TulikaC shares a practical cheat-sheet for adding OpenTelemetry sidecar extensions to PHP, Python, Node.js, and .NET apps running on Azure App Service for Linux, including setup steps, default settings, debugging tips, and sample repos.

OTEL Sidecar Extension Cheat-Sheet on Azure App Service for Linux

Author: TulikaC

This cheat-sheet summarizes core setup details for running OpenTelemetry (OTEL) sidecar extensions on Azure App Service for Linux. Learn the essential steps for PHP, Python, Node.js, and .NET, including library choices, configuration, troubleshooting, and links to sample code.

Quick Matrix by Language

Language	OTEL Libraries	Key App Settings	Startup Command Example	Sample Repo
PHP	Composer autoloader (`vendor/autoload.php`), PECL extension `opentelemetry.so`, Composer plugins (Slim, PSR-18)	`OTEL_PHP_AUTOLOAD_ENABLED=true`, `SCM_DO_BUILD_DURING_DEPLOYMENT=true`, `OTEL_EXPORTER_OTLP_ENDPOINT=http://127.0.0.1:4318`, Sidecar: map `OTEL_PHP_AUTOLOAD_ENABLED`	`cp /home/site/wwwroot/default /etc/nginx/sites-enabled/default && nginx -s reload && bash /home/site/wwwroot/startup.sh` (installs opentelemetry, sets up extension, starts `php-fpm`)	PHP Sample
Python	`opentelemetry-instrument` wrapper, auto-patches Flask/requests, installed via pip	`OTEL_TRACES_EXPORTER=otlp`, `OTEL_METRICS_EXPORTER=otlp`, `OTEL_LOGS_EXPORTER=otlp`, `OTEL_PYTHON_LOGGING_AUTO_INSTRUMENTATION_ENABLED=true`, `SCM_DO_BUILD_DURING_DEPLOYMENT=true`, Sidecar: map `OTEL_PYTHON_LOGGING_AUTO_INSTRUMENTATION_ENABLED`	`bash startup.sh` (includes `pip install -r requirements.txt` and runs with `opentelemetry-instrument`)	Python Sample
Node.js	npm packages: `@opentelemetry/sdk-node`, `@opentelemetry/auto-instrumentations-node`, `@opentelemetry/exporter-trace-otlp-http`; init in `tracing.js` and preload via `--require` or `NODE_OPTIONS`	`OTEL_TRACES_EXPORTER=otlp`, `OTEL_METRICS_EXPORTER=otlp`, `OTEL_LOGS_EXPORTER=otlp`, `SCM_DO_BUILD_DURING_DEPLOYMENT=true`	`node --require ./tracing.js <your-app>.js` (or set `NODE_OPTIONS=--require ./tracing.js`)	Node Sample
.NET	NuGet: `OpenTelemetry.Extensions.Hosting`, `OpenTelemetry.Instrumentation.AspNetCore`, `OpenTelemetry.Instrumentation.Http`, `OpenTelemetry.Exporter.OpenTelemetryProtocol`; configured in `Program.cs` via `AddOpenTelemetry()`	`OTEL_DOTNET_AUTO_TRACES_ENABLED=true`, `OTEL_DOTNET_AUTO_METRICS_ENABLED=true`, `OTEL_DOTNET_AUTO_LOGS_ENABLED=true`	No custom startup command needed	.NET Sample

Default App Settings for Backends

Azure Monitor (Application Insights):

APPLICATIONINSIGHTS_CONNECTION_STRING=<your-application-insights-connection-string>
OTEL_EXPORTER=azuremonitor
OTEL_EXPORTER_OTLP_ENDPOINT=http://127.0.0.1:4318
OTEL_SERVICE_NAME=<your-app-name>

Elastic APM:

ELASTIC_APM_ENDPOINT=https://<your-elastic-endpoint>
ELASTIC_APM_SECRET_TOKEN=<your-elastic-token>
OTEL_EXPORTER=elastic
OTEL_EXPORTER_OTLP_ENDPOINT=http://127.0.0.1:4318
OTEL_SERVICE_NAME=<your-app-name>

Notes:

These settings should be added to the main app; the sidecar reads and forwards relevant data.
Port :4318 used for OTLP/HTTP by default. Use :4317 for OTLP/gRPC if needed.
Assign a clear OTEL_SERVICE_NAME (e.g., myapp-api) for easier trace management.

Sample Repository

Complete code and container samples for all supported languages: https://github.com/Azure-Samples/sidecar-samples/tree/main/otel-sidecar

Troubleshooting Checklist

No telemetry appears:
- Check sidecar container status: Deployment Center → Containers → Running
- Verify environment variables like OTEL_EXPORTER_OTLP_ENDPOINT and backend credentials
- Inspect logs via Monitoring → Log stream (look for errors or success messages)
- For extra debugging: set OTEL_TELEMETRY_LOG_LEVEL=debug in App Settings and retest
Sidecar fails to start:
- Ensure resource plan meets requirements (e.g., P0v3 tier or higher)
- Required settings present for your backend (Application Insights or Elastic)
- Review sidecar startup logs for configuration errors
High memory usage:
- Enable sampling, filter unnecessary endpoints, reduce log verbosity
- Scale up app service plan if needed

Resources

Key Takeaways

With OTEL sidecar support, Azure App Service for Linux enables robust observability for code and container apps. Standard app settings, sample code, and troubleshooting practices simplify getting started with distributed tracing and metrics collection for multiple languages.

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