Re: [Haskell-cafe] RFC: Extendable and Easy-To-Use Logger (HLogger)

Jon, thanks for HLogger! For my (small) needs I was looking for a simple logging solution, and I couldn't get HSLogger to do what I wanted, whereas your simpleLogger fitted the bill perfectly. I suppose a good thing would be conditional buffering, as other noted: in development mode I want to get my log entries flushed to disk immediately, while in production I don't want to impact the performance of my running application by waiting for the logs. I didn't think that the invocations needed to be made easier: I just used "logNotice logger message", hard to do shorter. JP On Tue, Apr 12, 2011 at 11:45 PM, Henk-Jan van Tuyl wrote:

On Tue, 12 Apr 2011 19:10:09 +0200, Gregory Collins wrote:

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On Tue, Apr 12, 2011 at 6:40 PM, Jon Kristensen wrote:

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Hello Haskellers!

As I have now implemented everything that I could think of, I would like to ask the Haskell community to give some feedback on HLogger so that I can continuing improving it. Some questions:

Do you have any general/architectural thoughts on things I might be doing wrong?

1) Use "Text" as the string type, not "String"

2) Re: SimpleLogger: writing to and flushing the log file upon receiving each message is absolutely the wrong thing to do in high-performance code. Each write() is a context switch into the kernel, and doing it this way will kill your throughput (in messages per second). What we do in our webserver (which relies on high-throughput access logging) is to buffer messages to the log channel in memory, and perform the actual writes in a separate worker thread no more often than once every N seconds.

If you want to know what the last thing was that your application was doing, before it crashed (e.g. at the customers site), you better write every message immediately to disk.

Regards, Henk-Jan van Tuyl

-- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html --

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