Failsafe zoneminder with gluster and geo-replication.

Near year ago i configured zoneminder for monitoring my approach. But i got one problem, host that running zoneminder placed in same approach, so, if it will be stolen, it will be stolen with recordings. I spend a lot of time while choosing solution to organize replication on remote server. Most solution that i found work in “packet” mode, they start replication once in NN sec or after accumulating a certain number of events and usually use rsync. Rsync allow to reduce traffic usage, but increase time between event when new frame will be wrote on disk and event when frame will be wrote on remote side. In this situation every second counts, so I thought that solutions like “unison”, “inosync”, “csync2”, “lsyncd” not applicable.

I tried to use drbd, but get few problems. First – i do not have separate partition on host and can not shrink existing partitions to get new. I tried it with loopback devices, but drbd have deadlock bug when used with loopback. This solution work near two days after deadlock occurs, you can not read content of mounted fs or unmount it and only one solution to fix it that i found – reboot. Second problem – “split brain” situation, when master host restart. I did not spent time to found solution because all ready had first problem. May be it can be fixed with split-brain handlers script or with “heartbeat”. Drbd has great write speed in asynchronous mode and has small overhead, so, may be in another situation i will choose drbd.

Next what i tried was “glusterfs”, first i tried glusterfs 3.0. It was easily to configure it, and glusterfs was worked, but very slow. For good performance glusterfs need short latency between hosts. It useful for local networks but completely useless for hosts connected over slow links. Also glusterfs 3.0 did not have asynchronous write like in drbd. I temporarily thrown searching for solutions, but after a while in release notes for glusterfs 3.2 i found that gluster got “geo-replication“. First i think that this it what i need and before has understood (see conclusion) how it work i started to configure it.

If you will have troubles with configuration, installation  here you can find manual.
For Debian, first that you need is to add backports repository on host with zonemnider and on hosts where you planned to replicate data:

$ echo 'deb squeeze-backports \
main contrib non-free' >> /etc/apt/sources.list
$ apt-get update
$ apt-get install glusterfs-server

After that you must open ports for gluster on all hosts where you want to use it:

$ iptables -A INPUT -m tcp -p tcp --dport 24007:24047 -j ACCEPT 
$ iptables -A INPUT -m tcp -p tcp --dport 111 -j ACCEPT 
$ iptables -A INPUT -m udp -p udp --dport 111 -j ACCEPT 
$ iptables -A INPUT -m tcp -p tcp --dport 38465:38467 -j ACCEPT

If you do not planned to use glusterfs over NFS (as i) you can skip last rule.
After ports will opened, gluster installed and service running you need to add gluster peers. For example you run zoneminder on host “zhost” and want to replicate it on host “rhost” (do not forget add hosts in /etc/hosts on both sides).  Run “gluster” and add peer (here and below gluster commands must to be executed on master host, i.e. on zhost):

$ gluster
gluster> peer probe rhost

Let’s check it:

gluster> peer status
Number of Peers: 1
Hostname: rhost
Uuid: 5e95020c-9550-4c8c-bc73-c9a120a9e96e
State: Peer in Cluster (Connected)

Next  necessary to create volumes on both hosts, do not forget to create directories where gluster will save their files. For examples you planned to use “/var/spool/glusterfs”:

gluster> volume create zoneminder transport tcp zhost:/var/spool/glusterfs
Creation of volume zoneminder has been successful. Please start the volume to access data.
gluster> volume create zoneminder_rep transport tcp rhost:/var/spool/glusterfs
Creation of volume zoneminder_rep has been successful. Please start the volume to access data.
gluster> volume start zoneminder
Starting volume zoneminder has been successfu
gluster> volume start zoneminder_rep
Starting volume zoneminder_rep has been successfu

After that you must configure geo-replication:

gluster> volume geo-replication zoneminder gluster://rhost:zoneminder_rep start
Starting geo-replication session between zoneminder & gluster://rhost:zoneminder_rep has been successful

And check that it is work:

gluster> volume geo-replication status
MASTER               SLAVE                                              STATUS    
zoneminder           gluster://rhost:zoneminder_rep           starting...
gluster> volume geo-replication status
MASTER               SLAVE                                              STATUS    
zoneminder           gluster://rhost:zoneminder_rep           OK

Also i made next configurations:

gluster> volume geo-replication zoneminder gluster://  config sync-jobs 4
geo-replication config updated successfully
gluster> volume geo-replication zoneminder gluster://  config timeout 120
geo-replication config updated successfully
gluster> volume set zoneminder nfs.disable on
Set volume successful
gluster> volume set zoneminder_rep nfs.disable on
Set volume successful
gluster> volume set zoneminder nfs.export-volumes off
Set volume successful
gluster> volume set zoneminder_rep nfs.export-volumes off
Set volume successful
gluster> volume set zoneminder performance.stat-prefetch off
Set volume successful
gluster> volume set zoneminder_rep performance.stat-prefetch off
Set volume successful

I disabled nfs because i did not planned to use gluster volumes over nfs, also i disabled prefetch because they produce next error on geo-ip modules:

E [stat-prefetch.c:695:sp_remove_caches_from_all_fds_opened] (-->/usr/lib/glusterfs/3.2.7/xlator/mount/ [0x7f2006ba8ed0] (-->/usr/lib/glusterfs/3.2.7/xlator/debug/
(io_stats_setattr+0x14f) [0x7f200467db8f] (-->/usr/lib/glusterfs/3.2.7/xlator/performance/ [0x7f200489c99c]))) 0-zoneminder_rep-stat-prefetch: invalid argument: inode

In conclusion i must to say, that it is not a solution that i looked for, because as it turned out  gluster use rsync for geo-replication. Pros of this solution: it is work and easy to setup. Cons it is use rsync. Also i expected that debian squeeze can not mount gluster volumes in boot sequence, i tried to modify /etc/init.d/ but without result, so i just add mount command in zoneminder start script.

echo ‘cyclope:zoneminder      /var/cache/zoneminder   glusterfs       defaults        0       0’ >> /etc/fstab
And add ‘mount /var/cache/zoneminder’ in start section of /etc/init.d/zoneminder

Do not forget to stope zoneminder and copy content of /var/cache/zoneminder on new partition before using it.

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Posted in Linux related, Security related

3 Responses to “Failsafe zoneminder with gluster and geo-replication.”

  • j says:

    Just noting for posterity: I had great success in using lsyncd as a means of syncing zoneminder footage. The official docs are a little lacking in context IMO, just google for examples that other people have made. The two main settings you need in your config file are the ‘statusInterval’ parameter (in global config settings) and the ‘delay’ parameter (in your sync options). Set statusInterval to something between 1-5, so that it checks for changes every 1-5 seconds. The delay parameter is also important: Once lsyncd detects changes, the ‘delay’ option tells it to let changes accumulate for X more seconds before initiating a sync operation. I had it set to 3 seconds.

    With a statusInterval of 1 and a sync delay of 3, It takes about 3-4 seconds to start syncing data from the moment Zoneminder starts writing footage to the drive. One cool thing about lsyncd is that you only need to configure it on the local host- the remote host is just getting files pushed to it via rsync over ssh. Just make sure the remote host allows as many ssh connections as your specified maxProcesses in lsyncd.

    Another good reason to use tools like lsync instead of DRBD/Gluster: if your remote server is a cookie-cutter, cloud-hosted VM that doesn’t let you repartition your storage, you may not have the luxury of setting up separate partitions for your sync data. (not sure if Gluster specifically requires this, but all of the instructions seem to take separate disks as a given.)

    • Ivan says:

      Because I want to sync new frames fast as possible, i looked for solution that does not use rsync.
      Zoneminder creating a lot of dirs and small files, if synchronization app does not use inotify or something like fuse fs, then they must scan dirs with zoneminder data completely.
      It is a lot of work. Also, lsyncd scaning dir for changes every 3 seconds (in your example), after that, they will run rsync and wait 3 seconds again.
      If lsyncd pass to rsync only changes that they found, then you have gap between syncs frames that wrote while rsync ran + frames while lsyncd delay, so a lot of frames can be lost if you host with your zoneminder will run out of power or will be stolen.

    • Ivan says:

      Sorry, lsyncd uses inotify, so, you will have only gap between syncs.

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