to see logs about event that happened in the past. Scrolling thousands of lines might be annoying.

Use Cases

Operator wants to observe logs from specified offset.

Proposed change

Additional optional parameter offset should be added to handle the problem when operator want to show part of log.

Alternatives

An alternative would be to show all log all or specified amount of lines from tail and scroll up until you get what do you need.

Data model impact

None

REST API impact

The proposal will add new optional parameter ‘offset’ for request. This change will need bump in API microversion. In case of empty log or if log doesn’t contain this offset response should be empty.

Request:

URL:

/v2.1/{tenant_id}/servers/{server_id}/action

Method:

POST

JSON format:

{
    "os-getConsoleOutput": {
        "lines": 2,
        "offset": 10
    }
}

Response:

{
    "output": "ANOTHER\nLAST LINE"
}

Security impact

None

Notifications impact

None

Other end user impact

python nova client will be updated with new optional parameter to console-logs command. New command will looks like:

nova console-logs <instanced-id> –length 10 –offset 100

Performance Impact

Reduce amount of data transferred to python-novalcient.

Other deployer impact

None

Developer impact

None

Implementation

Assignee(s)

Primary assignee:

gstepanov

Work Items

• Update API microversion on getting console logs with offset parameter

• Update python-novaclient API by adding offset parameter

Dependencies

None

Testing

Would need new Tempest, functional and unit tests.

Documentation Impact

Docs needed for new API microversion and usage.

References

None