PRTG Manual: MQTT Subscribe Custom Sensor
This sensor is in beta status. The operating methods and the available settings can change at any time. Do not expect that all functions work properly, or that this sensor works as expected at all. Be aware that this sensor can be removed from PRTG at any time.
The MQTT Subscribe Custom sensor subscribes to a Message Queue Telemetry Transport (MQTT) topic and monitors up to five numeric values from the received JavaScript Object Notation (JSON) data.
The sensor can show the following:
- Numeric values returned by received JSON data
- This sensor requires MQTT credentials in the settings of the parent device.
- This sensor supports the IPv6 protocol.
- This sensor has a medium performance impact.
The Add Sensor dialog appears when you manually add a new sensor to a device. It only shows the setting fields that are required for creating the sensor. Therefore, you do not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.
The following settings in the Add Sensor dialog differ in comparison to the sensor's Settings tab.
Setting |
Description |
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Channel #1 - #5 Name |
Enter a meaningful name to identify the channel. Once you have created the sensor, you can change the name of the channel in the Channel Settings under Name. |
Channel #1 - #5 Unit |
Enter the unit for the numeric value that this sensor monitors. Once you have created the sensor, you can change the unit in the Channel Settings under Unit. |
Channel #1 - #5 |
You can create up to 5 different channels for this sensor. You have to define at least one data channel, so you see all available settings for Channel #1 without manually enabling it. Additionally, you can define Channel #2 up to Channel #5. To do so, choose between:
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Click the Settings tab of a sensor to change its settings.
Usually, a sensor connects to the IP Address or DNS Name of the parent device on which you created the sensor. See the device settings for details. For some sensors, you can explicitly define the monitoring target in the sensor settings. See below for details on available settings.
Setting |
Description |
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Sensor Name |
Enter a meaningful name to identify the sensor. By default, PRTG shows this name in the device tree, as well as in alarms, logs, notifications, reports, maps, libraries, and tickets.
|
Parent Tags |
Shows tags that the sensor inherits from its parent device, parent group, and parent probe. This setting is shown for your information only and cannot be changed here. |
Tags |
Enter one or more tags. Confirm each tag with the Spacebar key, a comma, or the Enter key. You can use tags to group objects and use tag-filtered views later on. Tags are not case-sensitive. Tags are automatically inherited.
The sensor has the following default tags that are automatically predefined in the sensor's settings when you add the sensor:
|
Priority |
Select a priority for the sensor. This setting determines the position of the sensor in lists. The highest priority is at the top of a list. Choose from the lowest priority ( |
Setting |
Description |
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Topic |
Enter the topic that you want to monitor. |
Channel #x JSONPath |
Enter the path to the numeric value in the received JSON structure that you want to monitor.
{ To query temperature, enter the following JSONPath: $.Sensor1.Temp To query humidity, enter the following JSONPath: $.Sensor2.Humidity |
Channel #2 - #5 |
This setting shows the option you selected for this channel in the Add Sensor dialog, Enable or Disable (default). If you created this channel, you can define the settings of this channel as described above. You can select Disable (default) if you no longer need the according channels. You can still see the channels, but they do not receive data anymore. |
Port |
Enter the port number for MQTT connections. The default port for unsecure connections is 1883 and the default port for secure connections is 8883. |
Setting |
Description |
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Primary Channel |
Select a channel from the list to define it as the primary channel. In the device tree, the last value of the primary channel is always displayed below the sensor's name. The available options depend on what channels are available for this sensor.
|
Graph Type |
Define how different channels are shown for this sensor:
|
Stack Unit |
This setting is only visible if you enable Stack channels on top of each other as Graph Type. Select a unit from the list. All channels with this unit are stacked on top of each other. By default, you cannot exclude single channels from stacking if they use the selected unit. However, there is an advanced procedure to do so. |
Setting |
Description |
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Result Handling |
Define what PRTG does with the sensor result:
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By default, all of the following settings are inherited from objects that are higher in the hierarchy. You should change them centrally in the root group settings if necessary. To change a setting for this object only, click under the corresponding setting name to disable the inheritance. You then see the options described below.
For more information, see section Inheritance of Settings.
Click to interrupt the inheritance.
Setting |
Description |
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Scanning Interval |
Select a scanning interval from the dropdown list. The scanning interval determines the amount of time that the sensor waits between two scans. Choose from:
|
If a Sensor Query Fails |
Select the number of scanning intervals that the sensor has time to reach and to check a device again if a sensor query fails. Depending on the option that you select, the sensor can try to reach and to check a device again several times before the sensor shows the Down status. This can avoid false alarms if the monitored device only has temporary issues. For previous scanning intervals with failed requests, the sensor shows the Warning status. Choose from:
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Schedules, Dependencies, and Maintenance Window
You cannot interrupt the inheritance for schedules, dependencies, and maintenance windows. The corresponding settings from the parent objects are always active. However, you can define additional schedules, dependencies, and maintenance windows. They are active at the same time as the parent objects' settings.
Setting |
Description |
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Schedule |
Select a schedule from the list. You can use schedules to monitor during a certain time span (days or hours) every week. Choose from:
|
Maintenance Window |
Select if you want to set up a one-time maintenance window. During a maintenance window, monitoring stops for the selected object and all child objects. They show the Paused status instead. Choose between:
|
Maintenance Begins |
This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the start date and time of the one-time maintenance window. |
Maintenance Ends |
This setting is only visible if you enable Set up a one-time maintenance window above. Use the date time picker to enter the end date and time of the one-time maintenance window. |
Dependency Type |
Select a dependency type. You can use dependencies to pause monitoring for an object depending on the status of a different object. You can choose from:
|
Dependency |
This setting is only visible if you enable Select a sensor above. Click |
Dependency Delay (Sec.) |
This setting is only visible if you enable Select a sensor above. Define a time span in seconds for the dependency delay. After the master sensor for this dependency returns to the Up status, PRTG additionally delays the monitoring of the dependent objects by the time span you define. This can prevent false alarms, for example, after a server restart or to give systems more time for all services to start. Enter an integer value.
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Click to interrupt the inheritance.
Setting |
Description |
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User Group Access |
Define the user groups that have access to the sensor. You see a table with user groups and group access rights. The table contains all user groups in your setup. For each user group, you can choose from the following group access rights:
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Click to interrupt the inheritance.
Setting |
Description |
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Channel Unit Types |
For each type of channel, select the unit in which PRTG displays the data. If you define this setting on probe, group, or device level, these settings can be inherited to all sensors underneath. You can set units for the following channel types (if available):
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For more information about sensor settings, see the following sections: