In-memory key-value store in C, Go and Python

Re:In-memory key-value store in C, Go and Python by timtadh on Wednesday March 21, 2012 @01:06AM (#3733221)

Looking at the go version[1] I am not sure if will work as expected. Maps in go are not thread safe.[2] So it could be the go version is out performing the others do to the lack of synchronisation. There are several ways to fix this in go, the easiest might just be to use a mutex around the accesses to the cache. But it would probably be better to use a readers writers lock.

edit: (that said I am not sure if the C version is thread safe either I haven't read the docs for the hash table he is using.)

edit 2: (looks like the C version is not thread safe either).

[1] https://github.com/grahamking/Key-Value-Polyglot/blob/master...

[2] http://golang.org/doc/go_faq.html#atomic_maps

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Re:In-memory key-value store in C, Go and Python by jbarham on Wednesday March 21, 2012 @01:18AM (#3733244)

You're correct that updating a map from multiple goroutines without synchronizing is unsafe. But the overhead of using a RWMutex (http://weekly.golang.org/pkg/sync/#RWMutex) in this case should be negligible compared to the I/O code.

The big win is that Go allows you to write straightforward concurrent code but under the hood uses high-performance system calls like epoll.

EDIT: Here's a thread-safe version: https://github.com/jbarham/Key-Value-Polyglot/blob/master/me.... Still plenty fast.

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Re:In-memory key-value store in C, Go and Python by teejae on Wednesday March 21, 2012 @10:40AM (#3734580)

FYI, In the Go version, the lock can be added more simply, without the rw:

// Synchronize map access between multiple goroutines. type cache struct { m map[string]string sync.RWMutex }

Then, you can just use:

cache.Lock/Unlock/RLock/RUnlock directly. It's clearer. The beauty of Go's mixins.

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Re:In-memory key-value store in C, Go and Python by ootachi on Wednesday March 21, 2012 @12:07PM (#3734986)

So much for CSP, if you're using threads and shared state.

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