Currently the "site" string is treated as case-sensitive in the site related configuration files for topology, it will cause trouble for users if they made a mistake about the letter case.
I created a site with name "Demo", but in the "Demo-hdfsAuditLog-application.conf" I set the site as "demo". It turned out that the policy din't work and in the storm log file there was a warning: "No alert definitions was found for site: demo, dataSource: hdfsAuditLog". Then I change the site in the conf files to "Demo" and everything works fine.
So I suggest to treat "site" string as case-insensitive to avoid such mistake.