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From Rodent of Unusual Size <Ken.C...@Golux.Com>
Subject [STATUS] (apr) Wed Dec 12 23:45:11 EST 2001
Date Thu, 13 Dec 2001 04:45:11 GMT
Last modified at [$Date: 2001/12/12 18:09:22 $]


    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


    * 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_*()
      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()
      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?)


    * Enable pools to have thread-specific locking in it.
        Status: There are two alternatives.  More investigation/analysis
                needs to be done to see if they can be merged 
                SVN is segfaulting with Sander's pool code.  Sander
                and Justin are investigating.
        Sander's submission:
        Brian's submission:
            Ian: <3C083414.1080208@cnet.com> (performance)
            Brian: <3C07D792.9070301@cnet.com> (code)
                   <3C0D6BB5.6010505@cnet.com> (performance)
            Justin: <20011205025611.GB22835@ebuilt.com> (code)
            Sander's patch:
                +1: Brian (non-binding), 
                    Ian (once we have a debug version of palloc etc),

    * 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?"

    * Win32: Implement apr_shm_ functions 
      Status: rbb insists he has thoughts about splitting apr_shm_*
              mechanisms to support muliple models (some sort of 'keyed'
              schema as well as anonymous inheritable shmem), and has a
              possible solution to the 'ask for 1MB, then ask for 4x256kb
              bogosity, so we are waiting on this.
      Justin says: "That problem should be fixed now because we ignore memory
                    management with shared memory on Unix (at least).  So, 
                    the Win32 guys should be able to go ahead if they want."

    * 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,

    * 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.

    * APR memory code
      The SMS code has been removed.  The abstraction made it perform
      far worse than pools.  Pools need probably be revamped to take
      a want_new_freelist parameter to get rid of the global locking
      on block allocation.
        Status: Sander volunteers
    * In line with the new SMS code is the fact that threading and pools
      just are not working together well.  This is due to the fact that
      the pool code has one global mutex (alloc_mutex) and one freelist
      (block_freelist) for all pools to share.  This means that only 
      one worker can be allocating memory at any given time.  This is 
      probably the reason why Apache 2.0 is faster with prefork MPM 
      (thread-disabled APR) than threaded MPM.  The solution to this
      is most likely to incorporate a rework of the pools to use the new
      SMS code and allow certain pools (i.e. request pools in httpd-2.0)
      to have an option for no locking (as they can't have contention
      by definition).  This would mean that the mutex and freelist
      must be moved inside of apr_pool_t.  Therefore, this is the 
      jumping-off point into SMS.  
        Justin: The SMS code has been checked into CVS (see above).
                To solve this problem, we want only one trivial SMS 
                per thread which acts as the parent for all SMSs in 
                that thread (giving us thread-local allocation).  
                Each descendant SMS should be something along the 
                lines of a tracking SMS.  That's how I see it anyway.
                There are other possibilities.  Any of those probably 
                work as well.  See the apr archives for more info.  
                We're still debating this.
        Sander: The SMS code has been removed (see above).

    * 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:

    * Add a way to query APR for what features it has at runtime (i.e. 
      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:
           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

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

                FreeBSD PR kern/32684:

    * Currently it is difficult if not impossible to return a proper
      status code from a thread using apr_thread_exit(), since the
      value must be a (apr_status_t*), but the pool where this would
      normally be allocated is in that same function immediately
      thereafter destroyed. Simply changing the type of this parameter
      to (apr_status_t) should solve the problem (along with some
      internal changes in apr_thread_join() to accomodate).
        Status: "I'll probably test and commit this soonish," says Aaron,
                "Here's the patch:"

    * 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.

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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