The Prometheus connector allows reading Prometheus.metrics as tables in Presto.
The mechanism for querying Prometheus is to use the Prometheus HTTP API. Specifically, all queries are resolved to Prometheus Instant queries
with a form like: http://localhost:9090/api/v1/query?query=up[21d]&time=1568229904.000”
In this case the
up metric is taken from the Presto query table name.
21d is the duration of the query. The Prometheus
corresponds to the
timestamp field. Presto queries are translated from their use of the
timestamp field to a duration and time value
as needed. Presto splits are generated by dividing the query range into attempted equal chunks.
to mount the Prometheus connector as the
replacing the properties as appropriate:
The following configuration properties are available:
Prometheus coordinator host address
The duration of each query to Prometheus
Width of overall query to Prometheus, will be divided into query-chunk-duration queries
How long the config values are cached
File holding bearer token for access to Prometheus
Not Exhausting Your Presto Available Heap#
prometheus.max-query-duration are values to protect Presto from
fetching too much data from Prometheus. The
prometheus.max-query-duration is the item of
On a Prometheus instance that has been running for awhile and depending
on data retention settings,
21d might be far too much. Perhaps
1h might be a more reasonable setting.
In the case of
1h it might be then useful to set
10m, dividing the
query window into 6 queries each of which can be handled in a Presto split.
Primarily query issuers can limit the amount of data returned by Prometheus by taking
WHERE clause limits on
timestamp, setting an upper bound and lower bound that define
a relatively small window. For instance:
SELECT * FROM prometheus.default.up WHERE timestamp > (NOW() - INTERVAL '10' second);
If the query does not include a WHERE clause limit, these config settings are meant to protect against an unlimited query.
Bearer Token Authentication#
Prometheus can be setup to require a Authorization header with every query. The value in
prometheus.bearer-token-file allows for a bearer token to be read from the configured file. This file
is optional and not required unless your Prometheus setup requires it.