I'm asked to tune a long starting app into a short time period

Question

Hi,

I'm asked to shorten the start-up period of a long starting app, however I have also to obligate to my managers to the amount of time i will reduce the startup - something like 10-20 seconds.

As I'm new in my company I said I can obligate with timeframe of months (its a big server and I'm new and I plan to do lazy load + performance tuning).

That answer was not accepted I was required to do some kind of a cache to hold important data in another server and then when my server starts up it would reach all its data from that cache - I find it a kind of a workaround and I don't really like it. do you like it?

What do you think I should do?

PS when I profiled the app I saw many small issues that make the start-up long (like 2 minutes) it would not be a short process to fix all and to make lazy load.

Any kind of suggestions would help.

Language is Java.

Thanks

Answer 1

Rule one of performance optimisation: measure it. Get hard figures. At each stage of optimisation measure the performance gain/loss/lack of change. You (and your managers) are not in a position to say that a particular optimisation will or will not work before you try it and measure it. You can always ask to test & measure a solution before implementing it.

Rule two of performance optimisation (or anything really): choose your battles. Please bear in mind that your managers may be very experienced with the system in question, and may know the correct solution already; there may be other things (politics) involved as well, so don't put your position at risk by butting heads at this point.

Answer 2

I agree with MatthieuF. The most important thing to do is to measure it. Then you need to analyze the measurements to see which parts are most costly and also which resource (memory, CPU, network, etc) is the bottleneck.

If you know these answers you can propose solutions. You might be able to create small tests (proof of concepts) of your solution so you can report back early to your managers.

There can be all kind of solutions for example simply buying more hardware might be the best way to go. It's also possible that buying more hardware will have no results and you need to make modifications. The modifications can be optimizing the software, the database or other software. It might be to choose better algorithms, to introduce caching (in expense of more memory usage) or introduce multi threading to take advantage of multiple CPU cores. You can also make modifications to the "surroundings" of your application such as the configuration/version of your operating system, Java virtual machine, application server, database server and others. All of these components have settings which can affect the performance.

Again, it's very important to measure, identify the problem, think of a solution, build solution (maybe in proof of concept) and measure if solution is working. Don't fall in to the trap of first choosing a solution without knowing the problem.

Answer 3

It sounds to me as if you've come in at a relatively junior position, and your managers don't (yet) trust your abilities and judgment.

I don't understand why they would want you to commit to a particular speed-up without knowing if it was achievable.

• Maybe they really understand the code and its problems, and know that a certain level of speed-up is achievable. In this case, they should have a good idea how to do it ... so try and get them to tell you. Even if their ideas are not great, you will get credit for at least giving them a try.

• Maybe they are just trying to apply pressure (or pass on pressure applied to them) in order to get you to work harder. In this case, I'd probably give them a worth-while but conservative estimate. Then spend some time investigating the problems more thoroughly. And if after a few days research you find that your "off the cuff" estimates are significantly off the mark, go back to the managers with a more accurate estimate.

On the technical side, a two minute start-up times sounds rather excessive to me. What is the application doing in all that time? Loading data structures from files or a database? Recalculating things? Profiling may help answer some of these questions, but you also need to understand the system's architecture to make sens of the profile stats.

Without knowing what the real issues are here, I'd suggest trying to get the service to become available early while doing some of the less critical initialization in the background, or lazily. (And your managers' idea of caching some important data may turn out to be a good one, if viewed in this light.) Alternatively, I'd see if it was feasible to implement a "hot standby" for the system, or replicate it in such a way that allowed you to reduce startup times.