Instrumenting a Go App for Observability

Introduction Key Concepts Step-by-Step Process Best Practices FAQ

1. Introduction

Observability is crucial for understanding the state of your applications in production. Instrumenting a Go application involves adding monitoring, logging, and tracing capabilities to gain insights into its behavior and performance.

2. Key Concepts

2.1 Definitions

Instrumentation: The process of adding code to a program to collect metrics, logs, and traces.
Metrics: Numerical data that represents the performance or behavior of an application.
Logging: The act of recording messages that describe the application's behavior during execution.
Tracing: A way to track the execution path of a request through the application.

3. Step-by-Step Process

3.1 Setting Up Prometheus

Install the Prometheus Go client library.

Tip: Use `go get github.com/prometheus/client_golang/prometheus` to install.

Initialize a new metrics registry.

var (
    requestCount = prometheus.NewCounterVec(
        prometheus.CounterOpts{
            Name: "http_requests_total",
            Help: "Total number of HTTP requests",
        },
        []string{"method", "handler"},
    )
)

func init() {
    prometheus.MustRegister(requestCount)
}

Instrument your HTTP handlers to track requests.

func handler(w http.ResponseWriter, r *http.Request) {
    requestCount.WithLabelValues("GET", "/").Inc()
    fmt.Fprintf(w, "Hello, World!")
}

Expose the metrics endpoint.

http.Handle("/metrics", promhttp.Handler())

Run Prometheus and configure it to scrape your application.

4. Best Practices

Instrument all critical paths in your application.
Use unique labels for metrics to avoid cardinality issues.
Regularly review and refactor instrumentation code.
Ensure logs are structured for easier querying.
Test your instrumentation in staging before deploying.

5. FAQ

What is the difference between metrics and logs?

Metrics are numerical values representing quantitative data, while logs are detailed records of events that occur within the application.

How do I know what to instrument in my application?

Focus on critical paths that impact user experience, areas of high latency, and components that frequently fail.

Can I use tracing with Prometheus?

Yes, you can combine tracing tools like Jaeger or OpenTelemetry with Prometheus to enhance observability.