[Hawkular-dev] OpenShift Deployment

[Viet Nguyen]

Hi all,

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

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

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.

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


Viet




----- Original Message -----
From: "Matthew Wringe" <mwringe at redhat.com>
To: "Discussions around Hawkular development" <hawkular-dev at 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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