1. Introduction to SRE
What is SRE?
Site Reliability Engineering (SRE) is a discipline that incorporates aspects of software engineering and applies them to infrastructure and operations problems. The goal is to create scalable and highly reliable software systems. It’s a practice of ensuring that applications and services run reliably, securely, and efficiently in production.
SREs are engineers who focus on system reliability, scalability, and performance, blending traditional software development skills with operations expertise.
History and Origin (Google’s Role)
The concept of SRE originated at Google in the early 2000s. Ben Treynor Sloss, a Google engineer, is credited with founding the first SRE team. Google recognized the need for software engineers to manage infrastructure as code and set reliability targets using metrics like SLOs and error budgets.
SRE became a formal discipline after Google published the “Site Reliability Engineering” book, making their practices public and adaptable by other organizations.
Key Goals and Philosophy
- Embrace Risk: Use SLOs and error budgets to define acceptable levels of risk.
- Service Reliability: Ensure high availability and performance.
- Automation First: Eliminate manual tasks with software solutions.
- Engineering Focus: Treat operations as a software problem.
- Measure Everything: Use metrics to drive decisions.
SRE vs DevOps
| Aspect | SRE | DevOps |
|---|---|---|
| Origin | Coined by Google | Cultural philosophy |
| Primary Focus | Reliability and uptime | Collaboration between Dev and Ops |
| Metrics-Driven | Strong emphasis on SLIs/SLOs | Varies by team |
| Operational Work | Max 50% (Toil reduction emphasized) | No strict boundaries |
| Approach | Software Engineering Approach to Operations | Process and tooling improvement |
2. Core Principles of SRE
Service Level Indicators (SLIs)
SLIs are carefully defined quantitative measures of some aspect of the level of service provided. Example SLIs include:
- Availability: % of successful HTTP 200 responses
- Latency: Request response time
- Error Rate: % of failed requests
Service Level Objectives (SLOs)
SLOs define the target value or range for an SLI. For example:
- “99.9% of requests should return HTTP 200 within 300ms”
Service Level Agreements (SLAs)
SLAs are formal agreements between a service provider and a customer based on SLOs. These often have contractual and financial penalties for non-compliance.
Error Budgets
Error Budgets represent the maximum allowable threshold of errors within a certain period. It balances innovation and reliability:
- If SLO is 99.9%, error budget is 0.1% of failed requests
- When budget is exhausted, focus shifts to stability
Toil Reduction
Toil is manual, repetitive, and automatable work that scales with service size. SRE teams aim to:
- Eliminate toil using scripts, automation, and self-healing systems
- Keep toil under 50% of SRE time
3. Responsibilities of an SRE Team
Incident Management
- On-call rotations
- Incident response and coordination
- Postmortems and root cause analysis
Capacity Planning
- Forecasting resource needs
- Monitoring traffic and scaling infrastructure
Change Management
- Deployment pipeline validation
- Safe releases with canary or blue-green deployments
Automation
- CI/CD pipelines
- Auto-remediation scripts
Monitoring and Observability
- Dashboards and alerts
- Distributed tracing
- Log aggregation
4. SRE Tools and Technologies
Monitoring Tools
- Prometheus: Time-series monitoring and alerting
- Grafana: Visualization of Prometheus metrics
Alerting Tools
- PagerDuty, Opsgenie: Incident alerting and escalation
CI/CD & Automation
- Jenkins, GitLab CI, ArgoCD, Spinnaker
- Terraform, Pulumi for infrastructure as code
Logging
- ELK Stack (Elasticsearch, Logstash, Kibana)
- Loki, Fluentd for log collection and analysis
5. SRE in Practice
Building SLIs/SLOs from Scratch
- Identify key user journeys
- Define critical reliability metrics (SLIs)
- Set realistic and measurable SLOs
Setting up Monitoring and Alerts
- Use Prometheus to collect metrics
- Grafana to build SLO dashboards
- Configure alert rules on SLI thresholds
Chaos Engineering
- Intentionally inject failures to test resilience
- Tools: Gremlin, Chaos Mesh, LitmusChaos
Real-world Incident Postmortem Example
Incident: High API latency during peak hours
- Impact: 15% requests exceeded 500ms
- Root Cause: Memory leak in middleware
- Resolution: Rolled back deployment
- Prevention: Added performance test in CI
6. SRE Implementation Strategies
Embedding SREs into Dev Teams
- SREs collaborate directly with product teams
- Offer observability guidance, review reliability plans
Central SRE Team Model
- SRE team supports multiple product teams
- Creates shared tools, sets org-wide reliability standards
Collaboration Across Teams
- Dev: Feature development
- Infra: Platform and scaling
- SRE: Reliability and automation across lifecycle
KPIs to Measure Effectiveness
- MTTR (Mean Time to Recover)
- % Toil vs Engineering Work
- SLO compliance rate
- Change failure rate
7. Advanced SRE Topics
Site Reliability at Scale
- Multi-region failover strategies
- Redundancy in cloud infrastructure
Multi-cloud/Hybrid-cloud SRE
- Unified observability stack
- Resilient architecture across providers
Reliability Modeling
- Use historical incident data to predict future risks
- Simulations and stress testing
Error Budget Policies
- Define clear protocols when error budget is exhausted
- Freeze deploys, increase test coverage
Production Readiness Checklists
- Performance and load tests
- Rollback strategies defined
- Alerts and dashboards reviewed
8. SRE Case Studies
- Origin of SRE
- SLIs/SLOs guide every launch
- “Blameless Postmortem” culture
Netflix
- Chaos Monkey for failure injection
- SRE teams focus on platform resilience
- SREs run large-scale Kafka and microservices
- Unified observability with internal tooling
Example Dashboard (Grafana)
- Uptime %
- Latency histogram
- Error rate over time
- SLO compliance gauge
9. SRE Career Path
Skills Needed
- Programming (Go, Python, Shell)
- Linux internals
- Networking
- Monitoring, metrics, CI/CD
Certifications and Learning Resources
- Google SRE Book (free online)
- Coursera: Site Reliability Engineering by Google
- SREcon (conferences)
- Linux Foundation’s SRE certification (LFS260)
Interview Tips
- Incident response scenario questions
- Coding + scripting tasks
- Designing high availability architecture
10. Conclusion
Future of SRE
- AI-based incident response (AIOps)
- Platform engineering integration
- SRE as a service model
How to Adopt SRE in Any Organization
- Start with small SLOs
- Establish monitoring culture
- Build error budgets
- Automate toil
Summary Checklist
- SLIs/SLOs defined for all services
- Monitoring + alerting setup
- Error budgets in use
- Postmortems practiced
- Toil measured and reduced
- Incident response defined
- Dashboards for all critical paths