Re(2): [Fab-user] Revert deployments

[Miguel A. Lamy]

Hi Jeff,

Thank you very much. It help a lot.

Your example gave me several ideas.

Miguel Lamy

address@hidden on segunda-feira, 19 de Janeiro de 2009 at 18:47  wrote:
:Hi Miguel,
:
:Fabric is only a tool for you to use -- it doesn't know anything about
:your application or how it works. All it really does is allow you to
:"script" shell commands and file uploads using Python.
:
:A good rule of thumb for writing Fabric scripts/recipes is to figure
:out how you would accomplish a given task by hand (i.e. by SSHing into
:the server and doing things there). Once you can do something by hand
:and know how it's done, you can then turn that knowledge into a series
:of Fabric run() or sudo() calls.
:
:So, in order to detect a failed deployment, you will have to figure
:out how to define what failure means in your situation, and how to
:detect that.
:
:
:For example -- and this is only one of many possible examples -- let's
:say your Java app writes logs to the file system. You could write a
:deploy script that does something like this pseudocode:
:
:- do normal deploy
:- read in last 100 lines of error log file
:- identify lines which are within a few minutes of the current time
:- search those lines for specific error strings or prefixes (such as
:"ERROR:" or "CRITICAL:)
:- If the errors are found, take steps to revert your deploy
:
:Obviously, you can package up those into their own subroutines, such
:as deploy(), errors(), and rollback(), and then your deploy script can
:be as simple as:
:
:def perform_deploy():
:    deploy()
:    if errors():
:        rollback()
:
:
:But, again, this is all up to you: Fabric can't do your problem
:solving for you -- it just makes it possible to implement the
:solution.
:
:Hope that helps somewhat!
:
:Best,
:Jeff
:
:On Mon, Jan 19, 2009 at 1:03 PM, Miguel A. Lamy <address@hidden> wrote:
:> Hi all,
:>
:> I am evaluating Fabric and a I'm bit lost sorry... I think I'm putting dumb 
question.
:>
:> I want to deploy Java Web application into several servers. In the past I 
used some shell scripts that
:stoped
:> myservers, rsynced my app to the servers, backuped the databases (Mysql, 
SqlServer and Oracle) and started
:> the application server (tipical Jboss and Oracle). I use ssh in all servers 
with public keys.
:>
:> I was doing the deployment  server by server and sometimes the process 
didn't run as expected and I have
:> crashs during the startup of the application because of some program errors 
or inconsistency in the
:databases.
:>
:> So I thought may be I can use some tool out there that simplify that work 
and revert my process with no
:> pain...
:>
:> I read some documentation from Fabric site and from the github.com but still 
don't know how can I run
:> myscripts in a way that can "detect" errors in deployment and run some 
rollback code that reverts errors
:> during the deployment.
:>
:> I understand that I can use variables to store command result status and 
define rollback commands that can
:be
:> executed but my question is... can Fabric "detect" errors and automatically 
execute rollback functions in
:> case of some trouble ?
:>
:> I want to deploy several servers and not be worried if one server didn't 
deployed correctly at 2.00AM and
:the
:> application server didn't start because of that failure. That server should 
automatically recover from that
:> bad deploy, revert to the previous status so in the morning I can analyse 
the errors and correct that
:errors
:> not worried that users can't run my application because of that failure.
:>
:> I'd appreciate any help given :-)
:>
:> (Sorry for my poor english)
:>
:> Miguel Lamy
:>
:>
:>
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