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Adds key traceSampled to MDC when set trace is observable #104

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Adds key traceSampled to MDC when set trace is observable #104

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ed7bba2
Adds key traceSampled to MDC when set trace is observable. Will be se…
Mar 25, 2019
f5eef9f
Addressing nits
Mar 26, 2019
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14 changes: 13 additions & 1 deletion tracing/src/main/java/com/palantir/tracing/Tracer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -331,8 +331,19 @@ static Optional<Trace> copyTrace() {
static void setTrace(Trace trace) {
currentTrace.set(trace);

// Give SLF4J appenders access to the trace id
// Give log appenders access to the trace id and whether the trace is being sampled
MDC.put(Tracers.TRACE_ID_KEY, trace.getTraceId());
setTraceSampledMdcIfObservable(trace.isObservable());
}

private static void setTraceSampledMdcIfObservable(boolean observable) {
if (observable) {
// Set to 1 to be consistent with values associated with http header key TraceHttpHeaders.IS_SAMPLED
MDC.put(Tracers.TRACE_SAMPLED_KEY, "1");
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Might add a comment describing why we're using 1 instead of true.

} else {
// To ensure MDC state is cleared when trace is not observable
MDC.remove(Tracers.TRACE_SAMPLED_KEY);
}
}

private static Trace getOrCreateCurrentTrace() {
Expand All @@ -347,5 +358,6 @@ private static Trace getOrCreateCurrentTrace() {
private static void clearCurrentTrace() {
currentTrace.remove();
MDC.remove(Tracers.TRACE_ID_KEY);
MDC.remove(Tracers.TRACE_SAMPLED_KEY);
}
}
1 change: 1 addition & 0 deletions tracing/src/main/java/com/palantir/tracing/Tracers.java
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Expand Up @@ -26,6 +26,7 @@
public final class Tracers {
/** The key under which trace ids are inserted into SLF4J {@link org.slf4j.MDC MDCs}. */
public static final String TRACE_ID_KEY = "traceId";
public static final String TRACE_SAMPLED_KEY = "traceSampled";
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We should document this key similarly to TRACE_ID_KEY and describe possible values.

private static final String DEFAULT_ROOT_SPAN_OPERATION = "root";
private static final char[] HEX_DIGITS =
{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
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16 changes: 16 additions & 0 deletions tracing/src/test/java/com/palantir/tracing/TracerTest.java
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Expand Up @@ -190,6 +190,22 @@ public void testSetTraceSetsCurrentTraceAndMdcTraceIdKey() throws Exception {
assertThat(MDC.get(Tracers.TRACE_ID_KEY)).isNull();
}

@Test
public void testSetTraceSetsMdcTraceSampledKeyWhenObserved() {
Tracer.setTrace(new Trace(true, "observedTraceId"));
assertThat(MDC.get(Tracers.TRACE_SAMPLED_KEY)).isEqualTo("1");
assertThat(Tracer.completeSpan()).isEmpty();
assertThat(MDC.get(Tracers.TRACE_SAMPLED_KEY)).isNull();
}

@Test
public void testSetTraceMissingMdcTraceSampledKeyWhenNotObserved() {
Tracer.setTrace(new Trace(false, "notObservedTraceId"));
assertThat(MDC.get(Tracers.TRACE_SAMPLED_KEY)).isNull();
assertThat(Tracer.completeSpan()).isEmpty();
assertThat(MDC.get(Tracers.TRACE_SAMPLED_KEY)).isNull();
}

@Test
public void testCompletedSpanHasCorrectSpanType() throws Exception {
for (SpanType type : SpanType.values()) {
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