I've been trying to figure out what the more generally accepted services for load testing are. I am trying to test functionality across a couple sites. I'd like to find out how many concurrent requests I can support, how many concurrent submissions I can support, etc. What are some commonly encountered tools/methodologies in Industry?
JMeter, or write your own load generation framework.
Mind the Network links, don't forget doing it within a Cloud provider's network boundary is not giving you the whole picture of how network traffic'll look like coming from the 'Net at large.
Generally, you're on the hook for the parallelization primitive (Director/worker/reaper/aggregator), and the test data generator/stager.
The actual runner itself is generally pretty dumb, and is just there to take it's chunk of the request load, and dump it's results.
Then you've got the results visualizer that consumes and aggregates everything.
People look at Performance testing/engineering as it's own specialty because you really have to take in everything as a whole. You can totally make a living out of just doing that.
It's surprisingly easy to slam a web service with a bunch of bots - I wrote a load generation tool for my engineering degree's honours thesis in a few weeks (and I wrote horrible code back then)
If JMeter or other off the shelf tools don't do what you need, writing your own load generator is the only other option. Fortunately, putting together a simple one is not that complicated.
Time spent learning JMeter is not time wasted. Figure out the parts that let you reuse scripts from code fragments - this is very valuable. It's also worthwhile to build complex scripts "by hand" a few times by clicking around - you will quickly learn where all the buttons are in the UI and how to translate back and forth between the UI controls and the XML fragments.
JMeter is great, as others have mentioned. If your task is simple enough and doesn’t require that request origins be distributed, you might be able to get away with (much less complex) Apache Bench.
Mind the Network links, don't forget doing it within a Cloud provider's network boundary is not giving you the whole picture of how network traffic'll look like coming from the 'Net at large.