petecooper and cakrit Typo: `stab_status` -> `stub_status` (#4984)
##### Summary

Typo: `stab_status` -> `stub_status`

##### Component Name

Docs / readme.

##### Additional Information

None.
Latest commit 39ad3c5 Dec 14, 2018

README.md

Data collection plugins

netdata supports internal and external data collection plugins:

  • internal plugins are written in C and run as threads inside the netdata daemon.

  • external plugins may be written in any computer language and are spawn as independent long-running processes by the netdata daemon. They communicate with the netdata daemon via pipes (stdout communication).

To minimize the number of processes spawn for data collection, netdata also supports plugin orchestrators.

  • plugin orchestrators are external plugins that do not collect any data by themeselves. Instead they support data collection modules written in the language of the orchestrator. Usually the orchestrator provides a higher level abstraction, making it ideal for writing new data collection modules with the minimum of code.

    Currently netdata provides plugin orchestrators BASH v4+ charts.d.plugin, node.js node.d.plugin and python v2+ (including v3) python.d.plugin.

Netdata Plugins

plugin lang O/S runs as modular description
apps.plugin C linux, freebsd external - monitors the whole process tree on Linux and FreeBSD and breaks down system resource usage by process, user and user group.
cgroups.plugin C linux internal - collects resource usage of Containers, libvirt VMs and systemd services, on Linux systems
charts.d.plugin BASH v4+ any external yes a plugin orchestrator for data collection modules written in BASH v4+.
checks.plugin C any internal - a debugging plugin (by default it is disabled)
diskspace.plugin C linux internal - collects disk space usage metrics on Linux mount points
fping.plugin C any external - measures network latency, jitter and packet loss between the monitored node and any number of remote network end points.
freebsd.plugin C freebsd internal yes collects resource usage and performance data on FreeBSD systems
freeipmi.plugin C linux, freebsd external - collects metrics from enterprise hardware sensors, on Linux and FreeBSD servers.
idlejitter.plugin C any internal - measures CPU latency and jitter on all operating systems
macos.plugin C macos internal yes collects resource usage and performance data on MacOS systems
nfacct.plugin C linux internal - collects netfilter firewall, connection tracker and accounting metrics using libmnl and libnetfilter_acct
node.d.plugin node.js any external yes a plugin orchestrator for data collection modules written in node.js.
plugins.d C any internal - implements the external plugins API and serves external plugins
proc.plugin C linux internal yes collects resource usage and performance data on Linux systems
python.d.plugin python v2+ any external yes a plugin orchestrator for data collection modules written in python v2 or v3 (both are supported).
statsd.plugin C any internal - implements a high performance statsd server for netdata
tc.plugin C linux internal - collects traffic QoS metrics (tc) of Linux network interfaces

Enabling and Disabling plugins

Each plugin can be enabled or disabled via netdata.conf, section [plugins].

At this section there a list of all the plugins with a boolean setting to enable them or disable them.

The exception is statsd.plugin that has its own [statsd] section.

Once a plugin is enabled, consult the page of each plugin for additional configuration options.

All external plugins are managed by plugins.d, which provides additional management options.

Internal Plugins

Each of the internal plugins runs as a thread inside the netdata daemon. Once this thread has started, the plugin may spawn additional threads according to its design.

Internal Plugins API

The internal data collection API consists of the following calls:

collect_data() {
    // collect data here (one iteration)
    
    collected_number collected_value = collect_a_value();
    
    // give the metrics to netdata
    
    static RRDSET *st = NULL; // the chart
    static RRDDIM *rd = NULL; // a dimension attached to this chart
    
    if(unlikely(!st)) {
        // we haven't created this chart before
        // create it now
        st = rrdset_create_localhost(
                "type"
                , "id"
                , "name"
                , "family"
                , "context"
                , "Chart Title"
                , "units"
                , "plugin-name"
                , "module-name"
                , priority
                , update_every
                , chart_type
        );

        // attach a metric to it
        rd = rrddim_add(st, "id", "name", multiplier, divider, algorithm);
    }
    else {
        // this chart is already created
        // let netdata know we start a new iteration on it
        rrdset_next(st);
    }
    
    // give the collected value(s) to the chart
    rrddim_set_by_pointer(st, rd, collected_value);
    
    // signal netdata we are done with this iteration
    rrdset_done(st);
}

Of course netdata has a lot of libraries to help you also in collecting the metrics. The best way to find your way through this, is to examine what other similar plugins do.

External Plugins

External plugins use the API and are managed by plugins.d.

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