fix: keep connections open

src/client.rs

@@ -69,14 +69,20 @@ pub struct ClientConfig {
     pub request_timeout_secs: Option<u64>,
     /// The timeout for idle sockets being kept alive
     pub pool_idle_timeout_secs: Option<u64>,
+    pub http2_keep_alive_interval_secs: Option<u64>,
+    pub http2_keep_alive_while_idle: bool,
 }
 
 impl Default for ClientConfig {
     fn default() -> Self {
         Self {
             endpoint: Endpoint::Production,
             request_timeout_secs: Some(DEFAULT_REQUEST_TIMEOUT_SECS),
-            pool_idle_timeout_secs: Some(600),
+            pool_idle_timeout_secs: None,
+            // Send HTTP/2 PING every 1 hour as per: https://developer.apple.com/documentation/usernotifications/sending-notification-requests-to-apns#Follow-best-practices-while-sending-push-notifications-with-APNs
+            // Reuse a connection as long as possible. In most cases, you can reuse a connection for many hours to days. If your connection is mostly idle, you may send a HTTP2 PING frame after an hour of inactivity. Reusing a connection often results in less bandwidth and CPU consumption.
+            http2_keep_alive_interval_secs: Some(60 * 60),
+            http2_keep_alive_while_idle: true,
         }
     }
 }
@@ -130,13 +136,17 @@ impl ClientBuilder {
                     endpoint,
                     request_timeout_secs,
                     pool_idle_timeout_secs,
+                    http2_keep_alive_interval_secs,
+                    http2_keep_alive_while_idle,
                 },
             signer,
             connector,
         } = self;
         let http_client = HttpClient::builder(TokioExecutor::new())
             .pool_idle_timeout(pool_idle_timeout_secs.map(Duration::from_secs))
             .http2_only(true)
+            .http2_keep_alive_interval(http2_keep_alive_interval_secs.map(Duration::from_secs))
+            .http2_keep_alive_while_idle(http2_keep_alive_while_idle)
             .build(connector.unwrap_or_else(default_connector));
 
         Client {