Changes between Version 1 and Version 2 of FAQ

01/21/06 16:22:18 (16 years ago)

Add FAQ for progressive slowdown problem


  • FAQ

    v1 v2  
    158158Q: Can I extract the hotspot status data in XML format ? 
    159159  A: Yes, the hotspots status list can be exported to a XML. In fact, the Google Maps mashup part of Wifidog relies on this feature. [ Île Sans Fil is also using it] to create a specially formatted display on its main website using [ an XSL stylesheet]. 
     161Q: My auth server used to be fast, but now it's slower and slower, even under no load 
     163  A: You have to: 
     165 1. Run VACUUM ANALYSE often from a script (it's a very cheap, non locking operation, and considering wifidog's very write heavy SQL mix, runing it every hour isn't excessive). 
     166 1. Make sure the above script works. 
     167 1. If you see you auth server getting progressively slower, run  VACUUM FULL ANALYSE once, and GO TO STEP 2. 
     169 Explanation:  If you run VACUUM ANALYSE regularily (every night or every hour) you shouldn't need VACUUM FULL ANALYSE. However, if you haven't run VACUUM ANALYSE for a long time, you have to run VACUUM FULL ANALYZE once.  
     171 What happens is that without VACUUMing the connection and node tables grows and grows (because they are written to frequently, and postgres being a true ACID database, keep past versions of tuples to insure read consistency).  Simply vacuuming doesn't reclaim the space used by old tuples, it just makes them available for reuse.  If you haven't run VACUUM in a long time, you probably have millions of free tuples that you would, never, ever  
     172use up in a single day.  VACUUM FULL ANALYZE fixes that.