Record error.type on failed collections in PeriodicMetricReader

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/export/PeriodicMetricReader.java

@@ -275,6 +275,12 @@ CompletableResultCode doRun() {
           Collection<MetricData> metricData;
           try {
             metricData = collectionRegistration.collectAllMetrics();
+          } catch (Throwable t) {
+            // Record the failure on the self-observability sample before it propagates to the
+            // outer handler; otherwise error.type is never set and collection failures are
+            // reported as successful collections.
+            error = t.getClass().getName();
+            throw t;
           } finally {
             long durationNanos = CLOCK.nanoTime() - startNanoTime;
             instrumentation.recordCollection(durationNanos / 1_000_000_000.0, error);

sdk/metrics/src/test/java/io/opentelemetry/sdk/metrics/SdkMeterProviderMetricsTest.java

@@ -12,10 +12,13 @@
 import io.opentelemetry.api.metrics.Meter;
 import io.opentelemetry.sdk.common.internal.SemConvAttributes;
 import io.opentelemetry.sdk.metrics.data.MetricData;
+import io.opentelemetry.sdk.metrics.export.MetricProducer;
 import io.opentelemetry.sdk.metrics.export.PeriodicMetricReader;
 import io.opentelemetry.sdk.testing.exporter.InMemoryMetricExporter;
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
 import org.junit.jupiter.api.Test;
 
 class SdkMeterProviderMetricsTest {
@@ -59,4 +62,44 @@ void simple() {
               });
     }
   }
+
+  @Test
+  void collectionFailureIsRecordedWithErrorType() {
+    InMemoryMetricExporter metricExporter = InMemoryMetricExporter.create();
+    AtomicBoolean shouldFail = new AtomicBoolean(true);
+    // Fail the first collection, then succeed so the recorded self-observability sample can be
+    // exported on the following flush.
+    MetricProducer failingProducer =
+        resource -> {
+          if (shouldFail.getAndSet(false)) {
+            throw new IllegalStateException("boom");
+          }
+          return Collections.emptyList();
+        };
+    try (SdkMeterProvider meterProvider =
+        SdkMeterProvider.builder()
+            .registerMetricReader(PeriodicMetricReader.create(metricExporter))
+            .registerMetricProducer(failingProducer)
+            .build()) {
+
+      meterProvider.forceFlush().join(10, TimeUnit.SECONDS);
+      metricExporter.reset();
+      // Export again to export the metric reader's self-observability metric.
+      meterProvider.forceFlush().join(10, TimeUnit.SECONDS);
+
+      assertThat(metricExporter.getFinishedMetricItems())
+          .anySatisfy(
+              m ->
+                  assertThat(m)
+                      .hasName("otel.sdk.metric_reader.collection.duration")
+                      .hasHistogramSatisfying(
+                          h ->
+                              h.hasPointsSatisfying(
+                                  p ->
+                                      p.hasAttributesSatisfying(
+                                          equalTo(
+                                              SemConvAttributes.ERROR_TYPE,
+                                              "java.lang.IllegalStateException")))));
+    }
+  }
 }