如何进行测试go例程？

Question

An example of this problem is when a user creates a resource and deletes a resource. We will perform the operation and also increment (decrement) a counter cache.

In testing, there is sometimes a race condition where the counter cache has not been updated by the go routine.

EDIT: Sorry about the confusion, to clarify: the counter cache is not in memory, it is actually a field in the database. The race condition is not to a variable in memory, it is actually that the goroutine might be slow to write into the database itself!

I currently use a 1 second sleep after the operation to ensure that the counter cache has been updated before testing the counter cache. Is there another way to test go routine without the arbitrary 1 second sleep to wait for the go routine to finish?

Cheers

Answer 1

In testing, there is sometimes a race condition where the counter cache has not been updated by the go routine. I currently use a 1 second sleep after the operation to ensure that the counter cache has been updated before testing the counter cache.

Yikes, I hate to say it, but you're doing it wrong. Go has first-class features to make concurrency easy! If you use them correctly, it's impossible to have race conditions.

In fact, there's a tool that will detect races for you. I'll bet it complains about your program.

One simple solution:

• Have the main routine create a goroutine for keeping track of the counter.
• the goroutine will just do a select and get a message to increment/decrement or read the counter. (If reading, it will be passed in a channel to return the number)
• when you create/delete resources, send an appropriate message to the goroutine counter via it's channel.
• when you want to read the counter, send a message for read, and then read the return channel.

(Another alternative would be to use locks. It would be a tiny bit more performant, but much more cumbersome to write and ensure it's correct.)