logger

Logger library for Nu Skin serverless applications.

@nuskin/logger is a logger library to aid in the development of Nu Skin serverless applications. CONTENTS

• @nuskin/logger
  • NPM and Github Repo
  • Installation
  • Usage
    • Logging
      • Logging Data
      • Setting the Logging Level
      • Scrubbing Sensitive Data
      • Tags
    • Correlation IDs
    • Text Scrubbing

NPM and Github Repo

https://www.npmjs.com/package/@nuskin/logger

Installation

Using npm:

$ npm install @nuskin/logger

Usage

Logging

The logger module provides logging utilities.

This module can

• log data
• set logging levels
• add tags to logs
• scrub sensitive data from logs
• add tracing tags to logs, to aid in debugging

Logging Data

The logging module exposes debug, info, warn, and error methods for logging data.

Log entries take the following form:

{"level":"...","msg":{...}}

If the message argument passed to the logging function is a string, the log's msg property takes the following form:

"msg":{"message":"<YOUR MESSAGE HERE>"}

The logging functions support JSON objects as messages. This is often recommended in practice. If the message object is a JSON object, the log's msg takes the following form:

"msg": { // YOUR OBJECT HERE // }

Examples:

const { logger: log } = require("@nuskin/logger");

// === Logging strings:

log.debug("Hello debug");
// LOGS: {"level":"debug","msg":{"message":"hello debug"}}

log.info("Hello info");
// LOGS: {"level":"info","msg":{"message":"hello info"}}

log.warn("Hello warn");
// LOGS: {"level":"warn","msg":{"message":"hello warn"}}

log.error("Hello error");
// LOGS: {"level":"error","msg":{"message":"hello error"}}

// === Logging an object:

log.info({ attr1: "it is cool", attr2: 42 });
// LOGS: {"level":"info","msg":{"attr1":"it is cool","attr2":42}}

Setting the Logging Level

The logging level can be set by calling logger.setLevel(). Logging calls made that are below the set logging level will not be written to the logs.

Example:

const { logger } = require("@nuskin/logger");

logger.setLevel("off"); // no logs are written

logger.setLevel("error"); // only error logs are written

logger.setLevel("warn"); // warn and error logs are written

logger.setLevel("info"); // info, warn, and error logs are written

logger.setLevel("debug"); // debug, info, warn, and error logs are written

Scrubbing Sensitive Data

The logger module can scrub sensitive data from your logs. This scrubbing is turned on by default. You can disable it by calling logger.setScrubbing().

logger.setScrubbing(false);

See the scrubber section for information on how to configure log scrubbing.

Tags

You can include a function-specific tag in your logs. Call logger.setTag() to set this tag. All logs written by your function will include your tag.

Tagged log entries take the following form:

{"level":"...", "tag": {...}, "msg": {...}}

If the provided tag is a string, the tag property takes the following form:

"tag":{"key":"<YOUR STRING HERE>"}

If the provided tag is a JSON object, the tag property takes the following form:

"tag":{ // YOUR OBJECT HERE // }

Examples:

const { logger: log } = require("@nuskin/logger");

// set the tag as a string
log.setTag("My new tag"); 
log.info({ myMessage: "message 1" });
// LOGS: {"level":"info","tag":{"key":"My new tag"},"msg":{"myMessage":"message 1"}}

// set the tag as an object
log.setTag({ requestId: "some Id", resourceId: "12345" }); 
log.info({ myMessage: "message 2" });
// LOGS: {"level":"info","tag":{"requestId":"some Id","resourceId":"12345"},"msg":{"myMessage":"message 2"}}

To clear the tag, call logger.setTag() with no arguments.

log.setTag();

Additional data can be merged into the current tag by calling logger.addTag().

log.setTag({ key1: "abc" });
log.addTag({ key2: "xyz" });
log.info({ myMessage: "message 1" });
// LOGS: {"level":"info","tag":{"key1":"abc","key2":"xyz"},"msg":{"myMessage":"message 1"}}

Correlation IDs

The log correlation ID is a special tag that can be applied to logs to correlate transactions between applications, and is especially useful when debugging execution chains that span multiple applications. The correlate module provides methods for extracting an already-set correlation ID from incoming HTTP events, batchEvents and lambda to lambda calls. If a correlation ID is not found in the incoming message a correlation ID is generated.

An incoming HTTP request or lambda to lambda call is inspected for a correlaton ID in the following order. If one is not found, a uuid is generated and provided.

1. The x-correlation-id header on an HTTP request
2. The x-request-id header on an HTTP request
3. The 'correlationId' top level attribute in the body of the request. This is for a lambda to lambda call.
4. The X_AMZN_TRACE_ID environment variable
5. The x-amzn-trace-id header on an HTTP request
6. The awsRequestID property of the Lambda context parameter passed to your handler function

Usage example: For HTTP and Lambda events, call correlate.captureCorrelationID(), passing in the event and context parameters passed to your function, to retrieve or generate the correlation ID. This correlation ID should then be added as a logging tag with the key nse.correlation_id.

const { correlate, logger } = require("@nuskin/logger");

// Lambda handler function
exports.handler = async function(event, context) {
    // capture or generate the correlation ID
    const correlationID = correlate.captureCorrelationId(event, context);

    // Tag all logging messages with the correlation ID
    logger.addTag({ "nse.correlation_id": correlationID });

    // ... handler code continues ... //
};

Usage example: For processing batch records, call correlate.captureRecordCorrelationID(), passing in the each record in the batch. This correlation ID should then be added as a logging tag with the key nse.correlation_id.

const { correlate, logger } = require("@nuskin/logger");

async function snsHandler(event) {
    for (const record of event.Records) {
        // capture or generate the correlation ID
        const correlationID = correlate.captureRecordCorrelationId(record);

        // Tag subsequent logging messages with this correlation ID
        logger.addTag({ "nse.correlation_id": correlationID });

        // ... code continues ... //

| :warning: WARNING | |:---------------------------| | This library uses a single global value to store the correlation ID. If you are processing batch records concurrently, it is likely the correlation and the associated tag will not be reliable. |  

If needed, an already-captured correlation ID can be retrieved by calling correlate.retrieveCorrelationId().

const savedCorrelationID = correlate.retrieveCorrelationId();

Text Scrubbing

The scrubber module provides text scrubbing features. It also provides configuration for the log scrubbing described in Scrubbing Sensitive Data. When a value is scrubbed, an md5 hash is created from the value being scrubbed. In the case of self referencing objects, the reference is replaced with a replacement string.

The scrubber can be configured to scrub particular object keys or to scrub any keys matching a regular expression. The scrubber module has a built-in list of common sensitive keys that it can include in a list of keys to scrub.

const { scrubber } = require("@nuskin/logger");

// Set scrubber to scrub specific keys
scrubber.setKeysToScrub(["sensitiveKey1", "Private_Data_Key"]);

// Set scrubber to scrub specific keys, and include default key list
scrubber.setKeysWithDefaultToScrub(["sensitiveKey1", "Private_Data_Key"]);

// Set scrubber to scrub any keys matching a pattern
scrubber.setPattern(/(my)?-sensitive-key-\d{2}/);

To change the replacement value for self referencing objects use scrubber.setReplacement() to set the value of this replacement string.

// Any self referenced object found will be replaced with "AAAAAAAAAA"
scrubber.setReplacement("AAAAAAAAAA");

The scrubber can be called directly on a JSON object to scrub sensitive data by calling scrubber.scrub(). Scrubbing is applied recursively, in other words any key at any level of the object that matches the scrubber's settings will have its value scrubbed.

const obj = {
    "key-01": "sensitive data here",
    "details": {
        "normal-stuff": "hello",
        "my-key-02": "more sensitive data"
    }
};
obj.b = obj

scrubber.setPattern(/(my)?-key-\d{2}/);
scrubber.setReplacement("...---...");

const scrubbedObj = scrubber.scrub(obj);
/* 
scrubbedObj:
{
    "key-01": "{HASHED VALUE}",
    "details": {
        "normal-stuff": "hello",
        "my-key-02": "{HASHED VALUE}"
    },
    b: "...---..."
}
 */

Any configuration settings provided to the scrubber module are used to scrub logs written by the logger module.

const { logger, scrubber } = require("@nuskin/logger");

// Set scrubber to scrub specific keys
scrubber.setKeysToScrub(["pi", "myPassword"]);
scrubber.setReplacement("::::::");

logger.info({"pi": "3.14159", "user": {"name":"Bob","myPassword": "password1"}});
// LOGS: {"level":"info","msg":{"pi":"::::::","user": {"name":"Bob","myPassword": "::::::"}}}