Pandora: Documentation en: Web Monitoring

From Pandora FMS Wiki
Revision as of 10:36, 25 July 2019 by Maria (talk | contribs) (Form Checking on a Website)
Jump to: navigation, search

Go back to Pandora FMS documentation index

1 Monitoring User Browsing Behavior

1.1 Introduction

In the Enterprise version, it is possible to monitor a Web using the WEB Server component, also called Goliat Server.

GoliatLogo 2.jpg

This functionality comes from an old project of the founder of Pandora FMS. Goliat F.I.S.T. was an open source project to perform dynamic load audits on web services. You can still find the source code (from 2002) whose updating stopped more or less in 2010 [1].

In Pandora FMS, it works as an independent server, similar to the network server, WMI server or remote plugin server. This system operates under the principle of web transaction, where each transaction is defined by one or more consecutive steps, which must be successfully concluded in order to consider that the transaction has been properly completed. The execution of a web transaction faithfully reproduces the complete browsing process that can include aspects such as authenticating yourself in a form, clicking on a menu option or filling in a form, verifying that each step returns a specific text string.

Any failure at any point in the process would result in a checking failure. The complete transaction includes the downloading of all resources (graphics, animations, etc.) that the actual navigation includes. In addition to performing response time and performance checks, it is possible to extract values from the web pages and then process them.

Goliat is able to monitor both HTTP and HTTPS in a transparent way for the user, supports session management through cookies, parameter passage, and of course, downloading the resources associated with each page. It also has important limitations such as the dynamic management of javascript at runtime. For more complex web transactions, Pandora FMS has another much more powerful (and complex) component called WUX Monitoring (Web User Experience).

1.2 Installation and Configuration

To be able to use Goliat, activate it in the Pandora FMS Enterprise server:

webserver 1

Depending on the number of requests you want to make, you may have to increase the number of threads and the default timeout:

web_threads 1 
web_timeout 60

There is an advanced configuration token that will allow you to change the type of library you use under Goliat, LWP or CURL. LWP is used by default, but if you encounter any issues (SSL connections, long timeouts or concurrency problems in case of many threads), switch to CURL:

web_engine curl

1.3 Creating Web Modules

To monitor a web page remotely, click on the modules tab. Then, select 'Create a new webserver module' and click on Create:


Click on Create to see a form appear, in which fill out the appropriate fields to monitor a web page. The name and, above all, the type of WEB check-up are the most basic ones:

Goliat types.jpg

There are several check types to choose from:

  • Remote HTTP module to check latency: it obtains the total time that elapses from the first request until the last one is checked (in a WEB test there are one or more intermediate requests that complete the transaction). If it is defined in the check definition that the transaction must be carried out more than once, the average time of each request is used.
  • Remote HTTP module to check server response: it shows the values 1 (OK) or 0 (CRITICAL) as a result from checking the entire transaction. If there are several attempts, but at least one of them has failed, the test as a whole is also considered to have failed. Precisely the number of attempts is sometimes used to avoid false positives. In case you may want to perform the test several times in case of a failure, use the retries field (see advanced fields below).
  • Remote HTTP module to retrieve numeric data: It retrieves a numeric value from an HTTP response using a regular expression.
  • Remote HTTP module to retrieve string data: It retrieves a string from an HTTP response using a regular expression.

Web Checks

This essential field defines the WEB check to be performed. This is defined in one or more steps, or simple requests. These simple requests must be written in a special format in the Web checks field. Checks start with the tab page task_begin and end with the tab page task_end.

A complete example of a simple transaction would be the following:

cookie 0
resource 0
check_string Apache Software Foundation

In this basic example, it is being checked whether there is a string in a web page. To that end, there is the variable check_string. This variable does not allow you to check HTML itself, it only searches for text sub-strings. If you look for "Apache Software Foundation" on the web and if that text string exists, the check will return OK (if it is Remote HTTP module to check server response)

To ensure that a string does not exist on a web page, you can use the variable' check_not_string':

check_not_string Section 3

There are several extra variables to check forms:

  • resource (1 or 0): Download all the web resources (images, videos, etc).
  • cookie (1 or 0): Keep a cookie or an open session for later checks.
  • variable_name: The name of a variable in a form.
  • variable_value: The value of the previous variable on the form.

By using these variables, it is possible to send data to forms and check whether they work appropriately or not.

Template warning.png

In some specific cases, the domain redirection may not work. To solve this problem, create a module that uses the final domain address after all redirections are completed.


Template warning.png

The arguments taken by the "check_string" syntax are not normal text strings, they are "regular expressions". That is to say, if you search for the string "Pandora FMS (4.0)" you will have to search for it with a regular expression, e. g. Pandora FMS \(4.0\). This allows you to perform much more powerful researches, but you should be aware that any character other than a letter or number will have to be escaped with \.


1.4 Checking the Latency of a Website

If you want to check the latency of a website, select the module type named Remote HTTP module to check latency. If you want to find out the latency of the website, the code should look like the one below.


Add the resource 1 configuration token so that the download time you calculate includes the download of all resources (javascript, CSS, images, etc.), thus calculating a more real data.


The download time of the website is NOT the time it takes to view a web site in a browser, as this usually depends on the loading time of Javascript, and Goliat downloads the javascript, but does not run it.


1.5 Website Checks through a Proxy

You can also carry out website checks by using a proxy. To configure the proxy, add the proxy URL in the 'Proxy URL' field which is located under 'Advanced options':

Goliat proxy conf.png

An example of the URL could be:

If the proxy requires an authentication, you may use an URL like this:

http://my_user:[email protected]:8080

1.6 Retrieving data from a website

You may not want to know whether a specific Web site is working or how long it takes, but to get a real time value, such as Google's stock market value. To that end, use a Remote HTTP module to retrieve numeric data with the appropriate regular expression:

get_content \d+\.\d+

The output will look like this:

Google stock quote.png

It is also possible to specify a more complex regular expression for collecting data from more complex HTTP responses with the get_content_advanced configuration token:

get_content_advanced <span id="yfs_l84_goog">([\d\.]+)</span>

Template warning.png

The part of the regular expression to be returned (which is defined in get_content_advanced) must be enclosed in brackets.


To configure the thresholds that trigger warning or critical status, use the module configuration to verify that the received string matches what is expected.

1.7 Form Checking on a Website

A more interesting check is that of a web form. However, this is much more complex than simply checking a text on a web page. This example check will use Pandora FMS's own console, log in, and will verify that it has been able to do it, verifying a text in the workspace section where it shows the data of the user who has logged in. If it is a default console, the admin user contains the description "Admin Pandora".

To be able to perform this type of checks, you must have the necessary credentials to be able to log in (since these values are used to "send" them to the HTML form). In addition, go to the page and get the HTML code to be able to see the names of the variables. Then, it is necessary to have a basic knowledge of HTML to understand how Goliat works. This example uses "admin" with the password "pandora" which are the default credentials. You should have changed them, if you have not done it yet, this would be a good time to do it!


The ideal procedure when designing a WEB transactional test with several steps is to test it step by step, in case something was missed in one of the steps.


Suppose that the login URL of Pandora FMS Console is:

Analyzing the HTML code, it is observed that the variables of the login form are:

  • nick: user name
  • pass: user password

The variables variable_name and variable_value should be used together to validate the form.

Firstly, access the form, send the user and password and authenticate (determining the success of that authentication will be seen in the following step).

variable_name nick
variable_value admin
variable_name pass
variable_value pandora
cookie 1
resource 1

With the previous task, it would have been possible to access and validate the website. Now it will be verified that you are actually registered in the website by searching for something on it that you can only see when you are registered. The cookie 1 token is used to maintain the persistence of cookies obtained in the previous step. Without them, it would not be possible to "simulate" a session.

In the second step, access the user details page and look for the phone, which by default for the "admin" user is 555-555-555. If you can see it, it means that you have logged in correctly in the console:

cookie 1
resource 1
check_string 555-555-5555

And finally, log out from the console and look for the logout message:

cookie 1
resource 1
check_string Logged out

Therefore, the total check process would look like this in Pandora FMS:

Goliat full sample.jpg

1.8 WEB query performance

The fields of the advanced properties are similar to those of other types of modules, although there are some different and specific fields of WEB checks:


This is the expiry time during the request. If it is exceeded, the request for verification will be discarded.

Agent browser id

This is the web browser identifier to be used, since certain pages only accept some web browsers (see for more information).


Pandora FMS will repeat the check the amount of times indicated in this parameter. If one of the checks fails, the check will be considered erroneous. Depending on the number of checks in the module, a certain number of pages will be obtained. That means that if the module consists of three checks, three pages will be downloaded, and if some value has been set in the Requests field, then the number of downloads will be multiplied by it. It is important to keep this in mind to know the total time it will take for the module to complete the operations.


It has nothing to do with requests and implies the opposite, i. e. if its value is > 1, and it fails the first time, it will retry a certain number of times until it succeeds. For example, with retries = 2 and Requests = 1, if the first test failed, it would be retried once more, and if the second one works, the check would be considered as valid. If it was Requests = 2, and Retries = 1, it would perform two checks, but if either failed, the test would be considered as failed.

1.9 Simple HTTP Authentication

Some websites might require HTTP authentication. This authentication method does not consist of the 'normal' user / password form. HTTP authentication is the one in which a pop-up appears, reporting that a certain site asks for credentials.

Conexion http.png

It can be configured in the advanced options (as seen in the previous screenshot) or directly in the WEB task definition with the following configuration tokens:

  • Check type - HTTP server check type.
  • http auth (login) - The user.
  • http auth (password) - The password.
  • Proxy auth realm - The auth realm's name.
  • Proxy auth (server) - The domain and HTTP port on which to listen on.
  • Proxy URL - Proxy server url
  • Proxy auth (login) - Proxy connection user
  • Proxy auth (pass) - Proxy connection password

This is a full example:

cookie 1
resource 1
check_string Pandora FMS Update Manager \(4.0\)
http_auth_realm Private area
http_auth_user admin
http_auth_pass xxxx

1.10 Webservice Monitoring

With Pandora FMS and Goliat's Web Surveillance features, you may also monitor web services and APIs which are based on the REST specification, but you may not carry out such a surveillance on SOAP or XML-RPC based web services.

Let us assume for a moment that you may want to check a web API through a specific call which returns a number (from '0' to 'n') if it works properly. If not, it will not return anything, which will be considered a failure by Pandora FMS:

check_string \n[0-9]+

This will return a reply like this one:

HTTP/1.1 200 OK
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Connection: close
Date: Mon, 13 May 2013 15:39:27 GMT
Pragma: no-cache
Server: Apache
Vary: Accept-Encoding
Content-Type: text/html
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Client-Date: Mon, 13 May 2013 15:39:27 GMT
Client-Response-Num: 1
Client-Transfer-Encoding: chunked
Set-Cookie: a81d4c5e530ad73e256b7729246d3d2c=pcasWqI6pZzT2x2AuWo602; path=/


This will generate an 'OK' (Green) module status, because the regular expression matching ('regexp') found the '0' just before a carriage return. It is important to check the entire response data - not just the 'data' section, so you can match the HTTP headers, too. For other responses, a different regular expression is required.

1.11 HTTPS Monitoring

Goliat is able to check both HTTP and HTTPS. To carry out checks on secured websites which use HTTPS, incorporate the protocol into its URL, e.g.:

cookie 1
resource 0
check_string Google

1.12 IPv6 Support

Goliat supports IPv6, although it needs to use FQDN addresses. This means that URLs must have full names (e.g. The numerical representation of IPv6 addresses (pe:[:: 1],[2404:6800:4004:4004:803::1014] etc.) is not valid for IPv6 checks by means of Goliat.

1.13 Advanced Options

1.13.1 Modifying HTTP Headers (available from versions 4.0.2 and above)

With the header option, you are able to modify HTTP headers or create your own. The example below changes the Host HTTP header:

header Host

1.13.2 Debugging Web Surveillance (available from versions 4.0.2 and above)

If you want to debug a website check, add the debug <log_file> option. The files log_file.req and log_file.res will be created along with the contents of the HTTP request and response:

debug /tmp/request.log

The website check above will generate the /tmp/request.log.req and /tmp/request.log.res files.

1.13.3 Using CURL instead of LWP

LWP sometimes crashes when multiple threads issue HTTPS requests simultaneously. To solve this problem, you just have to edit the file named '/etc/pandora/pandora_server.conf' and to add the below mentioned line to it:

web_engine curl

After you've restarted the Pandora FMS Server, the CURL binary is going to be used to perform website checks instead of LWP.

2 Distributed Transactional WEB Monitoring through Selenium

Selenium logo.png

In addition to the features of Goliat, which is an integral part of all Pandora FMS Enterprise versions, there is another way to perform Transactional Monitoring with Pandora FMS. This method involves using an agent-like approach instead of a centralized system. It allows you to distribute the load and use servers in remote networks to monitor different websites or applications.

In such a case, 'Selenium' is used as the back end instead of Goliat. It supports a navigation 'by clicks' which is much more precise than the ones offered by Goliat. The Selenium plug-in agent interacts with the Selenium Server - and this in turn with the system's browser. This method offers the possibility to browse the web using Chrome, Firefox or Internet Explorer. It runs on Windows and Linux, enables latency and session checks and supports navigation with heavy implementations of JavaScript and Java applets, Flash or any other technology, supported by browsers today.

The Selenium plug-in Documentation is very extensive and specific and can be found in the Pandora FMS Module Library, along with the Enterprise Selenium Plugin.

This feature has been improved, now you have Pandora FMS UX to automatize and monitor both desktop and web User eXperience sessions

Go back to the Pandora FMS Documentation Index