Sunday, May 11, 2008

ejabberd on Amazon EC2 Ubuntu AMI

It turned out to be harder that I expected to setup a Jabber (XMPP) server on an Ubuntu virtual machine (ami-ce44a1a7) within Amazon EC2. I chose to setup ejabberd since it was an easy to install via apt-get. I was a little nervous about working with a server built with Erlang since I knew nothing about it, but it was a reputable server and I was counting on not needing to have any Erlang knowledge to work with ejabberd. That was a correct assumption for the most part.

First, I logged into the VM and installed ejabberd:
apt-get install ejabberd
Next I edited the ejabberd config file, /etc/ejabberd/ejabberd.cfg, making kweiner@jabber.pop140.com an admin user and setting the hostname as jabber.pop140.com:
%% Admin user
{acl, admin, {user, "kweiner", "jabber.pop140.com"}}.

%% Hostname
{hosts, ["jabber.pop140.com"]}.
Next, I restarted the server and registered kweiner as a new user:
/etc/init.d/ejabberd restart
ejabberdctl register kweiner jabber.pop140.com mypasswd
Then I authorized traffic on ports 5222 (Jabber), 5223 (Jabber encrypted for old clients), 5269 (Other Jabber servers), and 5280 (Jabber web admin tool):
ec2-authorize default -p 5222
ec2-authorize default -p 5223
ec2-authorize default -p 5269
ec2-authorize default -p 5280
I could now hit the admin screen on which I logged in as kweiner@jabber.pop140.com:
http://jabber.pop140.com:5280/admin/
From here it was possible to add new users and browse server statistics. I experimented with adding users and using various Jabber clients like Gajim to send messages from one user to another.

My first problem came when I tried to communicate with users registered in other Jabber servers like Jabber.org and Google Talk. I struggled for hours trying to figure out why users on my server couldn't communicate with users from these other servers. Thankfully James Murty gave me a bit of help on this Jabber on EC2 message board thread. It turned out that I needed to configure SRV records in my DNS settings.

I logged into GoDaddy where my domain is registered and configured SRV records as follows:


After this, I was able to use nslookup to verify that the SRV records were setup properly:
kweiner~$ nslookup
> set type=srv
> _xmpp-server._tcp.pop140.com
Server: 66.75.160.63
Address: 66.75.160.63#53

Non-authoritative answer:
_xmpp-server._tcp.pop140.com service = 10 10 5269 jabber.pop140.com.
That did it! My jabber server was finally federating with other jabber servers and my users could talk to their users.

I encountered my next big problem when I tried to use jabber again after terminating and relaunching my AMI. ejabberd failed to start and I found the following error message in the /var/log/ejabberd/ejabberd.log:
application: ejabberd
exited: {bad_return,{{ejabberd_app,start,[normal,[]]},
{'EXIT',{{badmatch,{aborted,{no_exists,config}}},
[{ejabberd_config,set_opts,1},
{ejabberd_app,start,2},
{application_master,start_it_old,4}]}}}}

After some googling, I found that ejabberd associates itself with an Erlang node name, a concept I don't really understand that well. By default the node name was dynamically set based on the hostname for the machine. It looked something like this: ejabberd@domU-12-31-38-00-9D-63. This node name is somehow linked to the Mnesia database stored as files within /var/lib/ejabberd. The problem is that the hostname and therefore the node name changes everytime the AMI is relaunched which confuses ejabberd.

One solution I found is to explicitly set the node name. I did this by modifying /etc/default/ejabberd adding the line:
export ERLANG_NODE=ejabberd@jabber
This requires adding jabber as a host name inside /etc/hosts:
127.0.0.1 localhost.localdomain localhost jabber
I made those changes, removed all the database files from /var/lib/ejabberd, and restarted ejabberd. That did it! The node name was the same regardless of the hostname associated with the particular AMI instance.

This was a lot of effort, but it probably would have been easier if I had been familiar with Erlang applications and SRV DNS settings. I hope this post helps someone else struggling to setup ejabberd on EC2 as I did.

19 comments:

Gabriel said...

How do you cleaned up de mnesia database? What are those files? I have a similar problem, I have a server with fixed ip but the last weekend my ip changed and now I can't start my ejabberd server. Could you help me?
Thanks in advance.
Gabriel

Gabriel said...

I have a similar problem here. I have a server with fixed ip address but this weekend my service provider changed it, and now I can't start the ejabberd service. How can I clean the mnesia database? I will loose all my users doing this?
Thanks in advance.
Gabriel.

Don said...

This was all incredibly helpful, particularly the pitfall regarding the erlang node name. Thanks for posting this!

DLJ said...

I notice that the /etc/hosts file is reset following a reboot. Do you have a solution to make sure jabber is added for 127.0.0.1 please?

Thank you for posting this by the way, it really helped with setting up ejabberd in EC2.

DLJ said...

I notice that the /etc/hosts file is reset following a reboot. Do you have a solution to make sure jabber is added for 127.0.0.1 please?

Thank you for posting this by the way, it really helped with setting up ejabberd in EC2.

mIRC Ar┼čivleri said...

very nice blog number one topic.
Sohbet
Regards.

denil said...

Hi Ken,

I m totally confused on wht I need to do. Request youto kindly help me if possible.

I am running eJabberd server on a static ip, which is my pc.

I've my domain registered (say, mydomain) and hosted at godaddy.com and have created a subdomain named as chat.mydomain.com.

I want users to add user@chat.mydomain.com to their gtalk contact list and start chatting.

Now, i don't know how to establish the link from my godaddy sub-domain to the static ip where the server is running. I knw SRV entires need to be done but don't know the exact details.

Plz plz plz help of u can.

Regards,
Denil

gay sohbet said...

thnk you

Anonymous said...

Thanks a lot man! I've had this problem with the instance name and was suspecting your hypothesis myself, but couldn't get it right until that post.

vijesh said...

The works in this post is great. wish to know more about its working processes. Thanks for the wonderful post.....

Busto said...

I think there is one more step, and that is changing ERLANG_NODE=ejabberd to ERLANG_NODE=ejabberd@jabber in /usr/sbin/ejabberdctl

-Dan

Muhammed K K said...

Thanks, It helped a lot

gizlesene said...

thank you

Khantil Patel said...

Thanks Ken, your blog was really helpful!! Wonderful job!!

Khantil Patel said...

Thanks Ken, your blog was very helpful to setup Ejabberd on AWS Cloud!!! Wonderful Job!!

Gv said...

Thanks a lot for sharing.

Vaibhav Tolia said...

Hi

When I tried ec2-authorize default -p 5280

It says
GROUP default
PERMISSION default ALLOWS tcp 5222 5222 FROM CIDR 0.0.0.0/0 ingress

but somehow I'm not able to access the web admin tool, any pointers

shaalini soundiah said...

Hi Ken,

I am trying to set-up ejabberd server on Amazon instance with the hostname as the public domain name which i got in the EC2 instance(ec2-54-149-8-44.us-west-2.compute.amazonaws.com/) . I am trying to achieve federation of my jabber server with gchat which needs adding a srv record , is it possible for me to add srv for the public dns of EC2 instance

shaalini soundiah said...

Hi Ken,

I am trying to set-up ejabberd server on Amazon instance with the hostname as the public domain name which i got in the EC2 instance(ec2-54-149-8-44.us-west-2.compute.amazonaws.com/) . I am trying to achieve federation of my jabber server with gchat which needs adding a srv record , is it possible for me to add srv for the public dns of EC2 instance