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Hi,

In the near future we plan to add an additional web server to the Toolserver. This will provide redundancy if either server fails, as well as increasing capacity. Each server will be identically configured (with the same OS, software, etc.), and HTTP requests will be distributed evenly between the systems.

Some tools may require changes to function correctly in this environment:

* Any tool which stores data on a local disk (e.g. /tmp or /var/tmp) and expects to retrieve the data in a different request may find the data is not present if the subsequent request runs on a different web server. To fix this, such data should be stored in a location accessible from all systems (e.g. $HOME).

* Web frameworks supporting HTTP sessions often use local storage for session data. This will not work over multiple servers, for the same reason as local files. To fix this, configure your framework to store session data in $HOME or a MySQL database instead of local files. (No changes are needed for PHP, which is already configured this way.)

* Tools which expect server-specific details (e.g. hostname or IP address) to remain the same will not work. This is always a bad idea, but will now not work at all.

* Tools which require some kind of separate daemon will need to start the daemon on both systems, or communicate with the daemon over the network.

* Initially, there will be independent access and error logs for each system. To ease debugging of scripts, it will be possible to use a URL like http://wolfsbane.toolserver.org/~jsmith/mytool/ to force the request to a particular system. However, such URLs should not be used for any other purpose, since server names can change at any time, which would break the URLs.

In the future, we hope to have unified logs for all web servers.

We plan to have the additional web server operational within the next week or two.

- river.