[v7.5.x] Datasource: Allow configuring MaxConnsPerHost (#35519)

Allow configuring MaxConnsPerHost for HTTP data sources.

Ref #35321 
Ref #35257

conf/defaults.ini

@@ -155,6 +155,11 @@ tls_handshake_timeout_seconds = 10
 # waiting for the server to approve.
 expect_continue_timeout_seconds = 1
 
+# Optionally limits the total number of connections per host, including connections in the dialing,
+# active, and idle states. On limit violation, dials will block.
+# A value of zero (0) means no limit.
+max_conns_per_host = 0
+
 # The maximum number of idle connections that Grafana will keep alive.
 max_idle_connections = 100
 

conf/sample.ini

@@ -161,6 +161,11 @@
 # waiting for the server to approve.
 ;expect_continue_timeout_seconds = 1
 
+# Optionally limits the total number of connections per host, including connections in the dialing,
+# active, and idle states. On limit violation, dials will block.
+# A value of zero (0) means no limit.
+;max_conns_per_host = 0
+
 # The maximum number of idle connections that Grafana will keep alive.
 ;max_idle_connections = 100
 

docs/sources/administration/configuration.md

@@ -414,6 +414,11 @@ The length of time that Grafana will wait for a successful TLS handshake with th
 
 The length of time that Grafana will wait for a datasource’s first response headers after fully writing the request headers, if the request has an “Expect: 100-continue” header. A value of `0` will result in the body being sent immediately. Default is `1` second. For more details check the [Transport.ExpectContinueTimeout](https://golang.org/pkg/net/http/#Transport.ExpectContinueTimeout) documentation.
 
+### max_conns_per_host
+
+Optionally limits the total number of connections per host, including connections in the dialing, active, and idle states. On limit violation, dials are blocked. A value of `0` means that there are no limits. Default is `0`.
+For more details check the [Transport.MaxConnsPerHost](https://golang.org/pkg/net/http/#Transport.MaxConnsPerHost) documentation.
+
 ### max_idle_connections
 
 The maximum number of idle connections that Grafana will maintain. Default is `100`. For more details check the [Transport.MaxIdleConns](https://golang.org/pkg/net/http/#Transport.MaxIdleConns) documentation.

pkg/models/datasource_cache.go

@@ -167,7 +167,8 @@ func (ds *DataSource) GetHttpTransport() (*dataSourceTransport, error) {
 		TLSHandshakeTimeout:   time.Duration(setting.DataProxyTLSHandshakeTimeout) * time.Second,
 		ExpectContinueTimeout: time.Duration(setting.DataProxyExpectContinueTimeout) * time.Second,
 		MaxIdleConns:          setting.DataProxyMaxIdleConns,
-		MaxConnsPerHost:       setting.DataProxyMaxIdleConnsPerHost,
+		MaxConnsPerHost:       setting.DataProxyMaxConnsPerHost,
+		MaxIdleConnsPerHost:   setting.DataProxyMaxIdleConnsPerHost,
 		IdleConnTimeout:       time.Duration(setting.DataProxyIdleConnTimeout) * time.Second,
 	}
 

pkg/setting/setting.go

@@ -82,6 +82,7 @@ var (
 	DataProxyTimeout               int
 	DataProxyTLSHandshakeTimeout   int
 	DataProxyExpectContinueTimeout int
+	DataProxyMaxConnsPerHost       int
 	DataProxyMaxIdleConns          int
 	DataProxyMaxIdleConnsPerHost   int
 	DataProxyKeepAlive             int
@@ -809,6 +810,7 @@ func (cfg *Cfg) Load(args *CommandLineArgs) error {
 	DataProxyKeepAlive = dataproxy.Key("keep_alive_seconds").MustInt(30)
 	DataProxyTLSHandshakeTimeout = dataproxy.Key("tls_handshake_timeout_seconds").MustInt(10)
 	DataProxyExpectContinueTimeout = dataproxy.Key("expect_continue_timeout_seconds").MustInt(1)
+	DataProxyMaxConnsPerHost = dataproxy.Key("max_conns_per_host").MustInt(0)
 	DataProxyMaxIdleConns = dataproxy.Key("max_idle_connections").MustInt(100)
 	DataProxyMaxIdleConnsPerHost = dataproxy.Key("max_idle_connections_per_host").MustInt(2)
 	DataProxyIdleConnTimeout = dataproxy.Key("idle_conn_timeout_seconds").MustInt(90)