A working Posix thread library is needed for the server. On Solaris 2.5 we use SUN PThreads (the native thread support in 2.4 and earlier versions are not good enough) and on Linux we use LinuxThreads by Xavier Leroy, Xavier.Leroy@inria.fr.
The hard part of porting to a new Unix variant without good native thread support is probably to port MIT-pthreads. See `mit-pthreads/README' and Programming POSIX Threads.
The MySQL distribution includes a patched version of Provenzano's Pthreads from MIT (see MIT Pthreads web page). This can be used for some operating systems that do not have POSIX threads.
It is also possible to use another user level thread package named FSU Pthreads (see FSU pthread home page). This implementation is being used for the SCO port.
See the `thr_lock.c' and `thr_alarm.c' programs in the `mysys' directory for some tests/examples of these problems.
Both the server and the client need a working C++ compiler (we use gcc
and have tried SparcWorks). Another compiler that is known to work is the
IRIX cc.
To compile only the client use ./configure --without-server.
There is currently no support for only compiling the server. Nor is it likly to be added unless someone has a good reason for it.
If you want/need to change any `Makefile' or the configure script you must
get Automake and Autoconf. We have used the automake-1.2 and
autoconf-2.12 distributions.
All steps needed to remake everything from the most basic files.
/bin/rm */.deps/*.P /bin/rm -f config.cache aclocal autoheader aclocal automake autoconf ./configure --with-debug --prefix='your installation directory' # The makefiles generated above need GNU make 3.75 or newer. # (called gmake below) gmake clean all install init-db
If you run into problems with a new port, you may have to do some debugging of MySQL! See section 19.10 Debugging MySQL.
NOTE: Before you start debugging mysqld, first get the test
programs mysys/thr_alarm and mysys/thr_lock to work. This
will ensure that your thread installation has even a remote chance to work!
If you have some very specific problem, you can always try to debug
MySQL. To do this you must configure MySQL with the
option --with-debug. You can check whether or not
MySQL was compiled with debugging by doing: mysqld
--help. If the --debug flag is listed with the options then you
have debugging enabled. mysqladmin ver also lists the
mysqld version as mysql ... -debug in this case.
If you are using gcc or egcs, the recommended configure line is:
CC=gcc CFLAGS="-O6" CXX=gcc CXXFLAGS="-O6 -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --with-debug
This will avoid problems with the libstdc++ library and with C++ exceptions.
If you can cause the mysqld server to crash quickly, you can try to
create a trace file of this:
Start the mysqld server with a trace log in `/tmp/mysql.trace'.
The log file will get very BIG.
mysqld --debug --log
or you can start it with
mysqld --debug=d,info,error,query,general,where:O,/tmp/mysql.trace
which only prints information with the most interesting tags.
When you configure MySQL for debugging you automatically enable a
lot of extra safety check functions that monitor the health of mysqld.
If they find something "unexpected," an entry will be written to
stderr, which safe_mysqld directs to the error log! This also
means that if you are having some unexpected problems with MySQL and
are using a source distribution, the first thing you should do is to
configure MySQL for debugging! (The second thing, of course, is to
send mail to mysql@tcx.se and ask for help. Please use the
mysqlbug script for all bug reports or questions regarding the
MySQL version you are using!
On most system you can also start mysqld from gdb to get
more information if mysqld crashes.
shell> gdb /usr/local/libexec/mysqld gdb> run ... back # Do this when mysqld crashes info locals up info locals up ... (until you get some information about local variables) quit
On Linux you must use run --one-thread if you want to be able to
debug mysqld threads. In this case you can only have one thread
active at a time.
Include the above output in a mail generated with mysqlbug and
mail this to mysql@tcx.se.
If mysqld hangs you can try to use some system tools like
strace or /usr/proc/bin/pstack to examine where
mysqld has hanged.
If mysqld starts to eat up CPU or memory or if it "hangs", you
can use mysqladmin processlist status to find out if someone is
executing some query that takes a long time. It may be a good idea to
run mysqladmin -i10 processlist status in some window if you are
experiencing performance problems.
If mysqld dies or hangs, you should start mysqld with
--log. When mysqld dies again, you can check in the log file
for the query that killed mysqld. Note that before starting
mysqld with --log you should check all your tables with
isamchk. See section 13 Using isamchk for table maintenance and crash recovery.
If you are using a log file, mysqld --log, you should check the
'hostname' log files, that you can find in the database directory, for
any queries that could cause a problem. Try the command EXPLAIN
on all SELECT statements that takes a long time to ensure that
mysqld are using indexes properly. See section 7.21 EXPLAIN syntax (Get information about a SELECT). You should also test
complicated queries that didn't complete within the mysql command
line tool.
If you find the text mysqld restarted in the error log file
(normally named `hostname.err') you have probably found a query
that causes mysqld to fail. If this happens you should check all
your tables with isamchk (see section 13 Using isamchk for table maintenance and crash recovery), and test the
queries in the MySQL log files if someone doesn't work. If you
find such a query, try first upgrading to the newest MySQL
version. If this doesn't help and you can't find anything in the
mysql mail archive, you should report the bug to
online MySQL documentation
page.
If you get corrupted tables or if mysqld always fails after some
update commands, you can test if this bug is reproducible by doing the
following:
mysqladmin shutdown)
isamchk -s database/*.ISM. Repair any
wrong tables with isamchk -r database/table.ISM.
mysqld with --log-update
mysqld server.
mysqld server without --log-update
mysql < update-log. The update log
is saved in the MySQL database directory with the name
your-hostname.#.
ISAM code! ftp the tables + the update log to
ftp://www.mysql.com/pub/mysql/secret and we will fix this as soon as
possible!
The command mysqladmin debug will dump some information about
locks in use, used memory and query usage to the mysql log file. This
may help solve some problems. This command also provides some useful
information even if you haven't compiled MySQL for debugging!
If the problem is that some tables are getting slower and slower you
should try to repair the tables with isamchk to optimize the
table layout. You should also check the slow queries with EXPLAIN.
See section 13 Using isamchk for table maintenance and crash recovery.
You should also read the OS-specific section in this manual for problems that may be unique to your environment. See section 4.11 System-specific notes
I have tried to use the RTS thread packages with MySQL but stumbled on the following problems:
They use old version of a lot of POSIX calls and it is very tedious to make wrappers for all functions. I am inclined to think that it would be easier to change the thread libraries to the newest POSIX specification.
Some wrappers are already written. See `mysys/my_pthread.c' for more info.
At least the following should be changed:
pthread_get_specific should use one argument.
sigwait should take two arguments.
A lot of functions (at least pthread_cond_wait,
pthread_cond_timedwait)
should return the error code on error. Now they return -1 and set errno.
Another problem is that user-level threads use the ALRM signal and this
aborts a lot of functions (read, write, open...).
MySQL should do a retry on interrupt on all of these but it is
not that easy to verify it.
The biggest unsolved problem is the following:
To get thread-level alarms I changed `mysys/thr_alarm.c' to wait between
alarms with pthread_cond_timedwait(), but this aborts with error
EINTR. I tried to debug the thread library as to why this happens,
but couldn't find any easy solution.
If someone wants to try MySQL with RTS threads I suggest the following:
-DHAVE_rts_threads.
thr_alarm.
thr_alarm. If it runs without any "warning", "error" or aborted
messages, you are on the right track. Here follows a successful run on
Solaris:
Main thread: 1 Tread 0 (5) started Thread: 5 Waiting process_alarm Tread 1 (6) started Thread: 6 Waiting process_alarm process_alarm thread_alarm Thread: 6 Slept for 1 (1) sec Thread: 6 Waiting process_alarm process_alarm thread_alarm Thread: 6 Slept for 2 (2) sec Thread: 6 Simulation of no alarm needed Thread: 6 Slept for 0 (3) sec Thread: 6 Waiting process_alarm process_alarm thread_alarm Thread: 6 Slept for 4 (4) sec Thread: 6 Waiting process_alarm thread_alarm Thread: 5 Slept for 10 (10) sec Thread: 5 Waiting process_alarm process_alarm thread_alarm Thread: 6 Slept for 5 (5) sec Thread: 6 Waiting process_alarm process_alarm ... thread_alarm Thread: 5 Slept for 0 (1) sec end
MySQL is very dependent on the thread package used. So when choosing a good platform for MySQL, the thread package is very important.
There are at least three types of thread packages:
ps may show the different threads. If one thread aborts the
whole process aborts. Most system calls are thread-safe and should
require very little overhead. Solaris, HP-UX, AIX and OSF1 have kernel
threads.
In some systems kernel threads are managed by integrating user level threads in the system libraries. In such cases, the thread switching can only be done by the thread library and the kernel isn't really "thread aware".
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