A Collectd Plugin Written in Rust

Collectd gathers system and application metrics and stores the values in any manner. Since Collectd provides a plugin API, this collectd_plugin overlays a ergonomic, yet extremely low cost abstractions to interface with Collectd.

Usage

Put this in your Cargo.toml:

[dependencies]
collectd_plugin = "0.3"

Or, if you want Serde support, include features like this:

[dependencies]
collectd_plugin = { version = "0.3", features = ["serde"] }

Then put this in your crate root:

extern crate collectd_plugin;

Rust 1.20 or later is needed to build.

This repo is tested on the following:

Collectd 5.4 (Ubuntu 14.04)
Collectd 5.5 (Ubuntu 16.04)
Collectd 5.7 (Ubuntu 17.04)

Quickstart

Below is a complete plugin that dummy reports load values to collectd, as it registers a READ hook. For an implementation has the same behavior as Collectd's own load plugin, see plugins/load

#[macro_use]
extern crate collectd_plugin;
extern crate failure;

use collectd_plugin::{ConfigItem, Plugin, PluginCapabilities, PluginManager, PluginRegistration,
                      Value, ValueListBuilder};
use failure::Error;

#[derive(Default)]
struct MyPlugin;

// A manager decides the name of the family of plugins and also registers one or more plugins based
// on collectd's configuration files
impl PluginManager for MyPlugin {
    // A plugin needs a unique name to be referenced by collectd
    fn name() -> &'static str {
        "myplugin"
    }

    // Our plugin might have configuration section in collectd.conf, which will be passed here if
    // present. Our contrived plugin doesn't care about configuration so it returns only a single
    // plugin (itself).
    fn plugins(_config: Option<&[ConfigItem]>) -> Result<PluginRegistration, Error> {
        Ok(PluginRegistration::Single(Box::new(MyPlugin)))
    }
}

impl Plugin for MyPlugin {
    // We define that our plugin will only be reporting / submitting values to writers
    fn capabilities(&self) -> PluginCapabilities {
        PluginCapabilities::READ
    }

    fn read_values(&mut self) -> Result<(), Error> {
        // Create a list of values to submit to collectd. We'll be sending in a vector representing the
        // "load" type. Short-term load is first (15.0) followed by mid-term and long-term. The number
        // of values that you submit at a time depends on types.db in collectd configurations
        let values = vec![Value::Gauge(15.0), Value::Gauge(10.0), Value::Gauge(12.0)];

        // Submit our values to collectd. A plugin can submit any number of times.
        ValueListBuilder::new(Self::name(), "load")
            .values(&values)
            .submit()
    }
}

// We pass in our plugin manager type
collectd_plugin!(MyPlugin);

Motivation

There are four main ways to extend collectd:

Write plugin against the C api: <collectd/core/daemon/plugin.h>
Write plugin for collectd-python
Write plugin for collectd-java
Write a cli for the exec plugin
Write a service that writes to a unix socket

And my thoughts:

I'm not confident enough to write C without leaks and there isn't a great package manager for C.
Python and Java aren't self contained, aren't necessarily deployed on the server, are more heavy weight, and I suspect that maintenance plays second fiddle to the C api.
The exec plugin is costly as it creates a new process for every collection
Depending on the circumstances, writing to a unix socket could be good fit, but I enjoy the ease of deployment, and the collectd integration -- there's no need to re-invent logging scheme, configuration, and system init files.

Rust's combination of ecosystem, package manager, C ffi, single file dynamic library, and optimized code made it seem like a natural choice.

To Build

To ensure a successful build, the following steps are needed:

When building, you must supply the collectd version you'll be deploying:
- cargo build --features collectd-54
- cargo build --features collectd-55
- cargo build --features collectd-57
Your project crate type must be cdylib
If you want to use bindgen to generate the ffi functions, use the bindgen feature (still alongside the desired collectd version). Make sure you have an appropriate version of clang installed and collectd-dev
Collectd expects plugins to not be prefixed with lib, so cp target/debug/libmyplugin.so /usr/lib/collectd/myplugin.so
Add LoadPlugin myplugin to collectd.conf

Plugin Configuration

The load plugin in plugins/load demonstrates how to expose configuration values to Collectd.