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// Cadence - An extensible Statsd client for Rust! // // Copyright 2015-2017 TSH Labs // // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your // option. This file may not be copied, modified, or distributed // except according to those terms. //! An extensible Statsd client for Rust! //! //! [Statsd](https://github.com/etsy/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](http://graphite.readthedocs.org/)). //! //! 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. //! //! ``` toml //! [dependencies] //! cadence = "x.y.z" //! ``` //! //! Then, link to it in your library or application. //! //! ``` rust,no_run //! // 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. The examples start //! simple and work up to how you should be using Cadence in a production //! application. //! //! ### 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. //! //! ``` rust,no_run //! // 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); //! ``` //! //! ### Buffered UDP Sink //! //! While sending a metric over UDP is very fast, the overhead of frequent //! network calls can start to add up. This is especially true if you are //! writing a high performance application that emits a lot of metrics. //! //! To make sure that metrics aren't interfering with the performance of //! your application, you may want to use a `MetricSink` implementation that //! buffers multiple metrics before sending them in a single network //! operation. For this, there's `BufferedUdpMetricSink`. An example of //! using this sink is given below. //! //! ``` rust,no_run //! use std::net::UdpSocket; //! use cadence::prelude::*; //! use cadence::{StatsdClient, BufferedUdpMetricSink, DEFAULT_PORT}; //! //! let socket = UdpSocket::bind("0.0.0.0:0").unwrap(); //! socket.set_nonblocking(true).unwrap(); //! //! let host = ("metrics.example.com", DEFAULT_PORT); //! let sink = BufferedUdpMetricSink::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"); //! ``` //! //! As you can see, using this buffered UDP sink is no more complicated //! than using the regular, non-buffered, UDP sink. //! //! The only downside to this sink is that metrics aren't written to the //! Statsd server until the buffer is full. If you have a busy application //! that is constantly emitting metrics, this shouldn't be a problem. //! However, if your application only occasionally emits metrics, this sink //! might result in the metrics being delayed for a little while until the //! buffer fills. //! //! ### Asynchronous Metric Sink //! //! To make sure emitting metrics doesn't interfere with the performance //! of your application (even though emitting metrics is generally quite //! fast), it's probably a good idea to make sure metrics are emitted in //! in a different thread than your application thread. //! //! To allow you do this, there is `AsyncMetricSink`. This sink allows you //! to wrap any other metric sink and send metrics using a thread pool, //! asynchronously from the flow of your application. //! //! The requirements for the wrapped metric sink are that it is thread //! safe, meaning that it implements the `Send` and `Sync` traits. //! Additionally, the wrapped sink should implement the `Clone` trait since //! this is how the `AsyncMetricSink` is designed to be shared between //! threads (see the source code for the `AsyncMetricSink` for more info). //! If you're using the `AsyncMetricSink` with another sink from //! Cadence, you don't need to worry: they are all thread safe and implement //! the `Clone` trait. //! //! An example of using the `AsyncMetricSink` to wrap a buffered UDP //! metric sink is given below. //! //! ``` rust,no_run //! use std::net::UdpSocket; //! use cadence::prelude::*; //! use cadence::{StatsdClient, AsyncMetricSink, BufferedUdpMetricSink, //! DEFAULT_PORT}; //! //! let socket = UdpSocket::bind("0.0.0.0:0").unwrap(); //! socket.set_nonblocking(true).unwrap(); //! //! let host = ("metrics.example.com", DEFAULT_PORT); //! let udp_sink = BufferedUdpMetricSink::from(host, socket).unwrap(); //! let async_sink = AsyncMetricSink::from(udp_sink); //! let client = StatsdClient::from_sink("my.prefix", async_sink); //! //! client.count("my.counter.thing", 29); //! client.time("my.service.call", 214); //! client.incr("some.event"); //! ``` //! //! ### Counted, Timed, Gauged, Metered, Histogrammed, and MetricClient Traits //! //! Each of the methods that the Cadence `StatsdClient` struct uses to send //! metrics are implemented as a trait. There is also a trait that combines //! all of these other traits. If we want, we can just use one of the trait //! types 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 or want to abstract away all the //! implementation details of the client being used behind a trait and //! pointer. //! //! 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. //! //! ``` rust,no_run //! 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 metric client to keep track of the number of times the //! // 'getUserById' method gets called. //! pub struct MyUserDao { //! metrics: Box<MetricClient> //! } //! //! //! impl MyUserDao { //! // Create a new instance that will use the StatsdClient //! pub fn new<T: MetricClient + 'static>(metrics: T) -> MyUserDao { //! MyUserDao { metrics: Box::new(metrics) } //! } //! //! /// Get a new user by their ID //! pub fn get_user_by_id(&self, id: u64) -> Option<User> { //! self.metrics.incr("getUserById"); //! None //! } //! } //! //! //! // Create a new Statsd client that writes to "metrics.example.com" //! let host = ("metrics.example.com", DEFAULT_PORT); //! let metrics = 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(metrics); //! //! // 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 `QueuingMetricSink` wrapping an instance //! of the `BufferedMetricSink`. //! //! However, maybe you want to do something not covered by an existing sink. //! An example of creating a custom sink is below. //! //! ``` rust,no_run //! 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. //! //! ``` rust,no_run //! 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"); //! ``` //! extern crate crossbeam; #[macro_use] extern crate log; extern crate threadpool; pub const DEFAULT_PORT: u16 = 8125; pub use self::client::{Counted, Timed, Gauged, Metered, Histogrammed, MetricClient, StatsdClient}; pub use self::sinks::{MetricSink, ConsoleMetricSink, LoggingMetricSink, NopMetricSink, UdpMetricSink, BufferedUdpMetricSink}; pub use self::sinks::threadpool::AsyncMetricSink; pub use self::sinks::crossbeam::QueuingMetricSink; pub use self::types::{MetricResult, MetricError, ErrorKind, Counter, Timer, Gauge, Meter, Histogram}; pub mod prelude; mod client; mod io; mod sinks; mod types;