lambda-powertools-handler.ts

/** Full code available here: https://github.com/markilott/aws-cdk-lambda-powertools/blob/main/src/lambda/read-data/index.ts */
import { AWSError, DynamoDB } from 'aws-sdk';
import { Logger, injectLambdaContext } from '@aws-lambda-powertools/logger';
import { Metrics, MetricUnits, logMetrics } from '@aws-lambda-powertools/metrics';
import { Tracer, captureLambdaHandler } from '@aws-lambda-powertools/tracer';
import middy from '@middy/core';

/** Instantiate the PowerTools instances */
const logger = new Logger();
const tracer = new Tracer();
const metrics = new Metrics();

/** Wrap the AWS client in the tracer */
const docClient = tracer.captureAWSClient(new DynamoDB.DocumentClient({
    region: process.env.AWS_REGION,
}));

/**
 * Write a record to the DynamoDb table and create CloudWatch Logs.
 * This function is used for the Create and Update methods.
 */
const lambdaHandler = async (event: EventProps): Promise<FunctionResult> => {
    const { params, context } = event;
    const { requestId } = context;
    const {
        correlationId = requestId,
    } = params;

    /**
     * Add a correlationId (tracking code).
     * correlationId will be included with all logs, metrics and traces
     * and will be searchable/filterable in the CloudWatch console.
     */
    tracer.putAnnotation('correlationId', correlationId);
    logger.appendKeys({ correlationId });
    metrics.addMetadata('correlationId', correlationId);
    try {
        /** ... application logic that sets a colour for an item */
        
        /** Write JSON log with the result */
        logger.info('Colour', { data: colour });

        /**
         * Write the item colour to a custom metric.
         * This metric will have the "feature" dimension in addition to defaults.
         */
        const colourMetric = metrics.singleMetric();
        colourMetric.addDimension('feature', 'colourPicker');
        colourMetric.addMetric(colour, MetricUnits.Count, 1);

        /** ... write the item to DynamoDb, then log result if debugging is enabled */
        logger.debug('DynamoDb Item', { data: item });

        return result;
    } catch (err) {
        /** Adding the function_name dimension to match the default used in the PowerTools cold start metric */
        metrics.addDimension('function_name', process.env.AWS_LAMBDA_FUNCTION_NAME || 'unknown');

        if (statusCode === 400) {
            /** Add WARN level log and metric count for client errors */
            logger.warn(errorMessage, { data: params });
            metrics.addMetric('WARNING', MetricUnits.Count, 1);
        } else {
            /** Add ERROR level log and metric count for internal errors */
            logger.error(err.message, err);
            metrics.addMetric('ERROR', MetricUnits.Count, 1);
        }
        throw err;
    }
};

/** Wrap the handler with middy and inject PowerTools */
export const handler = middy(lambdaHandler)
    .use(captureLambdaHandler(tracer))
    /** clearState resets the correlationId for each invocation */
    .use(injectLambdaContext(logger, { clearState: true }))
    .use(logMetrics(metrics, { captureColdStartMetric: true }));