You can set up autoscaling groups via terraform just fine, with a little bit of care taken to ensure that you trigger on the right metrics.
If anything mail is pretty much the easiest thing you can possibly pick to scale, because the inbound mail will be automatically retried. And haproxy in front of SMTP servers works just fine (really, any load balancer that can load balance raw TCP connections, but I've used haproxy to load balance thousands of messages a second).
For your user-facing side you need a bit more resiliency, but nothing stops you from using a service like SES to back a traditional setup for sending either. Reliably scaling outbound mail is the easy bit - the hard part is the reputation management that managed mail services provides, and no specific deployment mechanism will solve that.
Sure, but for heavy/bursty traffic, you can still have downtime while new VMs spin up. Retries might save you or they might make the problem worse, depending on the size and pattern of the burst and how your auto-scaling config interacts with the retry config of various hosts.
It may seem like a nitpick or something not worth worrying about, and for most that's probably the case. But for some businesses it could be a crucial difference. My point is simply that this is a legitimate benefit of serverless that wasn't mentioned above--I didn't think that would be a controversial point.
That is no different for serverless. You don't magically escape startup times - you need to carefully ensure that cold startup times are low enough, or that you maintain excess capacity to compensate.
The precise extent is different between different platforms depending on overheads, but that just means the point at which you need to trigger scaling is different.
You can find lots of descriptions of approaches people have taken to keep serverless instances running to avoid the cold start delays to work around this... For autoscaling groups you'd instead configure the alarm points used to trigger the scaling accordingly.
Serverless platforms tends to assume the startup will be fast enough to keep the connection open rather than return an error, but that is a load balancer config issue - you can set up retries and wait for other platforms too if it makes sense.
(Though for email this really does not matter - retries for all commonly used mail servers follow some form of exponential backoff up to many hours at least; retries works just fine in practice)
> That is no different for serverless. You don't magically escape startup times - you need to carefully ensure that cold startup times are low enough, or that you maintain excess capacity to compensate.
Serverless deployments are just another ladder step up the abstraction level, continuing the tradition that hardware doesn't matter. Similar to code compiled into assembly or a garbage collector managing memory. In the common cases, these cases are harmless (otherwise they wouldn't be popular), but they generally hide what's actually happening. Doing a garbage collection on a 200MB app is generally pretty snappy. But doing one on a 32GB server app can take seconds or minutes.
Abstractions like these are fine, as long as the limits of the abstraction are well understood. Sadly, that is rarely the case.
> Reliably scaling outbound mail is the easy bit - the hard part is the reputation management that managed mail services provides, and no specific deployment mechanism will solve that.
^this. if you want to send email its not hard....but if you want that mail to pass spam filters its a different problem altogether. hosted services like SES and mailgun will expose problems in how you are using emails (not handling bounces, not handling unsubscribes, etc) and in our case was very helpful.
If anything mail is pretty much the easiest thing you can possibly pick to scale, because the inbound mail will be automatically retried. And haproxy in front of SMTP servers works just fine (really, any load balancer that can load balance raw TCP connections, but I've used haproxy to load balance thousands of messages a second).
For your user-facing side you need a bit more resiliency, but nothing stops you from using a service like SES to back a traditional setup for sending either. Reliably scaling outbound mail is the easy bit - the hard part is the reputation management that managed mail services provides, and no specific deployment mechanism will solve that.