Zabbix 6.0.0

We are also experiencing this issue. Most of the time reports are sent with correct PDFs but sometimes they are blank.

We have tried increasing the timeout value to the max of 30 seconds in /etc/zabbix/zabbix_web_service.conf but it has not fixed the issue.

I believe this issue is caused by the way the web service is waiting for the page to load.

In the source code for the web service there is this comment in the pdf_report_creator.go file:

// This comment is taken from the proof of concept example
//
// waitFor blocks until eventName is received.
// Examples of events you can wait for:
//     init, DOMContentLoaded, firstPaint,
//     firstContentfulPaint, firstImagePaint,
//     firstMeaningfulPaintCandidate,
//     load, networkAlmostIdle, firstMeaningfulPaint, networkIdle
//
// This is not super reliable, I've already found incidental cases where
// networkIdle was sent before load. It's probably smart to see how
// puppeteer implements this exactly.
func waitFor(ctx context.Context, eventNames []string) error {
...

The code is currently only listening for the "networkIdle" event but there may be a case where that event fires but the page is not fully loaded yet.

I have modified the code to listen for both the "networkIdle" and "load" events before creating the report to hopefully fix this issue.

I uploaded my modified version of the pdf_report_creator.go file to this ticket. I am not a GO programmer so the implementation may not be best practice.

Unfortunately waiting for both the "networkIdle" and "load" events did not resolve the issue - when the issue happens the PDF is no longer blank but the dashboard widgets were not fully loaded.

The log for that report did indicate that the "networkIdle" event fired before the "load" event:

2022/06/25 00:00:06.230499 received report request from 127.0.0.1:38314
2022/06/25 00:00:06.230907 making chrome headless request with parameters url: https://www.website.com/zabbix.php?action=dashboard.print&dashboardid=68&from=2022-06-24%2000%3A00%3A00&to=2022-06-25%2000%3A00%3A00, width: 1920, height: 572 for report request from 127.0.0.1:38314
2022/06/25 00:00:07.463019 fired networkAlmostIdle event
2022/06/25 00:00:07.463187 fired networkIdle event
2022/06/25 00:00:07.463199 hit expected networkIdle event
2022/06/25 00:00:07.464102 fired init event
2022/06/25 00:00:07.769960 fired load event
2022/06/25 00:00:07.769993 hit expected load event
2022/06/25 00:00:07.770002 hit all expected events
2022/06/25 00:00:07.921801 writing response for report request from 127.0.0.1:38314 

A different implementation will be needed to account for this behavior.

Hello, would it be possible to please move the solution and not just move it six months to the next sprint? I would appreciate if this functionality would be functional. Thank you so much

Looks like the same issue as described here: ZBX-23634

Currently there is no mechanism in Dashboard widget framework to tell some widget is fully loaded. Basically, the browser opens a specific widget using URL and then takes a screenshot. And there is no way to tell if it is fully loaded or not. Such functionality must be implemented in Dashboard widget framework.

This is because networkIdle is used, see:
https://pkg.go.dev/github.com/troyk/chromedp#WaitForJS
 
func WaitForNetworkIdle() Action
WaitForNetworkIdle should not be used unless absolutely necessary due to race conditions instead, wait for a known element to become visible or WaitforJS see https://github.com/chromedp/chromedp/issues/431

Should we add WaitVisible functionality ?

I would like Zabbix to prioritize this one as it means Scheduled Reports are basically useless since you can never be sure if it will generate properly or if the report will be empty.

mcbrineellis, this task is in progress now.

Available in versions:

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