CODEWITHSUNDEEP
c++clinux
punith
punith

Reputation: 1269

Configuration Storage

I want to store a lot of configuration data pertaining to cluster, process, IP addresses etc. I have worked on one such product earlier where LDAP was used for this purpose. Although it was PITA to configure it the first time, I liked the transactional LDAP part which helps in dynamic reloading of the configuration when there is a change. It can be done with a flat file using inotify, but that is not as good as transactional LDAP. But, as I said, the configuration was a real pain, and also I don't want to borrow the same idea of LDAP in this product.

So can anyone give me an idea about which will be the next best replacement, which makes entering configuration easy and also that can help in dynamic configuration and notify my process whenever there is a change in the configuration file and exactly what changed (directly or indirectly)?

I am planning to develop my product in C++ and C.

The configuration can be edited by an Admin, or if he is too lazy he can automate it using some script. Also through cli, but not by a running process, that will land me up in concurrency and locking issues.

My program is a daemon, some sort of cluster manager running on multiple nodes.

There is no wrapper provided for user to edit configuration.

I am only looking for Linux/Solaris platform.

Upvotes: 2

Views: 343

Answers (1)

Jonathan Leffler
Jonathan Leffler

Reputation: 753970

You have not really given enough background information for a good answer to be given. So, here are some of the unasked questions, the answers to which will influence your choice:

  • How is the configuration file edited? By your process, or by hand-editing, or by some other program?
  • How is the main program running - in the foreground with a user interacting, or in the background as a daemon?
  • If you expect people to hand-edit the configuration, then you can provide a wrapper script for doing so which sends a signal (conventionally SIGHUP) to the daemon to tell it to reread its configuration file.
  • If your main program is going to guide the user through the editing, then you really don't need to tell the program when the editing is complete. It already knows.
  • You mention Linux in the tags; can we assume that Windows portability is not an issue?

As to configuration file formats, you can go with the vogue (and bloat) of using XML. However, although that is a good tool for programs communicating, it is not very good for people to edit. You should look at E S Raymond's "The Art of UNIX Programming" which is a good general read and has a chapter on different configuration file formats. You should probably adopt one of the schemes outlined there. Which scheme is best depends in part on what information you have to capture in your configuration file.

If you're going to embed an interpreter (Perl, Lua, Tcl/Tk, ...) into your program, you might use that language to handle the configuration file...or you might not.

Upvotes: 1

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