The NodeJS agent for Apache SkyWalking

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SkyWalking NodeJS Agent

SkyWalking-NodeJS: The NodeJS Agent for Apache SkyWalking, which provides the native tracing abilities for NodeJS backend project.

SkyWalking: an APM(application performance monitor) system, especially designed for microservices, cloud native and container-based (Docker, Kubernetes, Mesos) architectures.

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Build npm version

Install SkyWalking NodeJS package from npmjs

$ npm install --save skywalking-backend-js

Set up NodeJS Agent

SkyWalking NodeJS SDK requires SkyWalking backend (OAP) 8.0+ and NodeJS >= 10.

import agent from 'skywalking-backend-js';

agent.start();

This will use default configurations to start the SkyWalking agent above, if you want to specify your own configurations, here are two methods.

  • Pass those values to agent.start method, such as:
agent.start({
  serviceName: 'my-service-name',
  serviceInstance: 'my-service-instance-name',
  collectorAddress: 'my.collector.address:port',
});

Note that all options given (including empty/null values) will override the corresponding default values, e.g. agent.start({ collectorAddress: '' }) will override the default value of collectorAddress to empty string, causing errors like DNS resolution failed.

  • Use environment variables.

The supported environment variables are as follows:

Environment VariableDescriptionDefault
SW_AGENT_NAMEThe name of the serviceyour-nodejs-service
SW_AGENT_INSTANCEThe name of the service instanceRandomly generated
SW_AGENT_COLLECTOR_BACKEND_SERVICESThe backend OAP server address127.0.0.1:11800
SW_AGENT_SECUREWhether to use secure connection to backend OAP serverfalse
SW_AGENT_AUTHENTICATIONThe authentication token to verify that the agent is trusted by the backend OAP, as for how to configure the backend, refer to the yaml.not set
SW_AGENT_LOGGING_LEVELThe logging level, could be one of error, warn, info, debuginfo
SW_AGENT_DISABLE_PLUGINSComma-delimited list of plugins to disable in the plugins directory (e.g. “mysql”, “express”)``
SW_COLD_ENDPOINTCold start detection is as follows: First span to run is considered a cold start. This span gets the tag coldStart set to ‘true’. This span also optionally gets the text ‘<cold>’ appended to the endpoint name if SW_COLD_ENDPOINT is set to ‘true’.false
SW_IGNORE_SUFFIXThe suffices of endpoints that will be ignored (not traced), comma separated.jpg,.jpeg,.js,.css,.png,.bmp,.gif,.ico,.mp3,.mp4,.html,.svg
SW_TRACE_IGNORE_PATHThe paths of endpoints that will be ignored (not traced), comma separated``
SW_HTTP_IGNORE_METHODComma-delimited list of http methods to ignore (GET, POST, HEAD, OPTIONS, etc...)``
SW_SQL_TRACE_PARAMETERSIf set to ‘true’ then SQL query parameters will be includedfalse
SW_SQL_PARAMETERS_MAX_LENGTHThe maximum string length of SQL parameters to log512
SW_MONGO_TRACE_PARAMETERSIf set to ‘true’ then mongodb query parameters will be includedfalse
SW_MONGO_PARAMETERS_MAX_LENGTHThe maximum string length of mongodb parameters to log512
SW_AWSLAMBDA_FLUSHIf set to ‘true’ then AWS Lambda functions will flush segment data when the handler finishes. false will be more optimal for high throughput applications but may lose spans.true
SW_AGENT_MAX_BUFFER_SIZEThe maximum buffer size before sending the segment data to backend'1000'

Note that the various ignore options like SW_IGNORE_SUFFIX, SW_TRACE_IGNORE_PATH and SW_HTTP_IGNORE_METHOD as well as endpoints which are not recorded due to exceeding SW_AGENT_MAX_BUFFER_SIZE all propagate their ignored status downstream to any other endpoints they may call. If that endpoint is running the Node Skywalking agent then regardless of its ignore settings it will not be recorded since its upstream parent was not recorded. This allows elimination of entire trees of endpoints you are not interested in as well as eliminating partial traces if a span in the chain is ignored but calls out to other endpopints which are recorded as children of ROOT instead of the actual parent.

Supported Libraries

There are some built-in plugins that support automatic instrumentation of NodeJS libraries, the complete lists are as follows:

LibraryPlugin Name
built-in http and https modulehttp / https
Expressexpress
Axiosaxios
MySQLmysql
MySQLmysql2
PostgreSQLpg
pg-cursorpg-cursor
MongoDBmongodb
Mongoosemongoose
RabbitMQamqplib
Redisioredis

Compatible Libraries

The following are packages that have been tested to some extent and are compatible because they work through the instrumentation of an underlying package:

LibraryUnderlying Plugin Name
requesthttp / https
request-promisehttp / https
koahttp / https

Experimental Azure Functions Support

The plugin AzureHttpTriggerPlugin provides a wrapper function for an Azure Functions Javascript HttpTrigger endpoint. This is an http server endpoint and it must be instrumented manually currently. So far all other plugins tested work within the HttpTrigger and so a trace can pass through the Function and on to other endpoints called by the function. How much sense it makes to instrument an Azure Function which already lives in the cloud and has robust monitoring incorporated is a good question, but at the least this plugin will allow those endpoints to show up in a Skywalking trace.

Usage:

const {default: agent, AzureHttpTriggerPlugin} = require('skywalking-backend-js');

agent.start({ ... });

module.exports = AzureHttpTriggerPlugin.wrap(async function (context, req) {

  /* contents of http trigger function */

});

All that needs to be done is the actual trigger function needs to be wrapped with azureHttpTriggerPlugin.wrap(), whether that function is a default export or an explicitly named entryPoint or run or index.

Experimental AWS Lambda Functions Support

The plugins AWSLambdaTriggerPlugin, AWSLambdaGatewayAPIHTTP and AWSLambdaGatewayAPIREST provide a wrapper functions for AWS Lambda Functions endpoints. AWSLambdaTriggerPlugin is a generic wrapper plugin which should work with any kind of Lambda trigger but also stores the least amount of informations since it does not know anything about the incoming data format. For this reason this type of trigger also can not link back to the caller, but it can create a new segment which will be propagated to all downstream children, this starting its own trace. AWSLambdaGatewayAPIHTTP and AWSLambdaGatewayAPIREST are specific wrappers for Lambda functions triggered by the GatewayAPI HTTP or REST triggers. They have the advantage of knowing the incoming data format and can thus extract existing trace segment information from incoming requests and chain correctly from upstream to any downstream endpoints.

Usage:

const {default: agent, AWSLambdaGatewayAPIHTTP} = require('skywalking-backend-js');

agent.start({ ... });

exports.handler = AWSLambdaGatewayAPIHTTP.wrap(async function (event, context, callback) {

  /* contents of http trigger function */

});

This is similar to Azure Functions wrapping, just wrap your handler function with AWSLambdaTriggerPlugin.wrap() or AWSLambdaGatewayAPIHTTP.wrap() or AWSLambdaGatewayAPIREST.wrap(). One thing to note is that AWS freezes processes in between invocations of lambda functions so whether you are doing async or sync handler functions with callbacks, you should make sure everything you need to do finishes before returning control to AWS or calling the synchronous callback. These plugins take this into account and automatically flush the segment buffers before closing a trace span.

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License

Apache 2.0