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fix: let per-event log fields override global-context keys instead of duplicating them #81

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Merged
OmarAlJarrah merged 1 commit into from
Jun 16, 2026
Merged

fix: let per-event log fields override global-context keys instead of duplicating them #81

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8 changes: 7 additions & 1 deletion sdk-core/src/main/kotlin/org/dexpace/sdk/core/instrumentation/LoggingEvent.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -166,10 +166,16 @@ public class LoggingEvent internal constructor(

val builder = logger.slf4j.atLevel(logger.slf4jLevel(level))

// Global context first so per-event fields can override on the SLF4J side.
// Global context first so per-event fields can override on the SLF4J side. A global-context
// key that is also a per-event field is skipped here and emitted once below from `fields`,
// letting the per-event value win. SLF4J's addKeyValue APPENDS rather than replaces, so
// emitting both would put two KeyValuePairs with the same name on the event — invalid
// duplicate-key JSON in JSON appenders. This mirrors the MDC dedup guard below.
val gc = logger.globalContext
if (gc.isNotEmpty()) {
val perEventKeys = fields
for ((k, v) in gc) {
if (perEventKeys?.containsKey(k) == true) continue
builder.addKeyValue(k, renderForLog(v))
}
}
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19 changes: 19 additions & 0 deletions sdk-core/src/test/kotlin/org/dexpace/sdk/core/instrumentation/LoggingEventTest.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -567,6 +567,25 @@ class LoggingEventTest {
assertEquals("global-trace", traceIdEntries.single().value)
}

@Test
fun `per-event field overrides globalContext key and is emitted exactly once`() {
// A key carried by both the logger's globalContext and a per-event field() must be
// emitted once, with the per-event value winning. Two KeyValuePair entries with the
// same key serialise to invalid duplicate-key JSON in JSON appenders.
val (logger, fake) = enabledLogger(mapOf("region" to "global"))
logger.atInfo().field("region", "event").log()

val rec = fake.records.single()
val regionEntries = rec.keyValues.filter { it.key == "region" }
assertEquals(
1,
regionEntries.size,
"expected exactly one region entry; a second from globalContext would be a duplicate KeyValuePair",
)
// The per-event field wins over the globalContext value.
assertEquals("event", regionEntries.single().value)
}

@Test
fun `MDC keys absent from globalContext are still folded`() {
// Guard the collision fix against over-skipping: an MDC key NOT present in
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