Thanks, though from the slides & description (haven't had a chance to check video yet), it seems to be related to upgrades, rather than deployments, is that right? — Is deployment a supported use-case for crx2oak, or is it only for upgrades?
1 person found this helpful
The blue-green deployment pattern post by Martin Fowler simply forgot a single item: What happens when blue is under constant change by its users while you prepare green?
This is the problem with AEM, as your blue publishs are under constant change by authoring users. Oh, and don't forget that you have your single point of truth as well, the authoring instance. There you cannot apply this pattern at all, if you don't want to have a planned downtime for the time of the deployment.
My conclusion: You cannot apply the classical blue-green approach.
I normally do deployments in a way, that I use planned service downtimes on authoring, but none on publish.
- initiate service downtime on author
- deploy author
- remove 1st half of the publishing instances from loadbalancer, so that the 2nd half is serving all the requests.
- deploy 1st half of the publish instances
- switch loadbalancer, so the 1st half now servces all the requests
- deploy 2nd half
- bring all back online
This is a modified version of the blue-green approach: I don't have a standby instance which just changes roles with the production instance. But I have enough redundancy in the frontend that I am able to perform the deployment without downtime.
what I meant by Blue-Green in this case was to have a 'Blue' and a 'Green' author instance, one which is the live Production instance, and one acting as Pre-Prod. For example:
- Deploy new release to non-live servers (green), both author and publish.
- Enforce a content freeze on live author (blue).
- Run a synchronisation of content between live & non-live servers.
- Put green servers live, and set blue to non-live
- Lift the content freeze for authors.
In theory, this set-up is quite feasible, even with a changing author, if we can quickly sync the latest changes from Blue back to Green — a minimal content freeze can be tolerable, especially if outside of normal business hours.
I'm still not clear as to whether this is a supported use-case of the tooling though?
the approach sounds good, but the problem is indeed step 3. And unless you know a method, which can achieve this really quickly (that means 2 min at max) in 99% of all cases, I would doubt that this is doable.
Fast synchronization between AEM instances (especially if 1 instance is weeks behind) is hard; especially problematic is the versioning stuff, because the API prevents it to create the versioning nodes directly via JCR APi (you have to use the versioning API for it).
So yes, in theory it's possible. But I haven't seen it implemented yet :-)
Yeah, that's the trouble alright
We could keep them closer than weeks apart by pulling content back from Production (e.g. by using nightly disk-level back-ups of Prod to do a restore over Pre-Prod), but agree that the trouble is getting over the last hurdle alright!
kautuksahni, you've marked this answer as 'resolved', so could you clarify if the use of crx2oak against a running instance is a supported use of the tool, or if it can only be run against offline instances?