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// Cadence - An extensible Statsd client for Rust!
//
// Copyright 2015-2021 Nick Pillitteri
//
// 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.
use std::io;
use std::io::Write;
use std::net::{SocketAddr, ToSocketAddrs, UdpSocket};
use std::sync::Mutex;
use crate::io::MultiLineWriter;
use crate::sinks::core::MetricSink;
use crate::types::{ErrorKind, MetricError, MetricResult};
// Default size of the buffer for buffered metric sinks. This
// is a rather conservative value, picked to make sure the entire
// buffer fits in a small UDP packet. Users may want to use a
// different value based on the configuration of the network
// their application runs in.
const DEFAULT_BUFFER_SIZE: usize = 512;
/// Attempt to convert anything implementing the `ToSocketAddrs` trait
/// into a concrete `SocketAddr` instance, returning an `InvalidInput`
/// error if the address could not be parsed.
// Public portion of the API (the sink constructors) is pass by value so
// there's no point in changing this to be pass by reference yet.
#[allow(clippy::needless_pass_by_value)]
fn get_addr<A: ToSocketAddrs>(addr: A) -> MetricResult<SocketAddr> {
match addr.to_socket_addrs()?.next() {
Some(addr) => Ok(addr),
None => Err(MetricError::from((
ErrorKind::InvalidInput,
"No socket addresses yielded",
))),
}
}
/// Implementation of a `MetricSink` that emits metrics over UDP.
///
/// This is the most basic version of `MetricSink` that sends metrics over
/// UDP. It accepts a UDP socket instance over which to write metrics and
/// the address of the Statsd server to send packets to.
///
/// Each metric is sent to the Statsd server when the `.emit()` method is
/// called, in the thread of the caller.
#[derive(Debug)]
pub struct UdpMetricSink {
addr: SocketAddr,
socket: UdpSocket,
}
impl UdpMetricSink {
/// Construct a new `UdpMetricSink` instance.
///
/// The address should be the address of the remote metric server to
/// emit metrics to over UDP. The socket should already be bound to a
/// local address with any desired configuration applied (blocking vs
/// non-blocking, timeouts, etc.).
///
/// # Example
///
/// ```no_run
/// use std::net::UdpSocket;
/// use cadence::{UdpMetricSink, DEFAULT_PORT};
///
/// let socket = UdpSocket::bind("0.0.0.0:0").unwrap();
/// let host = ("metrics.example.com", DEFAULT_PORT);
/// let sink = UdpMetricSink::from(host, socket);
/// ```
///
/// To send metrics over a non-blocking socket, simply put the socket
/// in non-blocking mode before creating the UDP metric sink.
///
/// # Non-blocking Example
///
/// Note that putting the UDP socket into non-blocking mode is the
/// default when sink and socket are automatically created with the
/// `StatsdClient::from_udp_host` method.
///
/// ```no_run
/// use std::net::UdpSocket;
/// use cadence::{UdpMetricSink, 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 = UdpMetricSink::from(host, socket);
/// ```
///
/// # Failures
///
/// This method may fail if:
///
/// * It is unable to resolve the hostname of the metric server.
/// * The host address is otherwise unable to be parsed
pub fn from<A>(to_addr: A, socket: UdpSocket) -> MetricResult<UdpMetricSink>
where
A: ToSocketAddrs,
{
let addr = get_addr(to_addr)?;
Ok(UdpMetricSink { addr, socket })
}
}
impl MetricSink for UdpMetricSink {
fn emit(&self, metric: &str) -> io::Result<usize> {
self.socket.send_to(metric.as_bytes(), &self.addr)
}
}
/// Adapter for writing to a `UdpSocket` via the `Write` trait
#[derive(Debug)]
pub(crate) struct UdpWriteAdapter {
addr: SocketAddr,
socket: UdpSocket,
}
impl UdpWriteAdapter {
pub(crate) fn new(addr: SocketAddr, socket: UdpSocket) -> UdpWriteAdapter {
UdpWriteAdapter { addr, socket }
}
}
impl Write for UdpWriteAdapter {
fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
self.socket.send_to(buf, &self.addr)
}
fn flush(&mut self) -> io::Result<()> {
Ok(())
}
}
/// Implementation of a `MetricSink` that buffers metrics before
/// sending them to a UDP socket.
///
/// Metrics are line buffered, meaning that a trailing "\n" is added
/// after each metric written to this sink. When the buffer is sufficiently
/// full and a write is attempted, the contents of the buffer are flushed to
/// a UDP socket and then the metric is written to the buffer. The buffer is
/// also flushed when this sink is destroyed.
///
/// The default size of the buffer is 512 bytes. This is the "safest"
/// size for a UDP packet according to the Etsy Statsd docs. The
/// buffer size can be customized using the `with_capacity` method
/// to create the sink if desired.
///
/// If a metric larger than the buffer is emitted, it will be written
/// directly to the underlying UDP socket, bypassing the buffer.
///
/// Note that since metrics are buffered until a certain size is reached, it's
/// possible that they may sit in the buffer for a while for applications
/// that do not emit metrics frequently or at a high volume. For these low-
/// throughput use cases, it may make more sense to use the `UdpMetricSink`
/// since it sends metrics immediately with no buffering.
#[derive(Debug)]
pub struct BufferedUdpMetricSink {
buffer: Mutex<MultiLineWriter<UdpWriteAdapter>>,
}
impl BufferedUdpMetricSink {
/// Construct a new `BufferedUdpMetricSink` instance with a default
/// buffer size of 512 bytes.
///
/// The address should be the address of the remote metric server to
/// emit metrics to over UDP. The socket should already be bound to a
/// local address with any desired configuration applied (blocking vs
/// non-blocking, timeouts, etc.).
///
/// Writes to this sink are automatically suffixed with a Unix newline
/// ('\n') by the sink and stored in a 512 byte buffer until the buffer
/// is full or this sink is destroyed, at which point the buffer will be
/// flushed.
///
/// # Example
///
/// ```no_run
/// use std::net::UdpSocket;
/// use cadence::{BufferedUdpMetricSink, DEFAULT_PORT};
///
/// let socket = UdpSocket::bind("0.0.0.0:0").unwrap();
/// let host = ("metrics.example.com", DEFAULT_PORT);
/// let sink = BufferedUdpMetricSink::from(host, socket);
/// ```
///
/// # Failures
///
/// This method may fail if:
///
/// * It is unable to resolve the hostname of the metric server.
/// * The host address is otherwise unable to be parsed
pub fn from<A>(sink_addr: A, socket: UdpSocket) -> MetricResult<BufferedUdpMetricSink>
where
A: ToSocketAddrs,
{
Self::with_capacity(sink_addr, socket, DEFAULT_BUFFER_SIZE)
}
/// Construct a new `BufferedUdpMetricSink` instance with a custom
/// buffer size.
///
/// The address should be the address of the remote metric server to
/// emit metrics to over UDP. The socket should already be bound to a
/// local address with any desired configuration applied (blocking vs
/// non-blocking, timeouts, etc.).
///
/// Writes to this sink are automatically suffixed with a Unix newline
/// ('\n') by the sink and stored in a buffer until the buffer is full
/// or this sink is destroyed, at which point the buffer will be flushed.
///
/// For guidance on sizing your buffer see the
/// [Statsd docs](https://github.com/etsy/statsd/blob/master/docs/metric_types.md#multi-metric-packets).
///
/// # Example
///
/// ```no_run
/// use std::net::UdpSocket;
/// use cadence::{BufferedUdpMetricSink, DEFAULT_PORT};
///
/// let socket = UdpSocket::bind("0.0.0.0:0").unwrap();
/// let host = ("metrics.example.com", DEFAULT_PORT);
/// let sink = BufferedUdpMetricSink::with_capacity(host, socket, 1432);
/// ```
///
/// # Failures
///
/// This method may fail if:
///
/// * It is unable to resolve the hostname of the metric server.
/// * The host address is otherwise unable to be parsed
pub fn with_capacity<A>(sink_addr: A, socket: UdpSocket, cap: usize) -> MetricResult<BufferedUdpMetricSink>
where
A: ToSocketAddrs,
{
let addr = get_addr(sink_addr)?;
Ok(BufferedUdpMetricSink {
buffer: Mutex::new(MultiLineWriter::new(UdpWriteAdapter::new(addr, socket), cap)),
})
}
}
impl MetricSink for BufferedUdpMetricSink {
fn emit(&self, metric: &str) -> io::Result<usize> {
let mut writer = self.buffer.lock().unwrap();
writer.write(metric.as_bytes())
}
fn flush(&self) -> io::Result<()> {
let mut writer = self.buffer.lock().unwrap();
writer.flush()
}
}
#[cfg(test)]
mod tests {
use super::{get_addr, BufferedUdpMetricSink, MetricSink, UdpMetricSink};
use std::net::UdpSocket;
#[test]
fn test_get_addr_bad_address() {
let res = get_addr("asdf");
assert!(res.is_err());
}
#[test]
fn test_get_addr_valid_address() {
let res = get_addr("127.0.0.1:8125");
assert!(res.is_ok());
}
#[test]
fn test_udp_metric_sink() {
let socket = UdpSocket::bind("0.0.0.0:0").unwrap();
let sink = UdpMetricSink::from("127.0.0.1:8125", socket).unwrap();
assert_eq!(7, sink.emit("buz:1|m").unwrap());
}
#[test]
fn test_non_blocking_udp_metric_sink() {
let socket = UdpSocket::bind("0.0.0.0:0").unwrap();
socket.set_nonblocking(true).unwrap();
let sink = UdpMetricSink::from("127.0.0.1:8125", socket).unwrap();
assert_eq!(7, sink.emit("baz:1|m").unwrap());
}
#[test]
fn test_buffered_udp_metric_sink() {
let socket = UdpSocket::bind("0.0.0.0:0").unwrap();
// Set the capacity of the buffer such that we know it will
// be flushed as a response to the metrics we're writing.
let sink = BufferedUdpMetricSink::with_capacity("127.0.0.1:8125", socket, 16).unwrap();
assert_eq!(8, sink.emit("foo:54|c").unwrap());
assert_eq!(8, sink.emit("foo:67|c").unwrap());
}
#[test]
fn test_buffered_udp_metric_sink_flush() {
let socket = UdpSocket::bind("0.0.0.0:0").unwrap();
// Set the capacity of the buffer such that it won't be flushed
// from a single write. Thus we can test the flush method.
let sink = BufferedUdpMetricSink::with_capacity("127.0.0.1:8125", socket, 64).unwrap();
assert_eq!(8, sink.emit("foo:54|c").unwrap());
assert!(sink.flush().is_ok());
}
}