[Server-devel] [PATCH] Introducing ds_backup.sh - a lightweight wrapper.

[martin.langhoff at gmail.com]

From: Martin Langhoff <martin at laptop.org>

ds_backup.sh gets  called from cron and/or from
NetworkManager, and decides whether it's a good time
to attempt a backup.

It also protects ds_backup.py from concurrent executions,
staggers clients to avoid stampedes, and keeps various
other demons at bay.
---
 ds_backup.sh |   77 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 77 insertions(+), 0 deletions(-)
 create mode 100755 ds_backup.sh

diff --git a/ds_backup.sh b/ds_backup.sh
new file mode 100755
index 0000000..739bb43
--- /dev/null
+++ b/ds_backup.sh
@@ -0,0 +1,77 @@
+#!/bin/bash
+#
+# Wrapper around ds_backup - will be called in 2 situations
+#
+#  - On cron, every 30 minutes during waking/school hours
+#    If you are calling this from cron, pass 'cron' as
+#    the first parameter.
+#
+#  - from a NetworkManager event when we
+#    associate to the school network. In that case, we get
+#    2 parameters - if, action
+#
+# Note: this wrapper _must_ be cheap to execute to avoid burning
+# battery.
+#
+# Author: Martin Langhoff <martin at laptop.org>
+#
+B_LEVEL=`cat /sys/class/power_supply/olpc-battery/capacity`
+AC_STAT=`cat /sys/class/power_supply/olpc-ac/online`
+
+# If we are on battery, and below 30%, leave it for later
+if [ $AC_STAT == "0" -a $B_LEVEL -lt 30 ]
+then
+	exit 0
+fi
+
+# If we have backed up recently, leave it for later. Use
+# -mtime 0 for "today"
+# -mtime -1 for "since yesterday"
+# -mtime -10 for in the last 10 days
+#
+# Using -daystart means that the script is more eager to backup
+# in the morning. Without -daystart, laptops backup "later in the day"
+# everyday, as they only start trying after 24hs...
+#
+# Another tack could be -mmin -1200 (20hs), which could be more stable.
+#
+if [ `find ~/.sugar/default/ds_backup-done -daystart -mtime 0 2>/dev/null` ]
+then
+    exit 0
+fi
+
+##
+## TODO: 
+## - Test: Can we see the XS?
+## - Handle being called from NM
+##
+
+### Ok, we are going to make a backup
+
+# make the lock dir if needed
+if [ ! -d ~/.sugar/default/lock ]
+then
+    mkdir ~/.sugar/default/lock
+fi
+
+#
+#  Sleep a random amount, not greater than 20 minutes
+#  We use this to stagger client machines in the 30 minute
+#  slots between cron invocations...
+#(sleep $(($RANDOM % 1200));
+
+# Execute ds_backup.py from the same
+# directory where we are. Use a flock
+# to prevent concurrent runs. If the
+# flock does not succeed immediately,
+# we quit.
+LOCKFILE=~/.sugar/default/lock/ds_backup.run
+flock -n $LOCKFILE `dirname $0 `/ds_backup.py
+EXITCODE=$?
+
+# Clean up the lock - if we can ;-)
+rm $LOCKFILE 2>/dev/null
+
+# Propagate the exit code of the flock/ds_backup invocation
+exit $EXITCODE
+
-- 
1.5.4.34.g053d9