Monday, March 17, 2014

CloudStack-BIND dns integration.

How to integrate CloudStack DNS with your organization DNS environment?
All recommendation bellow based on the approach of using one sub-domain per CloudStack network.
 1. The simplest way: conditional forwarding from windows DNS server to CloudStack VR for the corresponding sub-domain or (BIND) sub-domain delegation to the VR. 
pros: easy to build
con: VR are running as not authoritative DNS for sub-domain, each time new record added dnsmasq service restarts and you have 2-3 sec of downtime (up to v4.1), all request going to VR.
  2.  CloudStack --> BIND full integration:
Following program solves DNS integration issues between CloudStack VR's DNS service and BIND DNS.
This program assumes that you are using sub-domain per network(each network has own sub-domain) (IMHO the best way fro naming instances in CloudStack)
How it works:
On event or on schedule program call CloudStack API and get list of Networks and list of VM. Using theses lists and preconfigured domain settings it creates the zone file for BIND, push it to server and refresh BIND.
This program could be run using 2 different ways: 
  1.  being installed on DNS server and update DNS records on scheduled interval. (schedule driven)
  2.  being installed on CloudStack management server and listen for the new vm deployment using CloudStack catalina.out log. (event driven)

Proposed version running on heavy used CloudStack environment with very frequent SaltStack driven deployments with almost no issue. 



The script is under active development and testing and will be updated.
Version 2.0 released with all parameters now loaded from dns_builder.conf file and local and remote DNS servers support. 
PS:
Some times this script fails because of non-expeted  ClaudStack response:
 
    dns_table = get_dns()
  File "/usr/bin/dns_builder.py", line 134, in get_dns
    output+= vm['name'] + "." + net_dict[vm['nic'][0]['networkname']] + "\t\t\t300\tIN\tA\t" + vm['nic'][0]['ipaddress'] +" \n"
IndexError: list index out of range

Instead of exception handling to keep this script running I used supervisord daemon.
It starts the script, makes sure it running, restarts in case of failure and takes care of logs.
Part of supervizord.conf file related to the script:
[program:dns_builder]
command=/usr/bin/dns_builder.py      ; the program (relative uses PATH, can take args)
priority=100                ; the relative start priority (default 999)
autostart=true              ; start at supervisord start (default: true)
autorestart=true            ; retstart at unexpected quit (default: true)
;startsecs=10                ; number of secs prog must stay running (def. 10)
startretries=5              ; max # of serial start failures (default 3)
;exitcodes=0,2               ; 'expected' exit codes for process (default 0,2)
;stopsignal=QUIT             ; signal used to kill process (default TERM)
;stopwaitsecs=10             ; max num secs to wait before SIGKILL (default 10)
;user=chrism                 ; setuid to this UNIX account to run the program
log_stdout=true             ; if true, log program stdout (default true)
log_stderr=true             ; if true, log program stderr (def false)
logfile=/var/log/dns_builder.log    ; child log path, use NONE for none; default AUTO
logfile_maxbytes=1MB        ; max # logfile bytes b4 rotation (default 50MB)
logfile_backups=2          ; # of logfile backups (default 10)

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