View traces across projects

By default, the Trace Explorer page only searches your selected project for trace data. To view trace spans that are stored in multiple projects, as might occur when an application in one project makes a call into an application that another project hosts, do the following:

1. Create a trace scope that lists the default trace view for each project that stores spans for your trace. A project's default trace view corresponds to the view with the path _Trace/Spans/_AllSpans, where the fields _Trace, Spans, and _AllSpans refer to an observability bucket, dataset, and view. The dataset Spans stores your trace data. For information about trace scopes, see Create and manage trace scopes.

2. Update the observability scope.

   Note: To facilitate correlation between log and trace data, set the observability scope. This scope specifies which of your trace scopes and log scopes to use when the corresponding explorer pages open. If you don't configure the observability scope to list the resources that store your data, then you might not be able to correlate your trace and log data. To learn more, see Configure observability scopes for multi-project queries.

3. Open the Trace Explorer page to view your trace data. This page automatically searches the views listed in the default trace scope for trace data. If the default trace scope scope isn't accessible, then the page searches the project's _AllSpans view on the default dataset. This view provides read access to all trace data that the project stores.

   To change which views are searched for trace data, go to the toolbar and use the Scope element. For more information, see Configure which views the Trace Explorer searches.

   Your Identity and Access Management (IAM) roles on the views listed in the trace scope and the time-range setting determine what data the system displays. The trace scope only specifies which views the system searches for data.