diff --git a/addons/monitoring/README.md b/addons/monitoring/README.md
new file mode 100644
index 00000000..ffdb9e21
--- /dev/null
+++ b/addons/monitoring/README.md
@@ -0,0 +1,51 @@
+# Database Monitoring Add-On
+## Purpose
+The add-on tracks database connection usage and sends an email alert when usage reaches 70% of `max_connections`. Alerts are stateful (sent once per state change) to avoid spam. Emails include detailed metrics.
+
+## Key features
+- Monitors connection usage (Usage = Threads / max_connections).
+- Stateful notifications (one email per state change):
+  - `OK` — Usage < 70% (back to normal).
+  - `THRESHOLD` — Usage ≥ 70% (threshold exceeded).
+  - `STATUS_ERROR` — failed to get `mysqladmin status`.
+  - `MAXCONN_ERROR` — failed to get `max_connections` (`SHOW VARIABLES`).
+- Metrics from `mysqladmin status` and `SHOW VARIABLES LIKE 'max_connections'`.
+- Configurable schedule (Quartz cron) via add-on settings: 5, 10, 15, 20, 30, 40, 50 minutes.
+- Runs on all `sqldb` nodes (group execution).
+
+## How it works
+1. Install:
+   - Downloads `/usr/local/sbin/db-monitoring.sh` to all `sqldb` nodes.
+   - Creates a runner script `db-monitoring.js` that invokes the shell script on the `sqldb` group, passing `USER_SESSION` and `USER_EMAIL`.
+   - Installs a system cron job `/etc/cron.d/db-monitoring` and sets interval via `setSchedulerInterval` (every `N` minutes): `*/N * * * * root /usr/local/sbin/db-monitoring.sh check`.
+2. Runtime:
+   - Reads DB credentials from `/.jelenv`: `REPLICA_USER`/`REPLICA_PSWD`.
+   - Collects metrics: `mysqladmin status` and `SHOW VARIABLES LIKE 'max_connections'`.
+   - Calculates usage and determines state (OK/THRESHOLD/ERROR).
+   - Stores the last state in `/var/tmp/db-monitoring.status` and sends email only on state changes.
+   - On state change, triggers platform event `onCustomNodeEvent [name:executeScript]`, which calls the runner script and sends the email.
+   - Logs to `/var/log/db-monitoring.log`.
+
+## Email content and metrics
+Emails are HTML with bold labels and `<br/>` line breaks. Included:
+- Status:
+  - Uptime — node uptime (days/hours/minutes).
+  - Threads — current number of active connections.
+  - Slow queries — number of slow queries.
+  - Open tables — tables currently open.
+  - Queries per second avg — average queries per second since start.
+- max_connections — maximum concurrent connections.
+- Current threads (connections) — current connections count.
+- Usage — share of used connections (percent).
+- Timestamp — report time.
+
+## Logs and artifacts
+- Monitoring log: `/var/log/db-monitoring.log` (start/finish, email send, errors).
+- State file: `/var/tmp/db-monitoring.status` (last state to suppress duplicate emails).
+- Cron: `/etc/cron.d/db-monitoring` (interval managed by the add-on).
+
+## Configuration
+- Monitoring interval is controlled in the add-on settings (5/10/15/20/30/40/50 minutes).
+- The add-on updates cron with `setSchedulerInterval` to `*/N * * * *`.
+- Email sending uses platform messaging API and requires valid `session` and `userEmail`, which are passed by the add-on during event handling.
+
diff --git a/addons/monitoring/manifest.yml b/addons/monitoring/manifest.yml
new file mode 100644
index 00000000..52e0d6ce
--- /dev/null
+++ b/addons/monitoring/manifest.yml
@@ -0,0 +1,154 @@
+type: update
+name: Database Monitoring
+id: db-monitoring
+
+description:
+  text:  The Database Monitoring add-on tracks MySQL/MariaDB/Percona connection usage and sends single-on-state-change email alerts. It periodically collects mysqladmin status and max_connections, alerts when usage reaches 70%, and includes detailed metrics with human‑readable uptime. The check runs online without stopping database services and supports configurable intervals.
+  short: Email alerts for DB connection usage with detailed metrics.
+
+logo: /images/database-monitoring.png
+
+baseUrl: https://raw.githubusercontent.com/sych74/mysql-cluster/JE-66040/addons/monitoring
+
+mixins:
+  - https://cdn.jsdelivr.net/gh/jelastic-jps/mysql-cluster@3.0.0/scripts/common.yml
+
+targetNodes:
+  nodeType:
+    - mysql
+    - mariadb-dockerized
+    - mariadb
+    - perconadb
+
+settings:
+  main:
+    submitUnchanged: true
+    fields:
+      - name: monitorInterval
+        caption: Monitoring interval
+        type: list
+        editable: false
+        values:
+          - value: 5
+            caption: Every 5 minutes
+          - value: 10
+            caption: Every 10 minutes
+          - value: 15
+            caption: Every 15 minutes
+          - value: 20
+            caption: Every 20 minutes
+          - value: 30
+            caption: Every 30 minutes
+          - value: 40
+            caption: Every 40 minutes
+          - value: 50
+            caption: Every 50 minutes
+        default: 10
+
+      - name: user
+        caption: DB User
+        type: string
+        required: true
+      - name: password
+        caption: DB Password
+        type: string
+        inputType: password
+        required: true
+
+buttons:
+  - name: Configure
+    caption: Configure
+    action: configure
+    settings: main
+    loadingText: Configuring...
+    successText: The monitoring configs have been updated successfully.
+
+globals:
+  scriptSufix: db-monitoring
+  scriptName: ${env.name}-${globals.scriptSufix}
+  random: ${fn.random}
+
+onAfterClone:
+  install: ${baseUrl}/manifest.yml?_r=${fn.random}
+  envName: ${event.response.env.envName}
+  nodeGroup: ${targetNodes.nodeGroup}
+  settings:
+    install: true
+    monitorInterval: ${settings.monitorInterval}
+
+onInstall:
+  - getReplicaUser
+  - downloadScripts
+  - createScript
+  - setSchedulerInterval
+
+onUninstall:
+  - cleanupMonitoring
+
+onBeforeDelete:
+  - cleanupMonitoring
+
+onCustomNodeEvent [name:executeScript]:
+  script: |
+    let URL = "${platformUrl}${globals.scriptName}?appid=" + appid + "&token=${globals.random}&envName=${env.name}&uid=${user.uid}&session=" + session + "&userEmail=${user.email}";
+    let Transport = com.hivext.api.core.utils.Transport;
+      resp = new Transport().get(URL);
+      resp = JSON.parse(resp);
+      if (resp.response && resp.response != 0) {
+        return new Transport().get("${platformUrl}/1.0/environment/jerror/rest/jerror?appid=" + appid + "&actionname=db-monitoring&callparameters=" + URL + "&email=${user.email}&errorcode=4121&errormessage=" + encodeURIComponent(resp.response.message) + "&priority=high");
+      }
+      return { result: 0 }
+
+actions:
+  
+  downloadScripts:
+    - cmd[sqldb]: |-
+        curl -fsSL ${baseUrl}/scripts/db-monitoring.sh -o /usr/local/sbin/db-monitoring.sh
+        chmod +x /usr/local/sbin/db-monitoring.sh
+      user: root
+
+  createScript:
+    script: |
+      let Response = com.hivext.api.Response;
+      let Transport = com.hivext.api.core.utils.Transport;
+      let StrSubstitutor = org.apache.commons.lang3.text.StrSubstitutor;
+      let scriptBody = new Transport().get("${baseUrl}/scripts/db-monitoring.js");
+      scriptBody = new StrSubstitutor({token: "${globals.random}"}, "${", "}").replace(scriptBody);
+
+      var resp = api.dev.scripting.GetScript(appid, session, "${globals.scriptName}");
+      if (resp.result == Response.OK) {
+        api.dev.scripting.DeleteScript(appid, session, "${globals.scriptName}");
+      }
+      resp = api.dev.scripting.CreateScript(appid, session, "${globals.scriptName}", "js", scriptBody);
+      if (resp.result != 0) return resp;
+      java.lang.Thread.sleep(1000);
+      resp = api.dev.scripting.Build(appid, session, "${globals.scriptName}");
+      if (resp.result != 0) return resp;
+
+      let command = "sed -ri 's|PLATFORM_DOMAIN=.*|PLATFORM_DOMAIN=\"${platformUrl}\"|g' /usr/local/sbin/db-monitoring.sh; " +
+                    "sed -ri 's|USER_SCRIPT_PATH=.*|USER_SCRIPT_PATH=\"${platformUrl}${globals.scriptName}\"|g' /usr/local/sbin/db-monitoring.sh";
+      return api.env.control.ExecCmdByGroup("${env.name}", session, "sqldb", toJSON([{ command: command }]), true, false, "root");
+  
+  setSchedulerInterval:
+    - cmd[sqldb]: bash /usr/local/sbin/db-monitoring.sh setSchedulerTimeout --interval=${settings.monitorInterval}
+      user: root
+
+  cleanupMonitoring:
+    script: |
+      let envName = "${env.name}";
+      var resp = api.dev.scripting.GetScript(appid, session, "${globals.scriptName}");
+      if (resp.result == com.hivext.api.Response.OK) {
+        api.dev.scripting.DeleteScript(appid, session, "${globals.scriptName}");
+      }
+
+      resp = api.env.control.ExecCmdByGroup(envName, session, "sqldb", toJSON([
+        {command: "rm -f /etc/cron.d/db-monitoring || true"},
+        {command: "rm -f /usr/local/sbin/db-monitoring.sh || true"},
+        {command: "systemctl reload crond || service cron reload || true"}
+      ]), true, false, "root");
+      if (resp.result != 0) return resp;
+      
+      return { result: 0 };
+
+  configure:
+    - setSchedulerInterval
\ No newline at end of file
diff --git a/addons/monitoring/scripts/db-monitoring.js b/addons/monitoring/scripts/db-monitoring.js
new file mode 100644
index 00000000..00620678
--- /dev/null
+++ b/addons/monitoring/scripts/db-monitoring.js
@@ -0,0 +1,41 @@
+//@reg(envName, token, uid)
+
+var ROOT = "root";
+var envName = getParam("envName", "${env.envName}");
+var Response = com.hivext.api.Response;
+var SQLDB = "sqldb";
+
+function run() {
+    var tokenParam = String(getParam("token", "")).replace(/\s/g, "");
+    if (!session && tokenParam != "${token}") {
+        return {
+            result: Response.PERMISSION_DENIED,
+            error: "wrong token",
+            type: "error",
+            message: "Token [" + tokenParam + "] does not match",
+            response: { result: Response.PERMISSION_DENIED }
+        };
+    }
+    var info = jelastic.env.control.GetEnvInfo(envName, session);
+    if (info.result != 0) return info;
+
+    var resp;
+    var userEmail = getParam("userEmail", "");
+    var userSession = getParam("session", session);
+    api.marketplace.console.WriteLog(appid, session, "DB Monitoring: sendEmail started for env " + envName);
+    var command = "/usr/local/sbin/db-monitoring.sh sendEmail '" + userSession + "' '" + userEmail + "'";
+
+    resp = api.env.control.ExecCmdByGroup(envName, session, SQLDB, toJSON([{ command: command }]), true, false, ROOT);
+    if (resp.result != 0) return resp;
+
+    api.marketplace.console.WriteLog(appid, session, "DB Monitoring: sendEmail completed");
+    return { result: 0 };
+}
+
+try {
+    return run();
+} catch (ex) {
+    return { result: com.hivext.api.Response.ERROR_UNKNOWN, error: "Error: " + toJSON(ex) };
+}
+
+
diff --git a/addons/monitoring/scripts/db-monitoring.sh b/addons/monitoring/scripts/db-monitoring.sh
new file mode 100644
index 00000000..4b380bf8
--- /dev/null
+++ b/addons/monitoring/scripts/db-monitoring.sh
@@ -0,0 +1,254 @@
+#!/bin/bash
+PLATFORM_DOMAIN="{PLATFORM_DOMAIN}"
+USER_SCRIPT_PATH="{URL}"
+USER_SESSION="$1"
+USER_EMAIL="$2"
+THRESHOLD=70
+MONITORING_LOG=/var/log/db-monitoring.log
+STATUS_FILE=/var/tmp/db-monitoring.status
+HOSTNAME_SHORT=$(hostname -s 2>/dev/null || hostname)
+BODY_ERROR_PREFIX="DataBase monitoring error on ${HOSTNAME_SHORT}"
+# email notification via Virtuozzo API
+function sendEmailNotification(){
+    if [ -e "/usr/lib/jelastic/modules/api.module" ]; then
+        [ -e "/var/run/jem.pid" ] && return 0
+        echo $(date) ${HOSTNAME_SHORT} "Sending e-mail notification about high DB connections usage" | tee -a $MONITORING_LOG
+        SUBJECT="${HOSTNAME_SHORT}: MySQL connections usage reached threshold"
+        BODY="$1"
+        jem api apicall -s --connect-timeout 3 --max-time 15 [API_DOMAIN]/1.0/message/email/rest/send \
+          --data-urlencode "session=$USER_SESSION" \
+          --data-urlencode "to=$USER_EMAIL" \
+          --data-urlencode "subject=$SUBJECT" \
+          --data-urlencode body@- <<< "$BODY"
+        if [[ $? != 0 ]]; then
+            echo $(date) ${HOSTNAME_SHORT} "Sending of e-mail notification failed" | tee -a $MONITORING_LOG
+        else
+            echo $(date) ${HOSTNAME_SHORT} "E-mail notification is sent successfully" | tee -a $MONITORING_LOG
+        fi
+    else
+        echo $(date) ${HOSTNAME_SHORT} "Email notification is not sent because this functionality is unavailable for current platform." | tee -a $MONITORING_LOG
+    fi
+}
+
+# trigger sendevent for onCustomNodeEvent flow
+function trigger_sendevent(){
+    echo $(date) ${HOSTNAME_SHORT} "Trigger onCustomNodeEvent 'executeScript'" | tee -a $MONITORING_LOG
+    curl -fsSL --max-time 10 --retry 1 --retry-max-time 15 \
+      --location --request POST "${PLATFORM_DOMAIN}1.0/environment/node/rest/sendevent" \
+      --data-urlencode "params={'name': 'executeScript'}" >/dev/null 2>&1
+}
+
+function get_last_status(){
+    [ -f "$STATUS_FILE" ] && cat "$STATUS_FILE" || echo ""
+}
+
+function set_status(){
+    local status="$1"
+    echo "$status" > "$STATUS_FILE"
+}
+
+# Build reusable metrics body
+function build_metrics_body(){
+    local title="$1"
+    cat <<EOF
+<div style="font-family:monospace">
+<b>Database connections ${title} on ${HOSTNAME_SHORT}</b><br/>
+<br/>
+<b>STATUS</b><br/>
+<b>Uptime:</b> $UPTIME_HUMAN<br/>
+<b>Threads:</b> $THREADS<br/>
+<b>Slow queries:</b> $SLOW<br/>
+<b>Open tables:</b> $OPEN_TABLES<br/>
+<b>Queries per second avg:</b> $QPS<br/>
+<br/>
+<b>Max connections:</b> $MAX_CONNECTIONS<br/>
+<b>Current connections:</b> $THREADS<br/>
+<b>Usage:</b> ${USAGE_PCT}%<br/>
+<b>Timestamp:</b> $(date)
+</div>
+EOF
+}
+
+function send_on_status_change(){
+    local new_status="$1"
+    local last_status="$(get_last_status)"
+    if [ "$new_status" != "$last_status" ]; then
+        trigger_sendevent
+        set_status "$new_status"
+    else
+        echo "$(date) ${HOSTNAME_SHORT} Status '$new_status' unchanged, skipping email" >> $MONITORING_LOG
+    fi
+}
+
+# credentials check and load
+function check_credentials(){
+    source "/.jelenv"
+    DB_USER="$REPLICA_USER"
+    DB_PASSWORD="$REPLICA_PSWD"
+
+    if [ -z "$DB_USER" ] || [ -z "$DB_PASSWORD" ]; then
+        BODY=$(cat <<EOF
+<div style="font-family:monospace">
+<b>${BODY_ERROR_PREFIX}</b><br/>
+<br/>
+<b>Issue:</b> Missing REPLICA_USER or REPLICA_PSWD in environment variables<br/>
+<b>Observed values:</b> REPLICA_USER='${REPLICA_USER:-EMPTY}', REPLICA_PSWD='${REPLICA_PSWD:+SET}'<br/>
+<b>Action required:</b> Populate both variables in environment variables<br/>
+<b>Timestamp:</b> $(date)
+</div>
+EOF
+)
+        echo "$BODY" >> $MONITORING_LOG
+        send_on_status_change "CREDENTIALS_MISSING" "$BODY"
+        echo "Monitoring finished at $(date)" >> $MONITORING_LOG
+        exit 1
+    fi
+}
+
+# collect DB metrics using mysqladmin and mysql client
+function collect_metrics(){
+    STATUS_RAW=$(mysqladmin status -u"$DB_USER" -p"$DB_PASSWORD" 2>&1)
+    RET=$?
+    if [ $RET -ne 0 ] || [ -z "$STATUS_RAW" ]; then
+        OUT_ESC=$(printf '%s' "$STATUS_RAW" | sed -e 's/&/\&amp;/g' -e 's/</\&lt;/g' -e 's/>/\&gt;/g' | sed ':a;N;$!ba;s/\n/<br\/>/g')
+        BODY=$(cat <<EOF
+<div style="font-family:monospace">
+<b>${BODY_ERROR_PREFIX}</b><br/>
+<br/>
+<b>Action:</b> mysqladmin status<br/>
+<b>Exit code:</b> $RET<br/>
+<b>Output:</b> $OUT_ESC<br/>
+<b>Timestamp:</b> $(date)
+</div>
+EOF
+)
+        echo "$BODY" >> $MONITORING_LOG
+        send_on_status_change "STATUS_ERROR" "$BODY"
+        echo "Monitoring finished at $(date)" >> $MONITORING_LOG
+        exit 1
+    fi
+
+    UPTIME=$(echo "$STATUS_RAW" | grep -o 'Uptime: [0-9]\+' | awk '{print $2}')
+    THREADS=$(echo "$STATUS_RAW" | grep -o 'Threads: [0-9]\+' | awk '{print $2}')
+    QUESTIONS=$(echo "$STATUS_RAW" | grep -o 'Questions: [0-9]\+' | awk '{print $2}')
+    SLOW=$(echo "$STATUS_RAW" | grep -o 'Slow queries: [0-9]\+' | awk '{print $3}')
+    OPENS=$(echo "$STATUS_RAW" | grep -o 'Opens: [0-9]\+' | awk '{print $2}')
+    FLUSHES=$(echo "$STATUS_RAW" | grep -o 'Flush tables: [0-9]\+' | awk '{print $3}')
+    OPEN_TABLES=$(echo "$STATUS_RAW" | grep -o 'Open tables: [0-9]\+' | awk '{print $3}')
+    QPS=$(echo "$STATUS_RAW" | sed -n 's/.*Queries per second avg: \([0-9.]*\).*/\1/p')
+
+    UPTIME_HUMAN="$UPTIME"
+    if [[ "$UPTIME" =~ ^[0-9]+$ ]]; then
+        D=$((UPTIME/86400))
+        H=$(((UPTIME%86400)/3600))
+        M=$(((UPTIME%3600)/60))
+        UPTIME_HUMAN="${D} days ${H} hours ${M} minutes"
+    fi
+
+    VAR_RAW=$(mysql -Nse "SHOW VARIABLES LIKE 'max_connections';" -u"$DB_USER" -p"$DB_PASSWORD" 2>&1)
+    VAR_RC=$?
+    if [ $VAR_RC -eq 0 ]; then
+        MAX_CONNECTIONS=$(echo "$VAR_RAW" | awk '{print $2}')
+    fi
+
+    if ! [[ "$MAX_CONNECTIONS" =~ ^[0-9]+$ ]]; then
+        VAR_ESC=$(printf '%s' "$VAR_RAW" | sed -e 's/&/\&amp;/g' -e 's/</\&lt;/g' -e 's/>/\&gt;/g' | sed ':a;N;$!ba;s/\n/<br\/>/g')
+        BODY=$(cat <<EOF
+<div style="font-family:monospace">
+<b>${BODY_ERROR_PREFIX}</b><br/>
+<br/>
+<b>Issue:</b> Unable to determine max_connections<br/>
+<b>mysql SHOW VARIABLES exit:</b> ${VAR_RC}<br/>
+<b>mysql SHOW VARIABLES output:</b> ${VAR_ESC}<br/>
+<b>Timestamp:</b> $(date)
+</div>
+EOF
+)
+        echo "$BODY" >> $MONITORING_LOG
+        send_on_status_change "MAXCONN_ERROR" "$BODY"
+        MAX_CONNECTIONS=0
+    fi
+
+    USAGE_PCT=0
+    if [ "$MAX_CONNECTIONS" -gt 0 ]; then
+        USAGE_PCT=$(awk -v th="$THREADS" -v max="$MAX_CONNECTIONS" 'BEGIN { if (max>0) printf("%d", (th*100)/max); else print 0 }')
+    fi
+}
+
+# cron management: add scheduler and adjust interval
+function addScheduler(){
+    local cron_file="/etc/cron.d/db-monitoring"
+    echo "*/10 * * * * root /usr/local/sbin/db-monitoring.sh check >> /var/log/db-monitoring.log 2>&1" > "$cron_file"
+    chmod 0644 "$cron_file"
+    chown root:root "$cron_file"
+    systemctl reload crond
+    echo "$(date) ${HOSTNAME_SHORT} Cron installed at $cron_file" >> $MONITORING_LOG
+}
+
+function setSchedulerInterval(){
+    local INTERVAL=10
+    for i in "$@"; do
+        case $i in
+            --interval=*)
+            INTERVAL=${i#*=}
+            shift
+            shift
+            ;;
+            *)
+            ;;
+        esac
+    done
+    local cron_file="/etc/cron.d/db-monitoring"
+    [ -f "$cron_file" ] || addScheduler
+    sed -ri "s|^[#]*[^ ]+ +\* +\* +\* +\* +root .*$|*/${INTERVAL} * * * * root /usr/local/sbin/db-monitoring.sh check >> /var/log/db-monitoring.log 2>\&1|" "$cron_file"
+    systemctl reload crond
+    echo "$(date) ${HOSTNAME_SHORT} Cron interval set to every ${INTERVAL} minutes" >> $MONITORING_LOG
+}
+
+function check(){
+    echo "Monitoring started at $(date)" >> $MONITORING_LOG
+    check_credentials
+    collect_metrics
+    if [ "$USAGE_PCT" -ge "$THRESHOLD" ]; then
+        send_on_status_change "THRESHOLD"
+    else
+        send_on_status_change "OK"
+    fi
+    echo "Monitoring finished at $(date)" >> $MONITORING_LOG
+}
+
+function sendEmail(){
+    local USER_SESSION="$1"
+    local USER_EMAIL="$2"
+    echo "Send email started at $(date)" >> $MONITORING_LOG
+    check_credentials
+    collect_metrics
+    local status="$(get_last_status)"
+    local title="usage alert"
+    if [ "$status" = "OK" ]; then
+        title="back to normal"
+    fi
+    local BODY="$(build_metrics_body "$title")"
+    sendEmailNotification "$BODY"
+    echo "Send email finished at $(date)" >> $MONITORING_LOG
+}
+
+case "$1" in
+    setSchedulerInterval)
+        shift
+        setSchedulerInterval "$@"
+        ;;
+    check)
+        check
+        ;;
+    sendEmail)
+        shift
+        sendEmail "$@"
+        ;;
+    *)
+        echo "Usage: $0 {setSchedulerInterval --interval=N|check|sendEmail USER_SESSION USER_EMAIL}" | tee -a $MONITORING_LOG
+        exit 1
+        ;;
+esac
+
+exit 0
\ No newline at end of file