From e47a098d41acda52aad31bd6ae0140e59ad3746b Mon Sep 17 00:00:00 2001
From: Jared Patterson <jared@laravel.com>
Date: Sun, 15 Mar 2026 06:41:57 +1300
Subject: [PATCH] Idle Connection Timeout Configuration

- Adds configuration for connection pool idle connetion timeouts
- Decreases the default idle connection timeout to be < the Clickhouse keep-alive default (10s)

Fixes: #92
---
 config/README.md         | 2 ++
 config/config.go         | 5 +++++
 config/config_test.go    | 2 ++
 config/testdata/full.yml | 4 ++++
 proxy.go                 | 2 +-
 5 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/config/README.md b/config/README.md
index 45abf23f..a97812ae 100644
--- a/config/README.md
+++ b/config/README.md
@@ -40,6 +40,8 @@ max_error_reason_size: <byte_size>
 connection_pool:
   max_idle_conns: 100
   max_idle_conns_per_host: 2
+  # Connection idle timeout must be < Clickhouse `keep_alive_timeout`.
+  idle_conn_timeout: 9
 
 server:
   <server_config> [optional]
diff --git a/config/config.go b/config/config.go
index a8f94c4e..c7aa4ac3 100644
--- a/config/config.go
+++ b/config/config.go
@@ -42,6 +42,7 @@ var (
 	defaultConnectionPool = ConnectionPool{
 		MaxIdleConns:        100,
 		MaxIdleConnsPerHost: 2,
+		IdleConnTimeout:     Duration(9 * time.Second),
 	}
 
 	defaultExecutionTime = Duration(120 * time.Second)
@@ -1062,6 +1063,10 @@ type ConnectionPool struct {
 	// Maximum number of idle connections between chproxy and particuler ClickHouse instance
 	MaxIdleConnsPerHost int `yaml:"max_idle_conns_per_host,omitempty"`
 
+	// Time that an idle connection is kept in the pool before being discarded.
+	// Should be set below the ClickHouse server's keep_alive_timeout.
+	IdleConnTimeout Duration `yaml:"idle_conn_timeout,omitempty"`
+
 	// Catches all undefined fields
 	XXX map[string]interface{} `yaml:",inline"`
 }
diff --git a/config/config_test.go b/config/config_test.go
index 76c1e233..320ebdfb 100644
--- a/config/config_test.go
+++ b/config/config_test.go
@@ -219,6 +219,7 @@ var fullConfig = Config{
 	ConnectionPool: ConnectionPool{
 		MaxIdleConns:        100,
 		MaxIdleConnsPerHost: 2,
+		IdleConnTimeout:     Duration(9 * time.Second),
 	},
 
 	Users: []User{
@@ -946,6 +947,7 @@ param_groups:
 connection_pool:
   max_idle_conns: 100
   max_idle_conns_per_host: 2
+  idle_conn_timeout: 9s
 `, redisPort)
 	tested := fullConfig.String()
 	if tested != expected {
diff --git a/config/testdata/full.yml b/config/testdata/full.yml
index 020a5d9f..8c8b4193 100644
--- a/config/testdata/full.yml
+++ b/config/testdata/full.yml
@@ -111,6 +111,10 @@ connection_pool:
   # Number of connections per ClickHouse host to keep open
   # when they are not needed for clients.
   max_idle_conns_per_host: 2
+  # Idle Timeout For Connections To Clickhouse. This value must be < the Clickhouse
+  # `keep_alive_timeout` to prevent graceful disconnection race-conditions that can
+  # result in Bad Gateway (unable to reach host errors)
+  idle_conn_timeout: 9s
 
 # Settings for `chproxy` input interfaces.
 server:
diff --git a/proxy.go b/proxy.go
index 72ec90bb..0eaa0ccf 100644
--- a/proxy.go
+++ b/proxy.go
@@ -62,7 +62,7 @@ func newReverseProxy(cfgCp *config.ConnectionPool) *reverseProxy {
 		ForceAttemptHTTP2:     true,
 		MaxIdleConns:          cfgCp.MaxIdleConns,
 		MaxIdleConnsPerHost:   cfgCp.MaxIdleConnsPerHost,
-		IdleConnTimeout:       90 * time.Second,
+		IdleConnTimeout:       time.Duration(cfgCp.IdleConnTimeout),
 		TLSHandshakeTimeout:   10 * time.Second,
 		ExpectContinueTimeout: 1 * time.Second,
 	}