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diff --git a/collectors/node.d.plugin/README.md b/collectors/node.d.plugin/README.md new file mode 100644 index 000000000..dd977017d --- /dev/null +++ b/collectors/node.d.plugin/README.md @@ -0,0 +1,218 @@ +# node.d.plugin + +`node.d.plugin` is a netdata external plugin. It is an **orchestrator** for data collection modules written in `node.js`. + +1. It runs as an independent process `ps fax` shows it +2. It is started and stopped automatically by netdata +3. It communicates with netdata via a unidirectional pipe (sending data to the netdata daemon) +4. Supports any number of data collection **modules** +5. Allows each **module** to have one or more data collection **jobs** +6. Each **job** is collecting one or more metrics from a single data source + +# Motivation + +Node.js is perfect for asynchronous operations. It is very fast and quite common (actually the whole web is based on it). +Since data collection is not a CPU intensive task, node.js is an ideal solution for it. + +`node.d.plugin` is a netdata plugin that provides an abstraction layer to allow easy and quick development of data +collectors in node.js. It also manages all its data collectors (placed in `/usr/libexec/netdata/node.d`) using a single +instance of node, thus lowering the memory footprint of data collection. + +Of course, there can be independent plugins written in node.js (placed in `/usr/libexec/netdata/plugins`). +These will have to be developed using the guidelines of **[External Plugins](../plugins.d/)**. + +To run `node.js` plugins you need to have `node` installed in your system. + +In some older systems, the package named `node` is not node.js. It is a terminal emulation program called `ax25-node`. +In this case the node.js package may be referred as `nodejs`. Once you install `nodejs`, we suggest to link +`/usr/bin/nodejs` to `/usr/bin/node`, so that typing `node` in your terminal, opens node.js. +For more information check the **[[Installation]]** guide. + +## configuring `node.d.plugin` + +`node.d.plugin` can work even without any configuration. Its default configuration file is +[/etc/netdata/node.d.conf](node.d.conf) (to edit it on your system run `/etc/netdata/edit-config node.d.conf`). + +## configuring `node.d.plugin` modules + +`node.d.plugin` modules accept configuration in `JSON` format. + +Unfortunately, `JSON` files do not accept comments. So, the best way to describe them is to have markdown text files +with instructions. + +`JSON` has a very strict formatting. If you get errors from netdata at `/var/log/netdata/error.log` that a certain +configuration file cannot be loaded, we suggest to verify it at [http://jsonlint.com/](http://jsonlint.com/). + +The files in this directory, provide usable examples for configuring each `node.d.plugin` module. + + +## debugging modules written for node.d.plugin + +To test `node.d.plugin` modules, which are placed in `/usr/libexec/netdata/node.d`, you can run `node.d.plugin` by hand, +like this: + +```sh +# become user netdata +sudo su -s /bin/sh netdata + +# run the plugin in debug mode +/usr/libexec/netdata/plugins.d/node.d.plugin debug 1 X Y Z +``` + +`node.d.plugin` will run in `debug` mode (lots of debug info), with an update frequency of `1` second, evaluating only +the collector scripts `X` (i.e. `/usr/libexec/netdata/node.d/X.node.js`), `Y` and `Z`. +You can define zero or more modules. If none is defined, `node.d.plugin` will evaluate all modules available. + +Keep in mind that if your configs are not in `/etc/netdata`, you should do the following before running `node.d.plugin`: + +```sh +export NETDATA_USER_CONFIG_DIR="/path/to/etc/netdata" +``` + +--- + +## developing `node.d.plugin` modules + +Your data collection module should be split in 3 parts: + + - a function to fetch the data from its source. `node.d.plugin` already can fetch data from web sources, + so you don't need to do anything about it for http. + + - a function to process the fetched/manipulate the data fetched. This function will make a number of calls + to create charts and dimensions and pass the collected values to netdata. + This is the only function you need to write for collecting http JSON data. + + - a `configure` and an `update` function, which take care of your module configuration and data refresh + respectively. You can use the supplied ones. + +Your module will automatically be able to process any number of servers, with different settings (even different +data collection frequencies). You will write just the work needed for one and `node.d.plugin` will do the rest. +For each server you are going to fetch data from, you will have to create a `service` (more later). + +### writing the data collection module + +To provide a module called `mymodule`, you have create the file `/usr/libexec/netdata/node.d/mymodule.node.js`, with this structure: + +```js + +// the processor is needed only +// if you need a custom processor +// other than http +netdata.processors.myprocessor = { + name: 'myprocessor', + + process: function(service, callback) { + + /* do data collection here */ + + callback(data); + } +}; + +// this is the mymodule definition +var mymodule = { + processResponse: function(service, data) { + + /* send information to the netdata server here */ + + }, + + configure: function(config) { + var eligible_services = 0; + + if(typeof(config.servers) === 'undefined' || config.servers.length === 0) { + + /* + * create a service using internal defaults; + * this is used for auto-detecting the settings + * if possible + */ + + netdata.service({ + name: 'a name for this service', + update_every: this.update_every, + module: this, + processor: netdata.processors.myprocessor, + // any other information your processor needs + }).execute(this.processResponse); + + eligible_services++; + } + else { + + /* + * create a service for each server in the + * configuration file + */ + + var len = config.servers.length; + while(len--) { + var server = config.servers[len]; + + netdata.service({ + name: server.name, + update_every: server.update_every, + module: this, + processor: netdata.processors.myprocessor, + // any other information your processor needs + }).execute(this.processResponse); + + eligible_services++; + } + } + + return eligible_services; + }, + + update: function(service, callback) { + + /* + * this function is called when each service + * created by the configure function, needs to + * collect updated values. + * + * You normally will not need to change it. + */ + + service.execute(function(service, data) { + mymodule.processResponse(service, data); + callback(); + }); + }, +}; + +module.exports = mymodule; +``` + +#### configure(config) + +`configure(config)` is called just once, when `node.d.plugin` starts. +The config file will contain the contents of `/etc/netdata/node.d/mymodule.conf`. +This file should have the following format: + +```js +{ + "enable_autodetect": false, + "update_every": 5, + "servers": [ { /* server 1 */ }, { /* server 2 */ } ] +} +``` + +If the config file `/etc/netdata/node.d/mymodule.conf` does not give a `enable_autodetect` or `update_every`, these +will be added by `node.d.plugin`. So you module will always have them. + +The configuration file `/etc/netdata/node.d/mymodule.conf` may contain whatever else is needed for `mymodule`. + +#### processResponse(data) + +`data` may be `null` or whatever the processor specified in the `service` returned. + +The `service` object defines a set of functions to allow you send information to the netdata core about: + +1. Charts and dimension definitions +2. Updated values, from the collected values + +--- + +*FIXME: document an operational node.d.plugin data collector - the best example is the +[snmp collector](snmp/snmp.node.js)* |