Use systemd.timer instead of a cron job

The rational is that we need to spread the load on the mirrors
that apt update and unattended-upgrades cause. To do so, we
leverage the RandomizeDelay feature of systemd. The other advantage
is that the timer is not run at a fixed daily.daily time but
instead every 24h. This also fixes the problem that the randomized
deplay in the current apt.cron.daily causes other cron jobs to
be deplayed.

debian/apt-daily.service

@@ -0,0 +1,10 @@
+[Unit]
+Description=Apts daily jobs
+Documentation=man:apt(8)
+
+[Service]
+Type=oneshot
+ExecStart=/usr/lib/apt/apt.systemd.daily
+
+[Install]
+WantedBy=multi-user.target

debian/apt-daily.timer

@@ -0,0 +1,11 @@
+[Unit]
+Description=Runs apts daily activities
+
+[Timer]
+OnActiveSec=10min
+OnUnitInactiveSec=daily
+RandomizedDelaySec=1h
+Unit=apt-daily.service
+
+[Install]
+WantedBy=multi-user.target

debian/apt.dirs

@@ -15,4 +15,5 @@ var/lib/apt/mirrors/partial
 var/lib/apt/periodic
 var/log/apt
 usr/share/bug/apt
-usr/share/bash-completion/completions/
+usr/share/bash-completion/completions/
+lib/systemd/system/

debian/apt.install.in

@@ -5,3 +5,5 @@ scripts/dselect/* usr/lib/dpkg/methods/apt/
 usr/share/locale/*/*/apt.mo
 bin/libapt-private.so.* usr/lib/@DEB_HOST_MULTIARCH@/
 ../completions/bash/* /usr/share/bash-completion/completions/
+../debian/*.service /lib/systemd/system/
+../debian/*.timer /lib/systemd/system/

debian/apt.maintscript

@@ -1,3 +1,4 @@
 rm_conffile /etc/apt/apt.conf.d/20changelog 1.2.4~
-
+# we use a systemd timer unit now
+rm_conffile /etc/cron.daily/apt
 

debian/apt.cron.daily → debian/apt.systemd.daily

@@ -72,18 +72,6 @@
 #      2:  + command outputs     (remove -qq, remove 2>/dev/null, add -d)
 #      3:  + trace on            
 #
-#  APT::Periodic::RandomSleep "1800";
-#  - The apt cron job will delay its execution by a random
-#    time span between zero and 'APT::Periodic::RandomSleep'
-#    seconds.
-#    This is done because otherwise everyone would access the
-#    mirror servers at the same time and put them collectively
-#    under very high strain.
-#    You can set this to '0' if you are using a local mirror and
-#    do not care about the load spikes.
-#    Note that sleeping in the apt job will be delaying the
-#    execution of all subsequent cron.daily jobs.
-#
 
 check_stamp()
 {
@@ -294,25 +282,6 @@ do_cache_backup()
     fi
 }
 
-# sleep for a random interval of time (default 30min)
-# (some code taken from cron-apt, thanks)
-random_sleep()
-{
-    RandomSleep=1800
-    eval $(apt-config shell RandomSleep APT::Periodic::RandomSleep)
-    if [ $RandomSleep -eq 0 ]; then
-	return
-    fi
-    if [ -z "$RANDOM" ] ; then
-        # A fix for shells that do not have this bash feature.
-	RANDOM=$(( $(dd if=/dev/urandom bs=2 count=1 2> /dev/null | cksum | cut -d' ' -f1) % 32767 ))
-    fi
-    TIME=$(($RANDOM % $RandomSleep))
-    debug_echo "sleeping for $TIME seconds"
-    sleep $TIME
-}
-
-
 debug_echo()
 {
     # Display message if $VERBOSE >= 1
@@ -440,9 +409,7 @@ fi
 # deal with BackupArchiveInterval
 do_cache_backup $BackupArchiveInterval
 
-# sleep random amount of time to avoid hitting the 
-# mirrors at the same time
-random_sleep
+# ensure we don't do this on battery
 check_power || exit 0
 
 # include default system language so that "apt-get update" will

debian/rules

@@ -222,13 +222,17 @@ apt: build-binary build-manpages debian/apt.install
 	#   debian/$@/usr/lib/apt/apt-report-mirror-failure \
 
 	# move the apt-helper in place
-	mv debian/$@/usr/bin/apt-helper debian/$@/usr/lib/apt/apt-helper 
+	mv debian/$@/usr/bin/apt-helper debian/$@/usr/lib/apt/apt-helper
+	# install apt.systemd.daily helper in the right place
+	install -m755 debian/apt.systemd.daily debian/$@/usr/lib/apt/
 
 	dh_bugfiles -p$@
 	dh_lintian -p$@
 	dh_installexamples -p$@ $(BLD)/docs/examples/*
 	dh_installman -p$@ $(wildcard $(patsubst %,doc/en/%.[158],$(apt_MANPAGES)) $(patsubst %,doc/*/%.*.[158],$(apt_MANPAGES)))
-	dh_installcron -p$@
+	dh_systemd_enable -p$@ apt-daily.timer apt-daily.service 
+	dh_systemd_start -p$@ apt-daily.timer
+	dh_systemd_start -p$@ --no-start apt-daily.service
 	dh_installdocs -p$@
 	dh_installchangelogs -p$@
 	dh_installlogrotate -p$@