CODEWITHSUNDEEP
google-app-engine
Bogdan Zurac
Bogdan Zurac

Reputation: 6451

Moving app to GAE

Context:

We have a web application written in Java EE on Glassfish + MySQL with JDBC for storage + XMPP connection for GCM CCS upstream messaging + Quartz scheduler library. Those are the main components of the app.

We're wrapping up our app development stage and we're trying to figure out the best option for deploying it, considering future scalability, both in number of users and their geographical location (ex, multiple VMS on multiple continents, if needed). Currently we're using a single VM instance from DigitalOcean for both the application server and the MySQL server, which we can then scale up with some effort (not much, but probably more than GAE).

Questions:

1) From what I understood, Cloud SQL is replicated in multiple datacenters across the world, thus storage-wise, the geographical scalability is assured. So this is a bonus. However, we would need to update the DB interaction code in the app to make use of Cloud SQL structure, thus being locked-in to their platform. Has this been a problem for you ? (I haven't looked at their DB interaction code yet, so I might be off on this one)

2) Do GAE instances work pretty much like a normal VM would ? Are there any differences regarding this aspect ? I've understood the auto-scaling capability, but how are they geographically scalable ? Do you have to select a datacenter location for each individual instance ? Or how can you achieve multiple worldwide instance locations as Cloud SQL does right out of the box ?

3) How would the XMPP connection fare with multiple instances ? Considering each instance is a separate VM, that means each instance will have a unique XMPP connection to the GCM CCS server. That would cause multiple problems, ex if more than 10 instances are being opened, then the 10 simultaneous XMPP connections limit cap will be hit.

4) How would the Quartz scheduler fare with the instances ? Right now we're saving the scheduled jobs in the MySQL database and scheduling them at each server start. If there are multiple instances, that means the jobs will be scheduled on each instance; so if there are multiple instances, the jobs will be scheduled multiple times. We wouldn't want that.

So, if indeed problems 3 & 4 are like I described, what would be the solution to those 2 problems ? Having a single instance for the XMPP connection as well as a single instance for the Quartz scheduler ?

Upvotes: 0

Views: 76

Answers (1)

DanielViveiros
DanielViveiros

Reputation: 179

1) Although CloudSQL is a managed replicated RDBMS, you still need to chose a region when creating an instance. That said, you cannot expect the latency to be great seamlessly globally. You would still need to design a proper architecture to achieve that.

2) GAE isn't a VM in any sense. GAP is a PaaS and, therefore, a runtime environment. You should expect several differences: you are restricted to Java, PHP, GO and Python, the mechanisms GAE provide do you out-of-the-box and compatible third-parties libraries. You cannot install a middleware there, for example. On the other hand, you don't have to deal with anything from the infrastructure standpoint, having transparent high-availability and scalability.

3) XMPP is not my strong suit, but GAE offers a XMPP service, you should take a look at it. More info: https://developers.google.com/appengine/docs/java/xmpp/?hl=pt-br

4) GAE offers a cron service that works pretty well. You wouldn't need to use Quartz.

My last advice is: if you want to migrate an existing application, your best choice would probably be GCE + CloudSQL, not GAE.

Good luck!

Cheers!

Upvotes: 2

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