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.

Best,
Amit

On Mon, Oct 5, 2015 at 10:09 AM, Curry, Matthew <Matt.Curry(a)allstate.com>
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.

Matt

From: Dhilip Kumar S <dhilip.kumar.s(a)huawei.com>
Reply-To: "Discussions about Cloud Foundry projects and the system
overall." <cf-dev(a)lists.cloudfoundry.org>
Date: Monday, October 5, 2015 at 9:31 AM
To: "Discussions about Cloud Foundry projects and the system overall." <
cf-dev(a)lists.cloudfoundry.org>
Cc: Vinay Murudi <vinaym(a)huawei.com>, Krishna M Kumar <
krishna.m.kumar(a)huawei.com>, Liangbiao <rexxar.liang(a)huawei.com>,
Srinivasch ch <srinivasch.ch(a)huawei.com>
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
<https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_cloudfoundry-2Dincubator_healthcheck&d=BQMGaQ&c=gtIjdLs6LnStUpy9cTOW9w&r=5uKsnIXwfJIxHSaCSaJzvcn90bBlYQuxsJhof4ERK-Q&m=8v-kDNCf3N_TGthtUze_YzZR4BADnwPZ9BiNHtzQnF4&s=MkllX3Km4FRjbvpC1QE02cQWP_QcCOE2qDv-UQCgytk&e=>
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