Loki 3.5 - structured_metadata: msg="negative structured metadata bytes received" if no structured_metadata send or 0 Bytes (flowlogs-pipeline, Loki Alert State History)

[Nachtfalkeaw]

Describe the bug
An application (https://github.com/netobserv/flowlogs-pipeline) sends data directly to loki without any structured_metadata. This results in Loki error message.
The error message indicates that structured_metadata is zero bytes which is not negative.

May 4 22:14:47 u999fm1lo002p loki[1019654]: level=error ts=2025-05-04T20:14:47.357165682Z caller=push.go:202 org_id=tenant_02 msg="negative structured metadata bytes received" userID=tenant_02 retentionHours=8760 isAggregatedMetric=false policyName= size=0

To Reproduce
Steps to reproduce the behavior:

1. Started Loki 3.5
2. Started https://github.com/netobserv/flowlogs-pipeline
3. send logs to loki with no structured_metadata

Expected behavior
No error message. The error message should clearly indicate the source which send the logs with no structured_metadata.

Environment:

• Infrastructure: RHEL8
• Deployment tool: monolithic

Screenshots, Promtail config, or terminal output
N/A

Ticket at flowlogs-pipeline:
netobserv/flowlogs-pipeline#949

[Nachtfalkeaw]

I found out that this also happens for the Grafana Alerts which are sent to Lokia as "Alert State History" Feature. These do not contain structured_metadata, too and these create this message, too.

So this is not related to flowlogs-pipeline application but any other application, from Grafana stack, too . if not structured_metadata exists which results in 0 Bytes, this leads to this error message in Loki.

[Nachtfalkeaw]

Looks Like it was addresses Here
#17371