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Memcached – Architecture Questions to Autoscale Moodle on Google Cloud Platform

We’re setting up a Moodle for our LMS and we’re designing it to autoscale.

Here are the current stack specifications:

-Moodle Application (App + Data) baked into an image and launched into a Managed Instance Group

-Cloud SQL for database (MySQL 5.7 connected through Cloud SQL Proxy)

-Cloud Load Balancer – HTTPS load balancing with the managed instance group as backend + session affinity turned on

Questions:

  1. Do I still need Redis/Memcached for my session? Or is the load balancer session affinity enough?

  2. I’m thinking of using Cloud Filestore for the Data folder. Is this recommendable vs another Compute Engine?

  3. I’m more concerned of the session cache and content cache for future user increase. What would you recommend adding into the mix? Any advise on the CI/CD would also be helpful.

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2

Answers


  1. 0

    So, I can’t properly answer these questions without more information about your use case. Anyway, here’s my best 🙂

    1. How bad do you consider to be forcing the some users to re-login when a machine is taken down from the managed instance group? Related to this, how spiky you foresee your traffic will be? How many users will can a machine serve before forcing the autoscaler to kick in and more machines will be added or removed to/from the pool (ie, how dynamic do you think your app will need to be)? By answering these questions you should get an idea. Also, why not using Datastore/Firestore for user sessions? The few 10s of millisecond of latency shouldn’t compromise the snappy feeling of your app.

    2. Cloud Filestore uses NFS and you might hit some of the NFS idiosyncrasies. Will you be ok hitting and dealing with that? Also, what is an acceptable latency? How big is the blobs of data you will be saving? If they are small enough, you are very latency sensitive, and you want atomicity in the read/write operations you can go for Cloud BigTable. If latency is not that critical Google Cloud Storage can do it for you, but you also lose atomicity.

    3. Google Cloud CDN seems what you want, granted that you can set up headers correctly. It is a managed service so it has all the goodies without you lifting a finger and it’s cheap compared to serving stuff from your application/Google Cloud Storage/…

    4. Cloud Builder for seems the easy option, unless you want to support more advanced stuff that are not yet supported.

    Please provide more details so I can edit and focus my answer.

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  2. 0

    there is study for the autoscaling, using redis memory store show large network bandwidth from cache server, compare than compute engine with redis installed.
    moodle autoscaling on google cloud platform

    regarding moodle data, it show compute engine with NFS should have enough performance compare than filestore, much more expensive, as the speed also depend on the disk size.

    I use this topology for the implementation
    Autoscale Topology Moodle on GCP

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