You can view the call relationships between services or operations in a set of queried traces or spans in the Topology view in Trace Explorer.

The information visualized in the Topology view is based on a topology query, which can either be an out-of-the-box query or a custom query entered manually. Note that if the out-of-the-box or custom query has the group by clause, then the Topology view is not displayed.

The Topology view provides an overview of all the services or operations in a set of traces and enables you to focus on a particular service or operation, its call relationships, and the metrics generated in each call. Application Performance Monitoring builds the topology based on the parent-child relationship of individual spans. To begin exploring the Topology view and its features, click the Traces Quick Pick button and then click the Topology icon (). On doing so, you'll notice that the syntax of the out-of-the-box query in the Traces quick pick has changed to include the clauses that constitute a topology query:

TOPOLOGY FOR NODES BY <Specifies the nodes to aggregate the traces or spans. Typically, traces or 
                        spans are only aggregated by serviceName or serviceName and operationName.> 
SOURCE <TRACES | SPANS> WHERE <clause> ORDER BY <clause> FIRST <n> ROWS 
AGGREGATE LINKS BY <Specifies the metrics to be displayed for calls.>
ADD FINAL LINKS <Displays spans that represent calls to external services or databases, if specified.>
INCLUDE ROOTS <Displays arrows that represent the initial call to each root span.>

SOURCE queries traces or spans to select the traces that will be used to build the topology. Note that by default, only the top 100 traces are displayed in the topology, however, you can add FIRST <number> ROWS to the query to visualize a summarized topology of up to 200,000 traces.

Based on the topology query in the Traces quick pick, the services in the queried traces are displayed by default. The different colored nodes correspond to the monitored services in the trace that are also listed in the Services in Diagram legend, which can be viewed by clicking the Show Diagram Controls icon (). The gray nodes denote unknown clients or the external services or databases that are not monitored. The arrows between the nodes denote calls and you can hover the mouse over them to view the from and to services and the metrics, as specified in the query.

To view the operations in the trace in the Topology view, click the Show Operations icon (). In this view, all operations from the same service are in the same color, and when you hover the mouse over the arrows, the from and to service: operation are displayed, along with the metrics specified in the query.

Here's an image of the Topology view, which shows the services in a set of queried traces.

In the Topology view, you can:

• Select a metric in the Arrow Width drop-down list and the width of the arrows changes depending on the metric value. The calls with a higher value for the selected metric are denoted by a thicker arrow.
• Right-click in the white space to view a menu with options that allow you to show or hide specific types of nodes. You can then select the Show All option in the menu to view the entire topology for the query.
• Place the cursor on a node and right-click to view a menu with options that allow you to show or hide the various nodes and call relationships pertaining to the selected node.
• Click a service in the Services in Diagram legend to only view the nodes of that service, and their inbound and outbound calls. Other nodes that are not directly related to the nodes of the selected service are not displayed in the topology. This action can be performed when viewing either services or operations in the Topology view.

In addition, you can click the Table icon () in the Topology view to view the calls and metrics displayed in the topology in a tabular format.

To go back to the default view in Trace Explorer from the Topology view, click the Show recent queries icon () adjacent to the query field to view and select a recent trace query, or click one of the quick pick buttons such as Traces or Trace Services.