# Last Time

The last_time function returns last time in milliseconds when data is received for a given series.

The database tracks information about last insert times, last values, and insert counters for each series in a dedicated table, separate from the main data table.

Unlike the data table, the last insert table is updated with a delay of 15 seconds to minimize write load by de-duplicating updates that arrive within the delay interval.

As a result, values returned by the last_time function can be lagging behind by a few seconds.

# Query

Returns data for the most recent 30 second interval for each series.

SELECT * FROM "mpstat.cpu_busy"
  WHERE datetime > current_day
AND entity LIKE 'n%00%'
  WITH time > last_time - 30*SECOND

# Results

| entity       | datetime                 | value |
|--------------|--------------------------|------:|
| nurswgvml007 | 2016-09-08T07:47:24.000Z | 4.0   |
| nurswgvml007 | 2016-09-08T07:47:40.000Z | 4.1   |
| nurswgvml006 | 2016-09-08T07:47:26.000Z | 4.0   |
| nurswgvml006 | 2016-09-08T07:47:42.000Z | 66.0  |

# Query

Returns avg() for the most recent hour for each series.

SELECT entity, AVG(cpu_busy.value)
  FROM "mpstat.cpu_busy"
WHERE datetime > previous_month
  GROUP BY entity
WITH time > last_time - 1 * HOUR

# Results

| entity       | AVG(cpu_busy.value) |
|--------------|--------------------:|
| nurswgvml006 | 15.4                |
| nurswgvml007 | 8.0                 |
| nurswgvml009 | 5.9                 |
| nurswgvml010 | 4.6                 |
| nurswgvml011 | 3.2                 |
| nurswgvml102 | 1.2                 |
| nurswgvml301 | 0.9                 |
| nurswgvml502 | 2.3                 |

# Query

Same as above, grouped by period.

SELECT entity, datetime, AVG(cpu_busy.value)
  FROM "mpstat.cpu_busy"
WHERE datetime > previous_month
  GROUP BY entity, period(1 HOUR)
WITH time > last_time - 1 * HOUR

# Results

| entity       | datetime                 | AVG(cpu_busy.value) |
|--------------|--------------------------|--------------------:|
| nurswgvml006 | 2016-09-08T07:00:00.000Z | 15.4                |
| nurswgvml006 | 2016-09-08T08:00:00.000Z | 32.0                |
| nurswgvml007 | 2016-09-08T07:00:00.000Z | 8.0                 |
| nurswgvml007 | 2016-09-08T08:00:00.000Z | 8.2                 |
| nurswgvml009 | 2016-08-25T06:00:00.000Z | 5.8                 |
| nurswgvml009 | 2016-08-25T07:00:00.000Z | 6.0                 |
| nurswgvml010 | 2016-09-08T07:00:00.000Z | 4.2                 |
| nurswgvml010 | 2016-09-08T08:00:00.000Z | 4.1                 |
| nurswgvml011 | 2016-08-24T11:00:00.000Z | 1.7                 |
| nurswgvml011 | 2016-08-24T12:00:00.000Z | 3.5                 |
| nurswgvml102 | 2016-08-25T06:00:00.000Z | 1.3                 |
| nurswgvml102 | 2016-08-25T07:00:00.000Z | 1.1                 |
| nurswgvml301 | 2016-09-08T07:00:00.000Z | 0.9                 |
| nurswgvml301 | 2016-09-08T08:00:00.000Z | 0.1                 |
| nurswgvml502 | 2016-09-08T07:00:00.000Z | 1.9                 |
| nurswgvml502 | 2016-09-08T08:00:00.000Z | 5.9                 |