In some cases master can show pg_last_xact_replay_timestamp() from past,
which can cause the exporter to show ever-growing value for the lag.
By checking if the instance is in recovery we can avoid reporting some
huge number for master instance.
* Introduce histogram support
Prior to this change, the custom queries were restricted to counters and
gauges.
This change introduces a new ColumnUsage, namely HISTOGRAM, that expects
the column to contain an array of upper inclusive bounds for each
observation bucket in the emitted metric. It also expects three more
columns to be present with the suffixes:
- `_bucket`, containing an array of cumulative counters for the
observation buckets;
- `_sum`, the total sum of all observed values; and
- `_count`, the count of events that have been observed.
A flag has been added to the MetricMap struct to easily identify metrics
that should emit a histogram and the construction of a histogram metric
is aided by the pg.Array function and a new helper dbToUint64 function.
Finally, and example of usage is given in queries.yaml.
fixes#402
Signed-off-by: Corin Lawson <corin@responsight.com>
* Introduces tests for histogram support
Prior to this change, the histogram support was untested.
This change introduces a new integration test that reads a user query
containing a number of histogram metrics. Also, additional checks have
been added to TestBooleanConversionToValueAndString to test dbToUint64.
Signed-off-by: Corin Lawson <corin@responsight.com>
Update query for pg_stat_user_tables:
* Split up to multi-line format to make it easier to read.
* Remove duplicate of column `COALESCE(last_vacuum, '1970-01-01Z')`.
Signed-off-by: Ben Kochie <superq@gmail.com>
In the user queries.yml file, the created namespaces can now be optionally
cached by setting cache_seconds, which will prevent the query being re-run
within that timeframe if previous results are available.
Supercedes #211, credit to @SamSaffron for the original PR.
