I recently found a discussion of programming languages on a MMORPG hobbyist bulletin board. Much of the lore there was garbled, revolving around old but persistent myths of the performance characteristics of C, C++, and Java. I thought I'd share some hard-won wisdom.
To first state my claim to bonafides in this realm. In real life I'm a cloud scale software architect at the senior executive level, meaning I've got a couple of decades' experience building really big commercial systems with bazillions of users. Plus I've got twenty years hands-on writing TriadCity, which I hope I can say without boasting is the most technologically sophisticated textual RPG to date. So here's the true dope.
Under super heavy load — truly massively multiplayer scale — Java has a slight advantage over other languages in scalability and perceived responsiveness because under load its garbage collection mechanism makes more efficient use of CPU cycles than hand-rolled memory management. Yes, I realize that contradicts the claims that many developers will make, but, it's not hard to understand. If you profile an Apache web server under very heavy stress, you'll find it spending a large percentage of its cycles calling malloc() and free(), where every call requires some number of CPU instructions. At its core it's just doing lots of String processing, but there you go: memory in, memory out, many many millions and millions of times once the load gets going. At some point, memory management will crowd business logic out of the processor, and perceived degradation is no longer graceful.
By contrast, Java allocates its heap in just one go, when its runtime initializes. Garbage collection is a background process and on multi-core systems does its thing pretty efficiently. CPU time can be dedicated to business logic instead of system overhead. This plus team productivity are the two reasons Java dominates the market for enterprise application servers.
To highlight some qualifiers. A well-designed and written system in C or C++ will outperform a badly designed one in Java. "Better" is contextual: do you care about throughput, latency, graceful degradation under stress, or some other criterion? Maybe you're super proficient in one language over another: use that one.
Note in general that OO languages are a better match for game servers than procedural ones. I started TriadCity in C back in the day because at that time I was more proficient in C, and there was plenty of open source C game code to model things on. But I found in practice that some of the concepts I wanted to express just didn't "feel" intuitive in C, and it became harder and harder to be productive in the code base once it got large enough. Switching to Java solved these problems because thinking in objects maps more intuitively to virtual world concepts; and because, at least in my experience, it's far easier to organize a very large OO code base for extensibility and maintainability. I recently read a different hobbyist RPG board where the lead developer of a very popular old-school MUD written in C complained about the effort required to implement a new character class. I'm pretty sure I can tell you why it was so rough for him. I don't think it would have been as much of a chore in TriadCity.
To underscore this point: OO code bases scale better. Today TriadCity has about 40,000 server-side classes. No, seriously. But I can find them all easily, because organizing OO code is straightforward, and Java's package concept helps. More importantly, thoughtful OO design insulates you against brittleness, enabling evolution. Adding that new character class would have been less daunting in an OO world.
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