I would definitely think if the file is too large, it should be rolled more frequently. At least with log4j 1, you could set to roll not only daily, but half-day, and hourly (and maybe finer). That's the ideal way to handle this. Personally, I don't like the idea of writing directly to a compressed archive since, conceptually, it's not "archived" until it's closed; rather it should be compressed when it rolls over.
Cheers, Paul On Wed, May 28, 2014 at 12:55 PM, Ralph Goers <[email protected]> wrote: > So you are proposing writing two logs - one compressed and one > uncompressed - to handle this. I am wondering what the break-even point of > this would be. Many users use a size-base trigger instead so that a) the > compression won't take long and b) manipulating a large file is not so much > of a problem. > > What has me wondering about the usefulness of this is that when the file > gets so large that compression at rollover is a problem the file is > probably too large to manipulate effectively in something like vi. > > Ralph > > Sent from my iPad > > On May 28, 2014, at 10:27 AM, David Hoa <[email protected]> wrote: > > Yup, the tricky part would come on crash before close, interrupt, etc, > because I assume that that partially compressed file would be irrecoverable > (haven't verified this). Ideally, we'd be able to close it properly, but if > not, the log could, on startup, be recovered and compressed from the > parallel uncompressed log that was simultaneously being written by > another/the same appender. > > That would incur start up time to recover, which may be more acceptable in > the rare case of a crash. Else, if there's another compression technique > that leaves behind readable files even if not closed properly, that'd > eliminate the need for recovery. > > I'll open a jira ticket. Thanks for letting me share my thoughts on this. > > - David > > > On Wed, May 28, 2014 at 9:39 AM, Matt Sicker <[email protected]> wrote: > >> We can use GZIPOutputStream, DeflaterOutputStream, and ZipOutputStream >> all out of the box. >> >> What happens if you interrupt a stream in progress? No idea! But Gzip at >> least has CRC32 checksums on hand, so it can be detected if it's corrupted. >> We'll have to experiment a bit to see what really happens. I couldn't find >> anything in zlib.net's FAQ. >> >> >> On 28 May 2014 08:56, Ralph Goers <[email protected]> wrote: >> >>> What would happen to the file if the system crashed before the file is >>> closed? Would the file be able to be decompressed or would it be corrupted? >>> >>> Sent from my iPad >>> >>> On May 28, 2014, at 6:35 AM, Remko Popma <[email protected]> wrote: >>> >>> David, thank you for the clarification. I understand better what you are >>> trying to achieve now. >>> >>> Interesting idea to have an appender that writes to a GZipOutputStream. >>> Would you mind raising a Jira >>> <https://issues.apache.org/jira/browse/LOG4J2>ticket for that feature >>> request? >>> >>> I would certainly be interested in learning about efficient techniques >>> for compressing very large files. Not sure if or how the dd/direct I/O >>> mentioned in the blog you linked to could be leveraged from java. If you >>> find a way that works well for log file rollover, and you're interested in >>> sharing it, please let us know. >>> >>> >>> >>> On Wed, May 28, 2014 at 3:42 PM, David Hoa <[email protected]> wrote: >>> >>>> Hi Remko, >>>> >>>> My point about gzip, which we've experienced, is that compressing very >>>> large files (multi-GB) does have considerable impact on the system. The >>>> dd/direct I/O workaround avoid putting that much log data into your >>>> filesystem cache. For that problem, after I sent the email, I did look at >>>> the log4j2 implementation, and saw that in >>>> DefaultRolloverStrategy::rollover() it calls GZCompressionAction, so I see >>>> how I can write my own strategy and Action to customize how gzip is called. >>>> >>>> My second question was not about adding to existing gzip files; from >>>> what I know that's not possible. But if the GZipOutputStream is kept open >>>> and written to until closed by a rollover event, then the cost of gzipping >>>> is amortized over time rather than incurred when the rollover event gets >>>> triggered. The benefit is amortization of gzip so there's no resource usage >>>> spike; downside would be writing both compressed and uncompressed log files >>>> and maintaining rollover strategies for both of them. So a built in >>>> appender that wrote directly to gz files would be useful for this. >>>> >>>> Thanks, >>>> David >>>> >>>> >>>> On Tue, May 27, 2014 at 4:52 PM, Remko Popma <[email protected]>wrote: >>>> >>>>> Hi David, >>>>> >>>>> I read the blog post you linked to. It seems that the author was very, >>>>> very upset that a utility called cp only uses a 512 byte buffer. He then >>>>> goes on to praise gzip for having a 32KB buffer. >>>>> So just based on your link, gzip is actually pretty good. >>>>> >>>>> That said, there are plans to improve the file rollover mechanism. >>>>> These plans are currently spread out over a number of Jira tickets. One >>>>> existing request is to delete archived log files that are older than some >>>>> number of days. (https://issues.apache.org/jira/browse/LOG4J2-656, >>>>> https://issues.apache.org/jira/browse/LOG4J2-524 ) >>>>> This could be extended to cover your request to keep M compressed >>>>> files. >>>>> >>>>> I'm not sure about appending to existing gzip files. Why is this >>>>> desirable/What are you trying to accomplish with that? >>>>> >>>>> Sent from my iPhone >>>>> >>>>> On 2014/05/28, at 3:22, David Hoa <[email protected]> wrote: >>>>> >>>>> hi Log4j Dev, >>>>> >>>>> I am interested in the log rollover and compression feature in log4j2. >>>>> I read the documentation online, and still have some questions. >>>>> >>>>> - gzipping large files has performance impact on latencies/cpu/file >>>>> cache, and there's a workaround for that using dd and direct i/o. Is it >>>>> possible to customize how log4j2 gzips files (or does log4j2 already do >>>>> this)? See this link for a description of the common problem. >>>>> >>>>> http://kevinclosson.wordpress.com/2007/02/23/standard-file-utilities-with-direct-io/ >>>>> >>>>> - is it possible to use the existing appenders to output directly to >>>>> their final gzipped files, maintain M of those gzipped files, and >>>>> rollover/maintain N of the uncompressed logs? I suspect that the >>>>> complicated part would be in JVM crash recovery/ application restart. Any >>>>> suggestions on how best to add/extend/customize support for this? >>>>> >>>>> >>>>> Thanks, >>>>> David >>>>> >>>>> >>>>> >>>> >>> >> >> >> -- >> Matt Sicker <[email protected]> >> > >
