Hi Ajanthan,On Thu, Jul 11, 2013 at 4:33 PM, bala ajanthan <firstname.lastname@example.org> wrote:
Hi devs,I am not a LXC expert but like to share some thoughts.On Thu, Jul 11, 2013 at 2:19 PM, Lakmal Warusawithana <email@example.com> wrote:
In the current Stratos, cartridge run time is a VM. With this if we want to create a cartridge we have to do it for each and every IaaS that run Stratos. So cartridge creator have to spend lot of time on this. And it will be more costly when it comes to do a update of cartridges. We need to have a way to create universal cartridges.+1 for universal cartridges.But if the server (eg: wso2as) supports multi-tenancy already it is not good to spawn that server into some light weight container, rather we can spawn a vm(as it works in current model) or possibly LXC with more resource(we have to loose some i/o performance due to file system mounting). If the server is not multi-tenanted(eg:php) then we can spawn a container(lxc). This way we can optimize resource sharing and performance.
Again we can set this with the policy. If we want to run one cartridge process for VM, we can have in the policy.
The best option what I see is we can use LXC as Cartridge run time. Then when we create a LXC cartridge it will run on top of any IaaS, and only need Linux VM. Also it give more benefit like we can pack many cartridge runtime in single VM which give high utilization.Here if the implementation is abstracted(OS independent way) out such a way the container implementation is pluggable then we can run even .net cartridge also based on other implementation.
AFAIK there are no such OS independent way to have cartridge process. For windows based cartridge we can run one cartridge per VM based model.
Here auto scaling going to happen in two levels and it’s coupled with smart auto scaling policies, will discuss separate mail thread for what kind of auto scaling polices need for Stratos.
Here I have drow some sample scenarios. Before going into detail we need to get familiar with some terms
We can have partition for each cartridge type. For example we can have PHP Partition, Tomcat Partition ..etc. Partition may consist of one or many VM and this will come from policies. (will discuss in separate mail )
User can subscribe to cartridge with some unique alias, say subscription A
Cartridge Processes are runtime environment (LXC) of subscribed cartridge. For a one subscribed cartridge can have multiple Cartridge Processes depending on auto scaling policies.
To accomplish this, Stratos Cloud Controller (CC) need to expand to support LXC management. We need to have a cartridge store and it will store all Cartridges (LXC based images).So here we need a image registry.possible candidate may be Openstack galance. Docker has it own image registry.Yes we need to have a registry, but do not want to tie up with IaaS. It should work for all IaaSs.
Then CC can spin out Partition VM depending on policies associated with that cartridge type. A partition will have a CC LXC agent and for the first time it will copy relevant Cartridge images. When scaling request comes to CC it will communicate relevant Partition’s LXC agent and agent who is responsible for spinning up LXCs (Cartridge Processes).In addition to that the container can be showdown if there is no request for long time and we can start the container when there is a request.This way we can improve resource re-usage.We do not need to worry about the time to the first response hence the container boot up time is very minimal if we boot up the container(boot up a image snapshot. There is a way to save image like base image +changes using union file-system) without re initialize the cartridge.Yes it is another benefit that we can gain from LXC
So we need to implement this LXC agent (It should handle all LXC management). I am looking some help from expert who in the Apache Stratos community who may already worked on LXC. Maybe we can used existing open source tools. Docker  is one I found while doing some research.Consider warden also there they have abstracted out so that they were able to build a .net warden also.Thanks, will look into those.https://github.com/openstack/glance
Please share your expertise on this then we can finalize how we can implement this. We are in the process of organizing some google hangout sessions to conduct some technical discussion of Stratos and we can discuss this also in a hangout.
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