Support of preprocessing by Zabbix Proxy

Introduction

Item preprocessing can be resource intensive especially if it uses complex JavaScript code or aggressive data collection with throttling and validation. Zabbix Server may quickly become a bottleneck.

Support of preprocessing by Proxies may help to deliver scalability and get rid of the bottleneck.

Zabbix Acceptance

1. Proxy must support preprocessing
   1. Proxy preprocessing will always be enabled and cannot be disabled
   2. Proxy will always execute all preprocessing rules for all items and LLD rules
   3. Proxy will also preprocess dependent items
   4. If preprocessing failed, Proxy should provide detailed error message (preprocessing backtrace) as it will be implemented by Server (ZBXNEXT-5016)
2. Proxy will ignore history buffer when upgrading from earlier releases (4.0.x and earlier) to 4.2.x.

1. 1. Existing history buffer will never be sent to Server, it can be dropped
   2. Data will not be collected before first configuration sync with Server to avoid situation when both raw and pre-processed data is in history buffer
   3. Server will ignore history data sent from Proxies older than 4.2.0
2. Internal monitoring will be extended to monitor health of preprocessing as it is already supported on Server side.
3. Documentation
   1. It must be well described in the release notes
   2. Publish a blog post

Use cases

1. I want to offload Zabbix Server for normal preprocessing
2. I want to save network bandwidth and Zabbix Server resources if throttling and/or validation rules are used

Decisions made

1. No way to disable Proxy preprocessing
2. Proxies will always execute all preprocessing rules