Thursday, March 25, 2010

Lusca update: important bug fixes, portability work

I've finally found and fixed two annoying bugs in Lusca.

The first is that occasionally the rebuild processed failed to properly rebuild the cache contents and the proxy would start with an empty cache. This ended up being due to the undocumented IPC code in Lusca, inherited from Squid, which would "eat" a few bytes at the beginning of the child process lifetime to establish whether the child was active and ready. It would try to read a hello string ("hi there!\n\0") but it would read 32 bytes instead of the exact string length. If the child process started sending data straight away (as my store rebuild helpers do!) the initial part of their conversation could be eaten.

The real fix is to modify the helper IPC handshake so it's two way and fixed length rather than the hacky way it's done now. But the temporary workaround seems to work fine - just read the 11 bytes for the hello string, rather than up to 32 bytes.

The second was a weird situation involving the swap.state files in the UFS store dirs growing to enormous sizes, filling the cache_dir up. This was eventually traced back to the proxy being reconfigured once a minute on some deployments (in this case - pfsense!). The problem was quite simple in the end - a reconfigure would force the swap state logs to be closed and re-opened; but this didn't know whether the swap state logs were pointing at the live ones or the rebuilding ones. In the latter, the rebuild process was reading from swap.state and appending to; a reconfigure would close the file and append to swap.state. This meant that the rebuild process was reading from swap.state and appending to - thus never quite finishing the rebuild process.

Those have been fixed for *NIX ports and now the rebuild processe seems to be moving forward quite swimmingly!

I've also had a user pop up recently who is submitting portability fixes for cygwin (and under Windows 7, no less!) I've been committing fixes to the way header files are included so the code mostly compiles under both *NIX and Cygwin. Admittedly most of those portability fixes were my fault - I didn't really bother making my new code "autoconf/automake safe" but, thankfully, revisiting this choice isn't difficult. Thankyou for the continuous assistance with the Cygwin changes!

Finally, there's still 46 currently active issues in the issue tracker. Some are just placeholders for me to revisit certain bits of code (eg Issue #85 - figuring out how PURGE works!) but I'm still aiming to address, repair and close the majority of those issues - and release a few more stable snapshots! - before I begin including more development stuff into the main tree.

Not that the snapshots at the moment are unstable - far from it!

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