Hello CF,

Greetings from Huawei. Here is a quick idea that came up to our mind recently. Honestly we did not spend enormous time brainstorming this internally, but we thought we could go ahead and ask the community directly. It would be a great help to know if such an idea had already been considered and dropped by the community.

Proposal Motivations

The way health-check process is currently performed in cloud foundry is to run a command<https://github.com/cloudfoundry-incubator/healthcheck> periodically; if the exit status is non-zero then it is assumed that an application is non-responsive. We periodically repeat this process for all the applications. Which means that we actually scan the entire data center frequently to find one or few miss-behaving apps?



Why can’t we change the way health-check is done? Can it reflect the real-world? The hospitals don’t periodically scan the entire community looking for sick residents. Similarly, why can’t we report problems as and when they occur – just like the real-world?



How about a lightweight process that constantly monitors the application’s health and periodically reports in case an app is down or non-responsive etc. In a huge datacenter where thousands of apps are hosted, and each app has many instances. Wouldn’t it be better to make the individual app/container come and tell us(healthmanager) that there is a problem instead of scanning all of them? Push versus Pull model - Something like a babysitter residing within each container and taking care of the ‘app’ hosted by our customers.


How to accomplish this?
Our proposal is for BabySitter(BS) – an agent residing within each container optionally deployed using app-specific configuration. This agent sends out the collected metrics to health monitor in case of any anomaly – periodic time-series information etc. The agent should remember the configured threshold value that each app should not exceed; otherwise it triggers an alarm automatically to the health monitor in case of any threshold violations. The alarm even could be sent many times a second to the healthmonitor depending on the severity of the event, but the regular periodic ‘time-series’ information could be collected every second but sent once a minute to the HM. The challenge is design the application ‘bs’ as lightweight as possible.

This is our primary idea, we also thought it would make more sense if we club few more capabilities to babysitter like sshd (as a goroutine) and fileserver(as a goroutine) but before we bore you with all that details, we first want to understand what CF community thinks about this initial idea.

Thanks in advance,
Dhilip