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//! Watches a Kubernetes Resource for changes, with error recovery
//!
//! See [`watcher`] for the primary entry point.
use crate::utils::ResetTimerBackoff;
use async_trait::async_trait;
use backoff::{backoff::Backoff, ExponentialBackoff};
use derivative::Derivative;
use futures::{stream::BoxStream, Stream, StreamExt};
use kube_client::{
api::{ListParams, Resource, ResourceExt, VersionMatch, WatchEvent, WatchParams},
core::{metadata::PartialObjectMeta, ObjectList},
error::ErrorResponse,
Api, Error as ClientErr,
};
use serde::de::DeserializeOwned;
use smallvec::SmallVec;
use std::{clone::Clone, fmt::Debug, time::Duration};
use thiserror::Error;
use tracing::{debug, error, warn};
#[derive(Debug, Error)]
pub enum Error {
#[error("failed to perform initial object list: {0}")]
InitialListFailed(#[source] kube_client::Error),
#[error("failed to start watching object: {0}")]
WatchStartFailed(#[source] kube_client::Error),
#[error("error returned by apiserver during watch: {0}")]
WatchError(#[source] ErrorResponse),
#[error("watch stream failed: {0}")]
WatchFailed(#[source] kube_client::Error),
#[error("no metadata.resourceVersion in watch result (does resource support watch?)")]
NoResourceVersion,
#[error("too many objects matched search criteria")]
TooManyObjects,
}
pub type Result<T, E = Error> = std::result::Result<T, E>;
#[derive(Debug, Clone)]
/// Watch events returned from the [`watcher`]
pub enum Event<K> {
/// An object was added or modified
Applied(K),
/// An object was deleted
///
/// NOTE: This should not be used for managing persistent state elsewhere, since
/// events may be lost if the watcher is unavailable. Use Finalizers instead.
Deleted(K),
/// The watch stream was restarted, so `Deleted` events may have been missed
///
/// Should be used as a signal to replace the store contents atomically.
///
/// Any objects that were previously [`Applied`](Event::Applied) but are not listed in this event
/// should be assumed to have been [`Deleted`](Event::Deleted).
Restarted(Vec<K>),
}
impl<K> Event<K> {
/// Flattens out all objects that were added or modified in the event.
///
/// `Deleted` objects are ignored, all objects mentioned by `Restarted` events are
/// emitted individually.
pub fn into_iter_applied(self) -> impl Iterator<Item = K> {
match self {
Event::Applied(obj) => SmallVec::from_buf([obj]),
Event::Deleted(_) => SmallVec::new(),
Event::Restarted(objs) => SmallVec::from_vec(objs),
}
.into_iter()
}
/// Flattens out all objects that were added, modified, or deleted in the event.
///
/// Note that `Deleted` events may be missed when restarting the stream. Use finalizers
/// or owner references instead if you care about cleaning up external resources after
/// deleted objects.
pub fn into_iter_touched(self) -> impl Iterator<Item = K> {
match self {
Event::Applied(obj) | Event::Deleted(obj) => SmallVec::from_buf([obj]),
Event::Restarted(objs) => SmallVec::from_vec(objs),
}
.into_iter()
}
/// Map each object in an event through a mutator fn
///
/// This allows for memory optimizations in watch streams.
/// If you are chaining a watch stream into a reflector as an in memory state store,
/// you can control the space used by each object by dropping fields.
///
/// ```no_run
/// use k8s_openapi::api::core::v1::Pod;
/// use kube::ResourceExt;
/// # use kube::runtime::watcher::Event;
/// # let event: Event<Pod> = todo!();
/// event.modify(|pod| {
/// pod.managed_fields_mut().clear();
/// pod.annotations_mut().clear();
/// pod.status = None;
/// });
/// ```
#[must_use]
pub fn modify(mut self, mut f: impl FnMut(&mut K)) -> Self {
match &mut self {
Event::Applied(obj) | Event::Deleted(obj) => (f)(obj),
Event::Restarted(objs) => {
for k in objs {
(f)(k)
}
}
}
self
}
}
#[derive(Derivative)]
#[derivative(Debug)]
/// The internal finite state machine driving the [`watcher`]
enum State<K> {
/// The Watcher is empty, and the next [`poll`](Stream::poll_next) will start the initial LIST to get all existing objects
Empty {
continue_token: Option<String>,
objects: Vec<K>,
},
/// The initial LIST was successful, so we should move on to starting the actual watch.
InitListed { resource_version: String },
/// The watch is in progress, from this point we just return events from the server.
///
/// If the connection is disrupted then we propagate the error but try to restart the watch stream by
/// returning to the `InitListed` state.
/// If we fall out of the K8s watch window then we propagate the error and fall back doing a re-list
/// with `Empty`.
Watching {
resource_version: String,
#[derivative(Debug = "ignore")]
stream: BoxStream<'static, kube_client::Result<WatchEvent<K>>>,
},
}
impl<K: Resource + Clone> Default for State<K> {
fn default() -> Self {
Self::Empty {
continue_token: None,
objects: vec![],
}
}
}
/// Used to control whether the watcher receives the full object, or only the
/// metadata
#[async_trait]
trait ApiMode {
type Value: Clone;
async fn list(&self, lp: &ListParams) -> kube_client::Result<ObjectList<Self::Value>>;
async fn watch(
&self,
wp: &WatchParams,
version: &str,
) -> kube_client::Result<BoxStream<'static, kube_client::Result<WatchEvent<Self::Value>>>>;
}
/// A wrapper around the `Api` of a `Resource` type that when used by the
/// watcher will return the entire (full) object
struct FullObject<'a, K> {
api: &'a Api<K>,
}
/// Configurable list semantics for `watcher` relists
#[derive(Clone, Default, Debug, PartialEq)]
pub enum ListSemantic {
/// List calls perform a full quorum read for most recent results
///
/// Prefer this if you have strong consistency requirements. Note that this
/// is more taxing for the apiserver and can be less scalable for the cluster.
///
/// If you are observing large resource sets (such as congested `Controller` cases),
/// you typically have a delay between the list call completing, and all the events
/// getting processed. In such cases, it is probably worth picking `Any` over `MostRecent`,
/// as your events are not guaranteed to be up-to-date by the time you get to them anyway.
#[default]
MostRecent,
/// List calls returns cached results from apiserver
///
/// This is faster and much less taxing on the apiserver, but can result
/// in much older results than has previously observed for `Restarted` events,
/// particularly in HA configurations, due to partitions or stale caches.
///
/// This option makes the most sense for controller usage where events have
/// some delay between being seen by the runtime, and it being sent to the reconciler.
Any,
}
/// Accumulates all options that can be used on the watcher invocation.
#[derive(Clone, Debug, PartialEq)]
pub struct Config {
/// A selector to restrict the list of returned objects by their labels.
///
/// Defaults to everything if `None`.
pub label_selector: Option<String>,
/// A selector to restrict the list of returned objects by their fields.
///
/// Defaults to everything if `None`.
pub field_selector: Option<String>,
/// Timeout for the list/watch call.
///
/// This limits the duration of the call, regardless of any activity or inactivity.
/// If unset for a watch call, we will use 290s.
/// We limit this to 295s due to [inherent watch limitations](https://github.com/kubernetes/kubernetes/issues/6513).
pub timeout: Option<u32>,
/// Semantics for list calls.
///
/// Configures re-list for performance vs. consistency.
pub list_semantic: ListSemantic,
/// Maximum number of objects retrieved per list operation resyncs.
///
/// This can reduce the memory consumption during resyncs, at the cost of requiring more
/// API roundtrips to complete.
///
/// Defaults to 500. Note that `None` represents unbounded.
pub page_size: Option<u32>,
/// Enables watch events with type "BOOKMARK".
///
/// Requests watch bookmarks from the apiserver when enabled for improved watch precision and reduced list calls.
/// This is default enabled and should generally not be turned off.
pub bookmarks: bool,
}
impl Default for Config {
fn default() -> Self {
Self {
bookmarks: true,
label_selector: None,
field_selector: None,
timeout: None,
list_semantic: ListSemantic::default(),
// same default page size limit as client-go
// https://github.com/kubernetes/client-go/blob/aed71fa5cf054e1c196d67b2e21f66fd967b8ab1/tools/pager/pager.go#L31
page_size: Some(500),
}
}
}
/// Builder interface to Config
///
/// Usage:
/// ```
/// use kube::runtime::watcher::Config;
/// let wc = Config::default()
/// .timeout(60)
/// .labels("kubernetes.io/lifecycle=spot");
/// ```
impl Config {
/// Configure the timeout for list/watch calls
///
/// This limits the duration of the call, regardless of any activity or inactivity.
/// Defaults to 290s
#[must_use]
pub fn timeout(mut self, timeout_secs: u32) -> Self {
self.timeout = Some(timeout_secs);
self
}
/// Configure the selector to restrict the list of returned objects by their fields.
///
/// Defaults to everything.
/// Supports `=`, `==`, `!=`, and can be comma separated: `key1=value1,key2=value2`.
/// The server only supports a limited number of field queries per type.
#[must_use]
pub fn fields(mut self, field_selector: &str) -> Self {
self.field_selector = Some(field_selector.to_string());
self
}
/// Configure the selector to restrict the list of returned objects by their labels.
///
/// Defaults to everything.
/// Supports `=`, `==`, `!=`, and can be comma separated: `key1=value1,key2=value2`.
#[must_use]
pub fn labels(mut self, label_selector: &str) -> Self {
self.label_selector = Some(label_selector.to_string());
self
}
/// Sets list semantic to configure re-list performance and consistency
#[must_use]
pub fn list_semantic(mut self, semantic: ListSemantic) -> Self {
self.list_semantic = semantic;
self
}
/// Sets list semantic to `Any` to improve list performance
#[must_use]
pub fn any_semantic(self) -> Self {
self.list_semantic(ListSemantic::Any)
}
/// Disables watch bookmarks to simplify watch handling
///
/// This is not recommended to use with production watchers as it can cause desyncs.
/// See [#219](https://github.com/kube-rs/kube/issues/219) for details.
#[must_use]
pub fn disable_bookmarks(mut self) -> Self {
self.bookmarks = false;
self
}
/// Limits the number of objects retrieved in each list operation during resync.
///
/// This can reduce the memory consumption during resyncs, at the cost of requiring more
/// API roundtrips to complete.
#[must_use]
pub fn page_size(mut self, page_size: u32) -> Self {
self.page_size = Some(page_size);
self
}
/// Converts generic `watcher::Config` structure to the instance of `ListParams` used for list requests.
fn to_list_params(&self) -> ListParams {
let (resource_version, version_match) = match self.list_semantic {
ListSemantic::Any => (Some("0".into()), Some(VersionMatch::NotOlderThan)),
ListSemantic::MostRecent => (None, None),
};
ListParams {
label_selector: self.label_selector.clone(),
field_selector: self.field_selector.clone(),
timeout: self.timeout,
version_match,
resource_version,
// The watcher handles pagination internally.
limit: self.page_size,
continue_token: None,
}
}
/// Converts generic `watcher::Config` structure to the instance of `WatchParams` used for watch requests.
fn to_watch_params(&self) -> WatchParams {
WatchParams {
label_selector: self.label_selector.clone(),
field_selector: self.field_selector.clone(),
timeout: self.timeout,
bookmarks: self.bookmarks,
}
}
}
#[async_trait]
impl<K> ApiMode for FullObject<'_, K>
where
K: Clone + Debug + DeserializeOwned + Send + 'static,
{
type Value = K;
async fn list(&self, lp: &ListParams) -> kube_client::Result<ObjectList<Self::Value>> {
self.api.list(lp).await
}
async fn watch(
&self,
wp: &WatchParams,
version: &str,
) -> kube_client::Result<BoxStream<'static, kube_client::Result<WatchEvent<Self::Value>>>> {
self.api.watch(wp, version).await.map(StreamExt::boxed)
}
}
/// A wrapper around the `Api` of a `Resource` type that when used by the
/// watcher will return only the metadata associated with an object
struct MetaOnly<'a, K> {
api: &'a Api<K>,
}
#[async_trait]
impl<K> ApiMode for MetaOnly<'_, K>
where
K: Clone + Debug + DeserializeOwned + Send + 'static,
{
type Value = PartialObjectMeta<K>;
async fn list(&self, lp: &ListParams) -> kube_client::Result<ObjectList<Self::Value>> {
self.api.list_metadata(lp).await
}
async fn watch(
&self,
wp: &WatchParams,
version: &str,
) -> kube_client::Result<BoxStream<'static, kube_client::Result<WatchEvent<Self::Value>>>> {
self.api.watch_metadata(wp, version).await.map(StreamExt::boxed)
}
}
/// Progresses the watcher a single step, returning (event, state)
///
/// This function should be trampolined: if event == `None`
/// then the function should be called again until it returns a Some.
#[allow(clippy::too_many_lines)] // for now
async fn step_trampolined<A>(
api: &A,
wc: &Config,
state: State<A::Value>,
) -> (Option<Result<Event<A::Value>>>, State<A::Value>)
where
A: ApiMode,
A::Value: Resource + 'static,
{
match state {
State::Empty {
continue_token,
mut objects,
} => {
let mut lp = wc.to_list_params();
lp.continue_token = continue_token;
match api.list(&lp).await {
Ok(list) => {
objects.extend(list.items);
if let Some(continue_token) = list.metadata.continue_.filter(|s| !s.is_empty()) {
(None, State::Empty {
continue_token: Some(continue_token),
objects,
})
} else if let Some(resource_version) =
list.metadata.resource_version.filter(|s| !s.is_empty())
{
(Some(Ok(Event::Restarted(objects))), State::InitListed {
resource_version,
})
} else {
(Some(Err(Error::NoResourceVersion)), State::default())
}
}
Err(err) => {
if std::matches!(err, ClientErr::Api(ErrorResponse { code: 403, .. })) {
warn!("watch list error with 403: {err:?}");
} else {
debug!("watch list error: {err:?}");
}
(Some(Err(err).map_err(Error::InitialListFailed)), State::default())
}
}
}
State::InitListed { resource_version } => {
match api.watch(&wc.to_watch_params(), &resource_version).await {
Ok(stream) => (None, State::Watching {
resource_version,
stream,
}),
Err(err) => {
if std::matches!(err, ClientErr::Api(ErrorResponse { code: 403, .. })) {
warn!("watch initlist error with 403: {err:?}");
} else {
debug!("watch initlist error: {err:?}");
}
(
Some(Err(err).map_err(Error::WatchStartFailed)),
State::InitListed { resource_version },
)
}
}
}
State::Watching {
resource_version,
mut stream,
} => match stream.next().await {
Some(Ok(WatchEvent::Added(obj) | WatchEvent::Modified(obj))) => {
let resource_version = obj.resource_version().unwrap_or_default();
if resource_version.is_empty() {
(Some(Err(Error::NoResourceVersion)), State::default())
} else {
(Some(Ok(Event::Applied(obj))), State::Watching {
resource_version,
stream,
})
}
}
Some(Ok(WatchEvent::Deleted(obj))) => {
let resource_version = obj.resource_version().unwrap_or_default();
if resource_version.is_empty() {
(Some(Err(Error::NoResourceVersion)), State::default())
} else {
(Some(Ok(Event::Deleted(obj))), State::Watching {
resource_version,
stream,
})
}
}
Some(Ok(WatchEvent::Bookmark(bm))) => (None, State::Watching {
resource_version: bm.metadata.resource_version,
stream,
}),
Some(Ok(WatchEvent::Error(err))) => {
// HTTP GONE, means we have desynced and need to start over and re-list :(
let new_state = if err.code == 410 {
State::default()
} else {
State::Watching {
resource_version,
stream,
}
};
if err.code == 403 {
warn!("watcher watchevent error 403: {err:?}");
} else {
debug!("error watchevent error: {err:?}");
}
(Some(Err(err).map_err(Error::WatchError)), new_state)
}
Some(Err(err)) => {
if std::matches!(err, ClientErr::Api(ErrorResponse { code: 403, .. })) {
warn!("watcher error 403: {err:?}");
} else {
debug!("watcher error: {err:?}");
}
(Some(Err(err).map_err(Error::WatchFailed)), State::Watching {
resource_version,
stream,
})
}
None => (None, State::InitListed { resource_version }),
},
}
}
/// Trampoline helper for `step_trampolined`
async fn step<A>(
api: &A,
config: &Config,
mut state: State<A::Value>,
) -> (Result<Event<A::Value>>, State<A::Value>)
where
A: ApiMode,
A::Value: Resource + 'static,
{
loop {
match step_trampolined(api, config, state).await {
(Some(result), new_state) => return (result, new_state),
(None, new_state) => state = new_state,
}
}
}
/// Watches a Kubernetes Resource for changes continuously
///
/// Compared to [`Api::watch`], this automatically tries to recover the stream upon errors.
///
/// Errors from the underlying watch are propagated, after which the stream will go into recovery mode on the next poll.
/// You can apply your own backoff by not polling the stream for a duration after errors.
/// Keep in mind that some [`TryStream`](futures::TryStream) combinators (such as
/// [`try_for_each`](futures::TryStreamExt::try_for_each) and [`try_concat`](futures::TryStreamExt::try_concat))
/// will terminate eagerly as soon as they receive an [`Err`].
///
/// This is intended to provide a safe and atomic input interface for a state store like a [`reflector`].
/// Direct users may want to flatten composite events via [`WatchStreamExt`]:
///
/// ```no_run
/// use kube::{
/// api::{Api, ResourceExt}, Client,
/// runtime::{watcher, WatchStreamExt}
/// };
/// use k8s_openapi::api::core::v1::Pod;
/// use futures::TryStreamExt;
/// #[tokio::main]
/// async fn main() -> Result<(), watcher::Error> {
/// let client = Client::try_default().await.unwrap();
/// let pods: Api<Pod> = Api::namespaced(client, "apps");
///
/// watcher(pods, watcher::Config::default()).applied_objects()
/// .try_for_each(|p| async move {
/// println!("Applied: {}", p.name_any());
/// Ok(())
/// })
/// .await?;
/// Ok(())
/// }
/// ```
/// [`WatchStreamExt`]: super::WatchStreamExt
/// [`reflector`]: super::reflector::reflector
/// [`Api::watch`]: kube_client::Api::watch
///
/// # Recovery
///
/// The stream will attempt to be recovered on the next poll after an [`Err`] is returned.
/// This will normally happen immediately, but you can use [`StreamBackoff`](crate::utils::StreamBackoff)
/// to introduce an artificial delay. [`default_backoff`] returns a suitable default set of parameters.
///
/// If the watch connection is interrupted, then `watcher` will attempt to restart the watch using the last
/// [resource version](https://kubernetes.io/docs/reference/using-api/api-concepts/#efficient-detection-of-changes)
/// that we have seen on the stream. If this is successful then the stream is simply resumed from where it left off.
/// If this fails because the resource version is no longer valid then we start over with a new stream, starting with
/// an [`Event::Restarted`]. The internals mechanics of recovery should be considered an implementation detail.
pub fn watcher<K: Resource + Clone + DeserializeOwned + Debug + Send + 'static>(
api: Api<K>,
watcher_config: Config,
) -> impl Stream<Item = Result<Event<K>>> + Send {
futures::stream::unfold(
(api, watcher_config, State::default()),
|(api, watcher_config, state)| async {
let (event, state) = step(&FullObject { api: &api }, &watcher_config, state).await;
Some((event, (api, watcher_config, state)))
},
)
}
/// Watches a Kubernetes Resource for changes continuously and receives only the
/// metadata
///
/// Compared to [`Api::watch_metadata`], this automatically tries to recover the stream upon errors.
///
/// Errors from the underlying watch are propagated, after which the stream will go into recovery mode on the next poll.
/// You can apply your own backoff by not polling the stream for a duration after errors.
/// Keep in mind that some [`TryStream`](futures::TryStream) combinators (such as
/// [`try_for_each`](futures::TryStreamExt::try_for_each) and [`try_concat`](futures::TryStreamExt::try_concat))
/// will terminate eagerly as soon as they receive an [`Err`].
///
/// This is intended to provide a safe and atomic input interface for a state store like a [`reflector`].
/// Direct users may want to flatten composite events via [`WatchStreamExt`]:
///
/// ```no_run
/// use kube::{
/// api::{Api, ResourceExt}, Client,
/// runtime::{watcher, metadata_watcher, WatchStreamExt}
/// };
/// use k8s_openapi::api::core::v1::Pod;
/// use futures::TryStreamExt;
/// #[tokio::main]
/// async fn main() -> Result<(), watcher::Error> {
/// let client = Client::try_default().await.unwrap();
/// let pods: Api<Pod> = Api::namespaced(client, "apps");
///
/// metadata_watcher(pods, watcher::Config::default()).applied_objects()
/// .try_for_each(|p| async move {
/// println!("Applied: {}", p.name_any());
/// Ok(())
/// })
/// .await?;
/// Ok(())
/// }
/// ```
/// [`WatchStreamExt`]: super::WatchStreamExt
/// [`reflector`]: super::reflector::reflector
/// [`Api::watch`]: kube_client::Api::watch
///
/// # Recovery
///
/// The stream will attempt to be recovered on the next poll after an [`Err`] is returned.
/// This will normally happen immediately, but you can use [`StreamBackoff`](crate::utils::StreamBackoff)
/// to introduce an artificial delay. [`default_backoff`] returns a suitable default set of parameters.
///
/// If the watch connection is interrupted, then `watcher` will attempt to restart the watch using the last
/// [resource version](https://kubernetes.io/docs/reference/using-api/api-concepts/#efficient-detection-of-changes)
/// that we have seen on the stream. If this is successful then the stream is simply resumed from where it left off.
/// If this fails because the resource version is no longer valid then we start over with a new stream, starting with
/// an [`Event::Restarted`]. The internals mechanics of recovery should be considered an implementation detail.
#[allow(clippy::module_name_repetitions)]
pub fn metadata_watcher<K: Resource + Clone + DeserializeOwned + Debug + Send + 'static>(
api: Api<K>,
watcher_config: Config,
) -> impl Stream<Item = Result<Event<PartialObjectMeta<K>>>> + Send {
futures::stream::unfold(
(api, watcher_config, State::default()),
|(api, watcher_config, state)| async {
let (event, state) = step(&MetaOnly { api: &api }, &watcher_config, state).await;
Some((event, (api, watcher_config, state)))
},
)
}
/// Watch a single named object for updates
///
/// Emits `None` if the object is deleted (or not found), and `Some` if an object is updated (or created/found).
///
/// Compared to [`watcher`], `watch_object` does not return return [`Event`], since there is no need for an atomic
/// [`Event::Restarted`] when only one object is covered anyway.
pub fn watch_object<K: Resource + Clone + DeserializeOwned + Debug + Send + 'static>(
api: Api<K>,
name: &str,
) -> impl Stream<Item = Result<Option<K>>> + Send {
watcher(api, Config::default().fields(&format!("metadata.name={name}"))).map(|event| match event? {
Event::Deleted(_) => Ok(None),
// We're filtering by object name, so getting more than one object means that either:
// 1. The apiserver is accepting multiple objects with the same name, or
// 2. The apiserver is ignoring our query
// In either case, the K8s apiserver is broken and our API will return invalid data, so
// we had better bail out ASAP.
Event::Restarted(objs) if objs.len() > 1 => Err(Error::TooManyObjects),
Event::Restarted(mut objs) => Ok(objs.pop()),
Event::Applied(obj) => Ok(Some(obj)),
})
}
/// Default watch [`Backoff`] inspired by Kubernetes' client-go.
///
/// This fn has been moved into [`DefaultBackoff`].
#[must_use]
#[deprecated(
since = "0.84.0",
note = "replaced by `watcher::DefaultBackoff`. This fn will be removed in 0.88.0."
)]
pub fn default_backoff() -> DefaultBackoff {
DefaultBackoff::default()
}
/// Default watcher backoff inspired by Kubernetes' client-go.
///
/// The parameters currently optimize for being kind to struggling apiservers.
/// The exact parameters are taken from
/// [client-go's reflector source](https://github.com/kubernetes/client-go/blob/980663e185ab6fc79163b1c2565034f6d58368db/tools/cache/reflector.go#L177-L181)
/// and should not be considered stable.
///
/// This struct implements [`Backoff`] and is the default strategy used
/// when calling `WatchStreamExt::default_backoff`. If you need to create
/// this manually then [`DefaultBackoff::default`] can be used.
pub struct DefaultBackoff(Strategy);
type Strategy = ResetTimerBackoff<ExponentialBackoff>;
impl Default for DefaultBackoff {
fn default() -> Self {
Self(ResetTimerBackoff::new(
backoff::ExponentialBackoff {
initial_interval: Duration::from_millis(800),
max_interval: Duration::from_secs(30),
randomization_factor: 1.0,
multiplier: 2.0,
max_elapsed_time: None,
..ExponentialBackoff::default()
},
Duration::from_secs(120),
))
}
}
impl Backoff for DefaultBackoff {
fn next_backoff(&mut self) -> Option<Duration> {
self.0.next_backoff()
}
fn reset(&mut self) {
self.0.reset()
}
}