Description

This KB explains the bug details and RCA that causes Inconsistent Data reporting for Junos Telemetry on QFX10008 switches with more than 2 FPCs.

Symptoms

Post upgrade to Junos: 20.4R3-S4.8 flex, qfx10008 are not reporting data for sensor path "/components/component/properties/property/" at the subscribed sample interval of 60,000 ms.
Data is returned once every 8-10 mins. 18.2R3-S7.4 flex has no issues.
The issue started after the upgrade to 20.4R3-S4.8 flex.
The issue is still seen after the upgrade to 20.4R3-S7.2 flex as well.

Solution

- We are hitting a bug here matching confidential PR1669434.

Issue:
The Telemetry /components/ sensor might require multiple reporting intervals to complete the export cycle.

Workaround:
Not possible

Description:
On the Junos platforms when subscribed to a component sensor from an external collector, the components export platform-related information in a given sampling interval. However, if all the info cannot be sent in the configured sampling interval, the rest of the data might be sent in the next sampling interval. However, there is a restriction that chassisd daemon cannot send more than 15 export packets per sampling interval. If the amount of data cannot be accommodated in these 15 export packets then data has to go in the next sampling interval. This might lead to a slowing down of the export of information related to the platform sensors. This issue can be detected by monitoring data received at an external collector. There will not be any traffic impact due to this issue.

External-Trigger:
This issue might be seen if the following conditions are met:
* On Junos platforms
* Telemetry is enabled

Additional trigger found as per CFTS testing: 
* The issue is only seen when there are more than 2 FPCs on the QFX10008 device running telemetry.

Resolved-In:

evo:21.4R3-EVO
evo:22.1R2-EVO
evo:22.1R3-EVO
evo:22.2R2-EVO
evo:22.3R1-EVO
evo:22.4R1-EVO
junos:19.4R3-S13
junos:20.3X75-D50
junos:21.2R3-S5
junos:21.2R3-S6
junos:21.3R3-S1
junos:21.4R3
junos:22.1R2
junos:22.1R3
junos:22.2R2
junos:22.2R3
junos:22.3R1
junos:22.4R1

Modification History

2023-09-26: Initial publication