Re: [Proposal] Wanted a Babysitter for my applicatoin. ; -)


Thanks again Amit for the clarification on the executor part.

“The plan is that this can be solved within Diego's abstractions of tasks and LRPs”
Does this mean Diego will be capable of provisioning workloads other than garden-linux containers?

Ill add just one little point to clarify, but not pushing on the idea itself.

I should have been even more explicit When I mentioned HM, what I meant was the subsystem that was responsible for managing application’s health, I did not intend to point at HM9000 specifically. The idea was that the ‘babysitter’ should be able to fire up a HTTP POST to such a system automatically when any of its threshold value such as cpu, memory, disk exceeds, other times it simply collects and sends a consolidated metrics report once a minute.

Say for instance. A given app exceeds 90% CPU then the babysitter automatically sends the post message to a specified (discoverable endpoint).
Time: <time stamp>
Index: 3
CPU: 95
Mem: 50
Disk: 50


From: Amit Gupta [mailto:agupta(a)]
Sent: Tuesday, October 06, 2015 12:00 PM
To: Discussions about Cloud Foundry projects and the system overall.
Cc: Vinay Murudi; Krishna M Kumar; Liangbiao; Jianhui Zhou; Srinivasch ch
Subject: [cf-dev] Re: Re: Re: Re: [Proposal] Wanted a Babysitter for my applicatoin. ;-)

Hey Dhilip,

To clarify, we don't have a copy of executor for each garden-linux container. A single "cell" VM has one executor, one garden-linux, and many containers. The executor runs one monitor or "babysitter" process per each container.

What would be the benefit of running a monitor inside external systems which report to the HM? With Diego, there is no HM, so who exactly would it report to? And whatever it reports to, what can it do with that information? The Diego system components can take action when hearing about a failed container running in a Diego cell, it can schedule the process to be restarted, or whatever the right action may be given the crash restart policies. How can Diego or any Cloud Foundry component take action against an external system?

I think you highlight something valuable, that it would be nice for the platform to support running things other than apps, e.g. a MySQL database. The plan is that this can be solved within Diego's abstractions of tasks and LRPs, and it's true for perhaps most stateless non-app workloads, but things like databases are still hard, due to persistence being a hard problem. If you have not already seen it, Ted Young and Caleb Miles talk at the last CF Summit about this problem is a good one to watch:

Not all containers run sshd. Typically, the CC is responsible for requesting that an LRP have SSH access enabled, it's not conflated with Diego's responsibilities. It's also optional for the CC, users and space managers can opt to disable SSH (actually, I believe it's disabled by default).


On Mon, Oct 5, 2015 at 10:39 PM, Dhilip Kumar S <dhilip.kumar.s(a)<mailto:dhilip.kumar.s(a)>> wrote:
Hi All,

Thanks for the response.

Hi Amit,

Thanks for the info, I haven’t noticed that we run a copy of executor for each ‘garden-linux’ container that we launch. We do have a ‘push’ based container metrics collection and monitoring mechanism already in place then, In this case I can think of only the following benefits here.

1) This can become a unified health check approach as this binary can be packed within the container, it can even run inside a docker-container of an external system and keep pushing to a common HM. Or we could run this in the same VM as a My-SQL instance to get its health.

2) This can be a part of the SshD as we are running a daemon in every container anyways.

Ofcourse the original intention is to see if we could slightly alter the way diego’s monitoring/metrics collection works. If this is already implemented then I do not see a point perusing this idea.

Thanks for your time CF,

From: Amit Gupta [mailto:agupta(a)<mailto:agupta(a)>]
Sent: Tuesday, October 06, 2015 1:05 AM
To: Discussions about Cloud Foundry projects and the system overall.
Cc: Vinay Murudi; Krishna M Kumar; Liangbiao; Srinivasch ch
Subject: [cf-dev] Re: Re: [Proposal] Wanted a Babysitter for my applicatoin. ;-)

I'm not sure I see the benefit here.

Diego, for instance, runs a customizable babysitter alongside each app instance, and kills the container if the babysitter says things are going bad. This triggers an event that the system can react to, and the system also polls for container states because events can always be lost.

One thing to note is in this case, "the system" is the Executor, not HM9k (which doesn't exist in Diego), or the Converger (Diego's equivalent of HM9k), or Firehose or Cloud Controller which are very far removed from the container backend. In Diego, the pieces are loosely coupled, events/data in the system don't have to be sent through several layers of abstraction.


On Mon, Oct 5, 2015 at 10:09 AM, Curry, Matthew <Matt.Curry(a)<mailto:Matt.Curry(a)>> wrote:
We have been talking about something similar that we have labeled the Angry Farmer. I do not think you would need an agent. The firehose and cloud controller should have everything that you need. Also an agent does not give you the ability to really measure the performance of instances relative to each other which is a good indicator of bad state or performance.


From: Dhilip Kumar S <dhilip.kumar.s(a)<mailto:dhilip.kumar.s(a)>>
Reply-To: "Discussions about Cloud Foundry projects and the system overall." <cf-dev(a)<mailto:cf-dev(a)>>
Date: Monday, October 5, 2015 at 9:31 AM
To: "Discussions about Cloud Foundry projects and the system overall." <cf-dev(a)<mailto:cf-dev(a)>>
Cc: Vinay Murudi <vinaym(a)<mailto:vinaym(a)>>, Krishna M Kumar <krishna.m.kumar(a)<mailto:krishna.m.kumar(a)>>, Liangbiao <rexxar.liang(a)<mailto:rexxar.liang(a)>>, Srinivasch ch <<>>
Subject: [cf-dev] [Proposal] Wanted a Babysitter for my applicatoin. ;-)

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<> 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,

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