• Article Type: General
• Product: Aleph
• Product Version: 15.2

Description:
We have 2 web servers going through a load balancer to provide access to our Web OPAC.

We are experiencing a problem with printing/saving records: sometimes when a user clicks on "print" the OPAC displays "page not found". This seems to be because the load balancer directs the request at the 'wrong' web server, and the .sav file is actually in the $TMPDIR on the other server.

Other than using "sticky" sessions (we don't really want to use this, as it stops the load balancer from balacing traffic efficiently) is there any other way around this?

Would it be possible to use NFS on the $TMPDIR for both servers - effectively sharing one "folder" between the two? How are the file names for files in $TMPDIR assigned, and is it possible each server could assign the same 'name' to a file , or would the files always be named differently?

Resolution:
(1) Using NFS: $TMPDIR can be located on one server and shared with the other, if necessary, using NFS. Alternatively, the directory could be on an external drive available to both servers as a NFS share.

(2) File naming: the file names use a counter called "last-file-number". This is stored in an Oracle table (Z52 in the BIB Library), and so can be seen by both web servers (you can prove this by running UTIL-G-2 on both servers - the values should be the same).

This means that the file names should always be different (regardless of which server generated the file on the share).