1. Capture Tags - Java

15 minutes

Let’s add some tags to our traces, so we can find out why some customers receive a poor experience from our application.

Identify Useful Tags

We’ll start by reviewing the code for the creditCheck function of creditcheckservice (which can be found in the file /home/splunk/workshop/tagging/creditcheckservice-java/src/main/java/com/example/creditcheckservice/CreditCheckController.java):

@GetMapping("/check")
public ResponseEntity<String> creditCheck(@RequestParam("customernum") String customerNum) {
    // Get Credit Score
    int creditScore;
    try {
        String creditScoreUrl = "http://creditprocessorservice:8899/getScore?customernum=" + customerNum;
        creditScore = Integer.parseInt(restTemplate.getForObject(creditScoreUrl, String.class));
    } catch (HttpClientErrorException e) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Error getting credit score");
    }

    String creditScoreCategory = getCreditCategoryFromScore(creditScore);

    // Run Credit Check
    String creditCheckUrl = "http://creditprocessorservice:8899/runCreditCheck?customernum=" + customerNum + "&score=" + creditScore;
    String checkResult;
    try {
        checkResult = restTemplate.getForObject(creditCheckUrl, String.class);
    } catch (HttpClientErrorException e) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Error running credit check");
    }

    return ResponseEntity.ok(checkResult);
}

We can see that this function accepts a customer number as an input. This would be helpful to capture as part of a trace. What else would be helpful?

Well, the credit score returned for this customer by the creditprocessorservice may be interesting (we want to ensure we don’t capture any PII data though). It would also be helpful to capture the credit score category, and the credit check result.

Great, we’ve identified four tags to capture from this service that could help with our investigation. But how do we capture these?

Capture Tags

We start by adding OpenTelemetry imports to the top of the CreditCheckController.java file:

...
import io.opentelemetry.api.trace.Span;
import io.opentelemetry.instrumentation.annotations.WithSpan;
import io.opentelemetry.instrumentation.annotations.SpanAttribute;

Next, we use the @WithSpan annotation to produce a span for creditCheck:

@GetMapping("/check")
@WithSpan // ADDED
public ResponseEntity<String> creditCheck(@RequestParam("customernum") String customerNum) {
    ...

We can now get a reference to the current span and add an attribute (aka tag) to it:

...
try {
    String creditScoreUrl = "http://creditprocessorservice:8899/getScore?customernum=" + customerNum;
    creditScore = Integer.parseInt(restTemplate.getForObject(creditScoreUrl, String.class));
} catch (HttpClientErrorException e) {
    return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Error getting credit score");
}
Span currentSpan = Span.current(); // ADDED
currentSpan.setAttribute("credit.score", creditScore); // ADDED
...

That was pretty easy, right? Let’s capture some more, with the final result looking like this:

@GetMapping("/check")
@WithSpan(kind=SpanKind.SERVER)
public ResponseEntity<String> creditCheck(@RequestParam("customernum")
                                          @SpanAttribute("customer.num")
                                          String customerNum) {
    // Get Credit Score
    int creditScore;
    try {
        String creditScoreUrl = "http://creditprocessorservice:8899/getScore?customernum=" + customerNum;
        creditScore = Integer.parseInt(restTemplate.getForObject(creditScoreUrl, String.class));
    } catch (HttpClientErrorException e) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Error getting credit score");
    }
    Span currentSpan = Span.current();
    currentSpan.setAttribute("credit.score", creditScore);

    String creditScoreCategory = getCreditCategoryFromScore(creditScore);
    currentSpan.setAttribute("credit.score.category", creditScoreCategory);

    // Run Credit Check
    String creditCheckUrl = "http://creditprocessorservice:8899/runCreditCheck?customernum=" + customerNum + "&score=" + creditScore;
    String checkResult;
    try {
        checkResult = restTemplate.getForObject(creditCheckUrl, String.class);
    } catch (HttpClientErrorException e) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Error running credit check");
    }
    currentSpan.setAttribute("credit.check.result", checkResult);

    return ResponseEntity.ok(checkResult);
}

Redeploy Service

Once these changes are made, let’s run the following script to rebuild the Docker image used for creditcheckservice and redeploy it to our Kubernetes cluster:

./5-redeploy-creditcheckservice.sh java

Confirm Tag is Captured Successfully

After a few minutes, return to Splunk Observability Cloud and load one of the latest traces to confirm that the tags were captured successfully (hint: sort by the timestamp to find the latest traces):

Well done, you’ve leveled up your OpenTelemetry game and have added context to traces using tags.

Next, we’re ready to see how you can use these tags with Splunk Observability Cloud!