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 hjgt...@chello.nl wrote: On Tue, 12 Apr 2011 19:10:09 +0200, Gregory Collins g...@gregorycollins.net wrote: On Tue, Apr 12, 2011 at 6:40 PM, Jon Kristensen technol...@jonkristensen.com wrote: 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 -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- JP Moresmau http://jpmoresmau.blogspot.com/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] RFC: Extendable and Easy-To-Use Logger (HLogger)
On Tue, Apr 12, 2011 at 11:45 PM, Henk-Jan van Tuyl hjgt...@chello.nl wrote: 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. Yes, I suppose it would depend on your use case whether you wanted to optimize for throughput or for latency to secondary storage. I just know from experience that for high-throughput server applications, writing each message to disk is going to introduce unacceptable context-switching overhead. G -- Gregory Collins g...@gregorycollins.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] RFC: Extendable and Easy-To-Use Logger (HLogger)
Hello Haskellers! I have developed a very simple logging library to be extendable and easy-to-use. You can see the current release at http://hackage.haskell.org/package/hlogger/. The SimpleHLogger module is an example of what a HLogger implementation could look like. It could be used like this: import System.Log.SimpleHLogger main = do logger- simpleLogger test loggerLog logger (Just (LoggerTest, main)) Debug Test loggerStop logger 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: 1. Do you have any general/architectural thoughts on things I might be doing wrong? 2. Is the ease-of-use goal contradicting making this library useful in more complex applications? 3. Do I want to redesign HLogger to allow loggers to have a mutable state, and if so, how can I do that? 4. Is there a nice way to provide the module and the function than using (Just (LoggerTest, main)) (shortening it somehow, I guess)? Thanks! Warm regards, Jon Kristensen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] RFC: Extendable and Easy-To-Use Logger (HLogger)
On Tue, Apr 12, 2011 at 6:40 PM, Jon Kristensen technol...@jonkristensen.com wrote: 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. Is the ease-of-use goal contradicting making this library useful in more complex applications? Easy to use and high performance don't have to be contradictory, but you shouldn't neglect the latter. G -- Gregory Collins g...@gregorycollins.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] RFC: Extendable and Easy-To-Use Logger (HLogger)
On Tue, Apr 12, 2011 at 11:40 AM, Jon Kristensen technol...@jonkristensen.com wrote: Hello Haskellers! I have developed a very simple logging library to be extendable and easy-to-use. You can see the current release at http://hackage.haskell.org/package/hlogger/. The SimpleHLogger module is an example of what a HLogger implementation could look like. It could be used like this: import System.Log.SimpleHLogger main = do logger - simpleLogger test loggerLog logger (Just (LoggerTest, main)) Debug Test loggerStop logger 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: It looks very simple, which is nice. Just about the only things I would add: * A standard-out/standard-error logger * A monoid instance for the Logger type * Convinience functions for logging without context and logging at a specific error level: logError myLogger Oh no! logDebug myLogger a thing happened These might be in a separate module, so I can define them for myslef based on some logContext function, so that in my module I can define: logError msg = logContext Module.Name LogLevelError msg You might even be able to offer a separate package with TemplateHaskell splices to build these helpers. Maybe I'm going off the deep-end it terms of complexity. Have you looked into HsLogger at all? This project has a confusingly similar name - so much so I thought that your email was about HsLogger! Take care, Antoine Do you have any general/architectural thoughts on things I might be doing wrong? Is the ease-of-use goal contradicting making this library useful in more complex applications? Do I want to redesign HLogger to allow loggers to have a mutable state, and if so, how can I do that? Is there a nice way to provide the module and the function than using (Just (LoggerTest, main)) (shortening it somehow, I guess)? Thanks! Warm regards, Jon Kristensen ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] RFC: Extendable and Easy-To-Use Logger (HLogger)
On Tue, 12 Apr 2011 19:10:09 +0200, Gregory Collins g...@gregorycollins.net wrote: On Tue, Apr 12, 2011 at 6:40 PM, Jon Kristensen technol...@jonkristensen.com wrote: 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 -- ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
