Review logs to diagnose pipeline issues

Article
06/09/2020

TFS 2017 | TFS 2015

Pipeline logs provide a powerful tool for determining the cause of pipeline failures.

A typical starting point is to review the logs in your completed build or release. You can view logs by navigating to the pipeline run summary and selecting the job and task. If a certain task is failing, check the logs for that task.

In addition to viewing logs in the pipeline build summary, you can download complete logs which include additional diagnostic information, and you can configure more verbose logs to assist with your troubleshooting.

Configure verbose logs

To assist with troubleshooting, you can configure your logs to be more verbose.

To configure verbose logs for a single run, you can start a new build by choosing Queue build, and setting the value for the system.debug variable to true.
To configure verbose logs for all runs, edit the build, navigate to the Variables tab, and add a variable named system.debug, set its value to true, and select to Allow at Queue Time.
To configure verbose logs for a YAML pipeline, add the system.debug variable in the variables section:
```
variables:
  system.debug: true
```

View and download logs

To download all logs, navigate to the build results for the run, choose Download all logs as zip.

In addition to the pipeline diagnostic logs, the following specialized log types are available, and may contain information to help you troubleshoot.

Worker diagnostic logs
Agent diagnostic logs
Other logs

Worker diagnostic logs

You can get the diagnostic log of the completed build that was generated by the worker process on the build agent. Look for the worker log file that has the date and time stamp of your completed build. For example, worker_20160623-192022-utc_6172.log.

Agent diagnostic logs

Agent diagnostic logs provide a record of how the agent was configured and what happened when it ran. Look for the agent log files. For example, agent_20160624-144630-utc.log. There are two kinds of agent log files:

The log file generated when you ran config.cmd. This log:
- Includes this line near the top: Adding Command: configure
- Shows the configuration choices made.
The log file generated when you ran run.cmd. This log:
- Cannot be opened until the process is terminated.
- Attempts to connect to your Azure DevOps organization or Team Foundation Server.
- Shows when each job was run, and how it completed

Both logs show how the agent capabilities were detected and set.

Other logs

Inside the diagnostic logs you will find environment.txt and capabilities.txt.

The environment.txt file has various information about the environment within which your build ran. This includes information like what tasks are run, whether or not the firewall is enabled, PowerShell version info, and some other items. We continually add to this data to make it more useful.

The capabilities.txt file provides a clean way to see all capabilities installed on the build machine that ran your build.

Important

HTTP traces and trace files can contain passwords and other secrets. Do not post them on a public sites.

Use built-in HTTP tracing

If your agent is version 2.114.0 or newer, you can trace the HTTP traffic headers and write them into the diagnostic log. Set the VSTS_AGENT_HTTPTRACE environment variable before you launch the agent.listener.

Windows:
    set VSTS_AGENT_HTTPTRACE=true

macOS/Linux:
    export VSTS_AGENT_HTTPTRACE=true

Use full HTTP tracing - Windows

Start Fiddler.
We recommend you listen only to agent traffic. File > Capture Traffic off (F12)
Enable decrypting HTTPS traffic. Tools > Fiddler Options > HTTPS tab. Decrypt HTTPS traffic

Let the agent know to use the proxy:

set VSTS_HTTP_PROXY=http://127.0.0.1:8888

Run the agent interactively. If you're running as a service, you can set as the environment variable in control panel for the account the service is running as.
Restart the agent.

Use full HTTP tracing - macOS and Linux

Use Charles Proxy (similar to Fiddler on Windows) to capture the HTTP trace of the agent.

Start Charles Proxy.
Charles: Proxy > Proxy Settings > SSL Tab. Enable. Add URL.
Charles: Proxy > Mac OSX Proxy. Recommend disabling to only see agent traffic.
```
export VSTS_HTTP_PROXY=http://127.0.0.1:8888
```
Run the agent interactively. If it's running as a service, you can set in the .env file. See nix service
Restart the agent.

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