Azure Logger

Winston Logger with a custom Azure Application Insights Transport

Logging levels

• critical
• error
• warning
• event
• request
• dependency
• security
• audit
• info
• debug

Installation

If using npm:

npm install @dvsa/azure-logger

or if using Yarn

yarn add @dvsa/azure-logger

Specify the environment variables in a .env file, for example

LOG_LEVEL=event

NODE_ENV=development

APPLICATIONINSIGHTS_CONNECTION_STRING={APPLICATION_INSIGHTS_CONNECTION_STRING}

Example Use:

1. Create a file logger.ts and export the azure logger from it, instantiating it with the project and component names.

import { Logger } from '@dvsa/azure-logger';

export default new Logger('ftts', 'ftts-location-api');

2. For Azure Functions, two wrappers are provided to enable auto correlation of all logs and telemetry including external requests and dependencies. For HTTP triggers use the httpTriggerContextWrapper with req passed in. Use nonHttpTriggerContextWrapper for all other trigger types. For example, wrap a time trigger function in your function index file like so:

import { nonHttpTriggerContextWrapper } from '@dvsa/azure-logger';
import { AzureFunction, Context } from '@azure/functions';

const myTimeTrigger: AzureFunction = async (): Promise<void> => {
    // do something
};

export default async (context: Context): Promise<void> => nonHttpTriggerContextWrapper(myTimeTrigger, context);

Request and dependency log methods are still provided for manual tracing if it is needed e.g. for service bus correlation. These require context to be passed in to fetch the correct trace ids.

3. Whenever you want to log an item import the logger.ts file.

import logger from './logger';

function getData(): void {
    try {
        // Do calculations
    } catch(error) {
        logger.error(error);
    }
}

APPLICATIONINSIGHTS_CONNECTION_STRING

When using an Azure function app the following environment variable must be present and contain the connection string for the application insights instance you wish to use.

APPLICATIONINSIGHTS_CONNECTION_STRING