Dr. Dobb's is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Channels ▼


Coding In the Cloud

Gotcha #2: Session Life

Closely related to the issue of session persistence is session life. In many cases, sessions stored in memory stay in memory for long periods of time, which makes users happy because if they are interrupted for some reason they can return to the application and pick up where they left off.

This is a potential issue for applications when deployed in the cloud because it's not guaranteed that the server instance on which the session was created will still be on-line when a user returns to the application. It is possible that sessions can effectively be "lost" during relatively short periods of time due to a server instance becoming idle and subsequently being de-provisioned.

This gotcha is highly dependent on the cloud computing provider's definition of "idle" and how it is determined that an application instance should be de-provisioned. If it is based on current connections and idle time, losing sessions is likely. If the provider's provisioning services have visibility into the application server such that it can determine that sessions are still active and determining idle time is based on this information, at least in part, then this scenario is not likely to occur.


  • As with session persistence, you can use session mirroring or database backed sessions to avoid losing a session when an instance goes idle for too long.
  • Work with the cloud computing provider to determine whether you can set the parameters for what is considered "idle" and what is not. You may be able to idle the instance for the duration of a session, essentially using session-based quiescence rather than connection-based quiescence to determine when an application instance can be taken off-line. Be aware of the costs of doing so, however, as any instance, even idle, consumes some resources and will therefore incur charges.

Related Reading

More Insights

Currently we allow the following HTML tags in comments:

Single tags

These tags can be used alone and don't need an ending tag.

<br> Defines a single line break

<hr> Defines a horizontal line

Matching tags

These require an ending tag - e.g. <i>italic text</i>

<a> Defines an anchor

<b> Defines bold text

<big> Defines big text

<blockquote> Defines a long quotation

<caption> Defines a table caption

<cite> Defines a citation

<code> Defines computer code text

<em> Defines emphasized text

<fieldset> Defines a border around elements in a form

<h1> This is heading 1

<h2> This is heading 2

<h3> This is heading 3

<h4> This is heading 4

<h5> This is heading 5

<h6> This is heading 6

<i> Defines italic text

<p> Defines a paragraph

<pre> Defines preformatted text

<q> Defines a short quotation

<samp> Defines sample computer code text

<small> Defines small text

<span> Defines a section in a document

<s> Defines strikethrough text

<strike> Defines strikethrough text

<strong> Defines strong text

<sub> Defines subscripted text

<sup> Defines superscripted text

<u> Defines underlined text

Dr. Dobb's encourages readers to engage in spirited, healthy debate, including taking us to task. However, Dr. Dobb's moderates all comments posted to our site, and reserves the right to modify or remove any content that it determines to be derogatory, offensive, inflammatory, vulgar, irrelevant/off-topic, racist or obvious marketing or spam. Dr. Dobb's further reserves the right to disable the profile of any commenter participating in said activities.

Disqus Tips To upload an avatar photo, first complete your Disqus profile. | View the list of supported HTML tags you can use to style comments. | Please read our commenting policy.