Resiliency Patterns in AWS Serverless

Introduction

Resiliency patterns are essential for building robust AWS serverless applications that can gracefully handle failures and maintain service availability.

Key Concepts

• **Fault Tolerance**: The ability of a system to continue operating despite the presence of faults.
• **High Availability**: Ensuring a service is available and operational for the maximum possible time.
• **Disaster Recovery (DR)**: Processes and procedures to recover and protect a business IT infrastructure in the event of a disaster.
• **Graceful Degradation**: The strategy of allowing a system to continue operating at a reduced level of functionality when parts of it fail.

Resiliency Patterns

Here are some common resiliency patterns used in AWS serverless architectures:

1. Retry Pattern

   Automatically retry failed operations.

   
   const AWS = require('aws-sdk');
   const s3 = new AWS.S3();
   
   async function uploadWithRetry(bucket, key, body) {
       const maxRetries = 3;
       for (let attempt = 0; attempt < maxRetries; attempt++) {
           try {
               await s3.putObject({ Bucket: bucket, Key: key, Body: body }).promise();
               console.log('Upload succeeded');
               return;
           } catch (err) {
               console.error(`Attempt ${attempt + 1} failed: ${err.message}`);
               if (attempt === maxRetries - 1) throw err; // Rethrow if max attempts reached
           }
       }
   }
                       

2. Circuit Breaker Pattern

   Prevent the system from trying to execute an operation that is likely to fail.

   
   // Implementation of Circuit Breaker logic (pseudo-code)
   function executeWithCircuitBreaker(operation) {
       if (circuitOpen) {
           throw new Error("Circuit is open, not executing operation");
       }
       try {
           return operation();
       } catch (err) {
           openCircuit(); // Opens circuit after a failure
           throw err;
       }
   }
                       

3. Failover Pattern

   Automatically switch to a redundant or standby system when the primary system fails.

   
   // Example of a failover mechanism using AWS Route 53
   // Configure health checks and routing policies to enable failover
                       

Best Practices

To enhance resiliency in serverless applications, consider the following best practices:

• Utilize Amazon CloudWatch for monitoring and alerting.
• Implement retries with exponential backoff for transient errors.
• Use AWS Lambda's built-in error handling features.
• Design for failure by testing your application under failure conditions.

FAQ