While setting up some machines to use one of Penn State’s NTP sources, I was curious where their master time source was located. After reading a bunch of NTP documentation, I came across the ntptrace utility:
$ ntptrace -dv clock.psu.edu
DoTransmit(128.118.25.3)
DoTransmit to 128.118.25.3
ReceiveBuf(128.118.25.3, 128.118.25.3)
server 128.118.25.3, port 123
stratum 16, precision -16, leap 00
refid otc1.psu.edu delay 0.05704, dispersion 0.00000 offset 233.148443
rootdelay 0.00020, rootdispersion 0.44749, synch dist 0.44759
reference time: c7acb55e.088e4755 Sun, Feb 26 2006 18:16:46.033
originate timestamp: c7acb95f.f156e264 Sun, Feb 26 2006 18:33:51.942
transmit timestamp: c7acb876.c4037000 Sun, Feb 26 2006 18:29:58.765
DoTransmit(128.118.25.5)
DoTransmit to 128.118.25.5
ReceiveBuf(128.118.25.5, 128.118.25.5)
server 128.118.25.5, port 123
stratum 1, precision -29, leap 00
refid 'WWV' delay 0.03889, dispersion 0.00000 offset 233.022950
rootdelay 0.00000, rootdispersion 0.22423, synch dist 0.22423
reference time: c7acb95d.72909aed Sun, Feb 26 2006 18:33:49.447
originate timestamp: c7acb95f.de6d04e6 Sun, Feb 26 2006 18:33:51.868
transmit timestamp: c7acb876.d3904000 Sun, Feb 26 2006 18:29:58.826
This nifty little utility will print the stratum for each source between the client and the master, and will also decode and print the contents of each NTP message (the NTP RFC describes how each timestamp is used to compute the offset ) it receives. This is some sweeeeet livin’!
If you happen to read my blog, you may have noticed that I dig alternative music. One day while searching for cool new alternative music, I stumbled across pandora.com. This nifty site provides a medium to connect people to music based on a variety of musical heuristics, and it works really really well. If you get some time, check them out! You won’t be sorry!
While chatting with a friend last week, he mentioned that he uses the apachectl restart option to get Apache to reread configuration files. This works, but it forcefully terminates all children (even ones processing requests), and can lead to user sessions getting blotched. As of Apache 1.3, you can now use the apachectl graceful option to gracefully restart a web server:
$ apachectl graceful
This utilizes the generation values in the Apache scoreboard, and allows each child to die once they complete the request processing loop. If you are interested in seeing how this is done, check out prefork.c in the Apache source code.
While reading up on website performance monitoring applications last week, I came across the cricket HTTP-performance module. HTTP-performance allows you to graph the time it takes to connect to a website and to render a page. This sounded interesting, so I decided to download and install cricket. After reading through the beginners guide, I installed all of the required Perl modules, and proceeded to run the cricket compile script:
$ ./compile
Can't load '/usr/perl5/5.8.4/lib/i86pc-solaris-64int/auto/DB_File/DB_File.so' for module DB_File: ld.so.1: /usr/perl5/5.8.4/bin/perl: fatal: libdb-4.2.so: open failed: No such file or
directory at /usr/perl5/5.8.4/lib/i86pc-solaris-64int/XSLoader.pm line 68.
at /usr/perl5/5.8.4/lib/i86pc-solaris-64int/DB_File.pm line 251
Compilation failed in require at /home/rmatteso/cricket-1.0.5/lib/ConfigTree/Node.pm line 25.
BEGIN failed--compilation aborted at /home/rmatteso/cricket-1.0.5/lib/ConfigTree/Node.pm line 25.
Compilation failed in require at ./compile line 39.
BEGIN failed--compilation aborted at ./compile line 39.I
Ack!!!! – it looks like DB_File.so can’t find the BerkelyDB shared library:
$ ldd
/usr/perl5/5.8.4/lib/i86pc-solaris-64int/auto/DB_File/DB_File.so**
libdb-4.2.so => (file not found)
libc.so.1 => /lib/libc.so.1
libm.so.2 => /lib/libm.so.2
Since I hate using LD_LIBRARY_PATH, I decided to adjust the link line to include a hard coded runtime path. To determine which variable to edit, I searched the Makefile until I came to the following line:
$ less Makefile
$ (LD) (LDDLFLAGS) (LDFROM) (OTHERLDFLAGS) -o @ (MYEXTLIB)
$ (PERL_ARCHIVE) \ (LDLOADLIBS) (PERL_ARCHIVE_AFTER)
$ (EXPORT_LIST) (INST_DYNAMIC_FIX)
After locating this line, I added “-R/usr/sfw/lib:/usr/local/BerkeleyDB/lib” to the LDDLFLAGS variable and rebuilt the Perl module:
$ make
cc -c -I/usr/local/BerkeleyDB/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_TS_ERR
NO -DVERSION="1.814" -DXS_VERSION="1.814" "-I/usr/perl5/5.8.4/lib/i86pc-solaris-64
int/CORE" -D_NOT_CORE -DmDB_Prefix_t=size_t -DmDB_Hash_t=u_int32_t version.c
cc -c -I/usr/local/BerkeleyDB/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_TS_ERR
NO -DVERSION="1.814" -DXS_VERSION="1.814" "-I/usr/perl5/5.8.4/lib/i86pc-solaris-64
int/CORE" -D_NOT_CORE -DmDB_Prefix_t=size_t -DmDB_Hash_t=u_int32_t DB_File.c
Running Mkbootstrap for DB_File ()
chmod 644 DB_File.bs
rm -f blib/arch/auto/DB_File/DB_File.so
LD_RUN_PATH="/usr/local/BerkeleyDB/lib"
cc -G -R/usr/sfw/lib:/usr/local/BerkeleyDB/lib version.o DB_File.o -o blib/arch/auto/DB_File/DB_File.so -L/usr/local/BerkeleyDB/lib -ldb
chmod 755 blib/arch/auto/DB_File/DB_File.so
cp DB_File.bs blib/arch/auto/DB_File/DB_File.bs
chmod 644 blib/arch/auto/DB_File/DB_File.bs
Manifying blib/man3/DB_File.3
$ make install
Installing /usr/perl5/5.8.4/lib/i86pc-solaris-64int/auto/DB_File/DB_File.so
Files found in blib/arch: installing files in blib/lib into architecture dependent library tree
Installing /usr/perl5/5.8.4/man/man3/DB_File.3
Writing /usr/perl5/5.8.4/lib/i86pc-solaris-64int/auto/DB_File/.packlist
Appending installation info to /usr/perl5/5.8.4/lib/i86pc-solaris-64int/perllocal.pod
Everything seemed to work, but did the runpath get set correctly? A quick check revealed that it did:
$ dump -Lv
/usr/perl5/5.8.4/lib/i86pc-solaris-64int/auto/DB_File/DB_File.so
/usr/perl5/5.8.4/lib/i86pc-solaris-64int/auto/DB_File/DB_File.so:
DYNAMIC SECTION INFORMATION
.dynamic:
[INDEX] Tag Value
[1] NEEDED libdb-4.2.so
[2] NEEDED libc.so.1
[3] INIT 0xe030
[4] FINI 0xe050
[5] RUNPATH /usr/sfw/lib:/usr/local/BerkeleyDB/lib
[6] RPATH /usr/sfw/lib:/usr/local/BerkeleyDB/lib
This was a fun experience, since it finally forced me to sit down and read through the ELF standard (great read if you are into that kind of stuff).
While perusing digg.com this week, I came across a link to numerous awesome lectures at Berkeley University. The lectures are given by professors at Berkeley, and include courses on Biology, Chemistry, Computer Science (the OS course is awesome), Economics, History, Physics and Electrical Engineering. Good stuff!