Forum Discussion

AaronB_8424's avatar
AaronB_8424
Historic F5 Account
Apr 09, 2010

vers. 10.1 "session" table limits and monitoring

What are the limits for the session table? How many sessions can be stored? How can you check the number of sessions stored?

 

 

session

 

http://devcentral.f5.com/wiki/default.aspx/iRules/session.html

 

 

 

I understand this value will depend on a lot of factors (memory, box speed, size of each entry, etc). But, how big can the table get? How can I tell how many sessions are in the table and possibly what size it is (snmp, bigpipe command, etc)?

 

 

Thanks!

 

 

(LTM 6400 w 2gigs ram)

 

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  • Hamish's avatar
    Hamish
    Icon for Cirrocumulus rankCirrocumulus
    Apr 10, 2010
    Didn't sparkie or someone put some details in one of the tables tutorials previously? Let me take a quick look.

     

     

    H
  • Hamish's avatar
    Hamish
    Icon for Cirrocumulus rankCirrocumulus
    Apr 10, 2010
    Yep it was spark who wrote the table docs (Hard to find. It took me a while, the table command isn't documented in the iRules wiki that I can find. The article is at http://devcentral.f5.com/Default.aspx?tabid=63&articleType=ArticleView&articleId=2375)

     

     

    However I can't find the article I remember seeing that gave an indication on how much memory each table entry used... From memory you can see the information from tmctl counters somewhere... So assuming we can find which counter it is, we could write an iRule to create X thousand entries and then check that... And X more... And check again, to give a graph of how much memory for X number of table entries.

     

     

    H

     

     

    H
  • hoolio's avatar
    hoolio
    Icon for Cirrostratus rankCirrostratus
    Apr 12, 2010
    Hi Hamish,

     

     

    The table wiki page is in the standard format for all iRule wiki pages:

     

     

    http://devcentral.f5.com/wiki/default.aspx/iRules/table

     

     

    And there is a link on the wiki page to the series of table articles.

     

     

    http://devcentral.f5.com/Default.aspx?tabid=63&articleType=ArticleView&articleId=2375

     

     

    And here's one notable section:

     

     

     

    http://devcentral.f5.com/Default.aspx?tabid=63&articleType=ArticleView&articleId=2382

     

     

    Limitations

     

     

    As fantastic as the new session table is, it does have its limitations. You can't use the table command in RULE_INIT or any other global event. There's no way to access the session table outside of tmm. The ability to count and list keys is limited to subtables. Timestamps are limited to 1-second resolution, so there's no way to do counts for sub-second events.

     

     

    As you saw, you can use it for accurate counting, but that's not nearly as easy to use as we'd like it to be. We tried very hard to come up with a command, or set of commands, that would hide all the table manipulation and just do the counting for you, but everything we came up with was either very complicated or would always use the most computationally expensive method for counting, and that seemed like a bad tradeoff.

     

     

     

    Aaron