Reconnect clients lazily on proxy switch once we receive another message from them and drop them if they don't disconnect on their own within a minute

src/stratifier.c

@@ -254,6 +254,9 @@ struct stratum_instance {
 			 * or other problem and should be dropped lazily if
 			 * this is set to 2 */
 
+	bool reconnect; /* Do we need to send this client a reconnect message */
+	time_t reconnect_request; /* The time we sent a reconnect message */
+
 	user_instance_t *user_instance;
 	worker_instance_t *worker_instance;
 
@@ -1011,7 +1014,19 @@ static proxy_t *proxy_by_id(sdata_t *sdata, const int id)
 	return proxy;
 }
 
-static void reconnect_clients(sdata_t *sdata, const char *cmd);
+/* Iterates over all clients and sets the reconnect bool for the message
+ * to be sent lazily next time they speak to us. */
+static void reconnect_clients(sdata_t *sdata)
+{
+	stratum_instance_t *client, *tmp;
+
+	ck_rlock(&sdata->instance_lock);
+	HASH_ITER(hh, sdata->stratum_instances, client, tmp) {
+		client->reconnect = true;
+	}
+	ck_runlock(&sdata->instance_lock);
+}
+
 static void _update_notify(ckpool_t *ckp, const int id);
 
 static proxy_t *current_proxy(sdata_t *sdata)
@@ -1093,7 +1108,7 @@ static void update_subscribe(ckpool_t *ckp, const char *cmd)
 	/* Notify implied required now too */
 	_update_notify(ckp, id);
 	if (reconnect)
-		reconnect_clients(sdata, "");
+		reconnect_clients(sdata);
 }
 
 static void update_diff(ckpool_t *ckp);
@@ -1576,7 +1591,7 @@ static void stratum_broadcast_message(sdata_t *sdata, const char *msg)
 
 /* Send a generic reconnect to all clients without parameters to make them
  * reconnect to the same server. */
-static void reconnect_clients(sdata_t *sdata, const char *cmd)
+static void request_reconnect(sdata_t *sdata, const char *cmd)
 {
 	char *port = strdupa(cmd), *url = NULL;
 	stratum_instance_t *client, *tmp;
@@ -1825,7 +1840,7 @@ static void set_proxy(ckpool_t *ckp, sdata_t *sdata, const char *buf)
 	mutex_unlock(&sdata->proxy_lock);
 
 	_update_notify(ckp, id);
-	reconnect_clients(sdata, "");
+	reconnect_clients(sdata);
 }
 
 static int stratum_loop(ckpool_t *ckp, proc_instance_t *pi)
@@ -1933,7 +1948,7 @@ retry:
 	} else if (cmdmatch(buf, "noblock")) {
 		block_reject(sdata, buf + 8);
 	} else if (cmdmatch(buf, "reconnect")) {
-		reconnect_clients(sdata, buf);
+		request_reconnect(sdata, buf);
 	} else if (cmdmatch(buf, "proxy")) {
 		set_proxy(ckp, sdata, buf);
 	} else if (cmdmatch(buf, "loglevel")) {
@@ -3513,16 +3528,14 @@ static void free_smsg(smsg_t *msg)
 }
 
 /* Entered with client holding ref count */
-static void parse_instance_msg(sdata_t *sdata, smsg_t *msg, stratum_instance_t *client)
+static void parse_instance_msg(ckpool_t *ckp, sdata_t *sdata, smsg_t *msg, stratum_instance_t *client)
 {
 	json_t *val = msg->json_msg, *id_val, *method, *params;
 	int64_t client_id = msg->client_id;
-	char buf[256];
 
-	if (unlikely(client->reject == 2)) {
+	if (client->reject == 2 || (client->reconnect_request && time(NULL) - client->reconnect_request > 60)) {
 		LOGINFO("Dropping client %"PRId64" tagged for lazy invalidation", client_id);
-		snprintf(buf, 255, "dropclient=%"PRId64, client_id);
-		send_proc(client->ckp->connector, buf);
+		connector_drop_client(ckp, client_id);
 		goto out;
 	}
 
@@ -3557,6 +3570,20 @@ out:
 	free_smsg(msg);
 }
 
+/* Send a single client a reconnect request, setting the time we sent the
+ * request so we can drop the client lazily if it hasn't reconnected on its
+ * own one minute later */
+static void reconnect_client(sdata_t *sdata, stratum_instance_t *client)
+{
+	json_t *json_msg;
+
+	client->reconnect = false;
+	client->reconnect_request = time(NULL);
+	JSON_CPACK(json_msg, "{sosss[]}", "id", json_null(), "method", "client.reconnect",
+		   "params");
+	stratum_add_send(sdata, json_msg, client->id);
+}
+
 static void srecv_process(ckpool_t *ckp, char *buf)
 {
 	bool noid = false, dropped = false;
@@ -3633,7 +3660,11 @@ static void srecv_process(ckpool_t *ckp, char *buf)
 	if (unlikely(noid))
 		LOGINFO("Stratifier added instance %"PRId64" server %d", client->id, server);
 
-	parse_instance_msg(sdata, msg, client);
+	parse_instance_msg(ckp, sdata, msg, client);
+	/* The client is still active but has been issued a reconnect request
+	 * so use this opportunity to send it a reconnect message */
+	if (unlikely(client->reconnect))
+		reconnect_client(sdata, client);
 	dec_instance_ref(sdata, client);
 out:
 	free(buf);