# Prometheus scrape cycle and node exporter iteration syncronization

**URL:** <https://discuss.prometheus.io/t/prometheus-scrape-cycle-and-node-exporter-iteration-syncronization/1649>\
**Category:** Exporters and Metrics\
**Created:** [May 16, 2023, 7:05pm UTC](https://discuss.prometheus.io/t/prometheus-scrape-cycle-and-node-exporter-iteration-syncronization/1649 "2023-05-16T19:05:11Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![puneet336](https://avatars.discourse-cdn.com/v4/letter/p/65b543/32.png) [@puneet336](https://discuss.prometheus.io/u/puneet336)\
**Post date:** [May 16, 2023, 7:05pm UTC](https://discuss.prometheus.io/t/prometheus-scrape-cycle-and-node-exporter-iteration-syncronization/1649/1 "2023-05-16T19:05:11Z")

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Hi,  
I have a custom node exporter from which prometheus scrapes every 30 seconds.  
Issue is that sometimes -  
a) if the data volume is large ,node exporter takes longer , On top of that ,  
b) i need to clear the metrics to remove the old stale values before i set the metrics to the respective values again.  
The scenario a) causes mixup of data from 2 iterations and in scenario b) scrape cycle may get 0 values .

Expected behaviour → Iteration 1 starts → Node exporter collects raw data → clear metrics → process data and set metrics --\>Iteration 1 complete → Prometheus Scrapes Data.

Problem is : a) Iteration 1 starts → Node exporter collects raw data → clear metrics → ( Prometheus Scrapes Data ) → process data and set metric #1 → . process and set metric #N --\>Iteration 1 complete

b) Iteration1 starts → Node exporter collects raw data → clear metrics → process data and set metric#1 → ( Prometheus Scrapes Data ) --\>… process and set metric#n–\> Iteration 1 complete

So, Is there a way to enforce some syncronization between node exporter and prometheus scrape cycle ? example-  
Scenario 1) The node exporter prepared data in 20 seconds and Prometheus should start scraping from ( say) 30th second of every minute i.e.  
02:34:30  
Scenario 2) To expose all the metrics in one shot , example -  
Iteration2 starts → Node exporter collects raw data → clear metrics → process data and set metric#1 → --\>… process and set metric#n–\> Iteration 2 complete → expose metric.

something like - metric1.labels(STATE=x).set (y)  
metric1.expose()

I am okay to scrape old data , but dont want to -  
mix Iteration 1 and Iteration 2’s data or ,  
scrape the data when node exporter has cleared metric.

Scenario 3: make scrape wait till data collection iteration is complete.

Please do let me know if more information is required from my end here.

Regards  
Puneet