3.2 Test Filter Processor

To test your configuration, you’ll need to generate some trace data that includes a span named "/_healthz".

Exercise

Start the Gateway: In your Gateway terminal window start the Gateway.

../otelcol --config ./gateway.yaml

Start the Agent: In your Agent terminal window start the Agent.

../otelcol --config ./agent.yaml

Start the Loadgen: In the Loadgen terminal window, execute the following command to start the load generator with health check spans enabled:

../loadgen -health -count 5

The debug output in the Agent terminal will show _healthz spans:

InstrumentationScope healthz 1.0.0
Span #0
   Trace ID       : 0cce8759b5921c8f40b346b2f6e2f4b6
   Parent ID      :
   ID             : bc32bd0e4ddcb174
   Name           : /_healthz
   Kind           : Server
   Start time     : 2025-07-11 08:47:50.938703979 +0000 UTC
   End time       : 2025-07-11 08:47:51.938704091 +0000 UTC
   Status code    : Ok
   Status message : Success

They will not be present in the Gateway debug as they are dropped by the filter processor that was configured earlier.

Verify agent.out: Using jq, in the Test terminal, confirm the name of the spans received by the Agent:

​
jq -c '.resourceSpans[].scopeSpans[].spans[] | "Span \(input_line_number) found with name \(.name)"' ./agent.out
"Span 1 found with name /movie-validator"
"Span 2 found with name /_healthz"
"Span 3 found with name /movie-validator"
"Span 4 found with name /_healthz"
"Span 5 found with name /movie-validator"
"Span 6 found with name /_healthz"
"Span 7 found with name /movie-validator"
"Span 8 found with name /_healthz"
"Span 9 found with name /movie-validator"
"Span 10 found with name /_healthz"

Check the Gateway Debug output: Using jq confirm the name of the spans received by the Gateway:

​
jq -c '.resourceSpans[].scopeSpans[].spans[] | "Span \(input_line_number) found with name \(.name)"' ./gateway-traces.out

The gateway-metrics.out file will not contain any spans named /_healthz.

"Span 1 found with name /movie-validator"
"Span 2 found with name /movie-validator"
"Span 3 found with name /movie-validator"
"Span 4 found with name /movie-validator"
"Span 5 found with name /movie-validator"
Tip

To ensure optimal performance with the Filter processor, thoroughly understand your incoming data format and rigorously test your configuration. Use the most specific filtering criteria possible to minimize the risk of inadvertently dropping important data.

This configuration can be extended to filter spans based on various attributes, tags, or custom criteria, enhancing the OpenTelemetry Collector’s flexibility and efficiency for your specific observability requirements.

Important

Stop the Agent and the Gateway processes by pressing Ctrl-C in their respective terminals.