Send a heartbeat every second to ckdb to allow ckdb to send information not specifically requested while maintaining ckpool msg-response relationship. Do not send heartbeats if there are messages queued already for when ckdb is offline/busy.

src/stratifier.c

@@ -296,6 +296,7 @@ static int gen_priority;
 #define ID_USERSTATS 6
 #define ID_BLOCK 7
 #define ID_ADDRAUTH 8
+#define ID_HEARTBEAT 9
 
 static const char *ckdb_ids[] = {
 	"authorise",
@@ -307,6 +308,7 @@ static const char *ckdb_ids[] = {
 	"userstats",
 	"block",
 	"addrauth",
+	"heartbeat"
 };
 
 static void generate_coinbase(ckpool_t *ckp, workbase_t *wb)
@@ -1540,8 +1542,9 @@ static int send_recv_auth(stratum_instance_t *client)
 
 	free(json_msg);
 	if (likely(buf)) {
-		char *secondaryuserid, *response = alloca(128);
+		char *secondaryuserid, response[PAGESIZE] = {};
 
+		LOGINFO("Got ckdb response: %s", buf);
 		sscanf(buf, "id.%*d.%s", response);
 		secondaryuserid = response;
 		strsep(&secondaryuserid, ".");
@@ -2554,8 +2557,18 @@ static void ckdbq_process(ckpool_t *ckp, char *msg)
 		failed = false;
 		LOGWARNING("Successfully resumed talking to ckdb");
 	}
-	LOGINFO("Got ckdb response: %s", buf);
+	/* TODO: Process any requests from ckdb that are heartbeat responses
-	free(buf);
+	 * with specific requests. */
+	if (likely(buf)) {
+		char response[PAGESIZE] = {};
+
+		sscanf(buf, "id.%*d.%s", response);
+		if (safecmp(response, "ok"))
+			LOGINFO("Got ckdb response: %s", buf);
+		else
+			LOGWARNING("Got failed ckdb response: %s", buf);
+		free(buf);
+	}
 }
 
 static int transactions_by_jobid(int64_t id)
@@ -2935,9 +2948,41 @@ static void *statsupdate(void *arg)
 	return NULL;
 }
 
+/* Sends a heartbeat to ckdb every second to maintain the relationship of
+ * ckpool always initiating a request -> getting a ckdb response, but allows
+ * ckdb to provide specific commands to ckpool. */
+static void *ckdb_heartbeat(void *arg)
+{
+	ckpool_t *ckp = (ckpool_t *)arg;
+
+	pthread_detach(pthread_self());
+	rename_proc("heartbeat");
+
+	while (42) {
+		char cdfield[64];
+		ts_t ts_now;
+		json_t *val;
+
+		cksleep_ms(1000);
+		if (unlikely(!ckmsgq_empty(ckdbq))) {
+			LOGDEBUG("Witholding heartbeat due to ckdb messages being queued");
+			continue;
+		}
+		ts_realtime(&ts_now);
+		sprintf(cdfield, "%lu,%lu", ts_now.tv_sec, ts_now.tv_nsec);
+		JSON_CPACK(val, "{ss,ss,ss,ss}",
+				"createdate", cdfield,
+				"createby", "code",
+				"createcode", __func__,
+				"createinet", ckp->serverurl);
+		ckdbq_add(ckp, ID_HEARTBEAT, val);
+	}
+	return NULL;
+}
+
 int stratifier(proc_instance_t *pi)
 {
-	pthread_t pth_blockupdate, pth_statsupdate;
+	pthread_t pth_blockupdate, pth_statsupdate, pth_heartbeat;
 	ckpool_t *ckp = pi->ckp;
 	int ret = 1;
 	char *buf;
@@ -2987,6 +3032,8 @@ int stratifier(proc_instance_t *pi)
 	sauthq = create_ckmsgq(ckp, "authoriser", &sauth_process);
 	ckdbq = create_ckmsgq(ckp, "ckdbqueue", &ckdbq_process);
 	stxnq = create_ckmsgq(ckp, "stxnq", &send_transactions);
+	if (!ckp->standalone)
+		create_pthread(&pth_heartbeat, ckdb_heartbeat, ckp);
 
 	cklock_init(&workbase_lock);
 	if (!ckp->proxy)