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Visualization

Dagger works by building up a DAG of operations and evaluating them, often in parallel. By nature, this is a difficult thing to display. It's easy to show the output of one operation at a time, but as soon as you have parallelism, you'll get jumbled output that's hard to understand.

This quickly creates the need to visualize the pipeline, to understand what's going on. Dagger includes two features for this purpose.

Terminal UI (TUI)​

The Dagger CLI includes a real-time visualization feature called the terminal UI (TUI). It shows a full-blown DAG in a style similar to git log --graph, with the current state of your DAG's evaluation and a full snapshot of all output at the end.

The TUI is designed for rapid iteration, in the same way regular scripting works: you run a command, it shows live progress, and then leaves all the output in your terminal scrollback. Here's an example of it in action:

Dagger TUI

The TUI is driven by OpenTelemetry and is essentially a live-streaming OpenTelemetry trace visualizer. It represents Dagger API calls as OpenTelemetry spans with special metadata. If user code integrates with OpenTelemetry, related spans will appear in the TUI as first-class citizens.

The TUI renders a tree of Dagger API calls, represented as GraphQL queries. A parent-child relationship means that the child call is being made by the parent call.

  • A red X or green check indicates whether the call succeeded or failed.
  • A call's duration is rendered after its name.

The CLI has tiered verbosity: -v, -vv, -vvv (just like curl):

  • -v keeps spans visible after they complete, rather than disappearing after a brief pause;
  • -vv reveals internal and encapsulated spans;
  • -vvv reveals sub-100ms spans.

For additional debugging information, add the --debug flag to the dagger call command.

Traces​

Dagger Cloud provides Traces, a browser-based interface focused on tracing and debugging Dagger Functions. A Trace represents one invocation of a Dagger Function, run locally or in CI. It contains detailed information about the operations performed by the Dagger Function.

  • Traces provides a UI to debug what went wrong when something fails, focusing on tracing what happened and when it happened.
  • Traces also helps you optimize your Dagger Functions as you author them, by giving you the detailed step-by-step execution of your pipeline and the associated telemetry.

This is equally useful for debugging pipelines running on a developer's local environment and for pipelines in CI environments.

Here's an example of it in action:

Dagger Trace

info

Dagger uses OpenTelemetry as its telemetry protocol. Each Dagger Function call is represented as an OpenTelemetry trace. The operations performed by the Dagger Function are represented as OpenTelemetry spans. A span can emit several effects, which are the operations generated in the span. For example, the withDirectory() span generates all the necessary operations to provide a directory with excluded and included elements. For this, it first loads a directory, and then creates a new one from scratch inside the container, generating two distinct steps (effects).

Dagger is aware of the context it runs in. The Dagger Cloud dashboard classifies Traces depending on whether you triggered a run from your local development host or from your CI environment. You can select the appropriate view from the dashboard sidebar. Here's an example showing Traces generated in a CI environment:

Traces list

This initial view displays groups of Traces that belong to the same point in Git history. The grouping is determined by the branch/reference combination where Dagger was triggered. This is useful when you need to inspect all the Traces emitted at a specific, pinned point in the repository's version history

Here's a quick summary of what you'll see for each Trace group:

  • Repository name
  • Commit metadata, including comment and commit author
  • Indication of the run status: in progress, succeeded, or failed
  • The command used
  • The run start time
  • The run duration
important

All of the information listed above may not be available for a specific group, as it differs depending on whether the Trace is generated by a local run or a CI run. When Dagger runs in a CI environment like GitHub, GitLab, CircleCI, or Jenkins, additional Trace metadata is displayed based on the Git repository information available. Traces that run in CI but contain incomplete or no Git metadata are considered "orphaned" and will not be part of a group.

You can drill down into the details of a specific group by clicking it. This directs you to a list of Traces, together with detailed status and duration metadata for each. Each Dagger Function call is represented as a separate Trace, as shown below:

Trace details

You can click any of the Traces in the list to see detailed logs for each Trace. The flame graph at the top of the Trace shows the operations performed by the Dagger Function, with a visual cue of how much time each operation represents of the total duration, as shown below:

Trace log

If there are any errors, Dagger Cloud automatically surfaces the main error and error message in the list.

Trace error

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