Crate cadence [−] [src]
An extensible Statsd client for Rust!
Statsd is a network server that listens for metrics (things like counters and timers) sent over UDP and sends aggregates of these metrics to a backend service of some kind (often Graphite).
Cadence is a client written in Rust for interacting with a Statsd server. You might want to emit metrics (using Cadence, sending them to a Statsd server) in your Rust server application.
For example, if you are running a Rust web service you might want to record:
- Number of succesful requests
- Number of error requests
- Time taken for each request
Cadence is a flexible and easy way to do this!
Features
- Support for emitting counters, timers, gauges, and meters to Statsd over UDP.
- Support for alternate backends via the
MetricSink
trait. - A simple yet flexible API for sending metrics.
Install
To make use of Cadence in your project, add it as a dependency in your Cargo.toml
file.
[dependencies]
cadence = "x.y.z"
Then, link to it in your library or application.
// bin.rs or lib.rs extern crate cadence; // rest of your library or application
Usage
Some examples of how to use Cadence are shown below.
Simple Use
Simple usage of Cadence is shown below. In this example, we just import the client, create an instance that will write to some imaginary metrics server, and send a few metrics.
// Import the client. use cadence::prelude::*; use cadence::{StatsdClient, UdpMetricSink, DEFAULT_PORT}; // Create client that will write to the given host over UDP. // // Note that you'll probably want to actually handle any errors creating // the client when you use it for real in your application. We're just // using .unwrap() here since this is an example! let host = ("metrics.example.com", DEFAULT_PORT); let client = StatsdClient::<UdpMetricSink>::from_udp_host( "my.metrics", host).unwrap(); // Emit metrics! client.incr("some.counter"); client.time("some.methodCall", 42); client.gauge("some.thing", 7); client.meter("some.value", 5);
Counted, Timed, Gauged, and Metered Traits
Each of the methods that the Cadence StatsdClient
struct uses to send
metrics are implemented as a trait. If we want, we can just use the trait
type to refer to the client instance. This might be useful to you if you'd
like to swap out the actual Cadence client with a dummy version when you
are unit testing your code.
Each of these traits are exported in the prelude module. They are also available in the main module but aren't typically used like that.
use cadence::prelude::*; use cadence::{StatsdClient, UdpMetricSink, DEFAULT_PORT}; pub struct User { id: u64, username: String, email: String } // Here's a simple DAO (Data Access Object) that doesn't do anything but // uses a counter to keep track of the number of times the 'getUserById' // method gets called. pub struct MyUserDao<T: Counted> { counter: T } impl<T: Counted> MyUserDao<T> { // Create a new instance that will use the counter / client pub fn new(counter: T) -> MyUserDao<T> { MyUserDao{counter: counter} } /// Get a new user by their ID pub fn get_user_by_id(&self, id: u64) -> Option<User> { self.counter.incr("getUserById"); None } } // Create a new Statsd client that writes to "metrics.example.com" let host = ("metrics.example.com", DEFAULT_PORT); let counter = StatsdClient::<UdpMetricSink>::from_udp_host( "counter.example", host).unwrap(); // Create a new instance of the DAO that will use the client let dao = MyUserDao::new(counter); // Try to lookup a user by ID! match dao.get_user_by_id(123) { Some(u) => println!("Found a user!"), None => println!("No user!") };
Custom Metric Sinks
The Cadence StatsdClient
uses implementations of the MetricSink
trait
to send metrics to a metric server. Most users of the Candence library
probably want to use the UdpMetricSink
implementation. This is the way
people typically interact with a Statsd server, sending packets over UDP.
However, maybe you'd like to do something custom: use a thread pool, send multiple metrics at the same time, or something else. An example of creating a custom sink is below.
use std::io; use cadence::prelude::*; use cadence::{StatsdClient, MetricSink, DEFAULT_PORT}; pub struct MyMetricSink; impl MetricSink for MyMetricSink { fn emit(&self, metric: &str) -> io::Result<usize> { // Your custom metric sink implementation goes here! Ok(0) } } let sink = MyMetricSink; let client = StatsdClient::from_sink("my.prefix", sink); client.count("my.counter.thing", 42); client.time("my.method.time", 25); client.incr("some.other.counter");
Custom UDP Socket
Most users of the Cadence StatsdClient
will be using it to send metrics
over a UDP socket. If you need to customize the socket, for example you
want to use the socket in blocking mode but set a write timeout, you can
do that as demonstrated below.
use std::net::UdpSocket; use std::time::Duration; use cadence::prelude::*; use cadence::{StatsdClient, UdpMetricSink, DEFAULT_PORT}; let socket = UdpSocket::bind("0.0.0.0:0").unwrap(); socket.set_write_timeout(Some(Duration::from_millis(1))).unwrap(); let host = ("metrics.example.com", DEFAULT_PORT); let sink = UdpMetricSink::from(host, socket).unwrap(); let client = StatsdClient::from_sink("my.prefix", sink); client.count("my.counter.thing", 29); client.time("my.service.call", 214); client.incr("some.event");
Modules
prelude |
Export commonly used parts of Cadence for easy glob imports |
Structs
ConsoleMetricSink |
Implementation of a |
Counter |
Counters are simple values incremented or decremented by a client. |
Gauge |
Gauges are an instantaneous value determined by the client. |
LoggingMetricSink |
Implementation of a |
Meter |
Meters measure the rate at which events occur as determined by the server. |
MetricError |
Error generated by this library potentially wrapping another
type of error (exposed via the |
NopMetricSink |
Implementation of a |
StatsdClient |
Client for Statsd that implements various traits to record metrics. |
Timer |
Timers are a positive number of milliseconds between a start and end point. |
UdpMetricSink |
Implementation of a |
Enums
ErrorKind |
Potential categories an error from this library falls into. |
Constants
DEFAULT_PORT |
Traits
Counted |
Trait for incrementing and decrementing counters. |
Gauged |
Trait for recording gauge values. |
Metered |
Trait for recording meter values. |
MetricSink |
Trait for various backends that send Statsd metrics somewhere. |
Timed |
Trait for recording timings in milliseconds. |
Type Definitions
MetricResult |