When FreeBSD didn't have gethostbyname_r(), and gethostbyname() wasn't
thread-safe, Marc asked around and found out that the threaded solution
for this is to use getaddrinfo().  This makes sense because
getaddrinfo() is described as:

	getaddrinfo () function is defined for protocol-independent nodename-
	to-address translation.  It performs functionality of gethostbyname(3)
	and getservbyname(3),  in more sophisticated manner.

A number of platforms have getpwuid_r(), but not gethostbyname_r().  I
now realize it is because they are assuming you arew using getaddrinfo(),
which has freeaddrinfo() to free the allocated memory in a thread-safe
manner.

Right now, we call gethostname() from two places:

	port/getaddrinfo() (if backend)
	port/thread.c::pqGethostbyname()

and pqGethostbyname() (thread-safe) is called only by:

	port/getaddrinfo() (if frontend)
	libpq/fe-secure.c

If we convert fe-secure.c to use getaddrinfo(), then all host address
lookups go through getaddrinfo().  

Then, if we don't need our port/getaddrinfo(), we don't care about a
non-thread-safe gethostbyname() on that platform. This improves our
thread-safe support.  Specifically, it prevents host name lookups from
be serialized by our pthread locks.

Once everything goes through getaddrinfo(), I will modify my thread test
program to test gethostbyname() threading _only_ if getaddrinfo()
doesn't exist.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Sun, 14 Sep 2003 23:55:29 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
getaddrinfo() for threading instead of gethostbyname()

OK, the thread test program is read for platform testing,
src/tools/thread_test.  You will find the README, Makefile tests, and
program output to be very clear and almost error-proof.

Please run it on platforms we support and report back.  Thanks.

---------------------------------------------------------------------------

Bruce Momjian wrote:
> When FreeBSD didn't have gethostbyname_r(), and gethostbyname() wasn't
> thread-safe, Marc asked around and found out that the threaded solution
> for this is to use getaddrinfo().  This makes sense because
> getaddrinfo() is described as:
> 
> 	getaddrinfo () function is defined for protocol-independent nodename-
> 	to-address translation.  It performs functionality of gethostbyname(3)
> 	and getservbyname(3),  in more sophisticated manner.
> 
> A number of platforms have getpwuid_r(), but not gethostbyname_r().  I
> now realize it is because they are assuming you arew using getaddrinfo(),
> which has freeaddrinfo() to free the allocated memory in a thread-safe
> manner.
> 
> Right now, we call gethostname() from two places:
> 
> 	port/getaddrinfo() (if backend)
> 	port/thread.c::pqGethostbyname()
> 
> and pqGethostbyname() (thread-safe) is called only by:
> 
> 	port/getaddrinfo() (if frontend)
> 	libpq/fe-secure.c
> 
> If we convert fe-secure.c to use getaddrinfo(), then all host address
> lookups go through getaddrinfo().  
> 
> Then, if we don't need our port/getaddrinfo(), we don't care about a
> non-thread-safe gethostbyname() on that platform. This improves our
> thread-safe support.  Specifically, it prevents host name lookups from
> be serialized by our pthread locks.
> 
> Once everything goes through getaddrinfo(), I will modify my thread test
> program to test gethostbyname() threading _only_ if getaddrinfo()
> doesn't exist.
> 
> -- 
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman@candle.pha.pa.us               |  (610) 359-1001
>   +  If your life is a hard drive,     |  13 Roberts Road
>   +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Sat, 27 Sep 2003 12:25:52 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: getaddrinfo() for threading instead of gethostbyname()
On Sat, 27 Sep 2003, Bruce Momjian wrote:

> 
> OK, the thread test program is read for platform testing,
> src/tools/thread_test.  You will find the README, Makefile tests, and
> program output to be very clear and almost error-proof.
> 
> Please run it on platforms we support and report back.  Thanks.

Debian linux
kernel 2.2.x (- which was 2.0 or 2.2 of debian I think, can't remember)
glibc 2.1.3
gcc 2.95.2
it looks like the thread stuff is enabled in ports/linux in cvs tip

hmmmm...

software@ponder:~/database/postgres/pgsql/src/tools/thread$ make
gcc -O2 -g -Wall -Wmissing-prototypes -Wmissing-declarations -D_REENTRANT -D_THREAD_SAFE -D_POSIX_PTHREAD_SEMANTICS -I../../../src/include -D_GNU_SOURCE   -c -o thread_test.o thread_test.c
gcc -O2 -g -Wall -Wmissing-prototypes -Wmissing-declarations -D_REENTRANT -D_THREAD_SAFE -D_POSIX_PTHREAD_SEMANTICS -L../../../src/port  -Wl,-rpath,/usr/local/stow/postgresql-7.3.4/lib -lpthread thread_test.o -lpam -lz -lreadline -lcrypt -lresolv -lnsl -ldl -lm  -lpgport -o thread_test
software@ponder:~/database/postgres/pgsql/src/tools/thread$ ./thread_test 
Make sure you have added any needed 'THREAD_CPPFLAGS' and 'THREAD_LIBS'
defines to your template/$port file before compiling this program.

Your gethostbyname() is _not_ thread-safe
Your getpwuid() is _not_ thread-safe
Not all non-*_r functions are thread-safe.
Add this to your template/$port file:

NEED_REENTRANT_FUNCS=yes
software@ponder:~/database/postgres/pgsql/src/tools/thread$ 


Nigel


Sat, 27 Sep 2003 22:13:38 +0100 (BST)
"Nigel J. Andrews" <nandrews@investsystems.co.uk>
Re: getaddrinfo() for threading instead of gethostbyname()

Thanks.  That's what I needed.  Yes, I left the stuff enabled becuase
the new test is pretty much the same as the old one, but some OS's might
pass the tests if they only failed on gethostbyname().

---------------------------------------------------------------------------

Nigel J. Andrews wrote:
> On Sat, 27 Sep 2003, Bruce Momjian wrote:
> 
> > 
> > OK, the thread test program is read for platform testing,
> > src/tools/thread_test.  You will find the README, Makefile tests, and
> > program output to be very clear and almost error-proof.
> > 
> > Please run it on platforms we support and report back.  Thanks.
> 
> Debian linux
> kernel 2.2.x (- which was 2.0 or 2.2 of debian I think, can't remember)
> glibc 2.1.3
> gcc 2.95.2
> it looks like the thread stuff is enabled in ports/linux in cvs tip
> 
> hmmmm...
> 
> software@ponder:~/database/postgres/pgsql/src/tools/thread$ make
> gcc -O2 -g -Wall -Wmissing-prototypes -Wmissing-declarations -D_REENTRANT -D_THREAD_SAFE -D_POSIX_PTHREAD_SEMANTICS -I../../../src/include -D_GNU_SOURCE   -c -o thread_test.o thread_test.c
> gcc -O2 -g -Wall -Wmissing-prototypes -Wmissing-declarations -D_REENTRANT -D_THREAD_SAFE -D_POSIX_PTHREAD_SEMANTICS -L../../../src/port  -Wl,-rpath,/usr/local/stow/postgresql-7.3.4/lib -lpthread thread_test.o -lpam -lz -lreadline -lcrypt -lresolv -lnsl -ldl -lm  -lpgport -o thread_test
> software@ponder:~/database/postgres/pgsql/src/tools/thread$ ./thread_test 
> Make sure you have added any needed 'THREAD_CPPFLAGS' and 'THREAD_LIBS'
> defines to your template/$port file before compiling this program.
> 
> Your gethostbyname() is _not_ thread-safe
> Your getpwuid() is _not_ thread-safe
> Not all non-*_r functions are thread-safe.
> Add this to your template/$port file:
> 
> NEED_REENTRANT_FUNCS=yes
> software@ponder:~/database/postgres/pgsql/src/tools/thread$ 
> 
> 
> Nigel
> 
> 
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> 
>                http://archives.postgresql.org
> 

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Sat, 27 Sep 2003 17:48:03 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: getaddrinfo() for threading instead of gethostbyname()