Random thoughts of a warped mind…

September 17, 2014

Reconfig for service discovery

Filed under: Amazon EC2,Chef,Git,Linux,Redhat OpenShift,Ruby,Virtualization — Srinivas @ 09:49

Imagine a constantly changing fleet of servers… New servers (or virtual machines) going online as capacity is needed or being taken offline as load drops… Maybe you already use Chef/Puppet to bootstrap your servers and use their node attributes to populate N servers in a load balancer (Haproxy for example) configuration. 

Now adding/removing a new server (a backend, maybe a rails/tomcat server, whatever) would mean that chef-client has to run on all the haproxy boxes so they know about the new backend (or the one that went away). This would work if you  run chef-client every 5 minutes or so? But why? Chef/Puppet are primarily meant to bootstrap your servers and not to sync state. Enter Reconfig and service discovery.


August 4, 2014

PubKey for SSH public key setup

Filed under: Amazon EC2,Chef,Linux,Redhat OpenShift,Virtualization — Srinivas @ 13:13

Built and started using PubKey for managing user SSH public keys (add, update and revoke access) on my personal EC2 and Google compute fleet… Try it out – https://www.pubkey.in/console/ . Docs available on http://docs.pubkey.in and for you lazy sysads, there is a Chef cookbook available too from https://github.com/onepowerltd/pkagent_cookbook :-)



February 12, 2014

Sync S3 buckets in parallel mode via concurrent threads

Filed under: All,Amazon EC2,EC2,Git,Ruby,S3 — Srinivas @ 18:13

A week back I realized one of my core S3 buckets at work (which we use for all a bunch of app uploads that are always needed) was a us-west-2 only bucket and not US-Standard. (Dont like that, When S3 gives you 11 9s why not get a US Standard bucket???). Considering that we had varnish in multiple regions with this bucket as the backend, I wanted to do two things -

1. Migrate all data from this bucket to a US-Standard bucket

2. Migrate all data from this bucket to a EU/Ireland bucket as well (coz I have app servers etc out there as well which need the same data – Did’nt want to come across the pond for every object we had to retrieve). Why? Reduced latency and reduced B/W costs (costs nothing when a EC2 instance in EU has to pull an object from a EU bucket).


August 15, 2013

Github – swap origin urls

Filed under: All,Development,Git — Srinivas @ 16:07

Ever pull from a git repo that was open and you had pull access (ONLY) to and then wanted to push back to it later when you were granted that access? Chances are that you cloned from the git:// url (Git protocol) and trying to push back to it throws errors like this.


August 13, 2013

Dump http requests in-transit with tcpdump

Filed under: All,Amazon EC2,Linux,Virtualization — Srinivas @ 14:57

Note to self -

tcpdump -A -s 0 ‘tcp port 80 and (((ip[2:2] – ((ip[0]&0xf)<<2)) – ((tcp[12]&0xf0)>>2)) != 0)’

Handy on haproxy/varnish boxes to see requests/responses in realtime for debugging on-the-fly… As opposed to having to dump to trace file and analyzing off-server with wireshark or similar…

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