From 9ee4b716516b685f0ea9e1d35e7f31c64c806a79 Mon Sep 17 00:00:00 2001
From: adaxi <dev@adaxisoft.be>
Date: Sun, 18 Feb 2018 22:08:01 +0100
Subject: [PATCH 1/3] Send an email when not able to get last block header

---
 lib/worker.js | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/lib/worker.js b/lib/worker.js
index cb0b499..0aec1ce 100644
--- a/lib/worker.js
+++ b/lib/worker.js
@@ -521,6 +521,30 @@ function monitorNodes() {
     });
 }
 
+function monitorNodes() {
+    global.coinFuncs.getLastBlockHeader((err, block) => {
+        if (err !== null) {
+            return global.support.sendEmail(
+                global.config.general.adminEmail,
+                'Failed to query daemon for last block header',
+                `The worker failed to return last block header. Please verify if the daemon is running properly.`
+            );
+        }
+        const sql = 'SELECT blockID, hostname, ip FROM pools WHERE last_checkin > DATE_SUB(NOW(), INTERVAL 30 MINUTE)';
+        global.mysql.query(sql).then(pools => {
+            pools.forEach(({ blockID, hostname, ip }) => {
+                if (blockID < block.height - 3) {
+                    global.support.sendEmail(
+                        global.config.general.adminEmail,
+                        'Pool server is behind in blocks',
+                        `The pool server: ${hostname} with IP: ${ip} is ${(block.height - blockID)} blocks behind.`
+                    );
+                }
+            })
+        });
+    });
+}
+
 updateShareStats();
 updateBlockHeader();
 updatePoolStats();

From 308f2f01353bc8d08f87a34214b297d49d38aeb9 Mon Sep 17 00:00:00 2001
From: adaxi <dev@adaxisoft.be>
Date: Sun, 18 Feb 2018 22:08:59 +0100
Subject: [PATCH 2/3] Remove old function

---
 lib/worker.js | 17 -----------------
 1 file changed, 17 deletions(-)

diff --git a/lib/worker.js b/lib/worker.js
index 0aec1ce..0723bc0 100644
--- a/lib/worker.js
+++ b/lib/worker.js
@@ -504,23 +504,6 @@ function updateWalletStats() {
 
 }
 
-function monitorNodes() {
-    global.mysql.query("SELECT blockID, hostname, ip FROM pools WHERE last_checkin > date_sub(now(), interval 30 minute)").then(function (rows) {
-        global.coinFuncs.getLastBlockHeader(function (err, block) {
-            if (err !== null){
-                console.error("Issue in getting block header.  Skipping node monitor");
-                return;
-            }
-            rows.forEach(function (row) {
-                    if (row.blockID < block.height - 3) {
-                        global.support.sendEmail(global.config.general.adminEmail, "Pool server behind in blocks", "The pool server: "+row.hostname+" with IP: "+row.ip+" is "+(block.height - row.blockID)+ " blocks behind");
-                    }
-                }
-            );
-        });
-    });
-}
-
 function monitorNodes() {
     global.coinFuncs.getLastBlockHeader((err, block) => {
         if (err !== null) {

From 774a5254cc4f57a26a8e450e17886935709c2190 Mon Sep 17 00:00:00 2001
From: adaxi <dev@adaxisoft.be>
Date: Sun, 18 Feb 2018 22:33:23 +0100
Subject: [PATCH 3/3] Avoid spamming the administrator when the daemon is
 stuck.

---
 lib/worker.js | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/lib/worker.js b/lib/worker.js
index 0723bc0..1a0e545 100644
--- a/lib/worker.js
+++ b/lib/worker.js
@@ -504,13 +504,27 @@ function updateWalletStats() {
 
 }
 
+let lastBlockCheckIsOk = true;
 function monitorNodes() {
     global.coinFuncs.getLastBlockHeader((err, block) => {
         if (err !== null) {
-            return global.support.sendEmail(
+            if (lastBlockCheckIsOk) {
+                lastBlockCheckIsOk = false;
+                global.support.sendEmail(
+                    global.config.general.adminEmail,
+                    'Failed to query daemon for last block header',
+                    `The worker failed to return last block header. Please verify if the daemon is running properly.`
+                );
+            }
+            return
+        }
+        if (!lastBlockCheckIsOk) {
+            lastBlockCheckIsOk = true;
+            global.support.sendEmail(
                 global.config.general.adminEmail,
-                'Failed to query daemon for last block header',
-                `The worker failed to return last block header. Please verify if the daemon is running properly.`
+                'Quering daemon for last block header is back to normal',
+                `An warning was sent to you indicating that the the worker failed to return the last block header.
+                 The issue seems to be solved now.`
             );
         }
         const sql = 'SELECT blockID, hostname, ip FROM pools WHERE last_checkin > DATE_SUB(NOW(), INTERVAL 30 MINUTE)';
@@ -525,6 +539,7 @@ function monitorNodes() {
                 }
             })
         });
+        
     });
 }