Decreasing Ram usage

[Thomas Will]

Hello guys,  I am running my Prometheus in a docker container, have set my retention period to be 2days and also enabled Thanos at the back. I have two questions:-

1) For how much time Prometheus stores its metrics in ram and after that sends to the disc?

2) Is there any way to control our ram usage, like based on size or number of metrics, i.e. if ram size increases beyond a threshold, dump the data to the disc.

Cheers, all.

Thomas Will.

[Ben Kochie]

Prometheus only keeps up to 2 hours in memory. After this it is always written to disk and mmaped. There are no controls for this. The local retention time makes (almost) no difference to memory use.

The only control is to reduce the metrics collected.

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[Thomas Will]

Thank you, Ben, for replying. "by local retention" I am assuming that you are talking about the 2hr retention in ram. How it's not gonna affect the memory use, as we will be storing all the metrics in ram for 2hrs. right?

On Tuesday, April 14, 2020 at 4:15:12 PM UTC+5:30, Ben Kochie wrote:

Prometheus only keeps up to 2 hours in memory. After this it is always written to disk and mmaped. There are no controls for this. The local retention time makes (almost) no difference to memory use.

The only control is to reduce the metrics collected.

On Tue, Apr 14, 2020, 12:33 Thomas Will <thomasw...@gmail.com> wrote:

Hello guys,  I am running my Prometheus in a docker container, have set my retention period to be 2days and also enabled Thanos at the back. I have two questions:-

1) For how much time Prometheus stores its metrics in ram and after that sends to the disc?

2) Is there any way to control our ram usage, like based on size or number of metrics, i.e. if ram size increases beyond a threshold, dump the data to the disc.

Cheers, all.

Thomas Will.

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[Ben Kochie]

Local retention refers to on-disk retention. You said you set this to 2 days. The local disk retention could be 2 days or 15 days, it doesn't contribute significantly to memory use. Only 2 hours are kept in memory.

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