article Useful Synthetic ActiveGate logs in Troubleshooting

Useful Synthetic ActiveGate logs

HannahM — Wed, 25 Feb 2026 17:00:21 GMT

Summary

If you're using a Private Synthetic location, at some point, you'll want to check the logs for more information about what you're troubleshooting. Synthetic ActiveGates produce several logs that help diagnose issues with execution, scheduling, and communication in Synthetic Monitoring. This article summarises the most useful of these logs, where to find them, and what they contain.

Default locations for logs

You can also download the Support Archive from the WebUI by running the Dynatrace ActiveGate Diagnostics. This will only give you up to 7 days of Synthetic logs, so if you need a log that was last written before that, you'll need to find the file directly.

Helpful files and folders

Synthetic installation log

Linux: /var/log/dynatrace/synthetic/dynatracesynthetic-install_<datetimeOfInstall>.log
If this file doesn't exist, you can check /tmp/ for any dynatracesynthetic-install <datetimeOfInstall>.log files.
Windows: C:\ProgramData\dynatrace\autoupdater\log\Synthetic_<version>.log

The Synthetic installation log details the installation of the Synthetic module. This is the place to check if you see the Synthetic module update has failed or been skipped. It also provides information on the Chromium autoupdate.

It should be read alongside the Gateway installation log, which is located at:

Linux: /var/log/dynatrace/gateway/dynatracegateway-install_<datetime>.log
Windows: C:\ProgramData\dynatrace\gateway\log\dynatrace_ag_install_<datetime>.log

Synthetic Module start-up log (VUC Wrapper Launcher)

Linux: /var/log/dynatrace/synthetic/VucwrapperLauncher_<datetimeOfLaunch>.log
Windows: C:\ProgramData\dynatrace\synthetic\log\VucwrapperLauncher_<datetimeOfLaunch>.log

This log is written when the VUC service starts up and contains information such as the process ID and the port being used. It often contains useful information when the VUC service fails to start up or stops unexpectedly.

Synthetic Module (VUC) Logs

Linux: /var/log/dynatrace/synthetic
Windows: C:\ProgramData\dynatrace\synthetic\log\synthetic

vuc.log

This file captures the core VUC functionality logs. It includes logs related to the VUC's connection with the ActiveGate (e.g., localhost:9999/...), as well as startup/shutdown activities, common services, and the loading of configuration properties.

vuc-browser.log

This log provides detailed logging of the Browser Monitor module and includes visit lifecycle and execution messages. It contains information on screenshot storage, WebSocket issues, and other problems encountered during the startup of the Browser module and execution of Browser monitors. The outcome of the diagnostics test on startup can be found in this log by searching for DIAGNOSTICS TEST

vuc-browser.debug.log

This log provides debug-level details from the browser monitor diagnostics tests that are run when the Synthetic module starts up.

vuc-dns-execution.log

This log file details monitor execution events

vuc-http.log

This provides high-level HTTP Module logging, including monitor start and stop times, script loading, and detailed error information, such as "Unknown Method Error" and "Unexpected Error". The outcome of the diagnostics test on startup can be found in this log by searching for DIAGNOSTICS TEST

vuc-http-custom.log

Entries in this log are generated from JavaScript execution. You'll find log messages created by the API calls api.info(message), api.warn(message), and api.error(message).

vuc-http-execution.log

This log file details monitor execution events, including script execution failures, SSL communication errors, DNS query timeouts, and other unexpected errors.

vuc-http.debug.log

This log provides debug-level details of the diagnostics tests run by the HTTP monitor when the Synthetic module starts up.

vuc-icmp-execution.log

This log file details monitor execution events

vuc-multi.log

This log provides high-level NAM, Multi-protocol, module logging, and covers the execution and lifecycle of visits

vuc-multi.debug.log

This log provides debug-level details of the NAM diagnostics tests run when the Synthetic module starts up.

vuc-tcp-execution.log

This log file details monitor execution events

vuc-status.log

This log offers a summary of each VUC startup, including configuration settings and version information.

Synthetic Player (VUP) Logs

Location for individual Browser Monitor execution logs:

Linux: /var/tmp/dynatrace/synthetic/logs
Windows: C:\ProgramData\dynatrace\synthetic\temp\synthetic\logs

For archived logs:

Linux: /var/tmp/dynatrace/synthetic/archivedLogs
Windows: C:\ProgramData\dynatrace\synthetic\temp\synthetic\archivedLogs

Log File Format: <tenant_id>-<test_def_id>-<visit_id>-<timestamp>-ch.log

Hourly archive zip files of execution logs from the logs folder are created in the archivedLogs folder.

These logs provide details on:

WebSocket connections to the VUC.
VUP, browser, and JavaScript Agent versions.
Execution error codes and messages.
Custom log entries created by API calls (e.g., api.info).

What's Next

If you have any questions about the purpose of a synthetic log file, add a comment.

Re: Useful Synthetic ActiveGate logs

AurelienGravier — Tue, 23 Dec 2025 16:21:08 GMT

Hello @HannahM

I would like to leverage the execution logs of the synthetic tests to perform statistics based on these custom events (api.info) for each synthetic test.

I can detect my custom events by looking at the Synthetic Player logs, but there are no attributes to identify the synthetic entity related synthetic testID.

For example, below is a log entry:

How can I map the testID with the dt.entity.synthetic_test related to it ?

Thank you for your help.

Re: Useful Synthetic ActiveGate logs

HannahM — Mon, 29 Dec 2025 12:19:23 GMT

Hey Aurelian,

I can't remember how it's calculated right now, but you can find it in the vuc-browser.log by searching for the line where the test is fetched. This shows both the dt.entity.synthetic_test and the test definition ID (TESTID in the log above).

2025-12-29T10:50:50.537Z INFO [v=35146621929205573] [BM-PeriodicVisitFetcher-1] PeriodicVisitFetcher: Fetched to run BrowserVisit[35146621929205573/SYNTHETIC_TEST-A7D5C33596196D80/-6352957064417284736/-6352957064417284736], execType: ON_DEMAND, procMode: PROCESSING_STANDARD, weight: 1, run: 1/1, scriptLastModified: 2025-12-29T10:43:32.670Z, bf: BeaconForwarder{endpoint="https://localhost:9999/beacon/kqu36999", tenant="kqu36999", isSaaS=true}, meta: []]

In this example, SYNTHETIC_TEST-A7D5C33596196D80 is the dt.entity.synthetic_test and -6352957064417284736 is the TESTID.

If you want to find the id the other way, so from a monitor, find it's test definition id in the WebUI, you can check a link for one of the screenshots. For this monitor execution it's https://ruxit-synth-screencap.s3.amazonaws.com/prod-us-east-6-virginia/kqu36999/-6352957064417284736/35146621929205573/Action_1_regular.jpeg

I tried finding it in GRAIL but didn't have any luck. It will be in the browser_monitor_step_execution event, when that goes live next Quarter, but even then it was as part of the screenshot.thumbnail_uri rather than on it's own.

Re: Useful Synthetic ActiveGate logs

HannahM — Tue, 20 Jan 2026 13:11:02 GMT

@AurelienGravier apologies, I was obviously having a senior moment. The SYNTHETIC_TEST id and the TESTID from the logs are the HEX/ decimal versions of each other.

So for the example above, A7D5C33596196D80 (in hex) = -6352957064417284736 (in decimal)

Re: Useful Synthetic ActiveGate logs

AurelienGravier — Wed, 25 Mar 2026 20:20:35 GMT

Hi @HannahM ,

Sorry for coming back to this quite late, but I was busy with other topics.

Thank you very much, I was able to correlate custom events in the synthetic ActiveGate logs with the name of the synthetic monitor :

This will allow me to set up alerts based on the number of occurrences of custom events in my synthetic tests, generated through api.info().

Thank you very much for your support.

Regards Aurelien

article Useful Synthetic ActiveGate logs in Troubleshooting

Useful Synthetic ActiveGate logs

Summary

Default locations for logs

Helpful files and folders

Synthetic installation log

Synthetic Module start-up log (VUC Wrapper Launcher)

Synthetic Module (VUC) Logs

vuc.log

vuc-browser.log

vuc-browser.debug.log

vuc-dns-execution.log

vuc-http.log

vuc-http-custom.log

vuc-http-execution.log

vuc-http.debug.log

vuc-icmp-execution.log

vuc-multi.log

vuc-multi.debug.log

vuc-tcp-execution.log

vuc-status.log

Synthetic Player (VUP) Logs

What's Next

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