mxraid/mxraid_assemble: Wait if enclosures start slowly

Sometimes the disks in a enclosure are registered a bit
lately, so check if there is some dynamic (count of disks),
and if so -- just wait a little longer.

Note: this was only observed once 'in the wild', and the required
      delay would have been in the range of 50ms.

mxraid/mxraid_assemble

@@ -6,6 +6,8 @@ use Data::Dumper; $Data::Dumper::Sortkeys=1;
 use Getopt::Std;  $Getopt::Std::STANDARD_HELP_VERSION=1;
 sub HELP_MESSAGE{}
 sub VERSION_MESSAGE{}
+use Sys::Syslog;
+use Time::HiRes qw(usleep);
 
 import MxRaid::ConfData;
 import MxRaid::HostData;
@@ -60,6 +62,22 @@ sub exec_version {
   exit 0;
 }
 
+sub check_enclosures {
+  glob('/sys/class/enclosure/*') or return;
+
+  my $cnt_0 = () = (glob('/sys/block/sd[a-z]'), glob('/sys/block/sd[a-z][a-z]'));
+  usleep(0.3 * 1e6);
+  my $cnt_1 = () = (glob('/sys/block/sd[a-z]'), glob('/sys/block/sd[a-z][a-z]'));
+
+  if ( $cnt_0 != $cnt_1 ) { # then something still 'evolves', shout around and take a nap.
+    my ($prog) = $0 =~ m|([^/]+)$|;
+    openlog($prog,'pid','user');
+    Sys::Syslog::setlogsock('unix'); # with 'native' we get EOLs in the logfile, option "noeol" doesn't work
+    syslog('info', 'still discovering disks, diff is %d. Waiting 3 seconds ...', $cnt_1 - $cnt_0);
+    sleep 3;
+  }
+}
+
 my $ROOT=$<==0?1:0;
 
 my %opts;
@@ -88,6 +106,7 @@ my $MDADM_CONF_BASE = '/dev/shm/mdadm.conf'; # config for mdadm, created with in
 my $MDADM_ASSEMBLE_OPTIONS = '';
 
 my $cd = MxRaid::ConfData->new($MDADMCONF_DB); $cd->verbose($VERBOSE); $cd->load();
+check_enclosures(); # idle a bit if enclosures are attached ...
 my $hd = MxRaid::HostData->new($cd);           $hd->verbose($VERBOSE);
 my $utils = MxRaid::Utils->new();