Fix inconsistent exception logging patterns and add guidance

CONTRIBUTING.md

@@ -146,6 +146,15 @@ uses [google-java-format](https://github.com/google/google-java-format) library:
     synchronized (lock) { ... }
   }
   ```
+* When logging exceptions, pass the exception as the `Throwable` parameter to the logger
+  rather than stringifying it via `getMessage()` or concatenation. This ensures logging
+  frameworks can render the full stack trace.
+  ```java
+  // Do:
+  logger.log(Level.WARNING, "Failed to process request", exception);
+  // Don't:
+  logger.warning("Failed to process request: " + exception.getMessage());
+  ```
 * Don't
   use [gradle test fixtures](https://docs.gradle.org/current/userguide/java_testing.html#sec:java_test_fixtures) (
   i.e. `java-test-fixtures` plugin) to reuse code for internal testing. The test fixtures plugin has

exporters/common/src/main/java/io/opentelemetry/exporter/internal/grpc/GrpcExporter.java

@@ -126,12 +126,7 @@ private void onError(
       Throwable e) {
     metricRecording.finishFailed(e);
     logger.log(
-        Level.SEVERE,
-        "Failed to export "
-            + type
-            + "s. The request could not be executed. Error message: "
-            + e.getMessage(),
-        e);
+        Level.SEVERE, "Failed to export " + type + "s. The request could not be executed.", e);
     if (logger.isLoggable(Level.FINEST)) {
       logger.log(Level.FINEST, "Failed to export " + type + "s. Details follow:", e);
     }

exporters/common/src/main/java/io/opentelemetry/exporter/internal/http/HttpExporter.java

@@ -117,12 +117,7 @@ private void onError(
       Throwable e) {
     metricRecording.finishFailed(e);
     logger.log(
-        Level.SEVERE,
-        "Failed to export "
-            + type
-            + "s. The request could not be executed. Full error message: "
-            + e.getMessage(),
-        e);
+        Level.SEVERE, "Failed to export " + type + "s. The request could not be executed.", e);
     result.failExceptionally(FailedExportException.httpFailedExceptionally(e));
   }
 

opentracing-shim/src/main/java/io/opentelemetry/opentracingshim/TracerShim.java

@@ -108,10 +108,7 @@ public <C> SpanContext extract(Format<C> format, C carrier) {
       }
     } catch (RuntimeException e) {
       logger.log(
-          Level.WARNING,
-          "Exception caught while extracting span context; returning null. "
-              + "Exception: [{0}] Message: [{1}]",
-          new String[] {e.getClass().getName(), e.getMessage()});
+          Level.WARNING, "Exception caught while extracting span context; returning null.", e);
     }
 
     return null;

sdk-extensions/autoconfigure/src/main/java/io/opentelemetry/sdk/autoconfigure/AutoConfiguredOpenTelemetrySdkBuilder.java

@@ -501,8 +501,7 @@ private AutoConfiguredOpenTelemetrySdk buildImpl() {
           logger.fine("Closing " + closeable.getClass().getName());
           closeable.close();
         } catch (IOException ex) {
-          logger.warning(
-              "Error closing " + closeable.getClass().getName() + ": " + ex.getMessage());
+          logger.log(Level.WARNING, "Error closing " + closeable.getClass().getName(), ex);
         }
       }
       if (e instanceof ConfigurationException) {

sdk-extensions/autoconfigure/src/test/java/io/opentelemetry/sdk/autoconfigure/AutoConfiguredOpenTelemetrySdkTest.java

@@ -703,7 +703,7 @@ void configurationError_ClosesResources() {
     verify(tracerProvider).close();
     verify(meterProvider).close();
 
-    logs.assertContains("Error closing io.opentelemetry.sdk.trace.SdkTracerProvider: Error!");
+    logs.assertContains("Error closing io.opentelemetry.sdk.trace.SdkTracerProvider");
   }
 
   @Test

sdk-extensions/incubator/src/main/java/io/opentelemetry/sdk/extension/incubator/fileconfig/DeclarativeConfiguration.java

@@ -287,8 +287,7 @@ static <M, R> R createAndMaybeCleanup(
           logger.fine("Closing " + closeable.getClass().getName());
           closeable.close();
         } catch (IOException ex) {
-          logger.warning(
-              "Error closing " + closeable.getClass().getName() + ": " + ex.getMessage());
+          logger.log(Level.WARNING, "Error closing " + closeable.getClass().getName(), ex);
         }
       }
       if (e instanceof DeclarativeConfigException) {

sdk-extensions/jaeger-remote-sampler/src/main/java/io/opentelemetry/sdk/extension/trace/jaeger/sampler/JaegerRemoteSampler.java

@@ -128,14 +128,9 @@ private void onResponse(GrpcResponse grpcResponse) {
 
   private static void onError(Throwable e) {
     logger.log(
-        Level.SEVERE,
-        "Failed to execute "
-            + TYPE
-            + "s. The request could not be executed. Error message: "
-            + e.getMessage(),
-        e);
+        Level.SEVERE, "Failed to execute " + TYPE + "s. The request could not be executed.", e);
     if (logger.isLoggable(Level.FINEST)) {
-      logger.log(Level.FINEST, "Failed to execute " + TYPE + "s. Details follow: " + e);
+      logger.log(Level.FINEST, "Failed to execute " + TYPE + "s. Details follow:", e);
     }
   }
 

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/SdkDoubleHistogram.java

@@ -94,7 +94,7 @@ public DoubleHistogramBuilder setExplicitBucketBoundariesAdvice(List<Double> buc
         Objects.requireNonNull(bucketBoundaries, "bucketBoundaries must not be null");
         ExplicitBucketHistogramUtils.validateBucketBoundaries(bucketBoundaries);
       } catch (IllegalArgumentException | NullPointerException e) {
-        logger.warning("Error setting explicit bucket boundaries advice: " + e.getMessage());
+        logger.log(Level.WARNING, "Error setting explicit bucket boundaries advice", e);
         return this;
       }
       builder.setExplicitBucketBoundaries(bucketBoundaries);

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/SdkLongHistogram.java

@@ -99,7 +99,7 @@ public LongHistogramBuilder setExplicitBucketBoundariesAdvice(List<Long> bucketB
         boundaries = bucketBoundaries.stream().map(Long::doubleValue).collect(Collectors.toList());
         ExplicitBucketHistogramUtils.validateBucketBoundaries(boundaries);
       } catch (IllegalArgumentException | NullPointerException e) {
-        logger.warning("Error setting explicit bucket boundaries advice: " + e.getMessage());
+        logger.log(Level.WARNING, "Error setting explicit bucket boundaries advice", e);
         return this;
       }
       builder.setExplicitBucketBoundaries(boundaries);

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

@@ -266,7 +266,7 @@ private static Stream<Arguments> histogramsWithInvalidAdvice() {
                           .build();
                   return histogram::record;
                 },
-            "Error setting explicit bucket boundaries advice: Bucket boundaries must be in increasing order: 10.0 >= 9.0"),
+            "Error setting explicit bucket boundaries advice"),
         Arguments.of(
             (Function<SdkMeterProvider, Consumer<Long>>)
                 meterProvider -> {
@@ -279,7 +279,7 @@ private static Stream<Arguments> histogramsWithInvalidAdvice() {
                           .build();
                   return histogram::record;
                 },
-            "Error setting explicit bucket boundaries advice: Bucket boundaries must be in increasing order: 10.0 >= 9.0"),
+            "Error setting explicit bucket boundaries advice"),
         Arguments.of(
             (Function<SdkMeterProvider, Consumer<Long>>)
                 meterProvider -> {
@@ -291,6 +291,6 @@ private static Stream<Arguments> histogramsWithInvalidAdvice() {
                           .build();
                   return histogram::record;
                 },
-            "Error setting explicit bucket boundaries advice: bucketBoundaries must not be null"));
+            "Error setting explicit bucket boundaries advice"));
   }
 }