Support running as a daemon / service

[shinebayar-g]

Hi, first of all this project looks awesome. But I don't know if it's fitting for my use case, I couldn't figure it out all myself. So here goes my question

I have a directory that needed to be synced on 2 servers. I was considering to use lsyncd , but readme page says this project is better at doing master-master / two way sync.

I couldn't figure out how to run this software as background daemon or at startup. Actually couldn't even run it successfully.

Currently I've setup unison software. It's simple yet awesome. But downside is it's not realtime or automated. I made crontab entry for every minute to run the script to manually sync it.

If you don't mind could you please guide me through the process?

[stephenh]

Hi! Thanks for the kind words.

Running as a daemon definitely makes sense, but just isn't something I've gotten to needing/building.

Daemonizing the mirror server command would be pretty easy, b/c there is little config for it. But mirror client ... has a number of options that means mirror would probably need to learn about config files. E.g. setup a mirror.conf for the client daemon to read in.

Which would be great, but again just haven't gotten around to it.

I don't have a ton of free/hacking time lately, so personally won't get a chance to work on it. If you want to hack around with something like:

https://commons.apache.org/proper/commons-daemon/

Or maybe:

https://github.com/brianm/gressil

I can provide feedback on PRs/etc.

[shinebayar-g]

Thanks for the reply.
Unfortunately I'm not dev, just sys admin guy who is looking for some solution for realtime sync between 2 or more servers. For the moment I'll be looking for another solution, but definitely will keep an eye on the project.

[paranoidd]

Hey @shinebayar-g ! At our organisation we've basically followed the same path as you've described (Unison) and hit the same downsides (lack of real-time sync). As well as same conclusions regarding lsyncd :D

We simply packed mirror into a custom docker image and we're running this on each server. We've organised it in start topology (1 server and many clients). So far works like a charm, but it's not handling any severe production loads yet. We sync whole /var/www path with it, that stores deployed code (with Unison we've synced particular paths in that root)

[Invincibear]

@shinebayar-g You can use the following commands:
nohup /path/to/mirror/mirror server --enable-log-file > /dev/null 2>&1 &

nohup /path/to/mirror/mirror client --enable-log-file -h servergoeshere.com -l /testsync/ -r /testsync/ > /dev/null 2>&1 &

[fezzzza]

Funnily enough, I just finished writing a init.d script before looking here to put forward my own feature request, so I may as well post my (admittedly somewhat amateurish) attempt to daemonise:

Assuming mirror is installed in the path,
$ nano /etc/init.d/mirror-server
and put this in:

#! /bin/sh
#
### BEGIN INIT INFO
# Required-Start:    $local_fs $remote_fs $network $java
# Required-Stop:     $local_fs $remote_fs $network $java
# Provides:          mirror-server
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: File tree sync mirror server
# Description:       File tree sync mirror server
### END INIT INFO

NAME="mirror-server"
DESC="File tree mirror service"
SCRIPTNAME="/etc/init.d/$NAME"
SHUTDOWN_HELPER="pkill java"

# Load the variables
. /etc/mirror/mirror-server.conf

OPTIONS=""

if [ "$SKIP_LIMIT_CHECKS" = "TRUE" ] ; then
     OPTIONS="--skip-limit-checks"
fi
#additional option logic to be built here

case "$1" in
start)
        mirror server $OPTIONS > /var/log/mirror.log 2>&1 &
#change the first > to >> if you want to log everything ever
        echo "mirror service started"
        ;;
stop)
        pkill java >null 2>&1
        pkill mirror >null 2>&1
# this is obviously overkill and may kill needed processes
# but I don't see a graceful shutdown option available yet
# there is definitely room for improvement here
        ;;
status)
        if ps -Al| grep mirror|grep -v "mirror-server" >null 2>null  ; then
                echo "mirror server running"
        else
                echo "mirror server not running"
        fi
        ;;
*)
        echo "Usage: $SCRIPTNAME {start|stop|status}" >&2
        exit 3
        ;;
esac
:
exit 0

---

$ nano /etc/mirror/mirror-server.conf

#! /bin/sh
# uncomment this line to enable it
# other variables can go here, but must also be accounted for in the script
#SKIP_LIMIT_CHECKS=TRUE

---

$ chmod 755 /etc/init.d/mirror-server
$ chmod 755 /etc/mirror/mirror-server.conf
$ systemctl enable mirror-server

[stephenh]

@fezzzza nice, thanks!

[fezzzza]

Well, that at least works to give me an autostart on the server although someone more experienced with Linux than me pointed out that I'm actually running through systemd, though I guess it's backwards compatible with this init script. The client script I have devised so far does not work on autostart because it's trying to resolve DNS before the internet connectivity is fully up, but it seems to work at least manually. Here it is:

mirror-client can go in /usr/local/bin or your preferred location alongside the mirror executables which need to be in your $PATH:

#! /bin/sh
#
### BEGIN INIT INFO
# Required-Start: $local_fs $remote_fs $network $java $named $all
# Required-Stop: $local_fs $remote_fs $network $java $named $all
# Provides: mirror-client
# Default-Start: 3 5
# Default-Stop: 0 1 2 4 6
# Short-Description: File tree sync mirror client daemon
# Description: File tree sync mirror client daemon thru ssh tunnel
### END INIT INFO

NAME="mirror-client"
DESC="File tree mirror client service"
SCRIPTNAME="/etc/init.d/$NAME"
SHUTDOWN_HELPER="pkill java" #I have no idea whether this is correct

# Load the configuration
#root has them in /etc/mirror/mirror.conf, logs to /var/log/mirror.log
#user has them in ~/.mirror/mirror.conf, logs to ~/.mirror/mirror.log

LOGDIR=~/.mirror/
CONFDIR=~/.mirror/

if [ "$EUID" = 0 ] ; then #ie if we are root
        LOGDIR=/var/log/
        CONFDIR=/etc/mirror/
fi

echo $CONFDIR

LOGFILE="$LOGDIR"mirror-client.log #set a default that may be overwritten by CONFFILE load

CONFFILE=$2
if [ "$2" = "" ] ; then
        CONFFILE="$CONFDIR"mirror-client.conf
fi
. $CONFFILE

case "$1" in
start)
        echo "mirror start control received" >> $LOGFILE
        echo "ssh -f -L $CLIENTPORT:localhost:$SERVERPORT $USERNAME@$SERVERNAME -i $KEYFILE -N"
        ssh -f -L $CLIENTPORT:localhost:$SERVERPORT $USERNAME@$SERVERNAME -i $KEYFILE -N > $LOGFILE 2>&1
        SSHERRORLEVEL=$?
        if [ $SSHERRORLEVEL != 0 ] ; then
                echo "ssh tunnel failed - see $LOGFILE"
        fi
        if [ $SSHERRORLEVEL = 0 ] || [ "$FORCESTART" = "TRUE" ] ; then
                echo "mirror client $OPTIONS $INCLUDEOPTIONS $EXCLUDEOPTIONS -h localhost -l $CLIENTDIR -r $SERVER$
                mirror client $OPTIONS $INCLUDEOPTIONS $EXCLUDEOPTIONS -h localhost -l $CLIENTDIR -r $SERVERDIR >>$
                if [ $? = 0 ] ; then
                        echo "mirror client started"
                        echo "mirror client started" >> $LOGFILE
                else
                        echo "mirror client not started - see $LOGFILE"
                        echo "mirror client not started" >> $LOGFILE
                fi
        else
                echo "start mirror not attempted"
                echo "start mirror not attempted" >> $LOGFILE
        fi
        ;;
stop)
        #beware - if you have multiple mirror instances, this will kill them all
        echo "mirror stop control received" >> $LOGFILE
        PID=1 # until doesn't work quite as expected without this
        until [ "$PID" = "" ] ; do
                PID=$(ps -Al|grep mirror|grep -v "mirror-client"|awk '{print $4}')
                if [ "$PID" != "" ] ; then
                        echo "killing mirror with PID $PID" >> $LOGFILE
                        kill $PID >> $LOGFILE 2>&1
                fi
        done
        if ps -Al| grep java > /dev/null ; then
                echo "killing java" >> $LOGFILE
                pkill java >> $LOGFILE 2>&1
        # this is obviously overkill and may kill needed processes
        # but I don't see a graceful shutdown option yet
        fi
        if ps -Al| grep ssh|grep -v "ssh-agent" > /dev/null ; then
                echo "killing ssh" >> $LOGFILE
                pkill ssh >> $LOGFILE 2>&1
        fi
        echo "all mirror processes killed" >> $LOGFILE
        echo "all mirror processes killed"
        ;;
status)
        if ps -Al| grep ssh|grep -v "ssh-agent" > /dev/null ; then
                echo "ssh session detected - it might be our tunnel"
        else
                echo "ssh tunnel not found"
        fi
        if ps -Al| grep mirror|grep -v "mirror-client" > /dev/null ; then
                echo "mirror client running"
        else
                echo "mirror client not running"
        fi
        ;;
*)
        echo "Usage: $SCRIPTNAME {start|stop|status} alternative-file.conf" >&2
        exit 3
        ;;
esac
:
exit 0

mirror-client.conf either belongs in ~/.mirror or /etc/mirror if you are running it as root to daemonise:

#! /bin/sh
#
USERNAME=root
SERVERNAME=www.myserver.com
CLIENTPORT=49172
SERVERPORT=49172
CLIENTDIR=/var/www/html
SERVERDIR=/var/www/html
INCLUDEOPTIONS="--include file.ext --include example.dir/"
EXCLUDEOPTIONS="--exclude dir/file.ext --exclude log/"
#put as many include/exclude arguments as you need, just remember
#to include an "--include" or "--exclude" prefix for each one
#use of quote marks to delimit the file names seems to cause failure

#these options can easily be switched on by commenting or uncommenting
#Some require arguments. See "mirror help client" for details
#OPTIONS="$OPTIONS --enable-log-file"
#OPTIONS="$OPTIONS --debug-all"
#OPTIONS="$OPTIONS --debug-prefixes LIST_OF_PATHS" #replace LIST_OF_PATHS with your list
#OPTIONS="$OPTIONS --skip-limit-checks"
#OPTIONS="$OPTIONS --use-internal-patterns"

#FORCESTART=TRUE
#include this line if mirror should start regardless of SSH tunnel success

KEYFILE=/root/.ssh/id_rsa
#this assumes you have already set up your ssh authorisation
#by creating an SSH key pair using, eg, ssh-keygen
#and distributed the public key to the server in .ssh/authorized_keys

#LOGFILE=~/.mirror/mirror.log
#LOGFILE=/var/log/mirror.log
#this will override the default

Don't forget to make them both executable as before.

I'm abandoning any hope of getting this to autorun right now because my use case is a roaming laptop that will be ducking in and out of internet connectivity, and the 2 big unanswered questions for me are:

1. What happens to the ssh tunnel when internet connectivity drops and reconnects?
2. What happens to mirror when internet connectivity drops and reconnects?
   ...and right now for me I have bigger fish to fry, so I'm happy enough starting and stopping the client manually. That said, it would be nice if this sort of state management could be handled eventually. Perhaps it would make more sense to deal with both problems at once if/when request Provide built-in TLS/SSH security (instead of just SSH tunneling) #10 gets implemented.

Probably the wrong place to put a feature request, but seeing as I'm sharing my progress, just to keep things in one place:

I need to connect one workstation to multiple servers, dependent on which set of code I'm modifying, and don't believe that's possible at the moment. A simple fix would be to be able to have multiple instances of mirror running and specify the port number in the options (both client and server side) and thereby communicate with each server via multiple ssh tunnels, each with its own port number. As I'm handling connection state manually for the time being, I'll just start and stop whichever connection suits by modifying the above to select between specified .conf files. I've just edited the code above to show the variant for those who are interested. Anyone using this please be aware I'm under no delusion that this is "good" code, so use with caution!

Then the icing on the cake would be to implement rsync to minimise network traffic, but I know you've already put that down as a non-goal... just my 2p ;)

Thanks, Stephen, for your work so far - it's made my job as an amateurish webdev much easier.

[stephenh]

What happens to the ssh tunnel when internet connectivity drops and reconnects

FWIW http://www.harding.motd.ca/autossh/ might be "good enough" to keep auto-detect/reconnect the tunnels for you.

What happens to mirror when internet connectivity drops and reconnects

The tunneling aside, mirror should notice the disconnect, and repeatedly ping for when the reconnect is back, then reconnect and resync. It should generally just work. The only caveat is that if both sides have drifted way out of sync, mirror does a ~dumb "last-write-wins" union/merge.

Admittedly, I should really get around to implementing this; personally I boot up my server and laptop and then: 1) manually run ./mirror server and 2) manually run three ./mirror client commands for the three directories I sync between the two. It would be nice to have that just happen. Have a few other things I'm busy with, but will nudge it up on my list.

[fezzzza]

Thanks. I have updated my scripts above that you may freely incorporate into your package (you can see the edit history for older versions) and will further update it for autossh if and when I get a chance. Same warning goes though - I'm not really a bash programmer by any stretch of the imagination, so take nothing for granted that this is "good" code! However I've hit a bunch of problems that I've filed issues for, some of which are making it impossible for me to continue with mirror for the time being. Would love to come back to it if you get time to deal with these issues as it's wonderfully lightweight. Best of luck!

[Yamakasi]

@fezzzza thanks for the scrips, any update on these as well ?

/edit

Please update your copy/paste code as it's missing some quotes :)