Hi Kazu,
2011/8/19 Kazu Yamamoto
Hello Simon,
if you're going for such a solution, then why not use difference lists or even better bytestring builders as your representation of the not-yet-flushed logging journal? Bytestring builders (from the blaze-builder library) support a fast append and fast serialization from a number of formats to bytestring.
Difference lists are not necessary at this moment because a list is generated at once in the apacheFormat:
http://hackage.haskell.org/packages/archive/wai-logger/0.0.0/doc/html/src/Ne...
If my understanding is correct, blaze-builder does not help hPutLogStr. What I want to do is directly copy ByteString or List to *Handle's buffer*.
http://hackage.haskell.org/packages/archive/wai-logger/0.0.0/doc/html/src/Ne...
I see. Currently, builders cannot be executed directly on a Handle's buffer. This is functionality I wanted to have for a long time, but have not gotten around to implement it. Using bytestring builders you could avoid creating the intermediate [LogStr] list. You should get a performance benefit, when describing your log-message directly as a mapping to a builder and executing this builder on the handle's buffer, as this avoids the indirections from the list- and the LogStr-cells. Copying the byteStrings directly also works for builders using the 'copyByteString' function. You would get a further performance benefit, if you could avoid creating intermediate String values. For example, the new builder in the bytestring library provides functions for the decimal encoding of numbers directly into the output buffer using a fast C-implementation. The development repository of the new bytestring builders is available here [1]. Its API is finished, benchmarks look good, and a documentation draft exists. Hence, it would be cheap to give it a go and see how fast you could produce the log-messages using the new bytestring builders. I'd use criterion to compare mapM_ yourLogMessageWriter logMessageList against whnf (L.length . toLazyByteString . mconcat . map builderLogMessageWriter) logMessageList where logMessageList :: [(ZonedDate, Request, Status, Maybe Integer)] logMessageList = replicate 10000 ( your-message-params) This should be a fair comparison, as both implementations work on similarly large buffers. If that shows that builders are beneficial, then we can think about implementing output on a Handle's buffer directly. best regards, Simon PS: The new bytestring builder will very likely be released with the next GHC in November. [1] https://github.com/meiersi/bytestring