Problem Description

When sending monitoring data via zabbix_sender directly to the Zabbix Server, some items for certain hosts do not update, even though zabbix_sender logs show no errors (processed: N; failed: 0). All items have the same clock timestamp, but only a subset of values are accepted. Sending the same data directly to a proxy works perfectly.

Environment

• Zabbix version: 7.0.22

• Proxy setup: Two active proxies belong to a proxy group

• Hosts: Assigned to the proxy group

• Sender invocation: zabbix_sender.exe -z <Zabbix_Server>{{ -i data.txt}} (directly to Zabbix Server)

Steps to Reproduce

1. Prepare an input file with multiple items (2000+ lines) for hosts assigned to a proxy group.

1. Send the file using zabbix_sender with -z <Zabbix_Server>.

1. Check zabbix_sender logs – they show processed: N; failed: 0.

1. In the Zabbix UI, check "Latest data" for affected hosts – some items have not been updated (clock remains old).

Expected Behavior

All items with the same clock timestamp should be updated simultaneously.

Actual Behavior

Only a subset of items are updated. The rest retain old values. No errors are reported in zabbix_sender logs.

Additional Observations

• Sending the same data directly to a proxy (-z {}<Zabbix_Proxy_Host_1>) works fine – all items are updated.

• Item keys contain user macros: {$VMHOST_VMWARE:URL} and {}{$VMHOST_VMWARE:HOSTUUID}{}. If these macros are not defined for a host, the item does not exist and the value is silently dropped.

• The issue may be related to:

• • Undefined macros for some hosts → items not found → values rejected.

• • Packet size limits – the server may truncate or reject part of the batch (check MaxSenderSize, MaxRequestSize).

Request for Assistance

Please help us identify the root cause of this issue. Specifically:

1. What could cause zabbix_sender to report success while the server silently drops some items?

1. Are there any server-side logs or metrics we should check to diagnose this?

1. Could this be related to proxy group configuration or macro resolution?

1. Are there any known issues with large batches (2000+ items) when sending directly to the server with proxy groups?

Logs and Diagnostics

• zabbix_sender logs (with -vv) are available upon request.

• Zabbix Server logs are being collected and will be provided if needed.

Please let us know if you need any additional information.