Network Latency and AWS

Network Latency and AWS

by Clarissa S -
Number of replies: 4

Hi, All: 

Let's start off with my current environment:

  • Moodle 3.1
  • AWS Installation 
  • C4.Large single server installation (I'll get into this)
  • Full site HTTPS with SSL offloading on the load balancer
  • We use Captivate to create our files and are utilizing SCORM packages
  • We have about 5,000 students, but if I had to take a shot in the dark, we probably currently     have a max of 50 students at a time taking the courses

We are trying to move to full site HTTPS, but while playing the courses you get the following error:

"The SCORM player has determined that your Internet connection is unreliable or has been interrupted. If you continue in this SCORM activity, your progress may not be saved. You should exit the activity now, and return when you have a dependable Internet connection"

I've read somewhere in the Moodle documentation that typically full site HTTPS is not recommended because of performance, but we're pretty determined to maintain full site HTTPS.

So as outlined above, we have a single server installation of Moodle...so our PostgreSQL database, moodledata folder, and code all sit on one server.  The C4.Large has 3.75GB of RAM and 2 VPUs with a dedicated bandwidth of 500Mbps.  The network engineer with the keys to AWS (I can't get access to true metrics) says that even during peak, our CPU is around 10% and our peak network is around 5Mbps.  He gives me nothing on RAM usage, probably because it's not a standard metric that is given and you have to write a script to get that metric...which I'm fairly confident he never did.  He insists that the problem is not the server as it is "lightly loaded" and is really, really against changing the architecture (let's ignore disaster recovery, fault tolerance, etc).  He is really convinced that we should be able to run this off of a T2.Micro (1GB of RAM, 1 VPU).

His solution is for us to stop using SCORM completely.  He insists that SCORM and Captivate are the reasons we are having network issues because of all of the "extra kludge" they inject into the HTML5.  While I may agree to an extent, surely we can't have the only installation that is trying to run full site HTTPS with SCORM packages that we created with Captivate.

My question is, are there others out there with full site HTTPS and SCORM on AWS?  What architecture do you have in AWS?  Ideally, I want to to use RDS for the database, and a separate instance for moodledata and break up that architecture for many, many reasons outside of just performance. Given what I outlined, do you think that getting rid of SCORM (which myself, and pretty much the rest of the rest of the team outside the one network engineer are against) will help at all?  If we broke up the architecture like I was looking to do, would that alleviate our problem?  Or would our best bet be to not encrypt our course files (sign-on only HTTPS)?

Thanks all!

Average of ratings: Useful (1)
In reply to Clarissa S

Re: Network Latency and AWS

by Howard Miller -
Picture of Core developers Picture of Documentation writers Picture of Particularly helpful Moodlers Picture of Peer reviewers Picture of Plugin developers

We (up until recently, but only for reasons of cost) had about 100 sites on AWS with zero issues. 

HTTPS performance (actually, disabling caching) is now a thing of the past. You can use that if you want. 

I'm very sceptical about your engineer's analysis. Unfortunately, there's not a whole lot else I can say. There are lots of potential reasons for a problematic network connection.

I always blame the package in the first instance. Have you made basic checks for Javascript errors et al?

Average of ratings: Useful (1)
In reply to Howard Miller

Re: Network Latency and AWS

by Clarissa S -

Thanks for the reply!

I agree.  I'm pretty skeptical about his assessment as well.  Just even looking at Moodle's documentation about how to prioritize resources (RAM > Disk > CPU) and he's not even looking into memory performance at all (just gave us CPU and network), I know we're not looking at the whole picture at all.  

Do your sites also have the single server installation that we are running, or do you have the more fragmented build that a lot of articles and I believe also Moodle's documentation recommends?  Are you also running SCORM packages? 

I haven't done javascript error checking yet.  I will definitely look into it.  

Thanks!

In reply to Clarissa S

Re: Network Latency and AWS

by Howard Miller -
Picture of Core developers Picture of Documentation writers Picture of Particularly helpful Moodlers Picture of Peer reviewers Picture of Plugin developers

We had a separate database but I can't see it making a huge amount of difference if you don't. 

In reply to Howard Miller

Re: Network Latency and AWS

by Santhosh Kumar T -

Hi, we have the same issue.

Similar setup like yours. The SSL certificate is provided by digicert. Let us know if you got around fixing it.


Thanks