proxy: Remove the endpoint filter cache (#12488)

## Problem

The endpoint filter cache is still unused because it's not yet reliable
enough to be used. It only consumes a lot of memory.

## Summary of changes

Remove the code. Needs a new design.

neondatabase/cloud#30634

proxy/src/context/mod.rs

@@ -7,7 +7,7 @@ use once_cell::sync::OnceCell;
 use smol_str::SmolStr;
 use tokio::sync::mpsc;
 use tracing::field::display;
-use tracing::{Span, debug, error, info_span};
+use tracing::{Span, error, info_span};
 use try_lock::TryLock;
 use uuid::Uuid;
 
@@ -15,10 +15,7 @@ use self::parquet::RequestData;
 use crate::control_plane::messages::{ColdStartInfo, MetricsAuxInfo};
 use crate::error::ErrorKind;
 use crate::intern::{BranchIdInt, ProjectIdInt};
-use crate::metrics::{
-    ConnectOutcome, InvalidEndpointsGroup, LatencyAccumulated, LatencyTimer, Metrics, Protocol,
-    Waiting,
-};
+use crate::metrics::{LatencyAccumulated, LatencyTimer, Metrics, Protocol, Waiting};
 use crate::pqproto::StartupMessageParams;
 use crate::protocol2::{ConnectionInfo, ConnectionInfoExtra};
 use crate::types::{DbName, EndpointId, RoleName};
@@ -70,8 +67,6 @@ struct RequestContextInner {
     // This sender is only used to log the length of session in case of success.
     disconnect_sender: Option<mpsc::UnboundedSender<RequestData>>,
     pub(crate) latency_timer: LatencyTimer,
-    // Whether proxy decided that it's not a valid endpoint end rejected it before going to cplane.
-    rejected: Option<bool>,
     disconnect_timestamp: Option<chrono::DateTime<Utc>>,
 }
 
@@ -106,7 +101,6 @@ impl Clone for RequestContext {
             auth_method: inner.auth_method.clone(),
             jwt_issuer: inner.jwt_issuer.clone(),
             success: inner.success,
-            rejected: inner.rejected,
             cold_start_info: inner.cold_start_info,
             pg_options: inner.pg_options.clone(),
             testodrome_query_id: inner.testodrome_query_id.clone(),
@@ -151,7 +145,6 @@ impl RequestContext {
             auth_method: None,
             jwt_issuer: None,
             success: false,
-            rejected: None,
             cold_start_info: ColdStartInfo::Unknown,
             pg_options: None,
             testodrome_query_id: None,
@@ -183,11 +176,6 @@ impl RequestContext {
         )
     }
 
-    pub(crate) fn set_rejected(&self, rejected: bool) {
-        let mut this = self.0.try_lock().expect("should not deadlock");
-        this.rejected = Some(rejected);
-    }
-
     pub(crate) fn set_cold_start_info(&self, info: ColdStartInfo) {
         self.0
             .try_lock()
@@ -461,38 +449,6 @@ impl RequestContextInner {
     }
 
     fn log_connect(&mut self) {
-        let outcome = if self.success {
-            ConnectOutcome::Success
-        } else {
-            ConnectOutcome::Failed
-        };
-
-        // TODO: get rid of entirely/refactor
-        // check for false positives
-        // AND false negatives
-        if let Some(rejected) = self.rejected {
-            let ep = self
-                .endpoint_id
-                .as_ref()
-                .map(|x| x.as_str())
-                .unwrap_or_default();
-            // This makes sense only if cache is disabled
-            debug!(
-                ?outcome,
-                ?rejected,
-                ?ep,
-                "check endpoint is valid with outcome"
-            );
-            Metrics::get()
-                .proxy
-                .invalid_endpoints_total
-                .inc(InvalidEndpointsGroup {
-                    protocol: self.protocol,
-                    rejected: rejected.into(),
-                    outcome,
-                });
-        }
-
         if let Some(tx) = self.sender.take() {
             // If type changes, this error handling needs to be updated.
             let tx: mpsc::UnboundedSender<RequestData> = tx;