Highcharts Node.js Export Server

Convert Highcharts.JS charts into static image files.

Upgrade Notes

In most cases, v4 should serve as a drop-in replacement for v2 and v3. However, due to changes in the browser backend, various tweaks related to process handling (e.g., worker counts, and so on) may now have different effects than before.

Significant changes have been made to the API for using the server as a Node.js module. While a compatibility layer has been created to address this, it is recommended to transition to the new API described below. It is worth noting that the compatibility layer may be deprecated at some point in the future.

An important note is that the Export Server now requires Node.js v18.12.0 or a higher version.

Additionally, with the v3 release, we transitioned from HTTP to HTTPS for export.highcharts.com, so all requests sent to our public server now must use the HTTPS protocol.

Changelog

The v4 introduces numerous breaking changes. For further details, please refer to the changelog document provided below.

The full change log for all versions can be viewed here.

What & Why

This Node.js application/service converts Highcharts.JS charts into static image files, supporting PNG, JPEG, SVG, and PDF output. The input can be either SVG or JSON-formatted chart options.

The application is versatile and can be used as a CLI (Command Line Interface), an HTTP server, or as a Node.js module.

Use Cases

The primary use case for the Export Server is scenarios requiring headless conversion of charts. Common cases of using include automatic report generation, static caching, and incorporating charts into presentations or other documents.

In addition, the HTTP mode enables you to run your own Export Server for users, reducing reliance on the public https://export.highcharts.com/ server, which has rate limitations.

The HTTP server can be run either independently, integrating with your other applications and services, or in a way that directs the export buttons on your charts to your customized server.

To implement the latter, include the following configuration in your chart options:

{
  exporting: {
    url: "<IP to the self-hosted Export Server>"
  }
}

For systems that generate automatic reports, using the Export Server as a Node.js module is a great fit - especially if your report generator is also written in Node.js. Check here for examples.

Install

First, make sure you have Node.js installed. If not, visit nodejs.org, download and install Node.js for your platform. For compatibility reasons, version 18.12.0 or higher is required.

Once Node.js is installed, proceed to install the Export Server by opening a terminal and typing:

npm install highcharts-export-server -g

or:

git clone https://github.com/highcharts/node-export-server
npm install
npm link

Depending on your Node.js installation method, you might need to create a symlink from nodejs to node. For example, on Linux:

ln -s `which nodejs` /usr/bin/node

Running

To use the Export Server, simply run the following command with the correct arguments:

highcharts-export-server <arguments>

Configuration

There are four main ways of loading configurations:

• By loading default options from the lib/schemas/config.js file.
• By loading options from a custom JSON file.
• By providing configurations via environment variables from the .env file.
• By passing arguments through command line interface (CLI).

...or any combination of the four. In such cases, the options from the later step take precedence (config file -> custom JSON -> envs -> CLI arguments).

Default JSON Config

The JSON below represents the default configuration stored in the lib/schemas/config.js file. If no .env file is found (more details on the file and environment variables below), these options will be used.

The format, along with its default values, is as follows (using the recommended ordering of core and module scripts below):

{
  "puppeteer": {
    "args": []
  },
  "highcharts": {
    "version": "latest",
    "cdnURL": "https://code.highcharts.com/",
    "coreScripts": [
      "highcharts",
      "highcharts-more",
      "highcharts-3d"
    ],
    "moduleScripts": [
      "stock",
      "map",
      "gantt",
      "exporting",
      "parallel-coordinates",
      "accessibility",
      "annotations-advanced",
      "boost-canvas",
      "boost",
      "data",
      "data-tools",
      "draggable-points",
      "static-scale",
      "broken-axis",
      "heatmap",
      "tilemap",
      "tiledwebmap",
      "timeline",
      "treemap",
      "treegraph",
      "item-series",
      "drilldown",
      "histogram-bellcurve",
      "bullet",
      "funnel",
      "funnel3d",
      "geoheatmap",
      "pyramid3d",
      "networkgraph",
      "overlapping-datalabels",
      "pareto",
      "pattern-fill",
      "pictorial",
      "price-indicator",
      "sankey",
      "arc-diagram",
      "dependency-wheel",
      "series-label",
      "solid-gauge",
      "sonification",
      "stock-tools",
      "streamgraph",
      "sunburst",
      "variable-pie",
      "variwide",
      "vector",
      "venn",
      "windbarb",
      "wordcloud",
      "xrange",
      "no-data-to-display",
      "drag-panes",
      "debugger",
      "dumbbell",
      "lollipop",
      "cylinder",
      "organization",
      "dotplot",
      "marker-clusters",
      "hollowcandlestick",
      "heikinashi",
      "flowmap",
      "export-data",
      "navigator",
      "textpath"
    ],
    "indicatorScripts": [
      "indicators-all"
    ],
    "customScripts": [
      "https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.30.1/moment.min.js",
      "https://cdnjs.cloudflare.com/ajax/libs/moment-timezone/0.5.45/moment-timezone-with-data.min.js"
    ],
    "forceFetch": false,
    "cachePath": ".cache"
  },
  "export": {
    "infile": false,
    "instr": false,
    "options": false,
    "outfile": false,
    "type": "png",
    "constr": "chart",
    "height": 400,
    "width": 600,
    "scale": 1,
    "globalOptions": false,
    "themeOptions": false,
    "batch": false,
    "rasterizationTimeout": 1500
  },
  "customLogic": {
    "allowCodeExecution": false,
    "allowFileResources": false,
    "customCode": false,
    "callback": false,
    "resources": false,
    "loadConfig": false,
    "createConfig": false
  },
  "server": {
    "enable": false,
    "host": "0.0.0.0",
    "port": 7801,
    "benchmarking": false,
    "proxy": {
      "host": "",
      "port": 8080,
      "timeout": 5000
    },
    "rateLimiting": {
      "enable": false,
      "maxRequests": 10,
      "window": 1,
      "delay": 0,
      "trustProxy": false,
      "skipKey": "",
      "skipToken": ""
    },
    "ssl": {
      "enable": false,
      "force": false,
      "port": 443,
      "certPath": ""
    }
  },
  "pool": {
    "minWorkers": 4,
    "maxWorkers": 8,
    "workLimit": 40,
    "acquireTimeout": 5000,
    "createTimeout": 5000,
    "destroyTimeout": 5000,
    "idleTimeout": 30000,
    "createRetryInterval": 200,
    "reaperInterval": 1000,
    "benchmarking": false
  },
  "logging": {
    "level": 4,
    "file": "highcharts-export-server.log",
    "dest": "log/",
    "toConsole": true,
    "toFile": true
  },
  "ui": {
    "enable": false,
    "route": "/"
  },
  "other": {
    "nodeEnv": "production",
    "listenToProcessExits": true,
    "noLogo": false,
    "hardResetPage": false,
    "browserShellMode": true
  },
  "debug": {
    "enable": false,
    "headless": true,
    "devtools": false,
    "listenToConsole": false,
    "dumpio": false,
    "slowMo": 0,
    "debuggingPort": 9222
  }
}

Custom JSON Config

To load an additional JSON configuration file, use the --loadConfig <filepath> option. This JSON file can either be manually created or generated through a prompt triggered by the --createConfig option.

Environment Variables

These variables are set in your environment and take precedence over options from the lib/schemas/config.js file. They can be set in the .env file (refer to the .env.sample file). If you prefer setting these variables through the package.json, use export command on Linux/Mac OS X and set command on Windows.

Highcharts Config

• HIGHCHARTS_VERSION: Highcharts version to use (defaults to latest).
• HIGHCHARTS_CDN_URL: Highcharts CDN URL of scripts to be used (defaults to https://code.highcharts.com/).
• HIGHCHARTS_CORE_SCRIPTS: Highcharts core scripts to fetch (defaults to ``).
• HIGHCHARTS_MODULE_SCRIPTS: Highcharts module scripts to fetch (defaults to ``).
• HIGHCHARTS_INDICATOR_SCRIPTS: Highcharts indicator scripts to fetch (defaults to ``).
• HIGHCHARTS_FORCE_FETCH: The flag that determines whether to refetch all scripts after each server rerun (defaults to false).
• HIGHCHARTS_CACHE_PATH: In which directory should the fetched Highcharts scripts be placed (defaults to .cache).
• HIGHCHARTS_ADMIN_TOKEN: An authentication token that is required to switch the Highcharts version on the server at runtime (defaults to ``).

Export Config

• EXPORT_TYPE: The format of the file to export to. Can be jpeg, png, pdf or svg (defaults to png).
• EXPORT_CONSTR: The constructor to use. Can be chart, stockChart, mapChart or ganttChart (defaults to chart).
• EXPORT_DEFAULT_HEIGHT: The default height of the exported chart. Used when not found any value set (defaults to 400).
• EXPORT_DEFAULT_WIDTH: The default width of the exported chart. Used when not found any value set (defaults to 600).
• EXPORT_DEFAULT_SCALE: The default scale of the exported chart. Ranges between 0.1 and 5.0 (defaults to 1).
• EXPORT_RASTERIZATION_TIMEOUT: The specified duration, in milliseconds, to wait for rendering a webpage (defaults to 1500).

Custom Logic Config

• CUSTOM_LOGIC_ALLOW_CODE_EXECUTION: Controls whether the execution of arbitrary code is allowed during the exporting process (defaults to false).
• CUSTOM_LOGIC_ALLOW_FILE_RESOURCES: Controls the ability to inject resources from the filesystem. This setting has no effect when running as a server (defaults to false).

Server Config

• SERVER_ENABLE: If set to true, the server starts on 0.0.0.0 (defaults to false).
• SERVER_HOST: The hostname of the server. Additionally, it starts a server listening on the provided hostname (defaults to 0.0.0.0).
• SERVER_PORT: The port to be used for the server when enabled (defaults to 7801).
• SERVER_BENCHMARKING: Indicates whether to display a message with the duration, in milliseconds, of specific actions that occur on the server while serving a request (defaults to false).

Server Proxy Config

• SERVER_PROXY_HOST: The host of the proxy server to use, if it exists (defaults to ``).
• SERVER_PROXY_PORT: The port of the proxy server to use, if it exists (defaults to ``).
• SERVER_PROXY_TIMEOUT: The timeout for the proxy server to use, if it exists (defaults to ``).

Server Rate Limiting Config

• SERVER_RATE_LIMITING_ENABLE: Enables rate limiting for the server (defaults to false).
• SERVER_RATE_LIMITING_MAX_REQUESTS: The maximum number of requests allowed in one minute (defaults to 10).
• SERVER_RATE_LIMITING_WINDOW: The time window, in minutes, for the rate limiting (defaults to 1).
• SERVER_RATE_LIMITING_DELAY: The delay duration for each successive request before reaching the maximum limit (defaults to 0).
• SERVER_RATE_LIMITING_TRUST_PROXY: Set this to true if the server is behind a load balancer (defaults to false).
• SERVER_RATE_LIMITING_SKIP_KEY: Allows bypassing the rate limiter and should be provided with the skipToken argument (defaults to ``).
• SERVER_RATE_LIMITING_SKIP_TOKEN: Allows bypassing the rate limiter and should be provided with the skipKey argument (defaults to ``).

Server SSL Config

• SERVER_SSL_ENABLE: Enables or disables the SSL protocol (defaults to false).
• SERVER_SSL_FORCE: If set to true, the server is forced to serve only over HTTPS (defaults to false).
• SERVER_SSL_PORT: The port on which to run the SSL server (defaults to 443).
• SERVER_SSL_CERT_PATH: The path to the SSL certificate/key file (defaults to ``).

Pool Config

• POOL_MIN_WORKERS: The number of minimum and initial pool workers to spawn (defaults to 4).
• POOL_MAX_WORKERS: The number of maximum pool workers to spawn (defaults to 8).
• POOL_WORK_LIMIT: The number of work pieces that can be performed before restarting the worker process (defaults to 40).
• POOL_ACQUIRE_TIMEOUT: The duration, in milliseconds, to wait for acquiring a resource (defaults to 5000).
• POOL_CREATE_TIMEOUT: The duration, in milliseconds, to wait for creating a resource (defaults to 5000).
• POOL_DESTROY_TIMEOUT: The duration, in milliseconds, to wait for destroying a resource (defaults to 5000).
• POOL_IDLE_TIMEOUT: The duration, in milliseconds, after which an idle resource is destroyed (defaults to 30000).
• POOL_CREATE_RETRY_INTERVAL: The duration, in milliseconds, to wait before retrying the create process in case of a failure (defaults to 200).
• POOL_REAPER_INTERVAL: The duration, in milliseconds, after which the check for idle resources to destroy is triggered (defaults to 1000).
• POOL_BENCHMARKING: Indicates whether to show statistics for the pool of resources or not (defaults to false).

Logging Config

• LOGGING_LEVEL: The logging level to be used. Can be 0 - silent, 1 - error, 2 - warning, 3 - notice, 4 - verbose or 5 benchmark (defaults to 4).
• LOGGING_FILE: The name of a log file. The logToFile and logDest options also need to be set to enable file logging (defaults to highcharts-export-server.log).
• LOGGING_DEST: The path to store log files. The logToFile option also needs to be set to enable file logging (defaults to log/).
• LOGGING_TO_CONSOLE: Enables or disables showing logs in the console (defaults to true).
• LOGGING_TO_FILE: Enables or disables creation of the log directory and saving the log into a .log file (defaults to true).

UI Config

• UI_ENABLE: Enables or disables the user interface (UI) for the Export Server (defaults to true).
• UI_ROUTE: The endpoint route to which the user interface (UI) should be attached (defaults to /).

Other Config

• OTHER_NODE_ENV: The type of Node.js environment. The value controls whether to include the error's stack in a response or not. Can be development or production (defaults to production).
• OTHER_LISTEN_TO_PROCESS_EXITS: Decides whether or not to attach process.exit handlers (defaults to true).
• OTHER_NO_LOGO: Skip printing the logo on a startup. Will be replaced by a simple text (defaults to false).
• OTHER_HARD_RESET_PAGE: Determines whether the page's content should be reset from scratch, including Highcharts scripts (defaults to false).
• OTHER_BROWSER_SHELL_MODE: Decides whether to enable older but much more performant shell mode for the browser (defaults to true).

Debugging Config

• DEBUG_ENABLE: Enables or disables debug mode for the underlying browser (defaults to false).
• DEBUG_HEADLESS: Controls the mode in which the browser is launched when in the debug mode (defaults to true).
• DEBUG_DEVTOOLS: Decides whether to enable DevTools when the browser is in a headful state (defaults to false).
• DEBUG_LISTEN_TO_CONSOLE: Decides whether to enable a listener for console messages sent from the browser (defaults to false).
• DEBUG_DUMPIO: Redirects browser process stdout and stderr to process.stdout and process.stderr (defaults to false).
• DEBUG_SLOW_MO: Slows down Puppeteer operations by the specified number of milliseconds (defaults to 0).
• DEBUG_DEBUGGING_PORT: Specifies the debugging port (defaults to 9222).

Command Line Arguments

To supply command line arguments, add them as flags when running the application: highcharts-export-server --flag1 value --flag2 value ...

Available options:

• --infile: The input file should include a name and a type (.json or .svg) and must be a correctly formatted JSON or SVG file (defaults to false).
• --instr: An input in a form of a stringified JSON or SVG file. Overrides the --infile option (defaults to false).
• --options: An alias for the --instr option (defaults to false).
• --outfile: The output filename, accompanied by a type (jpeg, png, pdf, or svg). Ignores the --type flag (defaults to false).
• --type: The format of the file to export to. Can be jpeg, png, pdf, or svg (defaults to png).
• --constr: The constructor to use. Can be chart, stockChart, mapChart or ganttChart (defaults to chart).
• --height: The height of the exported chart. Overrides the option in the chart settings (defaults to 400).
• --width: The width of the exported chart. Overrides the option in the chart settings (defaults to 600).
• --scale: The scale of the exported chart. Ranges between 0.1 and 5.0 (defaults to 1).
• --globalOptions: Either a stringified JSON or a filename containing global options to be passed into the Highcharts.setOptions (defaults to false).
• --themeOptions: Either a stringified JSON or a filename containing theme options to be passed into the Highcharts.setOptions (defaults to false).
• --batch: Initiates a batch job with a string containing input/output pairs: "in=out;in=out;.." (defaults to false).
• --rasterizationTimeout: The specified duration, in milliseconds, to wait for rendering a webpage (defaults to 1500).
• --allowCodeExecution: Controls whether the execution of arbitrary code is allowed during the exporting process (defaults to false).
• --allowFileResources: Controls the ability to inject resources from the filesystem. This setting has no effect when running as a server (defaults to false).
• --customCode: Custom code to execute before chart initialization. It can be a function, code wrapped within a function, or a filename with the .js extension (defaults to false).
• --callback: JavaScript code to run during construction. It can be a function or a filename with the .js extension (defaults to false).
• --resources: Additional resources in the form of a stringified JSON. It may contain files (array of JS filenames), js (stringified JS), and css (stringified CSS) sections (defaults to false).
• --loadConfig: A file containing a pre-defined configuration to use (defaults to false).
• --createConfig: Enables setting options through a prompt and saving them in a provided config file (defaults to false).
• --enableServer: If set to true, the server starts on 0.0.0.0 (defaults to false).
• --host: The hostname of the server. Additionally, it starts a server listening on the provided hostname (defaults to 0.0.0.0).
• --port: The port to be used for the server when enabled (defaults to 7801).
• --serverBenchmarking: Indicates whether to display the duration, in milliseconds, of specific actions that occur on the server while serving a request (defaults to false).
• --proxyHost: The host of the proxy server to use, if it exists (defaults to false).
• --proxyPort: The port of the proxy server to use, if it exists (defaults to false).
• --proxyTimeout: The timeout for the proxy server to use, if it exists (defaults to 5000).
• --enableRateLimiting: Enables rate limiting for the server (defaults to false).
• --maxRequests: The maximum number of requests allowed in one minute (defaults to 10).
• --window: The time window, in minutes, for the rate limiting (defaults to 1).
• --delay: The delay duration for each successive request before reaching the maximum limit (defaults to 0).
• --trustProxy: Set this to true if the server is behind a load balancer (defaults to false).
• --skipKey: Allows bypassing the rate limiter and should be provided with the --skipToken argument (defaults to ``).
• --skipToken: Allows bypassing the rate limiter and should be provided with the --skipKey argument (defaults to ``).
• --enableSsl: Enables or disables the SSL protocol (defaults to false).
• --sslForce: If set to true, the server is forced to serve only over HTTPS (defaults to false).
• --sslPort: The port on which to run the SSL server (defaults to 443).
• --certPath: The path to the SSL certificate/key file (defaults to ``).
• --minWorkers: The number of minimum and initial pool workers to spawn (defaults to 4).
• --maxWorkers: The number of maximum pool workers to spawn (defaults to 8).
• --workLimit: The number of work pieces that can be performed before restarting the worker process (defaults to 40).
• --acquireTimeout: The duration, in milliseconds, to wait for acquiring a resource (defaults to 5000).
• --createTimeout: The duration, in milliseconds, to wait for creating a resource (defaults to 5000).
• --destroyTimeout: The duration, in milliseconds, to wait for destroying a resource (defaults to 5000).
• --idleTimeout: The duration, in milliseconds, after which an idle resource is destroyed (defaults to 30000).
• --createRetryInterval: The duration, in milliseconds, to wait before retrying the create process in case of a failure (defaults to 200).
• --reaperInterval: The duration, in milliseconds, after which the check for idle resources to destroy is triggered (defaults to 1000).
• --poolBenchmarking: Indicate whether to show statistics for the pool of resources or not (defaults to false).
• --logLevel: The logging level to be used. Can be 0 - silent, 1 - error, 2 - warning, 3 - notice, 4 - verbose or 5 - benchmark (defaults to 4).
• --logFile: The name of a log file. The logToFile and logDest options also need to be set to enable file logging (defaults to highcharts-export-server.log).
• --logDest: The path to store log files. The logToFile option also needs to be set to enable file logging (defaults to log/).
• --logToConsole: Enables or disables showing logs in the console (defaults to true).
• --logToFile: Enables or disables creation of the log directory and saving the log into a .log file (defaults to true).
• --enableUi: Enables or disables the user interface (UI) for the Export Server (defaults to false).
• --uiRoute: The endpoint route to which the user interface (UI) should be attached (defaults to /).
• --nodeEnv: The type of Node.js environment (defaults to production).
• --listenToProcessExits: Decides whether or not to attach process.exit handlers (defaults to true).
• --noLogo: Skip printing the logo on a startup. Will be replaced by a simple text (defaults to false).
• --hardResetPage: Determines whether the page's content should be reset from scratch, including Highcharts scripts (defaults to false).
• --browserShellMode: Decides whether to enable older but much more performant shell mode for the browser (defaults to true).
• --enableDebug: Enables or disables debug mode for the underlying browser (defaults to false).
• --headless: Controls the mode in which the browser is launched when in the debug mode (defaults to true).
• --devtools: Decides whether to enable DevTools when the browser is in a headful state (defaults to false).
• --listenToConsole: Decides whether to enable a listener for console messages sent from the browser (defaults to false).
• --dumpio: Redirects browser process stdout and stderr to process.stdout and process.stderr (defaults to false).
• --slowMo: Slows down Puppeteer operations by the specified number of milliseconds (defaults to 0).
• --debuggingPort: Specifies the debugging port (defaults to 9222).

HTTP Server

Apart from using as a CLI tool, which allows you to run one command at a time, it is also possible to configure the server to accept POST requests. The simplest way to enable the server is to run the command below:

highcharts-export-server --enableServer 1

Server Test

To test if the server is running correctly, you can send a simple POST request, e.g. by using Curl:

curl -H "Content-Type: application/json" -X POST -d '{"infile":{"title": {"text": "Chart"}, "xAxis": {"categories": ["Jan", "Feb", "Mar"]}, "series": [{"data": [29.9, 71.5, 106.4]}]}}' 127.0.0.1:7801 -o chart.png

The above should result in a chart being generated and saved in a file named chart.png.

SSL

To enable SSL support, add --certPath <path to key/crt> when running the server. Note that the certificate files needs to be named as such:

• server.crt
• server.key

HTTP Server POST Arguments

The server accepts the following arguments in a POST request body:

• infile: Chart options in the form of JSON or stringified JSON.
• options: An alias for the infile option.
• data: Another alias for the infile option.
• svg: A string containing SVG representation to render as a chart.
• type: The format of an exported chart (can be png, jpeg, pdf or svg). Mimetypes can also be used.
• constr: The constructor to use (can be chart, stockChart, mapChart or ganttChart).
• height: The height of the exported chart.
• width: The width of the exported chart.
• scale: The scale factor of the exported chart. Use it to improve resolution in PNG and JPEG, for example setting scale to 2 on a 600px chart will result in a 1200px output.
• globalOptions: Either a JSON or a stringified JSON with global options to be passed into Highcharts.setOptions.
• themeOptions: Either a JSON or a stringified JSON with theme options to be passed into Highcharts.setOptions.
• resources: Additional resources in the form of a JSON or a stringified JSON. It may contain files (array of JS filenames), js (stringified JS), and css (stringified CSS) sections.
• callback: Stringified JavaScript function to execute in the Highcharts constructor.
• customCode: Custom code to be executed before the chart initialization. This can be a function, code wrapped within a function, or a filename with the .js extension. Both allowFileResources and allowCodeExecution must be set to true for the option to be considered.
• b64: Boolean flag, set to true to receive the chart in the base64 format instead of the binary.
• noDownload: Boolean flag, set to true to exclude attachment headers from the response.

The server responds to application/json, multipart/form-data, and URL encoded requests.

CORS is enabled for the server.

It is recommended to run the server using pm2 unless running in a managed environment/container. Please refer to the pm2 documentation for details on how to set this up.

Available Endpoints

• POST

  • /: An endpoint for exporting charts.
  • /:filename - An endpoint for exporting charts with a specified filename parameter to save the chart to. The file will be downloaded with the {filename}.{type} name (the noDownload must be set to false).
  • /change_hc_version/:newVersion: An authenticated endpoint allowing the modification of the Highcharts version on the server through the use of a token.

• GET

  • /: An endpoint to perform exports through the user interface the server allows it.
  • /health: An endpoint for outputting basic statistics for the server.

Switching Highcharts Version at Runtime

If the HIGHCHARTS_ADMIN_TOKEN is set, you can use the POST /change_hc_version/:newVersion route to switch the Highcharts version on the server at runtime, ie. without restarting or redeploying the application.

A sample request to change the version to 10.3.3 is as follows:

curl -H 'hc-auth: <YOUR AUTH TOKEN>' -X POST <SERVER URL>/change_hc_version/10.3.3

e.g.

curl -H 'hc-auth: 12345' -X POST 127.0.0.1:7801/change_hc_version/10.3.3

This is useful to e.g. upgrade to the latest HC version without downtime.

Node.js Module

Finally, the Export Server can also be used as a Node.js module to simplify integrations:

// Import the Highcharts Export Server module
const exporter = require('highcharts-export-server');

// Export options correspond to the available CLI/HTTP arguments described above
const options = {
  export: {
    type: 'png',
    options: {
      title: {
        text: 'My Chart'
      },
      xAxis: {
        categories: ["Jan", "Feb", "Mar", "Apr"]
      },
      series: [
        {
          type: 'line',
          data: [1, 3, 2, 4]
        },
        {
          type: 'line',
          data: [5, 3, 4, 2]
        }
      ]
    }
  }
};

// Initialize export settings with your chart's config
const exportSettings = exporter.setOptions(options);

// Must initialize exporting before being able to export charts
await exporter.initExport(exportSettings);

// Perform an export
await exporter.startExport(exportSettings, async (error, info) => {
  // The export result is now in info
  // It will be base64 encoded (info.data)

  // Kill the pool when we are done with it
  await exporter.killPool();
});

CommonJS support

This package supports both CommonJS and ES modules.

Node.js API Reference

highcharts-export-server module

• server: The server instance which offers the following functions:

  • async startServer(serverConfig): The same as startServer described below.

    • {Object} serverConfig: The server configuration object.

  • closeServers(): Closes all servers associated with Express app instance.

  • getServers(): Get all servers associated with Express app instance.

  • enableRateLimiting(limitConfig): Enable rate limiting for the server.

    • {Object} limitConfig: Configuration object for rate limiting.

  • getExpress(): Get the Express instance.

  • getApp(): Get the Express app instance.

  • use(path, ...middlewares): Apply middleware(s) to a specific path.

    • {string} path: The path to which the middleware(s) should be applied.
    • {...Function} middlewares: The middleware functions to be applied.

  • get(path, ...middlewares): Set up a route with GET method and apply middleware(s).

    • {string} path: The route path.
    • {...Function} middlewares: The middleware functions to be applied.

  • post(path, ...middlewares): Set up a route with POST method and apply middleware(s).

    • {string} path: The route path.
    • {...Function} middlewares: The middleware functions to be applied.

• async startServer(serverConfig): Starts an HTTP server based on the provided configuration. The serverConfig object contains all server related properties (see the server section in the lib/schemas/config.js file for a reference).

  • {Object} serverConfig: The server configuration object.

• async initExport(options): Initializes the export process. Tasks such as configuring logging, checking cache and sources, and initializing the pool of resources happen during this stage. Function that is required to be called before trying to export charts or setting a server. The options is an object that contains all options.

  • {Object} options: All export options.

• async singleExport(options): Starts a single export process based on the specified options. Runs the startExport underneath.

  • {Object} options: The options object containing configuration for a single export.

• async batchExport(options): Starts a batch export process for multiple charts based on the information in the batch option. The batch is a string in the following format: "infile1.json=outfile1.png;infile2.json=outfile2.png;...". Runs the startExport underneath.

  • {Object} options: The options object containing configuration for a batch export.

• async startExport(settings, endCallback): Starts an export process. The settings contains final options gathered from all possible sources (config, env, cli, json). The endCallback is called when the export is completed, with an error object as the first argument and the second containing the base64 respresentation of a chart.

  • {Object} settings: The settings object containing export configuration.
  • {function} endCallback: The callback function to be invoked upon finalizing work or upon error occurance of the exporting process.

• async initPool(config): Initializes the export pool with the provided configuration, creating a browser instance and setting up worker resources.

  • {Object} config: Configuration options for the export pool along with custom puppeteer arguments for the puppeteer.launch function.

• async killPool(): Kills all workers in the pool, destroys the pool, and closes the browser instance.

• setOptions(userOptions, args): Initializes and sets the general options for the server instace, keeping the principle of the options load priority. It accepts optional userOptions and args from the CLI.

  • {Object} userOptions: User-provided options for customization.
  • {Array} args: Command-line arguments for additional configuration (CLI usage).

• async shutdownCleanUp(exitCode): Clean up function to trigger before ending process for the graceful shutdown.

  • {number} exitCode: An exit code for the process.exit() function.

• log(...args): Logs a message. Accepts a variable amount of arguments. Arguments after level will be passed directly to console.log, and/or will be joined and appended to the log file.

  • {any} args: An array of arguments where the first is the log level and the rest are strings to build a message with.

• logWithStack(newLevel, error, customMessage): Logs an error message with its stack trace. Optionally, a custom message can be provided.

  • {number} newLevel: The log level.
  • {Error} error: The error object.
  • {string} customMessage: An optional custom message to be logged along with the error.

• setLogLevel(newLevel): Sets the log level to the specified value. Log levels are (0 = no logging, 1 = error, 2 = warning, 3 = notice, 4 = verbose or 5 = benchmark).

  • {number} newLevel: The new log level to be set.

• enableFileLogging(logDest, logFile): Enables file logging with the specified destination and log file.

  • {string} logDest: The destination path for log files.
  • {string} logFile: The log file name.

• mapToNewConfig(oldOptions): Maps old-structured (PhantomJS) options to a new configuration format (Puppeteer).

  • {Object} oldOptions: Old-structured options to be mapped.

• async manualConfig(configFileName): Allows manual configuration based on specified prompts and saves the configuration to a file.

  • {string} configFileName: The name of the configuration file.

• printLogo(noLogo): Prints the Highcharts Export Server logo and version information.

  • {boolean} noLogo: If true, only prints version information without the logo.

• printUsage(): Prints the usage information for CLI arguments. If required, it can list properties recursively.

Examples

Samples and tests for every mentioned export method can be found in the ./samples and ./tests folders. Detailed descriptions are available in their corresponding sections on the Wiki.

Tips, Tricks & Notes

Note about Deprecated Options

At some point during the transition process from the PhantomJS solution, certain options were deprecated. Here is a list of options that no longer work with the server based on Puppeteer:

• async
• asyncRendering
• tmpdir
• dataOptions
• queueSize

Additionally, some options are now named differently due to the new structure and categorization. Here is a list of old names and their corresponding new names (old name -> new name):

• fromFile -> loadConfig
• sslOnly -> force or sslForce
• sslPath -> certPath
• rateLimit -> maxRequests
• workers -> maxWorkers

If you depend on any of the above options, the optimal approach is to directly change the old names to the new ones in the options. However, you don't have to do it manually, as there is a utility function called mapToNewConfig that can easily transfer the old-structured options to the new format. For an example, refer to the ./samples/module/options_phantomjs.js file.

Note about Chart Size

If you need to set the height or width of the chart, it can be done in two ways:

Set it in the chart config under:

• chart.height.
• chart.width.

Set it in the exporting config under:

• exporting.sourceHeight.
• exporting.sourceWidth.

The latter is preferred, as it allows you to set separate sizing when exporting and when displaying the chart on your web page.

Like previously mentioned, there are multiple ways to set and prioritize options, and the height, width and scale are no exceptions here. The priority goes like this:

1. Options from the export section of the provided options (CLI, JSON, etc.).
2. The sourceHeight, sourceWidth and scale from the chart.exporting section of chart's Highcharts options.
3. The height and width from the chart section of chart's Highcharts options.
4. The sourceHeight, sourceWidth and scale from the chart.exporting section of chart's Highcharts global options, if provided.
5. The height and width from the chart section of chart's Highcharts global options, if provided.
6. If no options are found to this point, the default values will be used (height = 400, width = 600 and scale = 1).

Note about Event Listeners

The Export Server attaches event listeners to process.exit, uncaughtException and signals such as SIGINT, SIGTERM and SIGHUP. This is to make sure that there are no memory leaks or zombie processes if the application is unexpectedly terminated.

Listeners are also attached to handle uncaught exceptions. If an exception occurs, the entire pool and browser instance are terminated, and the application is shut down.

If you do not want this behavior, start the server with --listenToProcessExits 0 or --listenToProcessExits false.

Be aware though, that if you disable this and you do not take great care to manually kill the pool of resources along with a browser instance, your server will bleed memory when the app is terminated.

Note about Resources

If --resources argument is not set and a file named resources.json exists in the folder from which the CLI tool was ran, it will use the resources.json file.

Note about Worker Count & Work Limit

The Export Server utilizes a pool of workers, where each worker is a Puppeteer process (browser instance's page) responsible for the actual chart rasterization. The pool size can be set with the --minWorkers and --maxWorkers options, and should be tweaked to fit the hardware on which you are running the server.

It is recommended that you start with the default 4, and work your way up (or down if 8 is too many for your setup, and things are unstable) gradually. The tests/other/stress-test.js script can be used to test the server and expects the server to be running on port 7801.

Each of the workers has a maximum number of requests it can handle before it restarts itself to keep everything responsive. This number is 40 by default, and can be tweaked with --workLimit. As with --minWorkers and --maxWorkers, this number should also be tweaked to fit your use case. Also, the --acquireTimeout option is worth to mention as well, in case there would be problems with acquiring resources. It is set in miliseconds with 5000 as a default value. Lastly, the --createTimeout and --destroyTimeout options are similar to the --acquireTimeout but for resource's create and destroy actions.

Usage

Injecting the Highcharts Dependency

In order to use the Export Server, Highcharts needs to be injected into the export template (see the ./templates folder for reference).

Since version 3.0.0, Highcharts is fetched in a Just-In-Time manner, making it easy to switch configurations. It is no longer required to explicitly accept the license, as in older versions. However, the Export Server still requires a valid Highcharts license to be used.

Using in Automated Deployments

Since version 3.0.0, when using in automated deployments, the configuration can be loaded either using environment variables or a JSON configuration file.

For a reference on available variables, refer to the configuration section above.

If you are using the Export Server as a dependency in your application, depending on your setup, it may be possible to set the environment variables in the package.json file as follows:

On Linux/Mac OS X:

{
  "scripts": {
    "preinstall": "export <variable1>=<value1>&&<variable2>=<value2>&&..."
  }
}

On Windows:

{
  "scripts": {
    "preinstall": "set <variable1>=<value1>&&<variable2>=<value2>&&..."
  }
}

Library Fetches

When fetching the built Highcharts library, the default behaviour is to fetch them from code.highcharts.com.

Installing Fonts

Does your Linux server not have Arial or Calibri? Puppeteer uses the system installed fonts to render pages. Therefore the Highcharts Export Server requires fonts to be properly installed on the system in order to use them to render charts.

Note that the default font-family config in Highcharts is "Lucida Grande", "Lucida Sans Unicode", Verdana, Arial, Helvetica, sans-serif".

Fonts are installed differently depending on your system. Please follow the below guides for font installation on most common systems.

Mac OS X

Install your desired fonts with the Font Book app, or place it in /Library/Fonts/ (system) or ~/Library/Fonts/ (user).

Linux

Copy or move the TTF file to the /usr/share/fonts/truetype (may require sudo privileges):

mkdir -p /usr/share/fonts/truetype
cp yourFont.ttf /usr/share/fonts/truetype/
fc-cache -fv

Windows

Copy or move the TTF file to C:\Windows\Fonts\:

copy yourFont.ttf C:\Windows\Fonts\yourFont.ttf

Google fonts

If you need Google Fonts in your custom installation, they can be had here: https://github.com/google/fonts.

Download them, and follow the above instructions for your OS.

Debug Mode

Version 4.0.0 introduced a new mode that allows debugging the Puppeteer browser instance. This is particularly useful when setting up a custom server. It helps to delve into the implementation, observe how things work, and analyze and resolve potential problems.

Launching

Setting the --enableDebug to true passes all debug options to the puppeteer.launch() function on startup. Together with the --headless option set to false, it launches the browser in a headful state providing a full version of the browser with a graphical user interface (GUI). While this serves as the minimal configuration to simply display the browser, Puppeteer offers additional options. Here is the full list:

• --enableDebug: Enables passing debug options to the puppeteer.launch().
• --headless: Sets the browser's state.
• --devtools: Allows turning on the DevTools automatically upon launching the browser.
• --listenToConsole: Allows listening to messages from the browser's console.
• --dumpio: Redirects the browser's process stdout and stderr to process.stdout and process.stderr respectively.
• --slowMo: Delays Puppeteer operations by a specified amount of milliseconds.
• --debuggingPort: Specifies a debugging port for a browser.

Debugging

There are two main ways to debug code:

• By adding a debugger statement within any client-side code (e.g., inside a page.evaluate callback). With the --devtools option set to true, the code execution will stop automatically.

• By running the export server with the --inspect-brk=<PORT> flag, and adding a debugger statement within any server-side code. Subsequently, navigate to chrome://inspect/, input the server's IP address and port (e.g., localhost:9229) in the Configure section. Clicking 'inspect' initiates debugging of the server-side code.

The npm run start:debug script from the package.json allows debugging code using both methods simultaneously. In this setup, client-side code is accessible from the devTools of a specific Puppeteer browser's page, while server-side code can be debugged from the devTools of chrome://inspect/.

For more details, refer to the Puppeteer debugging guide.

Additional Notes

• Ensure to set the --headless to false when the --devtools is set to true. Otherwise, there's a possibility that while DevTools may be recognized as enabled, the browser won't be displayed. Moreover, if a debugger is caught within the browser, it might lead to the entire debugging process getting stuck. In such scenarios, you can set the IP address and port (using the value of the --debuggingPort option) the same way as described in the section for debugging server-side code. This allows you to access DevTools and resume code execution.

• When using the --listenToConsole and --dumpio options, be aware that the server's console may become 'polluted' with messages from the browser. If you prefer to avoid this, simply set both options to false.

Performance Notice

In cases of batch exports, using the HTTP server is faster than the CLI. This is due to the overhead of starting Puppeteer for each job when using the CLI.

So it is better to write a bash script that starts the server and then performs a set of POSTS to it through e.g. Curl if not wanting to host the Export Server as a service.

Alternatively, you can use the --batch switch if the output format is the same for each of the input files to process:

highcharts-export-server --batch "infile1.json=outfile1.png;infile2.json=outfile2.png;..."

Other switches can be combined with this switch.

System Requirements

The system requirements largely depend on your use case.

The application is largely CPU and memory bound, so for heavy-traffic situations, it needs a fairly beefy server. It is recommended that the server has at least 1GB of memory regardless of traffic, and more than one core.

License

MIT. Note that a valid Highcharts License is also required to do exports.