Practical Time Series Tools - Time Series Databases - page 46

The current primary use of the direct bulk loader is to load large amounts of historical data in
a short amount of time. Going forward, the direct bulk loader may be deprecated in favor of
the file loader to isolate knowledge of the internal file formats.
The file loader has the advantage that it uses the REST API for bulk loading and therefore,
data being loaded by the file loader will be visible by queries as it is loaded.
These enhancements to Open TSDB are available on github . Over time, it is expected that
they will be integrated into the upstream Open TSDB project.
Accessing Data with Open TSDB
Open TSDB has a built-in user interface, but it also allows direct access to time series data
via a REST interface. In a few cases, the original data is useful, but most applications are
better off with some sort of summary of the original data. This summary might have multiple
data streams combined into one or it might have samples for a time period aggregated togeth-
er. Open TSDB allows reduction of data in this fashion by allowing a fixed query structure.
In addition to data access, Open TSDB provides introspection capabilities that allow you to
determine all of the time series that have data in the database and several other minor admin-
istrative capabilities.
The steps that Open TSDB performs to transform the raw data into the processed data it re-
turns include:
Selection
The time series that you want are selected from others by giving the metric name and
some number of tag/value pairs.
Grouping
The selected data can be grouped together. These groups determine the number of time
series that are returned in the end. Grouping is optional.
Down-sampling
It is common for the time series data retrieved by a query to have been sampled at a
much higher rate than is desired for display. For instance, you might want to display a
full year of data that was sampled every second. Display limitations mean that it is im-
possible to see anything more than about 1-10,000 data points. Open TSDB can down-
sample the retrieved data to match this limit. This makes plotting much faster as well.