InfluxDB - How can I limit the measures that a user can read by their tags?
First and foremost, I would suggest moving away from any version of InfluxDB before 1.0 as there have been a number of improvements to InfluxDB since 0.9.

At the moment there is no way to limit read and write access for a particular tag. This functionality is a planned feature in version 1.2 of Enterprise InfluxDB.

That being said there is one alternative implementation that I see as feasible. OSS InfluxDB allows administrations to set database level read and write permissions. You could use this to your advantage. Rather than have a single database and setting permissions on the tags within that database, you'd have a database for each user and give each user read and write access to that database.

One issue that comes to mind with this approach is that if you have 1000s of users, you'll end up having 1000s of databases. This may cause some weirdness within InfluxDB itself. If you did have 1000s of users, you could simply partition your users across multiple InfluxDB instances.