DC::DB - async. database and filesystem access for deliantra

 use DC::DB;

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

package DC::DB;

use common::sense;

use File::Path ();
use Carp ();
use Storable ();
use AnyEvent::Util ();
use Config;
use BDB;
use Fcntl ();

use DC;

our $ODBDIR  = "cfplus-" . BDB::VERSION_MAJOR . "." . BDB::VERSION_MINOR . "-$Config{archname}";
our $DBDIR   = "client-" . BDB::VERSION_MAJOR . "." . BDB::VERSION_MINOR . "-$Config{archname}";
our $DB_HOME = "$Deliantra::VARDIR/$DBDIR";

sub FIRST_TILE_ID () { 64 }

unless (-d $DB_HOME) {
   if (-d "$Deliantra::VARDIR/$ODBDIR") {
      rename "$Deliantra::VARDIR/$ODBDIR", $DB_HOME;
      print STDERR "INFO: moved old database from $Deliantra::VARDIR/$ODBDIR to $DB_HOME\n";
   } elsif (-d "$Deliantra::OLDDIR/$ODBDIR") {
      rename "$Deliantra::OLDDIR/$DBDIR", $DB_HOME;
      print STDERR "INFO: moved old database from $Deliantra::OLDDIR/$ODBDIR to $DB_HOME\n";
   } else {
      File::Path::mkpath [$DB_HOME]
         or die "unable to create database directory $DB_HOME: $!";
   }
}

BDB::max_poll_time 0.03;
BDB::max_parallel 1;

our $DB_ENV;
our $DB_ENV_FH;
our $DB_STATE;
our %DB_TABLE;
our $TILE_SEQ;

sub all_databases {
   opendir my $fh, $DB_HOME
      or return;

   grep !/^(?:\.|log\.|_)/, readdir $fh
}

sub try_verify_env($) {
   my ($env) = @_;

   open my $lock, "+>$DB_HOME/__lock"
      or die "__lock: $!";

   flock $lock, &Fcntl::LOCK_EX
      or die "flock: $!";

   # we look at the __db.register env file that has been created by now
   # and check for the number of registered processes - if there is
   # only one, we verify all databases, otherwise we skip this
   # we MUST NOT close the filehandle as longa swe keep the env open, as
   # this destroys the record locks on it.
   open $DB_ENV_FH, "<$DB_HOME/__db.register"
      or die "__db.register: $!";

   # __db.register contains one record per process, with X signifying
   # empty records (of course, this is completely private to bdb...)
   my $count = grep /^[^X]/, <$DB_ENV_FH>;

   if ($count == 1) {
      # if any databases are corrupted, we simply delete all of them

      for (all_databases) {
         my $dbh = db_create $env
            or last;

         # a failed verify will panic the environment, which is fine with us
         db_verify $dbh, "$DB_HOME/$_";

         return if $!; # nuke database and recreate if verification failure
      }

   }

   # close probably cleans those up, but we also want to run on windows,
   # so better be safe.
   flock $lock, &Fcntl::LOCK_UN
      or die "funlock: $!";

   1
}

sub try_open_db {
   File::Path::mkpath [$DB_HOME];

   undef $DB_ENV;
   undef $DB_ENV_FH;

   my $env = db_env_create;

   $env->set_errfile (\*STDERR);
   $env->set_msgfile (\*STDERR);
   $env->set_verbose (-1, 1);

   $env->set_flags (BDB::AUTO_COMMIT | BDB::REGION_INIT);
   $env->set_flags      (&BDB::LOG_AUTOREMOVE ) if BDB::VERSION v0, v4.7;
   $env->log_set_config (&BDB::LOG_AUTO_REMOVE) if BDB::VERSION v4.7;

   $env->set_timeout (3, BDB::SET_TXN_TIMEOUT);
   $env->set_timeout (3, BDB::SET_LOCK_TIMEOUT);

   $env->set_cachesize (0, 2048 * 1024, 0);

   db_env_open $env, $DB_HOME,
               BDB::CREATE | BDB::REGISTER | BDB::RECOVER | BDB::INIT_MPOOL | BDB::INIT_LOCK | BDB::INIT_TXN,
               0666;

   $! and die "cannot open database environment $DB_HOME: " . BDB::strerror;

   # now we go through the registered processes, if there is only one, we verify all files
   # to make sure windows didn'T corrupt them (as windows does....)
   try_verify_env $env
      or die "database environment failed verification";

   $DB_ENV = $env;

   1
}

sub table($) {
   $DB_TABLE{$_[0]} ||= do {
      my ($table) = @_;

      $table =~ s/([^a-zA-Z0-9_\-])/sprintf "=%x=", ord $1/ge;

      $DB_ENV#d#
         or return ::clienterror ("trying to create table $_[0] with empty db_env $DB_ENV" => 1);#d#

      my $db = db_create $DB_ENV;
      $db->set_flags (BDB::CHKSUM);

      db_open $db, undef, $table, undef, BDB::BTREE,
              BDB::AUTO_COMMIT | BDB::CREATE | BDB::READ_UNCOMMITTED, 0666;

      $! and "unable to open/create database table $_[0]: ". BDB::strerror;

      $db
   }
}

#############################################################################

our $WATCHER;
our $SYNC;
our $facemap;

sub exists($$$) {
   my ($db, $key, $cb) = @_;

   my $data;
   db_get table $db, undef, $key, $data, 0, sub {
      $cb->($! ? () : length $data);
   };
}

sub get($$$) {
   my ($db, $key, $cb) = @_;

   my $data;
   db_get table $db, undef, $key, $data, 0, sub {
      $cb->($! ? () : $data);
   };
}

sub put($$$$) {
   my ($db, $key, $data, $cb) = @_;

   db_put table $db, undef, $key, $data, 0, sub {
      $cb->($!);
      $SYNC->again unless $SYNC->is_active;
   };
}

sub do_table {
   my ($db, $cb) = @_;

   $db = table $db;

   my $cursor = $db->cursor;
   my %kv;

   for (;;) {
      db_c_get $cursor, my $k, my $v, BDB::NEXT;
      last if $!;
      $kv{$k} = $v;
   }

   $cb->(\%kv);
}

sub do_get_tile_id {
   my ($name, $cb) = @_;

   my $table = table "facemap";
   my $id;

   db_get $table, undef, $name => $id, 0;
   $! or return $cb->($id);

   unless ($TILE_SEQ) {
      $TILE_SEQ = $table->sequence;
      $TILE_SEQ->initial_value (FIRST_TILE_ID);
      $TILE_SEQ->set_cachesize (0);
      db_sequence_open $TILE_SEQ, undef, "id", BDB::CREATE;
   }

   db_sequence_get $TILE_SEQ, undef, 1, my $id;

   die "unable to allocate tile id: $!"
      if $!;
   
   db_put $table, undef, $name => $id, 0;
   $cb->($id);

}

sub get_tile_id_sync($) {
   my ($name) = @_;

   $facemap->{$name} ||= do {
      my $id;
      do_get_tile_id $name, sub {
         $id = $_[0];
      };
      BDB::flush;
      $id
   }
}

#############################################################################

sub path_of_res($) {
   utf8::downgrade $_[0]; # bug in unpack "H*"
   "$DB_HOME/res-data-" . unpack "H*", $_[0]
}

sub sync {
   # for debugging
   #DC::DB::Server::req (sync => sub { });
   DC::DB::Server::sync ();
}

sub unlink($$) {
   DC::DB::Server::req (unlink => @_);
}

sub read_file($$) {
   DC::DB::Server::req (read_file => @_);
}

sub write_file($$$) {
   DC::DB::Server::req (write_file => @_);
}

sub prefetch_file($$$) {
   DC::DB::Server::req (prefetch_file => @_);
}

sub logprint($$$) {
   DC::DB::Server::req (logprint => @_);
}

#############################################################################

package DC::DB::Server;

use common::sense;

use EV ();
use Fcntl;

our %CB;
our $FH;
our $ID = "aaa0";
our ($fh_r_watcher, $fh_w_watcher);
our $sync_timer;
our $write_buf;
our $read_buf;

sub fh_write {
   my $len = syswrite $FH, $write_buf;

   substr $write_buf, 0, $len, "";

   $fh_w_watcher->stop
      unless length $write_buf;
}

sub fh_read {
   my $status = sysread $FH, $read_buf, 16384, length $read_buf;

   die "FATAL: database process died\n"
      if $status == 0 && defined $status;

   while () {
      return if 4 > length $read_buf;
      my $len = unpack "N", $read_buf;

      return if $len + 4 > length $read_buf;

      substr $read_buf, 0, 4, "";
      my $res = Storable::thaw substr $read_buf, 0, $len, "";

      my ($id, @args) = @$res;
      (delete $CB{$id})->(@args);
   }
}

sub sync {
   # biggest mess evarr
   my $fds; (vec $fds, fileno $FH, 1) =  1;

   while (1 < scalar keys %CB) {
      my $r = $fds;
      my $w = length $write_buf ? $fds : undef;
      select $r, $w, undef, undef;

      fh_write if vec $w, fileno $FH, 1;
      fh_read  if vec $r, fileno $FH, 1;
   }
}

sub req {
   my ($type, @args) = @_;
   my $cb = pop @args;

   my $id = ++$ID;
   $write_buf .= pack "N/a*", Storable::freeze [$id, $type, @args];
   $CB{$id} = $cb;

   $fh_w_watcher->start;
}

sub do_unlink {
   unlink $_[0];
}

sub do_read_file {
   my ($path) = @_;

   utf8::downgrade $path;
   open my $fh, "<:raw", $path
      or return;
   sysread $fh, my $buf, -s $fh;

   $buf
}

sub do_write_file {
   my ($path, $data) = @_;

   utf8::downgrade $path;
   utf8::downgrade $data;
   open my $fh, ">:raw", $path
      or return;
   syswrite $fh, $data;
   close $fh;

   1
}

sub do_prefetch_file {
   my ($path, $size) = @_;

   utf8::downgrade $path;
   open my $fh, "<:raw", $path
      or return;
   sysread $fh, my $buf, $size;

   1
}

our %LOG_FH;

sub do_logprint {
   my ($path, $line) = @_;

   $LOG_FH{$path} ||= do {
      open my $fh, ">>:utf8", $path
         or warn "Couldn't open logfile $path: $!";

      $fh->autoflush (1);

      $fh
   };

   my ($sec, $min, $hour, $mday, $mon, $year) = localtime time;

   my $ts = sprintf "%04d-%02d-%02d %02d:%02d:%02d",
               $year + 1900, $mon + 1, $mday, $hour, $min, $sec;

   print { $LOG_FH{$path} } "$ts $line\n"
}

sub run {
   ($FH, my $fh) = AnyEvent::Util::portable_socketpair
     or die "unable to create database socketpair: $!";

   my $oldfh = select $FH; $| = 1; select $oldfh;
   my $oldfh = select $fh; $| = 1; select $oldfh;

   my $pid = fork;
   
   if (defined $pid && !$pid) {
      local $SIG{QUIT} = "IGNORE";
      local $SIG{__DIE__};
      local $SIG{__WARN__};
      eval {
         close $FH;

         while () {
            4 == read $fh, my $len, 4
               or last;
            $len = unpack "N", $len;
            $len == read $fh, my $req, $len
               or die "unexpected eof while reading request";

            $req = Storable::thaw $req;

            my ($id, $type, @args) = @$req;
            my $cb = DC::DB::Server->can ("do_$type")
               or die "$type: unknown database request type\n";
            my $res = pack "N/a*", Storable::freeze [$id, $cb->(@args)];
            (syswrite $fh, $res) == length $res
               or die "DB::write: $!";
         }
      };

      my $error = $@;

      eval {
         Storable::store_fd [die => $error], $fh;
      };

      warn $error
         if $error;

      DC::_exit 0;
   }

   close $fh;
   DC::fh_nonblocking $FH, 1;

   $CB{die} = sub { die shift };

   $fh_r_watcher = EV::io $FH, EV::READ , \&fh_read;
   $fh_w_watcher = EV::io $FH, EV::WRITE, \&fh_write;
}

sub stop {
   close $FH;
}

package DC::DB;

sub nuke_db {
   undef $DB_ENV;
   undef $DB_ENV_FH;

   File::Path::mkpath [$DB_HOME];
   eval { File::Path::rmtree $DB_HOME };
}

sub open_db {
   unless (eval { try_open_db }) {
      warn "$@";#d#
      eval { nuke_db };
      try_open_db;
   }

   # fetch the full face table first
   unless ($facemap) {
      do_table facemap => sub {
         $facemap = $_[0];
         delete $facemap->{id};
         my %maptile = reverse %$facemap;#d#
         if ((scalar keys %$facemap) != (scalar keys %maptile)) {#d#
            $facemap = { };#d#
            DC::error "FATAL: facemap is not a 1:1 mapping, please report this and delete your $DB_HOME directory!\n";#d#
         }#d#
      };
   }

   $WATCHER = EV::io BDB::poll_fileno, EV::READ, \&BDB::poll_cb;
   $SYNC = EV::timer_ns 0, 60, sub {
      $_[0]->stop;
      db_env_txn_checkpoint $DB_ENV, 0, 0, 0, sub { };
   };
}

END {
   db_env_txn_checkpoint $DB_ENV, 0, 0, 0
      if $DB_ENV;

   undef $TILE_SEQ;
   %DB_TABLE = ();
   undef $DB_ENV;
}

1;