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Aurelio, System Admin at Paessler AG

The HTTP Advanced sensor monitors the source code of a web page using Hypertext Transfer Protocol (HTTP). It supports authentication, content checks, and other advanced parameters.

The sensor can show the following:

  • Loading time
  • Bytes received
  • Download bandwidth (speed)
  • Time to first byte
HTTP Advanced SensorHTTP Advanced Sensor

Click here to enlarge: http://media.paessler.com/prtg-screenshots/http_advanced.png

Remarks

If you need to use SRP ciphers, please choose the "compatibility mode" in the sensor settings below.

  • Note: Bandwidth monitoring of fast internet connections may be inaccurate.

Add Sensor

The Add Sensor dialog appears when adding a new sensor to a device manually. It only shows the setting fields that are required for creating the sensor. Therefore, you will not see all setting fields in this dialog. You can change (nearly) all settings in the sensor's Settings tab later.

Sensor Settings

On the details page of a sensor, click on the Settings tab to change its settings.

Note: Usually, a sensor connects to the IP Address or DNS Name of the parent device on which you created this sensor. See the Device Settings for details. For some sensor types, you can define the monitoring target explicitly in the sensor settings. Please see below for details on available settings.

Basic Sensor Settings

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 this sensor inherits from its parent device, group, and probe. This setting is shown for your information only and cannot be changed here.

Tags

Enter one or more Tags, separated by space or comma. You can use tags to group sensors and use tag–filtered views later on. Tags are not case sensitive. We recommend that you use the default value.

You can add additional tags to it, if you like. Other tags are automatically inherited from objects further up in the device tree. These are visible above as Parent Tags.

Priority

Select a priority for the sensor. This setting determines where the sensor is placed in sensor lists. Top priority is at the top of a list. Choose from one star (low priority) to five stars (top priority).

HTTP Specific

Timeout (Sec.)

Enter a timeout in seconds for the request. If the reply takes longer than this value defines, the sensor will cancel the request and show a corresponding error message. Please enter an integer value. The maximum value is 900 seconds (15 minutes).

URL

Enter the URL the sensor connects to. It has to be URL encoded ! If you enter an absolute URL, the sensor uses this address independently from the IP address/DNS name setting of the device on which you create this sensor. You can enter an URL leading to a webpage (to measure the page source code's loading time), or enter the URL of an image or of another page asset to measure this element's availability and loading time.

PRTG uses a smart URL replacement which allows you to use the parent device's IP address/DNS name setting as part of the URL. For more information, please see section Smart URL Replacement below.

Request Method

Choose an HTTP request method to determine how the sensor will request the given URL.

  • GET : Request the website directly, like browsing the web. We recommend using this setting for a simple check of a web page.
  • POST : Send post form data to the URL. If this setting is chosen, you must enter the data that will be sent in the Postdata field below.
  • HEAD : Only request the HTTP header from the server; without the actual web page. Although this saves bandwidth since less data is transferred, it is not recommended because the measured request time is not the one experienced by your users and you might not be notified for slow results or timeouts.

Postdata

This field is only visible when you select the POST Request Method setting above. Enter the data part for the POST request here. Note: No XML is allowed here!

Content Type

This setting is only visible when you select the POST Request Method setting above. Define the content type of a POST request. Choose between:

  • Default (application/x-www-form-urlencoded) : This is the default content type used to encode the form data set for submission to the server.
  • Custom : If you need another content type than default, enter this content type below.

Custom Content Type

This field is only visible when you select Custom above. Define the content type which is needed, for example, XML, JSON, HTTP.

Server Name Indication

Shows the Server Name Identification (SNI) that the sensor automatically determined from the host address of the parent device or the target URL of the sensor. SNI has to be a Fully Qualified Domain Name (FQDN) . Please ensure it matches the configuration of the target server.

For details, please see section More for a link to the Knowledge Base article My HTTP sensors fail to monitor websites which use SNI. What can I do?

SNI Inheritance

Define if you want to inherit the Server Name Identification (SNI) from the parent device. See the Server Name Indication setting above which SNI is determined. Choose between:

  • Inherit SNI from parent device: The sensor determines the SNI from the host address of the parent device.
  • Do not inherit SNI from parent device: The sensor determines the SNI from the target URL as defined in the settings of this sensor.

HTTP Engine

Monitoring Engine

If you encounter unexpected errors with the standard method that is used to monitor an URL, try to use the compatibility mode which is based on .NET . Choose between:

  • Default/High Performance (recommended) : This is the default monitoring method for this sensor type.
  • Alternate/Compatibility Mode : Try this method as an alternative for websites that do not work with the default approach. Using the compatibility mode, this sensor executes an external exe . Because of this, this method needs more resources, but it can be helpful in particular cases.
    Note: If you select the compatibility mode, the options for the SSL method will be slightly different. You can also check for trusted certificates. Please see below.
    Note: When using the Compatibility Mode, Smart URL Replacement will not work, so this sensor will not use the IP Address/DNS value of the parent device automatically then.

SSL Specific (when using Compatibility Mode)

SSL Method

When using the compatibility mode, the SSL specific settings are a bit different to the default (automatically used) SSL settings. You can choose between:

  • SSL V3
  • TLS V1
  • SSL V3 or TLS V1 : This is the default setting.

Check SSL Certificates

Specify if the sensor will check the certificate of the monitored URL. Choose between:

  • Do not check used certificates : Do not consider the certificates of the monitored web pages. This the default setting.
  • Check if the used certificates are trusted : Inspect the certificates. If the certificate of the server is not trusted, the sensor shows a Down status and displays a corresponding message.

Note: This sensor type implicitly supports Server Name Identification (SNI), an extension to the TLS protocol.

Advanced Sensor Data

Protocol Version

Define the HTTP protocol version that the sensor uses when connecting to the URL. Choose between:

  • HTTP 1.0
  • HTTP 1.1 : This is the default setting.

User Agent

Choose which user agent string will be sent by this sensor when connecting to the URL defined above. Choose between:

  • Use PRTG's default string : Do not enter a specific user agent, use default setting. Usually, this is: Mozilla/5.0 (compatible; PRTG Network Monitor (www.paessler.com); Windows)
  • Use a custom string : Use a custom user agent. Define below.

Custom User Agent

This field is only visible if you enable custom user agent above. Enter a string which will be used as user agent when connecting to the URL specified above.

Use Custom HTTP Headers

Define if you want to send custom HTTP headers to the target URL. Choose between:

  • Do not use custom HTTP headers
  • Use custom HTTP headers

Custom HTTP Headers

This field is only available if you select using custom headers above. Enter a list of custom HTTP headers with theirs respective values that you want to transmit to the URL you define above, each pair in one line. The syntax of a header-value pair is header1:value1

Note: The sensor does not accept the header field names user-agent , content-length , host .

Note: Ensure that the HTTP header statement is valid! Otherwise, the sensor request will not be successful.

Content Changes

Define what the sensor will do if the content of the monitored web page (element) changes. You can choose between:

  • Ignore changes : No action will be taken on change.
  • Trigger 'change' notification : The sensor will send an internal message indicating that the web page content has changed. In combination with a Change Trigger , you can use this mechanism to trigger a notification whenever the web page content changes.

Require Keyword

Define if the sensor will check the result at the configured URL for keywords. Choose between:

  • Do not check for keyword (default) : Do not search for keywords in the result returned at the URL.
  • Set sensor to warning if keyword is missing : Check if a keyword exists in the result and set the sensor to a Warning status if yes.
  • Set sensor to error if keyword is missing: Check if a keyword exists in the result and set the sensor to a Down status if yes.

Note: The content check is only intended for html websites and might not work with other target URLs. For example, binary files are not supported.

Response Must Include

This field is only visible if you enable keyword checking above (include). Define which string must be part of the source code at the given URL. You can either enter plain text or a Regular Expression . Specify below. If the data does not include the search pattern, the sensor will show the status defined above. Please enter a string.

Check Method

Define in which format you have entered the search expression in the field above.

  • String search (default) : Search for the string as plain text. The characters * and ? work here as placeholder, whereas * stands for no or any number of characters and ? stands for exactly one character (as known from Windows search). This behavior cannot be disabled, so the literal search for these characters is not possible with plain text search. You can also search for HTML tags.

Exclude Keyword

Define if the sensor will check the result at the configured URL for keywords. Choose between:

  • Do not check for keyword (default) : Do not search for keywords in the result returned at the URL.
  • Set sensor to warning if keyword is found : Check if a keyword exists in the result and set the sensor to a Warning status if yes.
  • Set sensor to error if keyword is found: Check if a keyword exists in the result and set the sensor to a Down status if yes.

Note: The content check is only intended for html websites and might not work with other target URLs. For example, binary files are not supported.

Response Must Not include

This field is only visible if you enable keyword checking (exclude) above. Define which string must not be part of the source code at the given URL. You can either enter plain text or a Regular Expression . If the data does include this string, the sensor will show the status defined above. Please enter a string.

Check Method

Define in which format you have entered the search expression in the field above.

  • String Search (default) : Search for the string as plain text. The characters asterisk (* ) and question mark (? ) work here as placeholder, whereas * stands for no or any number of characters and ? stands for exactly one character (as known from Windows search). This behavior cannot be disabled, so the literal search for these characters is not possible with plain text search. You can also search for HTML tags.

Limit Download (kb)

Enter a maximum amount of data that the sensor can transfer per every single request. If you set content checks, please be aware that only the content downloaded up to this limit can be checked for search expressions.

Result Handling

Define what the sensor will do with the web page loaded at the given URL. Choose between:

  • Discard HTML result : Do not store the requested web page.
  • Store latest HTML result : Store the last result of the requested web page to the "Logs (Sensors)" directory (on the Master node, if in a cluster). File name: Result of Sensor [ID].txt . This is for debugging purposes, especially in combination with content checks. The file will be overridden with each scanning interval. For information on how to find the folder used for storage, please see Data Storage section.

Note: This sensor loads the source code at the given URL. If you set up a content check, only this source code is checked for the keywords. The code is not necessarily identical to the one used to display the page when opening the same URL in a web browser, as there may be a reload configured or certain information may be inserted after loading, for example, via Javascript. PRTG does not follow links to embedded objects nor does it execute scripts. Only the first page at the given URL is loaded and checked against the expressions configured. For debugging, please use the Result Handling option to write the source code file to disk and look up what exactly PRTG gets when calling the URL. If the URL configured does not point to a web page, but to a binary file, for example, to an image, you usually will not check for content.

Authentication

Authentication

Define if the web page at the configured URL needs authentication. Choose between:

  • No authentication needed
  • Web page needs authentication

User

This field is only visible if you enable authentication above. Enter a username. Please enter a string.

Password

This field is only visible if you enable authentication above. Enter a password. Please enter a string.

Authentication Method

This field is only visible if enable authentication above. Select the authentication method the given URL is protected with. Choose between:

  • Basic access authentication (HTTP) : Use simple HTTP authentication. This is the default setting and suitable for most cases.
    Note: This authentication method transmits credentials as plain text.
  • Windows NT LAN Manager (NTLM) : Use the Microsoft NTLM protocol for authentication. This is sometimes used in intranets for single sign-on.
  • Digest Access Authentication: Use digest access authentication that applies a hash function to the password which is safer than basic access authentication.

We recommend that you use the default value.

Sensor Display

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 will always be displayed below the sensor's name. The available options depend on what channels are available for this sensor. Note: You can set another primary channel later by clicking on the pin symbol of a channel in the sensor's Overview tab.

Graph Type

Define how different channels will be shown for this sensor.

  • Show channels independently (default) : Show an own graph for each channel.
  • Stack channels on top of each other : Stack channels on top of each other to create a multi-channel graph. This will generate an easy-to-read graph which visualizes the different components of your total traffic. Note: This option cannot be used in combination with manual Vertical Axis Scaling (available in the Sensor Channels Settings settings).

Stack Unit

This setting is only available if stacked graphs are selected above. Choose a unit from the list. All channels with this unit will be 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.

Inherited Settings

By default, all following settings are inherited from objects higher in the hierarchy and should be changed there, if necessary. Often, best practice is to change them centrally in the Root group's settings. To change a setting only for this object, disable inheritance by clicking on the check mark before the corresponding setting name. You will then see the options described below.

Proxy Settings for HTTP Sensors

HTTP Proxy Settings

The proxy settings determine how a sensor connects to a given URL. You can enter data for an HTTP proxy server that sensors will use when connecting via HTTP or HTTPS.

Note: This setting affects monitoring only and determines the behavior of HTTP sensors. To change proxy settings for the core server, please see System Administration—Core & Probes .

Note: The SSL Certificate Sensor and the SSL Security Check Sensor do not support HTTP proxies, but you can configure connections via SOCKS proxies in their sensor settings.

Name

Enter the IP address or DNS name of the proxy server to use. If you leave this field empty, no proxy will be used.

Port

Enter the port number of the proxy. Often, port 8080 is used. Please enter an integer value.

User

If the proxy requires authentication, enter the username for the proxy login.

Note: Only basic authentication is available! Please enter a string or leave the field empty.

Password

If the proxy requires authentication, enter the password for the proxy login.

Note: Only basic authentication is available! Please enter a string or leave the field empty.

Scanning Interval

Scanning Interval

Select a scanning interval (seconds, minutes, or hours) from the list. The scanning interval determines the time the sensor waits between two scans. You can change the available intervals in the system administration on PRTG on premises installations.

When a Sensor Reports an Error

Define the number of scanning intervals that a sensor has time to report an error before the sensor will be set to a Down status. The sensor can try to reach a device several times, depending on the setup you can specify here, to help avoid false alarms if the monitored device has only temporary issues. For previous scanning intervals with failed requests, the sensor will show a Warning status. Choose between:

  • Set sensor to "down" immediately : The sensor will show an error immediately after the first failed request.
  • Set sensor to "warning" for 1 interval, then set to "down" (recommended) : After the first failed request, the sensor will show a yellow warning status. If the following request also fails, the sensor will show an error.
  • Set sensor to "warning" for 2 intervals, then set to "down" : Show an error status only after three continuously failed requests.
  • Set sensor to "warning" for 3 intervals, then set to "down" : Show an error status only after four continuously failed requests.
  • Set sensor to "warning" for 4 intervals, then set to "down" : Show an error status only after five continuously failed requests.
  • Set sensor to "warning" for 5 intervals, then set to "down" : Show an error status only after six continuously failed requests.

Note: Sensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval until they show an error. It is not possible to set a WMI sensor "down" immediately, so the first option will not apply to these sensor types (all other options can apply).

Note: If a sensor has defined error limits for channels, this sensor will always be set to a Down status immediately, so no "wait" option will apply.

Note: If a channel uses lookup values, the sensor will always be set to a Down status immediately, so no "wait" options will apply.

Schedules, Dependencies, and Maintenance Window

Note: Inheritance for schedules, dependencies, and maintenance windows cannot be interrupted. The corresponding settings from the parent objects will always be active. However, you can define additional settings here. They will be active at the same time as the parent objects' settings.

Schedule

Select a schedule from the list. Schedules can be used to monitor for a certain time span (days, hours) every week. With the period list option it is also possible to pause monitoring for a specific time span. You can create new schedules and edit existing ones in the account settings.

Note: Schedules are generally inherited. New schedules will be added to existing ones, so all schedules are active at the same time.

Maintenance Window

Specify if you want to set up a one-time maintenance window. During a "maintenance window" period, this object and all child objects will not be monitored. They will be in a paused state instead. Choose between:

  • Not set (monitor continuously) : No maintenance window will be set and monitoring will always be active.
  • Set up a one-time maintenance window : Pause monitoring within a maintenance window. You can define a time span for a monitoring pause below and change it even for a currently running maintenance window.

Note: To terminate a current maintenance window before the defined end date, change the time entry in Maintenance Ends field to a date in the past.

Maintenance Begins

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the start date and time of the maintenance window.

Maintenance Ends

This field is only visible if you enabled the maintenance window above. Use the date time picker to enter the end date and time of the maintenance window.

Dependency Type

Define a dependency type. Dependencies can be used to pause monitoring for an object depending on the status of another. You can choose between:

  • Use parent : Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency.
  • Select object : Pause the current sensor if the device, where it is created on, is in Down status, or is paused by another dependency. Additionally, pause the current sensor if a specific other object in the device tree is in Down status, or is paused by another dependency. Select below.
  • Master object for parent : Make this sensor the master object for its parent device. The sensor will influence the behavior of the device, where it is created on: If the sensor is in Down status, the device will be paused. For example, it is a good idea to make a Ping sensor the master object for its parent device to pause monitoring for all other sensors on the device in case the device cannot even be pinged. Additionally, the sensor will be paused if the parent group of its parent device is in Down status, or if it is paused by another dependency.

Note: Testing your dependencies is easy! Simply choose Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later all dependent objects should be paused. You can check all dependencies in your PRTG installation by selecting Devices | Dependencies from the main menu bar.

Dependency

This field is only visible if the Select object option is enabled above. Click on the reading-glasses and use the object selector to choose an object on which the current sensor will depend.

Dependency Delay (Sec.)

Define a time span in seconds for a dependency delay. After the master object for this dependency goes back to Up status, PRTG will start monitoring the depending objects after this extra delayed. This can help to avoid false alarms, for example, after a server restart, by giving systems more time for all services to start up. Please enter an integer value.

Note: This setting is not available if you choose this sensor to Use parent or to be the Master object for parent . In this case, please define delays in the parent Device Settings or in the superior Group Settings .

Access Rights

User Group Access

Define which user group(s) will have access to the object you're editing. A table with user groups and types of access rights is shown: It contains all user groups from your setup. For each user group you can choose from the following access rights:

  • Inherited : Use the access rights settings of the parent object.
  • None : Users in this group cannot see or edit the object. The object neither shows up in lists nor in the device tree. Exception: If a child object is visible to the user, the object is visible in the device tree, though not accessible.
  • Read : Users in this group can see the object and review its monitoring results.
  • Write : Users in this group can see the object, review its monitoring results, and edit the object's settings. They cannot edit access rights settings.
  • Full : Users in this group can see the object, review its monitoring results, edit the object's settings, and edit access rights settings.

You can create new user groups in the System Administration—User Groups settings. To automatically set all objects further down in the hierarchy to inherit this object's access rights, set a check mark for the Revert children's access rights to inherited option.

For more details on access rights, please see the section User Access Rights .

Channel Unit Configuration

Channel Unit Types

For each type of sensor channel, define the unit in which data is displayed. If defined 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):

  • Bandwidth
  • Memory
  • Disk
  • File
  • Custom

Note: Custom channel types can be set on sensor level only.

Smart URL Replacement

Instead of entering a complete address in the URL field of an HTTP sensor, you can merely enter the protocol followed by colon and three slashes (that means you can enter either http:/// or https:/// or even a simple slash / as equivalent for http:/// ). PRTG will then fill in the parent device's IP address or DNS name in front of the third slash automatically. Whether this results in a valid URL or not, depends on the IP address or DNS name of the device where this HTTP sensor is created on. In combination with cloning devices, the smart URL replacement makes it easy to create many like devices.

For example, if you create a device with DNS name www.example.com and you put an HTTP sensor on it, you can provide values the following ways:

  • Providing the value https:/// in the URL field, PRTG will automatically create the URL https://www.example.com/ from that.
  • Using the value /help in the URL field, PRTG will automatically create and monitor the URL http://www.example.com/help
  • It is also possible to provide a port number in the URL field which will be taken over by the device's DNS name and internally added, for example, http://:8080/

Note: Smart URL replacement does not work for sensors running on the "Probe Device".

More

Knowledge Base: Which HTTP status code leads to which HTTP sensor status?

Knowledge Base: Which user agent should I use in the HTTP Advanced sensor's settings?

Knowledge Base: Is it possible to test a WSDL or SOAP service with PRTG?

Knowledge Base: My HTTP sensors fail to monitor websites which use SNI. What can I do?

Edit Sensor Channels

To change display settings, spike filter, and limits, switch to the sensor's Overview tab and click the gear icon of a specific channel. For detailed information, please see the Sensor Channels Settings section.

Notifications

Click the Notifications tab to change notification triggers. For detailed information, please see the Sensor Notifications Settings section.

Others

For more general information about settings, please see the Object Settings section.

Sensor Settings Overview

Feedback / Questions
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