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//! The `changes-stream` crate is designed to give you a
//! futures::Stream of CouchDB changes stream events.
use bytes::{buf::IntoIter, Bytes};
use futures_util::stream::Stream;
use log::error;
use serde_json::Value;
use std::{mem::replace, pin::Pin, task::Poll, time::Duration};
mod error;
mod event;
pub use error::Error;
pub use event::{Change, ChangeEvent, Event, FinishedEvent};
/// A structure which implements futures::Stream
pub struct ChangesStream {
/// metrics bytes counter
#[cfg(feature = "metrics")]
bytes: metrics::Counter,
/// metrics entries counter
#[cfg(feature = "metrics")]
entries: metrics::Counter,
/// Source of http chunks provided by reqwest
source: Pin<Box<dyn Stream<Item = reqwest::Result<Bytes>> + Send>>,
/// Buffer of current line and current chunk iterator
buf: (Vec<u8>, Option<IntoIter<Bytes>>),
}
impl ChangesStream {
/// Constructs a new `ChangesStream` struct with a post payload
///
/// Takes a single argument, `db`, which represents the
/// url of the data you wish to stream.
///
/// For example, to create a new `ChangesStream` struct
/// for the npmjs registry, you would write:
///
/// ```no_run
/// # use changes_stream2::{ChangesStream, Event};
/// # use futures_util::stream::StreamExt;
/// #
/// # #[tokio::main]
/// # async fn main() {
/// # let url = "https://replicate.npmjs.com/_changes?filter=_selector".to_string();
/// # let mut changes = ChangesStream::with_post_payload(url, &serde_json::json!({"selector": { "_id": { "$regex": "^_design/" }}})).await.unwrap();
/// # while let Some(event) = changes.next().await {
/// # match event {
/// # Ok(Event::Change(change)) => println!("Change ({}): {}", change.seq, change.id),
/// # Ok(Event::Finished(finished)) => println!("Finished: {}", finished.last_seq),
/// # Err(err) => println!("Error: {:?}", err),
/// # }
/// # }
/// # }
/// ```
pub async fn with_post_payload(db: String, payload: &Value) -> Result<Self, Error> {
let url = url::Url::parse(&db)?;
#[cfg(feature = "metrics")]
let database = regex::Regex::new(r"(?m)[_/]+")
.unwrap()
.replace_all(
&format!("{}_{}", url.host_str().unwrap_or_default(), url.path()),
"_",
)
.to_string();
let client = reqwest::ClientBuilder::new()
.connect_timeout(Duration::from_secs(60))
.read_timeout(Duration::from_secs(60))
.build()?;
let res = client.post(url).json(payload).send().await?;
let status = res.status();
if !status.is_success() {
let body = res.text().await.unwrap_or_default();
return Err(Error::InvalidResponse { status, body });
}
let source = Pin::new(Box::new(res.bytes_stream()));
#[cfg(feature = "metrics")]
let (bytes, entries) = {
let bytes_name = "couchdb_changes_bytes_total";
let entries_name = "couchdb_changes_entries_total";
metrics::describe_counter!(bytes_name, metrics::Unit::Bytes, "Changes stream bytes");
metrics::describe_counter!(
entries_name,
metrics::Unit::Count,
"Changes stream entries"
);
(
metrics::counter!(bytes_name, "database" => database.clone()),
metrics::counter!(entries_name, "database" => database),
)
};
Ok(Self {
#[cfg(feature = "metrics")]
bytes,
#[cfg(feature = "metrics")]
entries,
source,
buf: (Vec::new(), None),
})
}
/// Constructs a new `ChangesStream` struct
///
/// Takes a single argument, `db`, which represents the
/// url of the data you wish to stream.
///
/// For example, to create a new `ChangesStream` struct
/// for the npmjs registry, you would write:
///
/// ```no_run
/// # use changes_stream2::{ChangesStream, Event};
/// # use futures_util::stream::StreamExt;
/// #
/// # #[tokio::main]
/// # async fn main() {
/// # let url = "https://replicate.npmjs.com/_changes".to_string();
/// # let mut changes = ChangesStream::new(url).await.unwrap();
/// # while let Some(event) = changes.next().await {
/// # match event {
/// # Ok(Event::Change(change)) => println!("Change ({}): {}", change.seq, change.id),
/// # Ok(Event::Finished(finished)) => println!("Finished: {}", finished.last_seq),
/// # Err(err) => println!("Error: {:?}", err),
/// # }
/// # }
/// # }
/// ```
pub async fn new(db: String) -> Result<Self, Error> {
Self::with_post_payload(db, &serde_json::json!({})).await
}
}
impl Stream for ChangesStream {
type Item = Result<Event, Error>;
fn poll_next(
mut self: std::pin::Pin<&mut Self>,
cx: &mut std::task::Context<'_>,
) -> std::task::Poll<Option<Self::Item>> {
'main: loop {
if self.buf.1.is_none() {
match Stream::poll_next(self.source.as_mut(), cx) {
Poll::Pending => return Poll::Pending,
Poll::Ready(None) => return Poll::Ready(None),
Poll::Ready(Some(Ok(chunk))) => {
#[cfg(feature = "metrics")]
self.bytes.increment(chunk.len() as u64);
self.buf.1 = Some(chunk.into_iter())
}
Poll::Ready(Some(Err(err))) => {
error!("Error getting next chunk: {:?}", err);
return Poll::Ready(None);
}
}
} else {
let (line, chunk_iter) = &mut self.buf;
let iter = chunk_iter.as_mut().unwrap();
loop {
if let Some(byte) = iter.next() {
if byte == 0x0A {
// Found '\n', end of line
break;
}
line.push(byte);
} else {
// We need another chunk to fill the line
*chunk_iter = None;
continue 'main;
}
}
let line = replace(line, Vec::with_capacity(line.len() * 2));
if line.len() < 14 {
// skip prologue, epilogue and empty lines (continuous mode)
continue;
}
let mut len = line.len();
if line[len - 1] == 0x0D {
// 0x0D is '\r'. CouchDB >= 2.0 sends "\r\n"
len -= 1;
}
if line[len - 1] == 0x2C {
// 0x2C is ','
len -= 1;
}
let result = serde_json::from_slice::<ChangeEvent>(&line[..len])
.map(Event::Change)
.or_else(|error| {
serde_json::from_slice::<FinishedEvent>(&line[..len])
.map(Event::Finished)
.map_err(|_err| Error::ParsingFailed {
error,
json: String::from_utf8(line).unwrap_or_default(),
})
});
#[cfg(feature = "metrics")]
self.entries.increment(1);
return Poll::Ready(Some(result));
}
}
}
}