Dariusz on Software Quality

27/03/2010

How To Effectively Migrate Web Application Between Hosts

Filed under: en — Tags: , , , — dariusz.cieslak @

In Agile world there are no immutable constraints. Your requirements may change, libraries used may be replaced during development, application may outgrown your current server setup etc. I’ll show you how to make web application migration between servers as fast as possible: with minimum downtime and data consistency preserved (techniques also apply to hosting providers environment).

Known Problems

You may say: moving a site? No problem: just copy your files, database and voila! Not so fast. There are many quirks you may want to handle properly:

  • DNS propagation time
  • Database consistency
  • Preserve logs
  • Preserve external system configuration
  • Environment change impact integration tests

(more…)

31/01/2010

Does Your VPS Need A Dedicated IP Address? No!

Filed under: en — Tags: , , , — dariusz.cieslak @

6I believed dedicated server / VPS (Virtual Private Server) always requires dedicated IP adress. Until today.

I found (thanks, LowEndBox) interesting option where you can build your VPS totally custom parameters including shared IP address.How can it work? With shared IP? Youre joking! – you may ask. It works.

TOCICI offers “Nginx Accelerated Shared IP” wchich mean:

  • Your VPS will be hidden behind NAT like typical workstation
  • External Ngnix HTTP server will redirect HTTP traffic to your box based on URL domain
  • You can define custom ports to be forwarded to your box (SSH incoming traffic)

Pros:

  • Very cheap option (no cost of dedicated IP required, you can start VPS from 1-2 USD)
  • Security (by default no ports visible to external world)

Cons:

  • Standard ports except 80 (HTTP) unavailable: no DNS services
  • No HTTPS available (requires separate IP)
  • SSH login requires custom port (your local network may block high ports to prevent P2P)

The service fills gap between shared hosting and classic VPS. The only problem from my point of view is the distance between Europe and Portland, Oregon in the USA. 220 ms from Warsaw.

15/11/2009

Web apps measurment in action

Filed under: en — Tags: , , — dariusz.cieslak @

Graphs

Today I’d like to share some observations on web applications speed. My monitoring network checks almost one thousand of URL addresses and few interesting pictures are created here.

Lets see sample monitoring results from random URL (one week measurment): http://forum.magicsquad.eu (located currently in webh.pl hosting provider):

site-uptime.net-1As you can see typical site response time is almost four seconds! (DNS resolution time excluded) Measurment is performed from Cracow, Poland. Let’s see results from Chicago, USA:

(more…)

09/09/2009

fivebean.com shared hosting review

Filed under: en — Tags: , — dariusz.cieslak @

The story

After few months with a2b2.com without VPS panel (see: HyperVM exploit story) i decided to say bye-bye and move my monitoring node to another host. I selected small company fivebean.com for this purpose.

1First I thought about VPS but then saw few interesting options mentioned on shared hosting offer:

Ruby on Rails (FastCGI), PHP 5.2.9 (IONCube/Zend Optimizer), mySQL 5.0.67, Perl 5.8.8, Python 2.4.3, GD Graphics Library, ImageMagick 5+, CGI-BIN, SSI (server side includes), Trac, Subversion and more!

Looks like we have long running processes-friendly hosting! I asked them about rules and got the answer:

The CGI processes are executed by suexec and would run as the user (script owner). We currently do not have any process limitations on scripts but we do have
scripts that monitor for high usage and in which case we work with the user to resolve. If you have any other questions please let us know.

Seems very interesting. I appreciate hosts that control resource usage (CPU/disk) because that lowers possibility of abusing all resources on a server by one customer. Good.

(more…)

28/07/2009

Wydajność SAN na przykładzie RPS w OVH

Filed under: pl — Tags: — dariusz.cieslak @

SAN (Storage Area Network) jest w dużym uproszczeniu sieciowym systemem plików. Pozwala scentralizować zasoby dyskowe z kilku fizycznych serwerów i udostępnić je poprzez sieć przy wykorzystaniu np. NFS lub iSCSI. Daje to znaczne oszczędności dzięki czemu można zaoferować tanie serwery dedykowane oparte o Inel Atom i sieciowy dysk.

Taką właśnie ofertę przygotowało ponad rok temu francuskie OVH. Entuzjastyczne opinie (serwer dedykowany za taką cenę!) dość szybko zostały ostudzone poprzez informacje o bardzo słabej wydajności dostępu do macierzy dyskowej po sieci. Użytkownicy informowali o spadku wydajności dysku do 400 kB/sek. (współczesne dyski dają zwykle kilkadziesiąt MB/sek.).

Ostatnio OVH po wielu walkach zapanowało jak się zdaje nad QOS dla dysku, ale wyższa gwarancja transferu jest okupiona odpowiednio większym kosztem.

Z tego przykładu można wysnuć następujące wnioski:

  • w przyrodzie nie ma czegoś takiego jak “unlimited“
  • współdzielone zasoby bez limitów zwykle kończą się jakimś mechanizmem limitowania ze względu na skończoną przepustowość

Trend do wprowadzania limitów obserwujemy też w hostingu (coraz więcej dostawców mierzy aktywnie zużycie zasobów we współdzielonym hostingu). Mechanizmy typu VPS (gwarantowane stałe zasoby) stają się także coraz bardziej popularnym wyborem dla twórców serwisów internetowych.

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