websockets and mutli-threading

[Jonathan Berling]

I noticed that mg_websocket_write contains a comment that it's not thread safe. (Line 4195). What does this mean exactly? Does this mean that multiple threads cannot write to the same connection at the same time? Or does it mean that only one thread can write at any time, even if they are to different connections?

Thanks,

Jonathan

[Sergey Lyubka]

On Tue, Sep 24, 2013 at 5:46 PM, Jonathan Berling <jonbe...@gmail.com> wrote:

I noticed that mg_websocket_write contains a comment that it's not thread safe. (Line 4195). What does this mean exactly? Does this mean that multiple threads cannot write to the same connection at the same time? Or does it mean that only one thread can write at any time, even if they are to different connections?

For any given connection, only one thread should be writing to it.

Are you looking for broadcasting to all websocket connections?

 

Thanks,

Jonathan

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[Sergey Lyubka]

On Tue, Sep 24, 2013 at 6:03 PM, Sergey Lyubka <val...@gmail.com> wrote:

On Tue, Sep 24, 2013 at 5:46 PM, Jonathan Berling <jonbe...@gmail.com> wrote:

I noticed that mg_websocket_write contains a comment that it's not thread safe. (Line 4195). What does this mean exactly? Does this mean that multiple threads cannot write to the same connection at the same time? Or does it mean that only one thread can write at any time, even if they are to different connections?

For any given connection, only one thread should be writing to it.

That statement is ambiguous :-)  This is better: For any given connection, only one thread should be writing to it at any given time. That means, many threads could write into a given connection provided that writes are serialized by e.g. mutex lock.

[Jonathan Berling]

Thanks Sergey. That's what I wanted to know. I will have multiple
connections/threads, but no two threads will be writing to the same
connection at the same time. It sounds like my use case is supported.

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[Sergey Lyubka]

On Tue, Sep 24, 2013 at 6:59 PM, Jonathan Berling <jonbe...@gmail.com> wrote:

Thanks Sergey. That's what I wanted to know. I will have multiple
connections/threads, but no two threads will be writing to the same
connection at the same time. It sounds like my use case is supported.

Yes, your case is supported.

I was suggested to make mg_write and mg_read() thread-safe, I think this is a good thing to do.