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From adrien ruffie <adriennolar...@hotmail.fr>
Subject RE: zookeeper as systemd
Date Tue, 17 Jul 2018 06:01:57 GMT
thank you very much Norbert !

I take your useful suggestion, and try to launch zookeeper with your

service file.


Great thank,


Adrien

________________________________
De : Norbert Kalmar <nkalmar@cloudera.com.INVALID>
Envoyé : lundi 16 juillet 2018 16:18:36
À : user@zookeeper.apache.org
Objet : Re: zookeeper as systemd

Some prefer to use start-foreground to basically "bypass" the bash script
(and the background management), and make systemd care about it. Also to
ignore any nohup. So while it is also my understanding that the recommended
way is to start ZK with simple start, some use start-foreground to start as
a systemd service.

Type=simple - drawback is depending services (if any) will not know if it
is truly ready (sockets as well)
Type=forking - drawback is there might be some issues with the PID (file).
So you should also define where the pid file
is: PIDFILE="/var/run/zookeeper/zookeeper_server.pid"

Any combinations should work. It really comes down to preferans I think.

Disclaimer: I'm kind of trying to make educated guesses here, so a
Linux-slash-zookeeper guru could probably be more of a help here :)

This is how I would create systemd service file (this time using start not
start-foreground) - or something like that:
Put the systemd service file in: /etc/systemd/system/zookeeper.service

[Unit]

Description=Zookeeper

After=network.target syslog.target


[Service]

SyslogIdentifier=zookeeper

TimeoutStartSec=10min

Type=forking

User=zookeeper

Group=zookeeper

PIDFILE="/var/run/zookeeper/zookeeper_server.pid"

ExecStart=/usr/lib/zookeeper/bin/zkServer.sh start

ExecStop=/usr/lib/zookeeper/bin/zkServer.sh stop

WorkingDirectory=/var/lib/zookeeper


[Install]

WantedBy=multi-user.target


Of course not everything is required (User, Group, WorkingDirectory
possibly optional)


But I would dig deeper before saying anything for sure.


Regards,

Norbert

On Mon, Jul 16, 2018 at 3:01 PM adrien ruffie <adriennolarsen@hotmail.fr>
wrote:

> Thank Norbert for this good explanation.
>
> Yes I'm also a really lost here a bit ...
>
> But it's a zookeeper production's cluster of 5 nodes.
> It should be start instead start-foreground isn't it ? (with simple type)
> ________________________________
> De : Norbert Kalmar <nkalmar@cloudera.com.INVALID>
> Envoyé : lundi 16 juillet 2018 13:49:16
> À : user@zookeeper.apache.org
> Objet : Re: zookeeper as systemd
>
> The type is Linux config, and forking is used when we want the process to
> call fork() during startup. This should guarantee that when startup is
> finished, all ports are open. In my understanding, using FORKING will tell
> systemd the startup is complete and ports are open. See
> https://www.freedesktop.org/software/systemd/man/systemd.service.html for
> more information.
> TYPE=simple is mainly for daemons that don't use network channels, or they
> have their own socket activation.
>
> So in my opinion, TYPE=forking is better for ZK. But! Forking should
> require a PIDfile in order for it to work properly... but since systemd is
> used, it should know the PID as it is a supervisor. I'm also lost here a
> bit...
> Looking at ZK PID file should be
> available: ZOOPIDFILE="$ZOO_DATADIR/zookeeper_server.pid"
>
>
> About the simple start or start-foreground... I think I was quick to say
> only use simple start in prod environment. This is much more complicated,
> for example start-foreground would just make it ignore nohup.
>
> Doing some search, these 2 questions might help:
>
> https://stackoverflow.com/questions/40620544/systemd-zookeeper-service-failed
>
> https://askubuntu.com/questions/979498/how-to-start-a-zookeeper-daemon-after-booting-under-specific-user-in-ubuntu-serv
>
> Putting this all together, I think if you don't really care when socket is
> ready, just use TYPE=simple and call with start-foreground.
>
> Regards,
> Norbert
>
>
>
> On Mon, Jul 16, 2018 at 11:48 AM adrien ruffie <adriennolarsen@hotmail.fr>
> wrote:
>
> > Thank Nobert !
> >
> >
> > It really help me,
> >
> >
> > according to you, what would you recommend?
> >
> >
> > To launch with "Type=simple" and zkServer.sh start ?
> >
> > Or "Type=forking" and zkServer.sh start ?
> >
> >
> > Because start command launch Zookeeper as a Daemon,
> >
> > but if I use "Type=simple" the system already daemonize the process ...
> >
> > Do you think that can be daemonize a daemon ... ? Strange
> >
> >
> > I really ready to use "Type=forking" option but, according to this
> > following post
> >
> >
> > https://bbs.archlinux.org/viewtopic.php?id=191669
> >
> >
> > the "Type=forking" is not really recommended ...
> >
> > what do you think ?
> >
> >
> > Adrien
> >
> >
> > ________________________________
> > De : Norbert Kalmar <nkalmar@cloudera.com.INVALID>
> > Envoyé : lundi 16 juillet 2018 10:15
> > À : user@zookeeper.apache.org
> > Objet : Re: zookeeper as systemd
> >
> > Hi Adrien,
> >
> > zkServer.sh start-foreground - starts the ZooKeeper process in the
> > foreground. Good for debugging (thats what I use it for), or check
> > something, as you will have the logs printed to standard output (console
> > most probably).
> > The "start" is what you want to use in production environment. the
> process
> > will run in the background.
> >
> >    ' What is "After=network.target" ? ' - ZooKeeper should only start
> after
> > the network... available? I think this should be something like
> > After=network-online.target
> >
> > But looking at the others, I'm not entirely sure either what they really
> > do. But checko out this jira -
> > https://issues.apache.org/jira/browse/ZOOKEEPER-2095
> >
> > There was a patch about this, and they added systemd startup/conf files.
> >
> > Sorry, this is all I could come up with, as I'm not familiar with this
> part
> > either. Hope it helps.
> >
> > Regards,
> > Norbert
> >
> >
> > On Fri, Jul 13, 2018 at 5:30 PM adrien ruffie <adriennolarsen@hotmail.fr
> >
> > wrote:
> >
> > > Hello Zookeeper's users,
> > >
> > >
> > > I have 2 questions for you.
> > >
> > >
> > > what is the real difference between these 2 following commands ? (I
> don't
> > > find any documentation)
> > >
> > >
> > > zkServer.sh start-foreground
> > >
> > > and
> > >
> > > zkServer.sh start
> > >
> > >
> > >
> > > My second question is, how I can correctly start my zookeeper as a
> > > systemclt service ?
> > >
> > > What is the common best template to write into
> > > /etc/systemd/system/zookeeper.service ?
> > >
> > > Do you use Restart=always ? RestartSec=0s ?
> > >
> > > What is "After=network.target" ?
> > >
> > > If my Zookeeper does not really start in 300 sec, the process will be
> > > shutdown ?
> > >
> > >
> > > Do you have any example of zookeeper service file ?
> > >
> > >
> > > Because our zookeeper.service is right now:
> > >
> > >
> > > [Unit]
> > > Description=ZooKeeper
> > >
> > > [Service]
> > > Type=simple
> > > User=zookeeper
> > > Group=zookeeper
> > > ExecStart=/usr/local/zookeeper-3.4.9/bin/zkServer.sh start-foreground
> > >
> > > TimeoutSec=300
> > >
> > > [Install]
> > > WantedBy=multi-user.target
> > >
> > > ------------------- But I found this following on a blog:
> > >
> > >
> > > [Unit]
> > > Description=Apache Zookeeper
> > > After=network.target
> > >
> > > [Service]
> > > Type=forking
> > > User=zookeeper
> > > Group=zookeeper
> > > SyslogIdentifier=zookeeper
> > > Restart=always
> > > RestartSec=0s
> > > ExecStart=/usr/bin/zookeeper-server start
> > > ExecStop=/usr/bin/zookeeper-server stop
> > > ExecReload=/usr/bin/zookeeper-server restart
> > >
> > > [Install]
> > > WantedBy=multi-user.target
> > >
> > >
> > > Thank you very much and best regards
> > >
> > > Adrien
> > >
> >
>

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