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| garyng |
 Posted: Sat Aug 18, 2007 4:28 am |
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Joined: 15 Aug 2007
Posts: 7
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Hi,
Suppose I have 2 processes which shares the same socket(tcp_reader/tcp_writer) where the tcp_reader read the request from the socket then gen_server:cast() to tcp_writer to let it handle the sending.
So it is possible that tcp_writer may have a number of requests in the queue. Now if the reader process get a "shutdown" from the client, it would send a message to the writer and let it stop as well(to get in front of all the queued send request), after it has finished the one on hand.
If I implement the receive loop, I can use the timeout == 0 tricks but not sure how it should be done in gen_server. |
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| francesco |
| Posted: Mon Aug 20, 2007 7:20 am |
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Joined: 07 Jul 2006
Posts: 249
Location: London
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Unfortunately, OTP behaviors (Including gen_servers and FSMs) lack selective receives (And thereof priorities). The only way to solve the selective receive problem in a clean way is to implement your own behavior. (See Ulf Wiger's presentation at the EUC two years ago, http://www.erlang.se/euc/05/1500Wiger.ppt ) or search on selective receive in the search field on the bottom left.
To solve your problem, however, I would look into using exit signals and links, as that is the way it is usually solved.
If you want dirty workarounds for selective receives in gen_servers, let me know. It will however have to be after lunch, as I will loose my appetite 
Francesco
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http://www.erlang-consulting.com |
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| Jan Henry Nystrom |
| Posted: Mon Aug 20, 2007 8:13 am |
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Joined: 09 Oct 2006
Posts: 28
Location: Uppsala, Sweden
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garyng wrote: Hi,
[Snip]
If I implement the receive loop, I can use the timeout == 0 tricks but not sure how it should be done in gen_server.
Hi,
I hope you forgive the self promotion nature of this, but I have a generic server version that does the selective receive (fiendishly expensive which is was puts Francesco off his food). It will be presented at the Erlang Workshop in October with a discussion on general issues concerning selective receive. I will release the code on trap exit as soon as I have the time to write the proper documentation.
/Cheers Henry |
_________________
Jan Henry Nystrom
Training & Research Manager @ Erlang Training and Consulting Ltd
http://www.erlang-consulting.com |
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| garyng |
| Posted: Mon Aug 20, 2007 10:07 am |
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Joined: 15 Aug 2007
Posts: 7
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francesco wrote:
To solve your problem, however, I would look into using exit signals and links, as that is the way it is usually solved.
Can I have a pointer on how to do it that way ? |
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| number |
| Posted: Mon Jun 04, 2012 8:38 am |
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Joined: 04 Jun 2012
Posts: 18
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