On Wed, Dec 6, 2017 at 3:17 PM, Viet Nguyen <vnguyen@redhat.com> wrote:

Hi all,

TL;DR: Technically it's ALL-IN-ONE POD but make HawkularService an option aka "sidecar" container

I believe the 'sidecar' container concept is more used for when you have a main container and then a small container to add in some functionality (eg auth proxy, metric agent, etc)

In our case it would just be a pod with two containers which are tightly coupled.

Would our team also look at providing Prometheus (without HS) as the defacto choice for OpenShift?

For Hawkular Services, we will have our own Prometheus which is private to our needs. Someone will not be able to use our pod and optionally only use Prometheus from it.

What I'm proposing is still technically an ALL-IN-ONE pod option. However, instead of looking at (Prometheus + HS) as a monolithic solution we can position HS as an enhancement to the plain vanilla Prometheus. This add-on sidecar[1] approach can satisfy both Middleware users and non-middleware community users who may not necessarily need HawkularServices. Let's say I want to use library X and X only comes with X+Y (which will cost me CPU and RAM resources) I may be less inclined to use the library.

We are not entertaining this idea and conceptually its closer to having Hawkular Services as the main container and p8s as the side car container.

If someone wants middleware monitoring, they have to use our pod with Hawkular Services and p8s. Its important that we control how our own p8s instance works and to prevent someone from modifying it to their own purposes (it would be too difficult to handle all the different scenarios here).

If someone wants p8s for something other than middleware monitoring, then they will have to use a different p8s pod.

[1] more on "sidecar" containers
http://blog.kubernetes.io/2015/06/the-distributed-system-toolkit-patterns.html

Viet

----- Original Message -----
From: "Matthew Wringe" <mwringe@redhat.com>
To: "Discussions around Hawkular development" <hawkular-dev@lists.jboss.org>
Sent: Monday, November 27, 2017 7:38:50 AM
Subject: [Hawkular-dev] OpenShift Deployment

With the changes that are now going to include Prometheus, how do we want to deploy this in OpenShift?

We can have a few options:

ALL-IN-ONE CONTAINER
We put both Hawkular Services and Prometheus in the same container.

Pros:
- easy to deploy in plain docker (but this doesn't appear to be a usecase we are targetting anyways)
- shares the same network connection (even localhost) and ip address (eg but both services are on the different ports).
- Does't require any special wiring of components.
- Can share the same volume mount
- version of components can't get out of sync.

Cons:
- workflow doesn't work nicely. Docker containers are meant to only run a single application and running two can cause problems. Eg lifecycle events would become tricky and require some hacks to get around things.
- can't independently deploy things
- can't reuse or share any existing Prometheus docker containers.

ALL-IN-ONE POD
Hawkular Services and Prometheus are in their own containers, but they are both deployed within the same pod.

Pros:
- shares the same network connection.
- bound to the same machine (useful if sharing the same hostpath pv) and don' need to worry about external network configurations (eg firewalls between OpenShift nodes)
- pvs can be shared or separate.
- lifecycle events will work properly.

Cons:
- lifecycle hooks will mean that both containers will have to pass before either one will enter the ready state. So if Prometheus is failing for some reason, Hawkular Services will not be available under the service.
- cannot independently update one container. If we need to deploy a new container we will need to bring down the whole pod.
- are stuck with a 1:1 ratio between Hawkular Services and Prometheus

SEPARATE PODS
Hawkular Services and Prometheus have their own separate pods.

Pros:
- can independently run components and each component has its own separate lifecycle
- if in the future we want to cluster Hawkular Services. this will make it a lot easier and will also allow for running an n:m ratio between Hawkular Services and Prometheus
- probably the more 'correct' way to deploy things as we don't have a strong requirement for Hawkular Services and Prometheus to run together.

Cons:
- more complex wiring. We will need to have extra services and routes created to handle this. This mean more things running and more chances for things to go wrong. Also more things to configure
- reusing a PV between Hawkular Services and Prometheus could be more challenging (especially if we are using hostpath pvs). Updating the Prometheus scrape endpoint may require a new component and container.

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