impr(proxy): Move the CancelMap to Redis hashes (#10364)

## Problem
The approach of having CancelMap as an in-memory structure increases
code complexity,
as well as putting additional load for Redis streams.

## Summary of changes
- Implement a set of KV ops for Redis client;
- Remove cancel notifications code;
- Send KV ops over the bounded channel to the handling background task
for removing and adding the cancel keys.


Closes #9660

proxy/src/serverless/mod.rs

@@ -43,7 +43,7 @@ use tokio_util::task::TaskTracker;
 use tracing::{info, warn, Instrument};
 use utils::http::error::ApiError;
 
-use crate::cancellation::CancellationHandlerMain;
+use crate::cancellation::CancellationHandler;
 use crate::config::{ProxyConfig, ProxyProtocolV2};
 use crate::context::RequestContext;
 use crate::ext::TaskExt;
@@ -61,7 +61,7 @@ pub async fn task_main(
     auth_backend: &'static crate::auth::Backend<'static, ()>,
     ws_listener: TcpListener,
     cancellation_token: CancellationToken,
-    cancellation_handler: Arc<CancellationHandlerMain>,
+    cancellation_handler: Arc<CancellationHandler>,
     endpoint_rate_limiter: Arc<EndpointRateLimiter>,
 ) -> anyhow::Result<()> {
     scopeguard::defer! {
@@ -318,7 +318,7 @@ async fn connection_handler(
     backend: Arc<PoolingBackend>,
     connections: TaskTracker,
     cancellations: TaskTracker,
-    cancellation_handler: Arc<CancellationHandlerMain>,
+    cancellation_handler: Arc<CancellationHandler>,
     endpoint_rate_limiter: Arc<EndpointRateLimiter>,
     cancellation_token: CancellationToken,
     conn: AsyncRW,
@@ -412,7 +412,7 @@ async fn request_handler(
     config: &'static ProxyConfig,
     backend: Arc<PoolingBackend>,
     ws_connections: TaskTracker,
-    cancellation_handler: Arc<CancellationHandlerMain>,
+    cancellation_handler: Arc<CancellationHandler>,
     session_id: uuid::Uuid,
     conn_info: ConnectionInfo,
     // used to cancel in-flight HTTP requests. not used to cancel websockets

proxy/src/serverless/websocket.rs

@@ -12,7 +12,7 @@ use pin_project_lite::pin_project;
 use tokio::io::{self, AsyncBufRead, AsyncRead, AsyncWrite, ReadBuf};
 use tracing::warn;
 
-use crate::cancellation::CancellationHandlerMain;
+use crate::cancellation::CancellationHandler;
 use crate::config::ProxyConfig;
 use crate::context::RequestContext;
 use crate::error::{io_error, ReportableError};
@@ -129,7 +129,7 @@ pub(crate) async fn serve_websocket(
     auth_backend: &'static crate::auth::Backend<'static, ()>,
     ctx: RequestContext,
     websocket: OnUpgrade,
-    cancellation_handler: Arc<CancellationHandlerMain>,
+    cancellation_handler: Arc<CancellationHandler>,
     endpoint_rate_limiter: Arc<EndpointRateLimiter>,
     hostname: Option<String>,
     cancellations: tokio_util::task::task_tracker::TaskTracker,