Be more defensive in setting metadata for observability events

Without this change it was possible in some of the ITs,
depending on the mock response from the server, to have NPEs being thrown.
These NPEs didn't affect the response, but they did
clutter up the logs

Author: geoand

core/runtime/src/main/java/io/quarkiverse/langchain4j/runtime/listeners/MetricsChatModelListener.java

@@ -16,7 +16,6 @@
 import io.micrometer.core.instrument.Counter;
 import io.micrometer.core.instrument.Meter;
 import io.micrometer.core.instrument.Metrics;
-import io.micrometer.core.instrument.Tag;
 import io.micrometer.core.instrument.Tags;
 import io.micrometer.core.instrument.Timer;
 import io.quarkiverse.langchain4j.cost.Cost;
@@ -78,9 +77,10 @@ public void onResponse(ChatModelResponseContext responseContext) {
 
         ChatModelRequest request = responseContext.request();
         ChatModelResponse response = responseContext.response();
-        Tags tags = Tags.of(
-                Tag.of("gen_ai.request.model", request.model()),
-                Tag.of("gen_ai.response.model", response.model()));
+        Tags tags = Tags.of("gen_ai.request.model", request.model());
+        if (response.model() != null) {
+            tags = tags.and("gen_ai.response.model", response.model());
+        }
         if (ContextLocals.duplicatedContextActive()) {
             String aiServiceClassName = ContextLocals.get(AiServiceConstants.AI_SERVICE_CLASS_NAME);
             if (aiServiceClassName != null) {
@@ -112,10 +112,13 @@ public void onError(ChatModelErrorContext errorContext) {
             return;
         }
 
-        Tags tags = Tags.of(
-                Tag.of("gen_ai.request.model", errorContext.request().model()),
-                Tag.of("gen_ai.response.model", errorContext.partialResponse().model()),
-                Tag.of("error.type", aiMessage.text()));
+        Tags tags = Tags.of("gen_ai.request.model", errorContext.request().model());
+        if (errorContext.partialResponse().model() != null) {
+            tags = tags.and("gen_ai.response.model", errorContext.partialResponse().model());
+        }
+        if (aiMessage.text() != null) {
+            tags = tags.and("error.type", aiMessage.text());
+        }
         duration.withTags(tags).record(endTime - startTime, TimeUnit.NANOSECONDS);
     }
 

core/runtime/src/main/java/io/quarkiverse/langchain4j/runtime/listeners/SpanChatModelListener.java

@@ -61,7 +61,10 @@ public void onResponse(ChatModelResponseContext responseContext) {
         Span span = (Span) attributes.get(OTEL_SPAN_KEY_NAME);
         if (span != null) {
             ChatModelResponse response = responseContext.response();
-            span.setAttribute("gen_ai.response.id", response.id()).setAttribute("gen_ai.response.model", response.model());
+            span.setAttribute("gen_ai.response.id", response.id());
+            if (response.model() != null) {
+                span.setAttribute("gen_ai.response.model", response.model());
+            }
             if (response.finishReason() != null) {
                 span.setAttribute("gen_ai.response.finish_reasons", response.finishReason().toString());
             }