Collector

Responsible for writing Events to the Archive.

Collectors are write-only programs that generate Events for a particular set of Namespaces from some other device or service. Generally, Collectors should be grouped so that data that is requested/recorded together is within the same Collector.

There can be multiple instances of the same collector if you want different Namespaces to be collected at different intervals (ex: if downloading from Google Takeout, you may wish to synchronize all of your youtube videos once per month because it is a lot of data, but synchronize your chats every day because it isn't much data)

There are four main types of Collectors:

1. Historical. These run once for a set of data, and then they are done.
2. Samplers. These run at a fixed interval, and query the current values of some external device or service. This current value is recorded. Note that data for one of these Collectors is only recorded while the Collector is running (however, they are much simpler to write). These are great for things like location, heart rate, mood, current window title, etc.
3. Synchronizers. These run at a fixed interval, and query the external device or service for its full state, then record any differences from the last run. These are more complicated to write because they must maintain some state about what Events have already been recorded (typically a date of last synchronization, or a set of unique ids), but they can be very useful. These are great for things like email, facebook messages, flickr, other web services, etc.