From 3f265a4d73e3ed1e2628e740d9ca29732dc610a7 Mon Sep 17 00:00:00 2001
From: syukumoto <98008304+syukumoto@users.noreply.github.com>
Date: Mon, 13 Jul 2026 17:59:30 +0900
Subject: [PATCH] Document handling of empty OperationId in logs

Added information about empty OperationId in application logs and how to instrument logging with Application Insights agent.

Background
When a Java Azure Functions app enables the OpenTelemetry integration
(`telemetryMode: "OpenTelemetry"` in host.json), application logs written by
the function code can be ingested into Application Insights with an empty
`operation_Id`. As already noted in the "Duplicate OperationId" entry,
`operation_Id` is derived from the incoming `traceparent` and is applied only
to telemetry emitted within the invocation context. Application logs that are
forwarded by the Functions host (rather than emitted within the invocation
context) are therefore recorded without an `operation_Id`, so they don't
correlate with the invocation's request and trace in the end-to-end
transaction view.
---
 articles/azure-functions/opentelemetry-howto.md | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/articles/azure-functions/opentelemetry-howto.md b/articles/azure-functions/opentelemetry-howto.md
index 500cdc72940a4..627ca6e2ddee1 100644
--- a/articles/azure-functions/opentelemetry-howto.md
+++ b/articles/azure-functions/opentelemetry-howto.md
@@ -617,6 +617,16 @@ Triggers such as HTTP, Service Bus, and Event Hubs depend on context propagation
 
 In Azure Functions, the `OperationId` used for correlating telemetry comes directly from the `traceparent` value in the incoming request or message. If multiple calls reuse the same `traceparent` value, they all get the same `OperationId`.
 
+### Application logs have an empty OperationId
+
+Application logs written by your function code can appear in the traces table with an empty operation_Id. As a result, they don't correlate with the invocation's request and trace in the end-to-end transaction view.
+
+As described in Duplicate OperationId, the operation_Id is applied to telemetry that is emitted within the invocation context. Application logs emitted outside that context—for example, logs that the Functions host forwards—are recorded without an operation_Id.
+
+If you need OperationId in your application logs, use the Application Insights agent to instrument your logging framework instead of the OpenTelemetry mode: enable the agent as described in [Enable Azure Monitor OpenTelemetry for .NET, Node.js, Python, and Java applications](https://learn.microsoft.com/en-us/azure/azure-monitor/app/opentelemetry-enable?tabs=java). The agent stamps the trace context (operation_Id = trace ID) on the logs it emits within the invocation context.
+
+Make sure telemetryMode isn't set to OpenTelemetry in your `host.json`. If you added `"telemetryMode": "OpenTelemetry"`, remove it.
+
 ### Configure OpenTelemetry with environment variables
 
 You can configure OpenTelemetry behavior by using its standard environment variables. These variables provide a consistent way to control behavior across different languages and runtimes. You can adjust sampling strategies, exporter settings, and resource attributes. For more information about supported environment variables, see the [OpenTelemetry documentation](https://opentelemetry.io/docs/languages/sdk-configuration/).