Hi All,
I’m new to Telegraf and would to understand more on how timestamp value on metrics are determined. Especially, how the timestamp value related to the “data collection interval” of the agent?
I’ve played around and setting the agent’s interval to “60s”:
[agent]
## Default data collection interval for all inputs
interval = "60s"
When I output the data using the “http” output plugin, what I’ve observed is the timestamp value of the metrics are not always exactly the same as at the time of the http payload is pushed.
What I mean is, I do see the http output plugin is sending the output payload at 60 second interval, e.g. at 00:00:00, 00:01:00, 00:02:00, 00:03:00, etc. However, when I look at the metric’s timestamp values at the corresponding payload, some time the timestamp value on some metric is a few second earlier, like, 00:00:57, 00:01:58, 00:02:56, etc (after converting the epoch value to readable datetime)
So I’m just wondering, is that mean the data collection time of each input plugin will not always be the same as data “pushing”/output time?
And is there a way to tune the agent to make this (i.e. the timestamp of metric and data pushing time) as close as possible? as I’ve notice there are quite a few configuration parameters on the agent related to timing of data collection/flushing/precision, etc, but I’m not sure which one might help to tune the metric timestamp as close to the output pushing time as possible.
Hoping the experts in the forum can share some light on this.
Thanks.
Hello @ericco,
Each input plugin collects metrics based on the configured interval. The timestamp of a metric reflects the time it was collected by the input plugin. The Telegraf agent processes the collected data and pushes it to the outputs (like HTTP) at the defined intervals. However, the timestamps embedded in the metrics themselves do not represent the time the data is sent—they represent when the data was collected.
Timestamps can differ bc of internal processing times. Telegraf collects, processes, and sends data in discrete steps. This processing can introduce slight delays between when the data is collected and when it’s outputted. Also the system clock resolution and timing may introduce minor deviations when aligning collection and output intervals."
agent config options related to time:
precision: Collected metrics are rounded to the precision specified as an interval (integer + unit, ex: 1ns, 1us, 1ms, and 1s . Precision isn’t used for service inputs, such as logparser and statsd.
If you want the flush to align closely with collection intervals, adjust the flush_interval:
flush_interval: Default data flushing interval for all outputs. Don’t set this below interval. Maximum flush_interval is flush_interval + flush_jitter
To add on what @Anaisdg said, the metric timestamp might also be extracted from the received metric itself, depending on the input. Even if that is not the case, there might be a collection_jitter (see documentation) set.
