purge ===== The purge tool is a kind of magnifying glass into your squid-2 cache. You can use purge to have a look at what URLs are stored in which file within your cache. The purge tool can also be used to release objects which URLs match user specified regular expressions. A more troublesome feature is the ability to remove files squid does not seem to know about any longer. USE AT YOUR OWN RISK! NO GUARANTEES, WHATSOEVER! DON'T BLAME US! YOU HAVE BEEN WARNED! compilation =========== Purge has been successfully compiled under the following OSes: SYSTEM g++ native ------ --- ------ Solaris 2.7 yes CC IRIX 6.5 yes CC -n32 Linux 2.0.36 yes (g++ IS native) FreeBSD 4.x yes gmake port must be installed (g++ IS supported) The recent move of the Linux community towards glibc2 may cause some troubles, though. The compilation requires GNU make, no other make will work correctly. The source distribution contains all files checked into the revision control repository. Therefore, you will need to install GNU RCS first (which in turn needs the GNU diffutils). The repository also contains the prototypical Perl implementation. The user interface in the C++ implementation changed a little when compared to the Perl one. You will have to state at least one regular expression for purge to start working. Also, printing the complete cache URLs, you will need to specify the "-e ." regular expression. In order to compile the purge tool, untar the source distribution and change into the purge directory. With RCS and GNU make installed, just say "make". GNU make will automagically retrieve all necessary files from the repository and create the binary. Systems not stated above will need to retrieve the makefile (use "co -l Makefile" for this) and add their own platform specific definitions to section [2] in the makefile. squid preparation ================= In order to use purge for real PURGEs, you will have to enable this feature in squid. By default, PURGE is disabled. You should watch closely for whom you enable the PURGE ability, otherwise total stranger just might wipe your cache content. The following lines will need to be added to your squid.conf (you may want to add further networks to the src_local ACL): acl purge method PURGE acl src_local src 127.0.0.0/8 http_access allow purge src_local http_access deny purge Reconfigure or restart (preferred) your squid after changing the configuration file. modes of operation ================== Usage: purge [-a] [-c cf] [-d l] [-(f|F) fn | -(e|E) re] [-p h[:p]] [-P #] [-s] [-v] [-C dir [-H]] [-n] -a display a little rotating thingy to indicate that I am alive (tty only). -c c squid.conf location, default "/usr/local/squid/etc/squid.conf". -C dir base directory for content extraction (copy-out mode). -d l debug level, an OR of different debug options. -e re single regular expression per -e instance (use quotes!). -E re single case sensitive regular expression like -e. -f fn name of textfile containing one regular expression per line. -F fn name of textfile like -f containing case sensitive REs. -H prepend HTTP reply header to destination files in copy-out mode. -n do not fork() when using more than one cache_dir. -p h:p cache runs on host h and optional port p, default is localhost:3128. -P # if 0, just print matches; otherwise OR the following purge modes: 0x01 really send PURGE to the cache. 0x02 remove all caches files reported as 404 (not found). 0x04 remove all weird (inaccessible or too small) cache files. 0 and 1 are recommended - slow rebuild your cache with other modes. -s show all options after option parsing, but before really starting. -v show more information about the file, e.g. MD5, timestamps and flags. --- &< snip, snip --- -a is a kind of "i am alive" flag. It can only be activated, if your stdout is a tty. If active, it will display a little rotating line to indicate that there is actually something happening. You should not use this switch, if you capture your stdout in a file, or if your expression list produces many matches. The -a flag is also incompatible with the (default) multi cache_dir mode. default: off See also: -n -c cd CHANGED! this option lets you specify the location of the squid.conf file. Purge now understands about more than one cache_dir, and does so by parsing Squid's configuration file. It knows about both ways of Squid-2 cache_dir specifications, and will automatically try to use the correct one. default: /usr/local/squid/etc/squid.conf -C cd if you want to rescue files from your cache, you need to specify the directory into which the files will be copied. Please note that purge will try to establish the original server's directory structure. This switch also activates copy-out mode. Please do not use copy-out mode with any purge mode (-P) other than 0. For instance, if you specified "-C /tmp", Purge will try to recreate /tmp/www.server.1/url/path/file, and so forth. default: off See also: -H, -P -d l lets you specify a debug level. Differents bits are reserved for different output. default: 0 -e re the "-e" options let you specify one regular expression at the -E re commandline. This is useful, if there is only a handful you want to check. Please remember to escape the shell metachars used in your regular expression. The use of single quotes around your expression is recommended. The capital letter version works case sensitive, the lower caps version does not. default: (no default) -f fn if you have more than a handful of expression, or want to check -F fn the same set at regular intervals, the file option might be more useful to you. Each line in the text file will be regarded as one regular expression. Again, the capital letter version works case sensitive, the lower caps version does not. default: (no default) -H if in copy-out mode (see: -C), you can specify to keep the HTTP Header in the recreated file. default: off See also: -C -n by specifying the "-n" switch, you will tell Purge to process one cache_dir after another, instead of doing things in parallel. If you have more than one cache_dir in your configuration, Purge will fork off a worker process for each cache_dir to do the checks for optimum speed - assuming a decently designed cache. Since parallel execution will put quite some load on the system and its controllers, it is sometimes preferred to use less resources, though it will take longer. default: parallel mode for more than one cache_dir -p h[:p] Some cache admins (i.e. me) use a different port than 3128. The purge tool will need to connect to your cache in order to send the PURGE request (see -P). This option lets you specify the host and port to connect to. The port is optional. The port can be a name (check your /etc/services) or number. It is separated from the host name portion by a single colon, no spaces allowed. default: localhost:3128 -P # If you want to do more than just print your cache content, you will need to specify this option. Each bit is reserved for a different action. Only the use of the LSB is recommended, the rest should be considered experimental. no bit set: just print bit#0 set: send PURGE for matches bit#1 set: unlink object file for 404 not found PURGEs bit#2 set: unlink weird object files If you use a value other than 0 or 1, you will need to slow rebuild your cache content. A warning message will remind you of that. If you use bit#1, all unsuccessful PURGEs will result in the object file in your cache directory to be removed, because squid does not seem to know about it any longer. Beware that the asyncio might try to remove it after the purge tool, and thus complains bitterly. Bit#1 only makes sense, if Bit#0 is also set, otherwise it has no effect (since the HTTP status 404 is never returned). Bit#2 is reserved for strange files which do not even contain a URL. Beware that these files may indicate a new object squid currently intends to swap onto disk. If the file suddenly went away, or is removed when squid tries to fetch the object, it will complain bitterly. You must slow rebuild your cache, if you use this option. It is recommended that if you dare to use bit#1 or bit#2, you should only grant the purge tool access to your squid, e.g. move the HTTP and ICP listening port of squid to a different non-standard location during the purge. default: 0 (just print) -s If you specify this switch, all commandline parameters will be shown after they were parsed. default: off -v be verbose in the things reported about the file. See the output section below. output ====== In regular mode, the output of purge consists of four columns. If the URL contains not encoded whitespaces, it may look as if there are more columns, but the last one is the URI. # name meaning - ------ ----------------------------------------------------------- 1 file name of cache file eximed which matches the re. 2 status return result of purge request, " 0" in print mode. 3 size object size including stored headers, not file size. 4 uri perceived uri Example for non-verbose output in print-mode: /cache3/00/00/0000004A 0 5682 http://graphics.userfriendly.org/images/slovenia.gif In verbose mode, additional columns are inserted before the uri. Time stamps are reported using hexadecimal notation, and Squid's standard for reporting "no such timestamp" == -1, and "unparsable timestamp" == -2. # name meaning - ------ ----------------------------------------------------------- 1 file name of cache file eximed which matches the re. 2 status return result of purge request, " 0" in print mode "-P 0". 3 size object size including stored headers, not file size. 4 md5 MD5 of URI from file, or "(no_md5_data_available)" string. 5 ts UTC of Value of Date: header in hex notation 6 lr UTC of last time the object was referenced 7 ex UTC of Expires: header 8 lr UTC of Last-Modified: header 9 flags Value of objects flags field in hex, see: Programmers Guide 10 refcnt number of times the object was referenced. 11 uri STORE_META_URL uri or "strange_file" Example for verbose output in print-mode: /cache1/00/00/000000B7 0 406 7CFCB1D319F158ADC9CFD991BB8F6DCE 397d449b 39bf677b ffffffff 3820abfc 0460 1 http://www.netscape.com/images/nc_vera_tile.gif limitations =========== o Purge does not slow rebuild the cache for you. o It is still relatively slow, especially if your machine is low on memory and/or unable to hold all OS directory cache entries in main memory. o should never be used on "busy" caches with purge modes higher than 1. TODO ==== 1) use the stat() result on weird files to have a look at their ctime and mtime. If they are younger than, lets say 30 seconds, they were just created by squid and should not be removed. 2) Add a query before purging objects or removing files, and add another option to remove nagging for the experienced user. 3) The reported object size may be off by one.