Jan 20, 2022 jeff's Blog

An Important Upcoming Shutdown Effecting MIT App Inventor

MIT App Inventor relies on services running both on campus and in several cloud computing providers (Google, Amazon and IBM).

We distribute our services based on various factors, including cost. Our least costly services are those which we run on campus.

This coming weekend (January 22, 2022 - January 24, 2022) the computer room that we use on campus will be shutdown for some power infrastructure work.

Systems in that computer room that are not connected to an uninterruptible power supply (UPS) will be shutdown. Those connected to a UPS may stay up. Which is to say the official word is that they should stay up, but when I asked about a confidence level, the answer I received was “we have never done this before.”

Anticipating this shutdown, we will be moving critical services provided from this computer room into the cloud. Some services that are not critical and are difficult to move easily will remain down for the weekend.

The services that will not be available are mostly those needed by the developers of MIT App Inventor. People who use MIT App Inventor should not be effected. Report any issue in our Community Forum, which will not be effected and will be operational.

The Buildservers

One of the important services we run from on campus are our “Build Servers.” This is a set of largish systems, 21 in all, each with 8 CPU cores, that are used when folks instruct MIT App Inventor to package an Android application. Each buildserver can process 8 simultaneous builds.

On Friday, we will move this service to AWS. However, instead of 21 servers, we will only operate 9 both because it is a weekend and because large servers in AWS are not cheap. Of these 9, 3 will be normal instances and 6 will be what AWS calls “spot” instances. Spot instances are available at a significant discount, but are subject to being shutdown by AWS if the resources they are using are needed for regular instances (aka, people paying more!). We have done this in the past and have not had an issue. However, there is a risk that some or all of these spot instances may be shutdown, which will leave us with only 3 running buildservers, which may be enough to limp along, but some people may get the “buildserver busy” message when they attempt to package an app. We will be monitoring the situation throughout the weekend and will restart any spot instances that are shutdown. However, there are times when we will be sleeping, so monitoring may not be as close during the late evening and early morning on the east coast of the United States (GMT-5).