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From Rodent of Unusual Size <Ken.C...@Golux.Com>
Subject [STATUS] (apr) Wed Jan 30 23:45:11 EST 2002
Date Thu, 31 Jan 2002 04:45:11 GMT
APACHE PORTABLE RUNTIME (APR) LIBRARY STATUS:			-*-text-*-
Last modified at [$Date: 2002/01/29 16:10:14 $]

Release:

    2.0a9   : released December 12, 2000
    2.0a8   : released November 20, 2000
    2.0a7   : released October 8, 2000
    2.0a6   : released August 18, 2000
    2.0a5   : released August 4, 2000
    2.0a4   : released June 7, 2000
    2.0a3   : released April 28, 2000
    2.0a2   : released March 31, 2000
    2.0a1   : released March 10, 2000

RELEASE SHOWSTOPPERS:

    * Must namespace protect all include/apr_foo.h headers.  Jon Travis
      has especially observed these including apr and Apache-1.3.
        Message-ID: <20020128100116.A4288@covalent.net>

    * complete the efforts started by DougM for cleaner fn naming
      conventions: see proposed name changes in renames_pending
      and offer up any additions/vetos/clarifications.
      DougM offered to complete the work with his nifty perl rename
      script at the hackathon. 

    * When Win32 apr_proc_create was fixed, the apr_proc_t hproc
      member was added for that platform.  That's a problem (and
      was when pid was abused as well) since nobody goes and cleans
      up hproc after the process is dead.  Can't do a pool cleanup,
      since apr_proc_create didn't allocate the apr_proc_t storage.
      (Aren't transparent types swell?)  Suggestions?

    * The new lock API is a full replacement for the old API, but is
      not yet complete on all platforms. Components that are incomplete
      or missing include:
      Beos: apr_thread_cond_*()
            Initial code committed. Aaron has some concerns, David agrees
            and will find time to address the issues.
      Netware: apr_proc_mutex_*() (Is proc_mutex unnecessary on Netware?)
      OS/2: apr_thread_cond_*(), apr_proc_mutex_*()

      Less critical components that we may wish to add at some point:
      Beos: apr_thread_rwlock_try*lock()
            apr_proc_mutex_trylock()
      Unix: apr_thread_rwlock_*() for platforms w/o rwlocks in pthread
      Win32: apr_thread_rwlock_try*lock(), apr_thread_cond_timedwait(),
             apr_proc_mutex_*() (Is proc_mutex unnecessary on Win32?)

RELEASE NON-SHOWSTOPPERS BUT WOULD BE REAL NICE TO WRAP THESE UP:

    * Need to contemplate apr_strftime... platforms vary.  OtherBill
      suggested this solution (but has no time to implement):
        Document our list of 'supported' escapes.
        Run some autoconf/m4 magic against the complete list we support.
        Move the strftime re-implementation from time/win32 to time/unix.
        Add some APR_HAVE_STRFTIME magic to use the system fn, or fail
        over to time/unix/strftime.c.
        Message-ID: <025e01c1a891$bf41f660$94c0b0d0@v505>

    * Using reentrant libraries with non-threaded APR
        - Anecdotal evidence exists that suggests it is bad to
          mix reentrant and non-reentrant libraries and therefore
          we should always use the reentrant versions.
        - Unfortunately, on some platforms (AIX 4.2.1) defining
          the reentrant flag (-D_THREAD_SAFE) causes builds to fail,
          and so one would expect --disable-threads to fix this.
          Although this has been fixed for that particular version
          of AIX, it may be useful to only enable the reentrant
          versions when threads are enabled.
        How will we deal with this issue once APR becomes a standalone
        library? It is perfectly legitimate to have apps needing
        both versions (threaded/reentrant and non-threaded/non-reentrant)
        on the same machine.

    * Pools debugging
        - Find a way to do check if a pool is used in multiple
          threads, while the creation flags say it isn't.  IOW,
          when the pool was created with APR_POOL_FNEWALLOCATOR,
          but without APR_POOL_FLOCK.
          Currently, no matter what the creation flags say, we always
          create a lock.  Without it integrity_check() and
          apr_pool_num_bytes() blow up (because they traverse pools
          child lists that possibly belong to another thread, in
          combination with the pool having no lock).  However,
          this might actually hide problems like creating a child pool
          of a pool belonging to another thread.
          Maybe a debug function apr_pool_set_owner(apr_thread_t *) in
          combination with extra checks in integrity_check() will point
          out these problems.  apr_pool_set_owner() would need to be called
          everytime the owner(the thread the pool is being used in) of
          the pool changes.

        - Implement apr_pool_join and apr_pool_lock.  Those functions
          are noops at the moment.

        - Add stats to the pools code.  We already have basic stats
          in debug mode.  Stats that tell us about wasted memory
          in the production code require more thought.
            Status: Sander Striker is looking into this (low priority)

    * Deal with largefiles properly on those platforms that support it.

      Justin says: Linux refuses to have largefile support and largefiles
                   at the sametime.  Largefile autoconf patch:
                   http://www.apache.org/~jerenkrantz/apr_largefile.m4

    * Get OTHER_CHILD support into Win32
        Status: Bill S. is looking into this

    * Win32 apr_proc_create fails to create 16 bit apps detached
      (a win32 bug.)  The question - test in advance (slow) or
      recover gracefully from failure and try again?  Only the test
      method will work on Win9x, since it will appear to work, only
      to encounter mangled pipes.  Win2K (NT?) simply fails.

    * SysV semaphore support isn't usable by Apache when started as
      root because we don't have a way to allow the semaphore to be
      used by the configured User and Group.  Current work-around:
      change the initial permissions to 0666.  Needed code:  See
      1.3's http_main.c, SysV sem flavor of accept_mutex_init().
      Status: Jim will look into this

    * Build scripts do not recognise AIX 4.2.1 pthreads
      Justin says: "Is this still true?"

    * FirstBill says we need a new procattr, APR_CREATE_SUSPENDED (or
      something similar) to direct ap_create_process to create the
      process suspended. We also need a call to wake up the suspended 
      process.  This may not be able to be implemented everywhere though.
        Status: OtherBill asks, why?  What is the benefit, how is it
        portably implemented?  Unless this creates some tangible that
        mirrors another platform, then I'm -1.

    * Replace tables with a proper opaque ADT that has pluggable
      implementations (including something like the existing data type,
      plus hash tables for speed, with options for more later).
	Status: fanf is working on this.

    * add a version number to apr_initialize() as an extra failsafe against
      (APR) library version skew.
      MsgID: <Pine.LNX.4.10.10005231712380.31927-100000@nebula.lyra.org>
      Status: Greg +1 (volunteers), Jeff +1, Ryan +1, Tony -0(?), david +1

    * add apr_crypt() and APR_HAS_CRYPT for apps to determine whether the
      crypt() function is available, and a way to call it (whether it is
      located in libc, libcrypt, or libufc)
      Justin says: Should apr_crypt() be in apr-util?

        Status: Greg +1 (volunteers)

    * configure.in does post-processing on the AC_OUTPUT files (for
      VPATH support). This means that config.status doesn't do the
      right thing when you re-run it. We ought to revamp the makefiles 
      to do the right AC_SUBST stuff rather than depend upon rewriting.

      Sascha: As the rewriter is a crude hack, I would not worry too
              much about it.  It is designed to go away once we have
              a proper build system in place.
              
              One of the perceived deficiencies of automake is that it
              uses AC_SUBST too often, thereby slowing down the task of
              generating Makefiles significantly, because it applies
              dozens of substitutions to each Makefile.  And why?  Make's
              built-in macro processing is much more powerful, and
              combined with the include facility, generating Makefiles
              becomes simpler and faster.
      Justin says: "I think this got fixed with Roy's build changes."

    * use os_(un)cork in network_io/unix/sendrecv.c for FreeBSD's
      sendfile implementation.

      david: The socket options stuff is now in and using it should
             reduce the number of syscalls that are required for 
             os_cork and uncork, so the code should be reviewed to
             make use of the new calls.  If no-one beats me to it I'll
             get around to it soonish...

    * toss the per-Makefile setup of INCLUDES; shift to rules.mk.in
        rbb: This is a bad thing IMHO.  If we do this, then we
             can't use these makefiles for anything else.  For example,
             apr-util

    * add the rest of the pool accessor declare/impl macros.
      Justin says: Both thread and file have the accessors now.  Any others?
      Status: Greg volunteers

    * I think apr_open_stderr() and friends dup() the descriptor. That
      would allow the new/returned file to be closed (via pool cleanup
      or manually) without accidentally closing stderr/out.
      Justin says: Is this "I think it should?"

    * need to export the shared library extension (e.g. ".so") for the
      platform. clients need to use this to construct filenames to
      pass to apr_dso_load()
      -- note on Win32 we distinguish 'apache module' names from other 
         'loadable module' names, so be careful with Apache's directive.

    * Possible gmtime_r replacement in explode_time
      On Solaris (and possibly others), the gmtime_r libc function obtains
      a mutex.  We have seen 21/25 threads being blocked in this mutex on 
      a threaded httpd MPM when requesting static pages.  It may be worth 
      it to hand optimize this since there is no real need for a mutex at 
      the system level (straight arithmetic from what I can tell).  If you 
      have access to the Solaris source code:
        osnet_volume/usr/src/lib/libc/port/gen/time_comm.c.

    * Add a way to query APR for what features it has at runtime (i.e. 
      threads).
      Justin says: I'm not completely sold on this, but it has been mentioned 
                   before and at least added to STATUS.

    * apr_xlate.h generates a bunch of compiler warnings.
      Jeff asks: which platform?
      Justin says: Solaris with Forte 6.1.

    * fcntl() oddness on Solaris.  Under high loads, fcntl() decides to
      return error code 46 (ENOLCK).

      httpd (prefork MPM) error log says (predictably):

      (46)No record locks available: couldn't grab the accept mutex
 
      All of the children report this and subsequently exits.  httpd is now 
      hosed.  AFAICT, this does not look to be an out-of-fds error.
 
      Solaris's man page says:
        ENOLCK
           The  cmd argument is F_SETLK, F_SETLK64, F_SETLKW,  or
           F_SETLKW64  and  satisfying the lock or unlock request
           would result in the number of locked  regions  in  the
           system exceeding a system-imposed limit.

      Justin says: What is this system-imposed limit and how do we change it?
                   This gives me more rationale for switching the default
                   interprocess lock mechanism to pthread (if available).

    * Generate a good bug report to send to the FreeBSD hackers that details
      the problems we have seen with threads and system calls (specifically
      sendfile data is corrupted).  From our analysis so far, we don't think 
      that this is an APR issue, but rather a FreeBSD kernel issue.  Our
      current solution is to just disable threads across the board on
      FreeBSD.

      MsgID: <20010828091959.D17570@ebuilt.com>
        Status: Fixed in -CURRENT.  MFC in about a week.  Continuing
                testing with threads on FreeBSD.

                FreeBSD PR kern/32684:
                  http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/32684

    * There are some optimizations that can be done to the new
      apr_proc_*() functions (on UNIX). One that may reduce pointer
      indirection would be to make the apr_proc_mutex_unix_lock_methods_t
      first-class members of the apr_proc_mutex_t structure.

    * Condition variables are tricky enough to use, and even trickier
      to implement properly. We could really use a better test case
      for those subtle quirks that sometimes creep into CV implementations.

    * Once we are fully satisfied with the new lock API, we can
      begin to migrate the old API to be implemented on top of the
      new one, or just decide to get rid of it altogether.
      
    * FreeBSD returns 45 (EOPNOTSUPP) when the lockfile is on a NFS
      partition when you call fcntl(F_SETLKW).  It may be good if we 
      can somehow detect this and error out when creating the lock
      rather than waiting for the error to occur when acquiring lock.

    * Fix autoconf tests for strerror_r on BeOS and remove the hack in
      misc/unix/errorcodes.c to get error reporting working.  Committed as
      the solution is elusive at present.

    * implement APR_PROGRAM_ENV and APR_PROGRAM_PATH on BeOS, OS/2,
      Netware, and Win32.

Documentation that needs writing:

    * API documentation
        Ian Says: APR Stuff in now in Doxygen format, which is the first step.

    * apr-site needs to be revamped with Anakia/XHTML.

Stuff waiting for code thawing after Beta 1:

    * Identify and implement those protection bits that have general 
        usefulness, perhaps hidden, generic read-only [immutable],
        effective current user permissions, etc.

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