Going with the all-in-one pod approach, there is also the question of how many volumes we want to use.

We can have everything in one volume with multiple directories (eg /p8s, /hawkular-inventory, etc). This would make it easier to install as we only have to have one directory to deal with.

Of we could have multiple volumes, one for Hawkular Services and one for Prometheus. This might give us some more flexibility in the future, but I can't see why we would need this extra complexity at the moment.

Any thoughts on this? Or maybe some perspective I am missing?

On Mon, Dec 4, 2017 at 5:35 AM, Thomas Heute <theute@redhat.com> wrote:

+1

On Thu, Nov 30, 2017 at 2:56 PM, Matthew Wringe <mwringe@redhat.com> wrote:

Yeah, I think we should go with the all-in-one pod approach for now. If we discover certain use cases that wont work properly we can re-evaluate. 

On Thu, Nov 30, 2017 at 5:15 AM, Lucas Ponce <lponce@redhat.com> wrote:

On Thu, Nov 30, 2017 at 10:55 AM, Lucas Ponce <lponce@redhat.com> wrote:

On Mon, Nov 27, 2017 at 4:38 PM, Matthew Wringe <mwringe@redhat.com> wrote:

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

One technical requeriment is that Hawkular Services needs to now where is Prometheus server at initialization.

 

One technical requeriment is that Hawkular Services needs to *know* where is Prometheus server at initialization.

[Sorry, typing fast]

So, I guess that all-in-one pod will simplify things on this case.

I would start with this architecture first and harden the basic scenarios.

 

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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