When to use fibers and when to use co-routines in Tarantool?

Question

In Tarantool, are fibers used when the Lua code author wants Tarantool to schedule the execution? Are co-routines (in the Tarantool/LuaJIT process) used when the Lua code author wants to be in control of the execution?

In Tarantool, fibers are synonymous with coroutines. We suggest you always use our fibers, rather than Lua coroutines, since they are more powerful. Our entire I/O stack is integrated with them: sockets, files, net.box, mysql, postgresql, etc. — Kostja, Mar 22 '16 at 11:08
There are some tasks that coroutines could be used for, like iterators. It is perfectly valid to use both coroutines and fibers simultaneously but that may cause a confusion. Coroutine yield may fail with an infamous `attempt to yield across C-call boundary`, while fibers work in this situation. — Nick Zavaritsky, Mar 22 '16 at 11:45

score 6 · Accepted Answer · edited Mar 22 '16 at 17:39

6

In Tarantool, fibers are synonymous with coroutines. The fibers are more integrated to Tarantool I/O etc, you should use them instead of lua coroutines. We suggest you always use our fibers, rather than Lua coroutines, since they are more powerful. Our entire I/O stack is integrated with them: sockets, files, net.box, mysql, postgresql, etc.

Link to docs: http://tarantool.org/doc/reference/fiber.html

There are some tasks that coroutines could be used for, like iterators. It is perfectly valid to use both coroutines and fibers simultaneously but that may cause a confusion. Coroutine yield may fail with an infamous attempt to yield across C-call boundary, while fibers work in this situation.

edited Mar 22 '16 at 17:39

dgo.a

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answered Mar 22 '16 at 11:12

Vasiliy Soshnikov

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Thanks for the speedy reply. – dgo.a Mar 22 '16 at 11:33
Are there any other negative side-effects to look out for? – aleclarson Feb 10 '18 at 02:30

score 3 · Answer 2 · answered Feb 10 '18 at 06:51

Fiber stack is larger than one of a coroutine. It's mmapp'ed to 64KB, and is at least one OS page (4KB usually). Fiber context switching incurs extra overhead, since it hides/restores registers in addition to hiding/restoring the coroutine. Fiber context switches break JIT in LuaJIT, since LuaJIT is not able to hide/restore traced execution. Unlike coroutines, fibers work well with all non-blocking IO which is built into the application server: whenver a fiber yields implicitly on a IO call, another fiber kicks in. But not another coroutine, of course, you'll have to take care of this yourself if you're using them.

When to use fibers and when to use co-routines in Tarantool?

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