Importance Of SLA, SLO, SLI For Cloud-Native Applications
SLA (Service Level Agreement), SLO (Service Level Objective), and SLI (Service Level Indicator) are important for cloud-native applications because they provide a way to define and measure the performance and availability of services and ensure that they meet the needs of the customers.
SLA (Service Level Agreement) is a legal contract between a service provider and a customer that guarantees a certain measurable level of service. They are often drawn up with specific financial consequences if the provider fails to deliver the guaranteed service level. SLAs are usually composed of many individual SLOs to help formalize the details of what is being promised. It typically includes details such as service availability, response time, and resolution time for service requests. SLAs are commonly used in industries such as information technology and telecommunications. An SLA is a legally binding agreement between the service provider and the customer; these are more important in cloud-native applications where the enterprise or application developers use the infrastructure from a cloud provider.
SLO (Service Level Objective) is a specific, measurable goal for the performance of a service. It is a target that the service provider aims to meet or exceed to fulfill the terms of the SLA. Service-level objectives (SLOs) have become a vital way for teams to set specific, measurable targets that ensure users are receiving agreed-upon service levels. while staying within error budgets. This is important for cloud-native applications because it provides a clear and measurable goal for the performance of services, which can be used to ensure that services are meeting the needs of the customers
Service-level objectives are an agreed-upon targets within an SLA that must be achieved for each activity, and service to satisfy requirements for customer success. SLOs represent the performance or health of a service that should be achieved. These can include business metrics such as uptime, and availability; service metrics, such as application performance; or technical metrics, such as dependencies to third-party services, underlying CPU, and the cost of running a service.
Some business metrics such as uptime can directly be measured; some metrics such as Sales revenue, Conversion rates, Net Profit Margin, Net Promoter score should be measured using a proxy to indirectly measure by combining several metrics. If the SLA for a website is 99.95% uptime, its corresponding SLO could be 99.95% availability of the login services.
In another example, Net Profit Margin increases when the cost of running a service is minimized and the cost of running a service could be related to the Storage time plus CPU time. This example gives an SLO that can directly relate to infrastructure on which application is running. It should be observed that the SLA here relates directly to the expectations that the user could expect from the cloud provider on which the application is running.
Error budgets are an allowance for a certain amount of failure or technical debt within an SLO. For example, if your SLO guarantees 99.5% availability of a website over a year, your error budget is .05% of a year; which translates to 1.46 hrs., assuming 365 days and 8 hrs. every day. Error budgets allow development teams to make informed decisions between new development vs operations and polishing existing software. Properly set and defined SLOs should have error budgets that give developers space to innovate without impacting operation.
SLIs provide the actual quantified measurement that represents the performance of a service. Most SLIs are measured in percentages to express the service level delivered. For example, if your SLO is to deliver 99.5% availability, the actual measurement may be 99.8%, which means you’re meeting your agreements and you have happy customers. To gain an understanding of long-term trends, you can visually represent SLIs in a histogram that shows actual performance in the overall context of your SLOs. SLOs, together with service-level indicators (SLIs), deliver the performance promised in service-level agreements (SLAs) and other business level objectives (BLOs).
Monitoring is an important aspect of cloud-native applications as it allows organizations to understand the performance behavior of their applications, services, and infrastructure. In a cloud-native environment, applications are often distributed and run on multiple servers, making it difficult to track and troubleshoot issues. Monitoring provides visibility into the behavior and performance of the application, enabling organizations to quickly identify and resolve problems.
Monitoring can help organizations understand the health of their applications, detect errors, and troubleshoot issues in real-time. This allows organizations to improve their service level performance and allows SRE teams to be proactive to prevent outages. It also enables them to track the usage of resources and optimize their costs. Additionally, monitoring can also help organizations to improve their security posture. By monitoring network traffic and application logs, organizations can detect and respond to security threats and breaches in a timely manner.
Overall, monitoring is crucial to measure SLIs to ensure availability, performance, security, and cost-effectiveness of cloud-native applications. It enables organizations to make informed decisions, improve customer satisfaction, and respond quickly to issues that may arise.
In summary, an SLA is a contract between the provider and the customer, an SLO is a target and an SLI is an actual metric that is used to measure if the target is met. They are all related in that the SLA defines the expected level of service, the SLO sets a specific goal for performance, and the SLI is used to measure whether that goal is being met.