What is SLA?

Service Level Agreement (SLA) — is an official agreement between a service provider and a client, defining the level of service to be provided.

Main components of SLA:

• Description of provided services: Clear statement of what the service includes.
• Performance metrics (KPIs): Measurable indicators used to assess service quality, for example:
  • Availability (Uptime/Availability)
  • Response Time
  • Error Rate
• Target indicators: Specific numerical values for each metric (e.g., 99.99% availability).
• Compensation conditions (Service Credits): What happens if the service provider does not meet the target indicators (e.g., discount on service costs).
• Reporting and monitoring procedures: How performance tracking and reporting will be conducted.
• Duration of the agreement: The period for which the SLA is valid.

Example of an availability metric in Golang applied to a web service:

// Example of an availability metric (pseudo-code)
var (
	totalRequests = prometheus.NewCounter(...) // Total number of requests
	successfulRequests = prometheus.NewCounter(...) // Number of successful requests (status 2xx)
)

// In the request handler
func handleRequest(...) {
	totalRequests.Inc()
	// ... request processing ...
	if success {
		successfulRequests.Inc()
	}
}

// Calculating availability (roughly)
// Availability = (successfulRequests / totalRequests) * 100

SLA is an important tool for ensuring transparency and accountability in the relationship between the service provider and the client.