<%NUMBERING1%>.<%NUMBERING2%>.<%NUMBERING3%> PRTG Manual: HTTP Advanced Sensor

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 spaces or commas. 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.

There are default tags that are automatically predefined in a sensor's settings when you add a sensor. See section Default Tags below.

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

It is not possible to enter tags with a leading plus (+) or minus (-) sign, nor tags with parentheses (()) or angle brackets (<>).

Priority

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

Timeout (Sec.)

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

URL

Enter the URL that 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 parent device. You can enter the URL of a web page (to measure the loading time of the page's source code), or enter the URL of an image or of a page asset to measure this element's availability and loading time.

Monitoring an image or a page asset can create a high amount of memory load. We recommend that the size of the elements that you want to monitor does not exceed 200 MB.

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

Request Method

Select an HTTP request method to determine how the sensor requests the URL:

• GET: Directly request the website, like browsing the web. We recommend that you use this setting for a simple check of the web page.
• POST: Send post form data to the URL. If you select this setting, you must enter the data that is sent in the Postdata field below.
• HEAD: Only request the HTTP header from the server without the actual web page. Although this saves bandwidth because 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 of slow results or timeouts.

Postdata

This field is only visible if you enable POST above. Enter the data part for the POST request.

No Extensible Markup Language (XML) is allowed here.

Content Type

This field is only visible if you enable POST above. Define the content type of a POST request:

• Default (application/x-www-form-urlencoded): Use the default content type to encode the form data set for submission to the server.
• Custom: If you need a custom content type, enter the content type below.

Custom Content Type

This field is only visible if you enable Custom above. Define the custom content type, for example, XML, JavaScript Object Notation (JSON), or 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. The SNI has to be a fully qualified domain name (FQDN). Make sure that it matches the configuration of the target server.

For details, see the Knowledge Base: My HTTP sensors fail to monitor websites which use SNI. What can I do?

SNI Inheritance

Define if you want to inherit the SNI from the parent device:

• 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.

Monitoring Engine

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

• Default/High Performance (recommended): This is the default monitoring method for this sensor.
• 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 executable program. Because of this, this method needs more resources but it can be helpful in some cases.
  If you select the compatibility mode, the options for the SSL method are slightly different. You can also check for trusted certificates. See below.
  When using the compatibility mode, Smart URL Replacement does not work, so this sensor does not automatically use the IP Address/DNS value of the parent device.

SSL Method

When using the compatibility mode, the Secure Sockets Layer (SSL) specific settings are a bit different from the default (automatically used) SSL settings. You can choose from:

• SSL 3.0
• TLS 1.0, TLS 1.1, TLS 1.2
• SSL 3.0, TLS 1.0, TLS 1.1, TLS 1.2: This is the default setting.

Check SSL Certificates

Specify if the sensor checks the certificate of the URL:

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

Protocol Version

Define the HTTP protocol version that the sensor uses when connecting to the target URL:

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

User Agent

Choose which user agent string the sensor sends when connecting to the target URL:

• Use the default string: Do not enter a specific user agent and use the 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 Use a custom string above. Enter the string to be used as the user agent when connecting to the target URL.

HTTP Headers

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

• Do not use custom HTTP headers: Do not use custom HTTP headers.
• Use custom HTTP headers: Use custom headers. Define below.

Custom HTTP Headers

This field is only visible if you enable Use custom HTTP headers above. Enter a list of custom HTTP headers and values that you want to transmit to the URL, each pair in one line. The syntax of a header-value pair is header1:value1

The sensor does not support the header field names user-agent, content-length, and host.

Ensure that the HTTP header statement is valid. Otherwise, the sensor request cannot be successful.

Content Changes

Define what the sensor does if the content of the monitored web page (element) changes:

• Ignore changes: No action is taken on change.
• Trigger 'change' notification: The sensor sends an internal message that indicates 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 checks the result at the configured URL for keywords:

• 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. If it exists, set the sensor to a Warning status.
• Set sensor to error if keyword is missing: Check if a keyword exists in the result. If it exists, set the sensor to a Down status.

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 the search string that must be part of the source code at the specified URL. You can enter a simple string in plain text or a regular expression.

The search string must be case sensitive.

If the data does not include the search pattern, the sensor shows the status defined above.

Search Method

Define the method with which you want to provide the search string:

• Simple string search: Search for a simple string in plain text.

The characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character (as known from the Windows search). You cannot change this behavior. The literal search for these characters is only possible with a regular expression.
You can also search for HTML tags.

• Regular expression: Search with a regular expression (regex).

PRTG supports Perl Compatible Regular Expression (PCRE) regex. You cannot use regex options or flags. For more details, see section Regular Expressions.

Exclude Keyword

Define if the sensor checks the result at the configured URL for keywords:

• 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. If it exists, set the sensor to a Warning status.
• Set sensor to error if keyword is found: Check if a keyword exists in the result. If it exists, set the sensor to a Down status.

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 the search string that must not be part of the source code at the specified URL. You can enter a simple string in plain text or a regular expression.

The search string must be case sensitive.

If the data does include this string, the sensor shows the status defined above.

Search Method

Define the method with which you want to provide the search string:

• Simple string search: Search for a simple string in plain text.

The characters * and ? work as placeholders. * stands for no number or any number of characters and ? stands for exactly one character (as known from the Windows search). You cannot change this behavior. The literal search for these characters is only possible with a regular expression.
You can also search for HTML tags.

• Regular expression: Search with a regex.

PRTG supports Perl Compatible Regular Expression (PCRE) regex. You cannot use regex options or flags. For more details, see section Regular Expressions.

Download Limit (KB)

Enter the maximum amount of data (in kilobytes) that is transferred per request.

If you set content checks, be aware that they might be incomplete because only the content downloaded up to this limit is checked for search expressions.

Result Handling

Define what the sensor does with the data loaded at the URL:

• Discard HTML result: Do not store the requested data.
• Store latest HTML result: Store the last result of the requested data to the \Logs\sensors subfolder of the PRTG data directory on the probe system (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 is overwritten with each scanning interval.

This option is not available when the sensor runs on the hosted probe of a PRTG hosted by Paessler instance.

Authentication

Define if authentication is necessary on the web page at the configured URL:

• No authentication needed
• Web page needs authentication

User

This field is only visible if you enable Web page needs authentication above. Enter a username. Enter a string.

Password

This field is only visible if you enable Web page needs authentication above. Enter a password. Enter a string.

Authentication Method

This field is only visible if you enable Web page needs authentication above. Select the authentication method that the URL is protected with:

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

We recommend that you use the default value.

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.

You can set a different primary channel later by clicking the pin symbol of a channel on the sensor's Overview tab.

Graph Type

Define how different channels are shown for this sensor:

• Show channels independently (default): Show a 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 generates a graph that visualizes the different components of your total traffic.
  This option cannot be used in combination with manual Vertical Axis Scaling (available in the channel settings).

Stack Unit

This field 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.

Click to interrupt the inheritance. See section Inheritance of Settings for more information.

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

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

The SSL Certificate sensor and the SSL Security Check sensor do not support HTTP proxies but you can configure connections via SOCKS proxies in the sensors' settings.

Name

Enter the IP address or Domain Name System (DNS) name of the proxy server. If you leave this field empty, no proxy is used.

Port

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

User

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

Only basic authentication is available. Enter a string or leave the field empty.

Password

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

Only basic authentication is available. Enter a string or leave the field empty.

Click to interrupt the inheritance. See section Inheritance of Settings for more information.

Scanning Interval

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

If a Sensor Query Fails

Define the number of scanning intervals that the sensor has time to reach and check a device again in case a sensor query fails. Depending on the option that you select, the sensor can try to reach and check a device again several times before the sensor shows a 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 a Warning status. Choose from:

• Set sensor to down immediately: Set the sensor to a Down status immediately after the first failed request.
• Set sensor to warning for 1 interval, then set to down (recommended): Set the sensor to a Warning status after the first failed request. If the following request also fails, the sensor shows an error.
• Set sensor to warning for 2 intervals, then set to down: Set the sensor to a Down status only after three consecutively failed requests.
• Set sensor to warning for 3 intervals, then set to down: Set the sensor to a Down status only after four consecutively failed requests.
• Set sensor to warning for 4 intervals, then set to down: Set the sensor to a Down status only after five consecutively failed requests.
• Set sensor to warning for 5 intervals, then set to down: Set the sensor to a Down status only after six consecutively failed requests.

Sensors that monitor via Windows Management Instrumentation (WMI) always wait at least one scanning interval before they show a Down status. It is not possible to immediately set a WMI sensor to a Down status, so the first option does not apply to these sensors. All other options can apply.

If you define error limits for a sensor's channels, the sensor immediately shows a Down status. No "wait" option applies.

If a channel uses lookup values, the sensor immediately shows a Down status. No "wait" options apply.

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 settings here. They are 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 or hours) every week.

You can create schedules, edit schedules, or pause monitoring for a specific time span. For more information, see section Account Settings—Schedules.

Schedules are generally inherited. New schedules are added to schedules that you already set up, 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, the selected object and all child objects are not monitored. They are in a Paused status instead. Choose between:

• Not set (monitor continuously): No maintenance window is set and monitoring is always 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 an active maintenance window.

To terminate an active maintenance window before the defined end date, change the time entry in Maintenance Ends to a date in the past.

Maintenance Begins

This field 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 maintenance window.

Maintenance Ends

This field 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 maintenance window.

Dependency Type

Define 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:

• Use parent: Use the dependency type of the parent object.
• Select a sensor: Use the dependency type of the parent object. Additionally, pause the current object if a specific sensor is in a Down status or in a Paused status caused by another dependency.

• Master sensor for parent: Make this sensor the master object for its parent device. The sensor influences the behavior of its parent device: If the sensor is in a Down status, the device is 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 is paused if the parent group is paused by another dependency.

To test your dependencies, select Simulate Error Status from the context menu of an object that other objects depend on. A few seconds later, all dependent objects are paused. You can check all dependencies under Devices | Dependencies in the main menu bar.

Dependency

This field is only visible if you enable Select a sensor above. Click the Search button and use the object selector to select a sensor on which the current object will depend.

Dependency Delay (Sec.)

This field is only visible if you enable Select a sensor above. Define a time span in seconds for dependency delay.

After the master sensor for this dependency comes back to an Up status, monitoring of the dependent objects is additionally delayed by the defined time span. This can prevent false alarms, for example, after a server restart, by giving systems more time for all services to start up. Enter an integer value.

This setting is not available if you set this sensor to Use parent or to be the Master sensor for parent. In this case, define delays in the parent device settings or in its parent group settings.

Click to interrupt the inheritance. See section Inheritance of Settings for more information.

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:

• Inherited: Inherit the access rights settings of the parent object.
• No access: Users in this user group cannot see or edit the sensor. The sensor neither shows up in lists nor in the device tree.
• Read access: Users in this group can see the sensor and view its monitoring results. They cannot edit any settings.
• Write access: Users in this group can see the sensor, view its monitoring results, and edit its settings. They cannot edit its access rights settings.
• Full access: Users in this group can see the sensor, view its monitoring results, edit its settings, and edit its access rights settings.

For more details on access rights, see section Access Rights Management.

Click to interrupt the inheritance. See section Inheritance of Settings for more information.

Channel Unit Types

For each type of 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

Custom channel types can be set on sensor level only.