Zabbix architectures

Before compiling Zabbix, we need to take a look at the prerequisites. The web frontend will need at least the following versions:

Instead, the Zabbix server will need:

To install all the dependencies on a Red Hat Enterprise Linux distribution, we can use yum (from root), but first of all, we need to include the EPEL repository with the following command:

# yum install epel-release

Using yum install, install the following package:

# yum install zlib-devel postgresql-devel glibc-devel curl-devel gcc automake postgresql libidn-devel openssl-devel net-snmp-devel rpm-devel OpenIPMI-devel iksemel-devel libssh2-devel openldap-devel

To configure the sources to create the agent, we need to run the following command:

# ./configure --enable-agent
# make

In both the previous sections, the command line ends right before the installation; indeed, we didn't run the following command:

# make install

I advise you not to run the make install command but use the checkinstall software instead. This software will create the package and install the Zabbix software.

You can download the software from ftp://ftp.pbone.net/mirror/ftp5.gwdg.de/pub/opensuse/repositories/home:/ikoinoba/CentOS_CentOS-6/x86_64/checkinstall-1.6.2-3.el6.1.x86_64.rpm.

Note that checkinstall is only one of the possible alternatives that you have to create a distributable system package.

# yum install rpm-build rpmdevtools

# mkdir -p ~/rpmbuild/{BUILD,RPMS,SOURCES,SPECS,SRPMS}

The package made things easy; it is easy to distribute and upgrade the software, plus we can create a package for different versions of a package manager: RPM, deb, and tgz.

Now, we need to convert to root or use the sudo checkinstall command followed by its options:

# checkinstall --nodoc -R --install=no -y 

If you don't face any issue, you should get the following message:

******************************************************************
 Done. The new package has been saved to
 /root/rpmbuild/RPMS/x86_64/zabbix-2.4.4-1.x86_64.rpm
 You can install it in your system anytime using:
      rpm -i zabbix-2.4.4-1.x86_64.rpm
******************************************************************

Now, to install the package from root, you need to run the following command:

# rpm -i zabbix-2.4.4-1.x86_64.rpm

Finally, Zabbix is installed. The server binaries will be installed in <prefix>/sbin, utilities will be in <prefix>/bin, and the man pages will be under the <prefix>/share location.

To provide a complete picture of all the possible install methods, you need to be aware of the steps required to install Zabbix using the prebuilt rpm packages.

The first thing to do is install the repository:

# rpm -ivh http://repo.zabbix.com/zabbix/2.4/rhel/6/x86_64/zabbix-2.4.4-1.el6.x86_64.rpm

This will create the yum repo file, /etc/yum.repos.d/zabbix.repo, and will enable the repository.

Now, it is easy to install our Zabbix server and web interface; you can simply run this command on the server:

# yum install zabbix-server-pgsql

And in the web server, bear in mind to first add the yum repository:

# yum install zabbix-web-pgsql

To install the agent, you only need to run the following command:

# yum install zabbix-agent

Also, if you have a local firewall active where you're deploying your Zabbix agent, you need to properly configure iptables to allow the traffic against Zabbix's agent port with the following command that you need to run as root:

# iptables -I INPUT 1 -p tcp --dport 10050 -j ACCEPT
# iptables-save

For the server configuration, we only have one file to check and edit:

/usr/local/etc/zabbix_server.conf

The configuration files are located inside the following directory:

/usr/local/etc

We need to change the /usr/local/etc/zabbix_server.conf file and write the username, relative password, and the database name there; note that the database configuration will be done later on in this chapter and that, by now, you can write the planned username/password/database name. Then, in the zabbix account, you need to edit:

# vi /usr/local/etc/zabbix_server.conf

Change the following parameters:

DBHost=localhost
DBName=zabbix
DBUser=zabbix
DBPassword=<write-here-your-password>

chmod 600/usr/local/etc/zabbix_server.conf

The location of the default external scripts will be as follows:

/usr/local/share/zabbix/externalscripts 

This depends on the datadir compile-time installation variable. The alertscripts directory will be in the following location:

/usr/local/share/zabbix/alertscripts 

Now, we need to configure the agent. The configuration file is where we need to write the IP address of our Zabbix server. Once done, it is important to add two new services to the right runlevel to be sure that they will start when the server enters on the right runlevel.

To complete this task, we need to install the start/stop scripts on the following:

There are several scripts prebuilt inside the misc folder located at the following location:

zabbix-2.4.4/misc/init.d

This folder contains different startup scripts for different Linux variants, but this tree is not actively maintained and tested, and may not be up to date with the most recent versions of Linux distributions, so it is better to take care and test it before going live.

Once the start/stop script is added inside the /etc/init.d folder, we need to add them to the service list:

# chkconfig --add zabbix-server
# chkconfig --add zabbix-agentd

Now, all that is left is to tell the system which runlevel it should start them on; we are going to use runlevels 3 and 5:

# chkconfig --level 35 zabbix-server on
# chkconfig --level 35 zabbix-agentd on

Also, in case you have a local firewall active in your Zabbix server, you need to properly configure iptables to allow traffic against Zabbix's server port with the following command that you need to run as root:

# iptables -I INPUT 1 -p tcp --dport 10051 -j ACCEPT
# iptables-save

Currently, we can't start the server; before starting up our server, we need to configure the database.

Now, from your web browser, you need to open the following URL:

http://<server_ip_or_name>/zabbix

The first screen that you will meet is a welcome page; there is nothing to do there other than to click on Next. When on the first page, you may get a warning on your browser that informs you that the date / time zone is not set. This is a parameter inside the php.ini file. All the possible time zones are described on the official PHP website at http://www.php.net/manual/en/timezones.php.

The parameter to change is the date/time zone inside the php.ini file. If you don't know the current PHP configuration or where it is located in your php.ini file, and you need detailed information about which modules are running or the current settings, then you can write a file, for example, php-info.php, inside the Zabbix directory with the following content:

<?phpphpinfo();phpinfo(INFO_MODULES);
?>

Now point your browser to http://your-zabbix-web-frontend/zabbix/php-info.php.

You will have your full configuration printed out on a web page. The following screenshot is more important; it displays a prerequisite check, and, as you can see, there is at least one prerequisite that is not met:

On standard Red-Hat/CentOS 6.6, you only need to set the time zone; otherwise, if you're using an older version, you might have to change the following prerequisites that most likely are not fulfilled:

PHP option post_max_size           8M    16M    Fail
PHP option max_execution_time      30    300    Fail
PHP option max_input_time          60    300    Fail
PHP bcmath                         no           Fail
PHP mbstring                       no           Fail
PHP gd  unknown                          2.0    Fail
PHP gd PNG support                 no           Fail
PHP gd JPEG support                no           Fail
PHP gd FreeType support            no           Fail
PHP xmlwriter                      no           Fail
PHP xmlreader                      no           Fail

Most of these parameters are contained inside the php.ini file. To fix them, simply change the following options inside the /etc/php.ini file:

[Date]
; Defines the default timezone used by the date functions
; http://www.php.net/manual/en/datetime.configuration.php#ini.date.timezone
date.timezone = Europe/Rome

; Maximum size of POST data that PHP will accept.
; http://www.php.net/manual/en/ini.core.php#ini.post-max-size
post_max_size = 16M

; Maximum execution time of each script, in seconds
; http://www.php.net/manual/en/info.configuration.php#ini.max-execution-time
max_execution_time = 300

; Maximum amount of time each script may spend parsing request data. It's a good
; idea to limit this time on productions servers in order to eliminate unexpectedly
; long running scripts.
; Default Value: -1 (Unlimited)
; Development Value: 60 (60 seconds)
; Production Value: 60 (60 seconds)
; http://www.php.net/manual/en/info.configuration.php#ini.max-input-time
max_input_time = 300

; Maximum amount of time each script may spend parsing request data. It's a good
; idea to limit this time on productions servers in order to eliminate unexpectedly
; long running scripts.
; Default Value: -1 (Unlimited)
; Development Value: 60 (60 seconds)
; Production Value: 60 (60 seconds)
; http://www.php.net/manual/en/info.configuration.php#ini.max-input-time
max_input_time = 300

To solve the issue of the missing library, we need to install the following packages:

We will use the following command to install these packages:

# yum install php-xml php-bcmath php-mbstring php-gd

The whole list or the prerequisite list is given in the following table:

php-net-socket module

Every time you change a php.ini file or install a PHP extension, the httpd service needs a restart to get the change. Once all the prerequisites are met, we can click on Next and go ahead. On the next screen, we need to configure the database connection. We simply need to fill out the form with the username, password, IP address, or hostname and specify the kind of database server we are using, as shown in the following screenshot:

If the connection is fine (this can be checked with a test connection), we can proceed to the next step. Here, you only need to set the proper database parameters to enable the web GUI to create a valid connection, as shown in the following screenshot:

There is no check for the connection available on this page, so it is better to verify that it is possible to reach the Zabbix server from the network. In this form, it is necessary to fill Host (or IP address) of our Zabbix server. Since we are installing the infrastructure on three different servers, we need to specify all the parameters and verify that the Zabbix server port is available on the outside of the server.

Once we fill this form, we can click on Next. After this, the installation wizard prompts us to view Pre-Installation summary, which is a complete summary of all the configuration parameters. If all is fine, just click on Next; otherwise, we can go back and change our parameters. When we go ahead, we see that the configuration file has been generated (for example, in this installation the file has been generated in /usr/share/zabbix/conf/zabbix.conf.php).

It can happen that you may get an error instead of a success notification, and most probably, it is about the directory permission on our conf directory at /usr/share/zabbix/conf. Remember to make the directory writable to the httpd user (normally, Apache is writable) at least for the time needed to create this file. Once this step is completed, the frontend is ready and we can perform our first login.

Zabbix is a good monitoring system because it is really lightweight. Unfortunately, every observed system will spend a bit of its resources to run the agent that acquires and measures data and metrics against the operating system, so it is normal if the agent introduces a small (normally very small) overhead on the guest system. This is known as the observer effect. We can only accept this burden on our server and be aware that this will introduce a slight distortion in data collection, bearing in mind that we should keep it lightweight to a feasible extent while monitoring the process and our custom checks.

The Zabbix agent's job is to collect data periodically from the monitored machine and send metrics to the Zabbix server (that will be our aggregation and elaboration server). Now, in this scenario, there are certain important things to consider:

Considering the first point, it is important to think what should be monitored on our host and the kind of work that our host will do; or, in other words, what function it will serve.

There are some basic metrics of operating systems that are, nowadays, more or less standardized, and those are: the CPU workload, percentage of free memory, memory usage details, usage of swap, the CPU time for a process, and all this family of measure, all of them are built-in on the Zabbix agent.

Having a set of items with built-in measurement means that they are optimized to produce as little workload as possible on the monitored host; the whole of Zabbix's agent code is written in this way.

All the other metrics can be divided by the service that our server should provide.

Doing a practical example and considering monitoring the RDBMS, it will be fundamental to acquire:

Our different custom RDBMS metrics can be: the number of users connected, the use of cache systems, the number of full table scans, and so on.

All those kinds of metrics will be really useful and can be easily interpolated and compared against the same time period in a graph. Graphs have some strongpoints:

Coming back to our practical example, well, currently we are acquiring data from our RDBMS and our operating system. We can compare the workload of our RDBMS and see how this reflects the workload against our OS. Now?

Most probably, our core business is the revenue of a website, merchant site, or a web application. We assume that we need to keep a website in a three-tier environment under control because it is quite a common case. Our infrastructure will be composed of the following actors:

In real life, most probably, this is the kind of environment that Zabbix will be configured in. We need to be aware that every piece and every component that can influence our service should be measured and stored inside our Zabbix monitoring system. Generally, we can consider it to be quite normal to see people with a strong system administration background to be more focused on operating system-related items as well. We also saw people writing Java code that needs to be concentrated on some other obscure measure, such as the number of threads. The same kind of reasoning can be done if the capacity planner talks with a database administrator or a specific guy from every sector.

This is a quite important point because the Zabbix implementer should have a global vision and should remember that, when buying new hardware, the interface will most likely be a business unit.

This business unit very often doesn't know anything about the number of threads that our system can support but will only understand customer satisfaction, customer-related issues, and how many concurrent users we can successfully serve.

Having said that, it is really important to be ready to talk in their language, and we can do that only if we have certain efficient items to graph.

Now, if we look at the whole infrastructure from a client's point of view, we can think that if all our pages are served in a reasonable time, the browsing experience will be pleasant.

Our goal in this case is to make our clients happy and the whole infrastructure reliable. Now, we need to have two kinds of measures:

We need to quantify the response time related to the user's navigation, and we need to know how much a user can wait in front of a web page to get a response, keeping in mind that the whole browsing experience needs to be pleasant. We can measure and categorize our metrics with these three levels of response time:

Now, we have our thresholds and we can measure the response of a web page during normal browsing, and in the meantime, we can set a trigger level to warn us when the response time is more than two seconds for a page.

Now we need to relate that to all our other measures: the number of users connected, the number of sessions in our application server, and the number of connections to our database. We also need to relate all our measures to the response time and the number of users connected. Now, we need to measure how our system is serving pages to users during normal browsing.

This can be defined as a baseline. It is where we currently are and is a measure of how our system is performing under a normal load.

Now that we know how we are, and we have defined the threshold for our goal, along with the pleasant browsing experience, let's move forward.

We need to know which one is our limit and, more importantly, how the system should reply to our requests. Since we can't hire a room full of people that can click on our website like crazy, we need to use software to simulate this kind of behavior. There is interesting open source software that does exactly this. There are different alternatives to choose from—one of them is Siege (https://www.joedog.org/2013/07/siege-3-0-3-url-encoding/).

Seige permits us to simulate a stored browser history and load it on our server. We need to keep in mind that users, real users, will never be synchronized between them. So, it is important to introduce a delay between all the requests. Remember that if we have a login, then we need to use a database of users because application servers cache their object, and we don't want to measure how good the process is in caching them. The basic rule is to create a real browsing scenario against our website, so users who login can log out with just a click and without any random delay.

The stored scenarios should be repeated x times with a growing number of users, meaning Zabbix will store our metrics, and, at a certain point, we will pass our first threshold (1-2 seconds per web page). We can go ahead until the response time reaches the value of our second threshold. There is no way to see how much load our server can take, but it is well known that appetite comes with eating, so I will not be surprised if you go ahead and load your server until it crashes one of the components of your infrastructure.

Drawing graphs that relate the response time to the number of users on a server will help us to see whether our three-tier web architecture is linear or not. Most probably, it will grow in a linear pattern until a certain point. This segment is the one on which our system is performing fine. We can also see the components inside Zabbix, and from this point, we can introduce a kind of delay and draw some conclusions.

Now, we know exactly what to expect from our system and how the system can serve our users. We can see which component is the first that suffers the load and where we need to plan a tuning.

Capacity planning can be done without digging and going deep into what to optimize. As we said earlier, there are two different tasks—performance tuning and capacity planning—that are related, of course, but different. We can simply review our performance and plan our infrastructure expansion.

We can also perform performance tuning, but be aware that there is a relation between the time spent and the performance obtained, so we need to understand when it is time to stop our performance tuning, as shown in the following graph:

One of the most important features of Zabbix is the capacity to store historical data. This feature is of vital importance during the task of predicting trends. Predicting our trends is not an easy task and is important considering the business that we are serving, and when looking at historical data, we should see whether there are repetitive periods or whether there is a sort of formula that can express our trend.

For instance, it is possible that the online web store we are monitoring needs more and more resources during a particular period of the year, for example, close to public holidays if we sell travels. While doing a practical example, you can consider the used space on a specific server disk. Zabbix gives us the export functionality to get our historical data, so it is quite easy to import them in a spreadsheet. Excel has a curve fitting option that will help us a lot. It is quite easy to find a trend line using Excel that will tell us when we are going to exhaust all our disk space. To add a trend line into Excel, we need to create, at first, a "scatter graph" with our data; here, it is also important to graph the disk size. After this, we can try to find a mathematical equation that is more close to our trend. There are different kinds of formulae that we can choose; in this example, I used a linear equation because the graphs are growing with a linear relation.

The graph that comes out from this process permits us to know, with a considerable degree of precision, when we will run out of space.

Now, it is clear how important it is to have a considerable amount of historical data, bearing in mind the business period and how it influences data.

The graph obtained is shown in the following screenshot, and from this graph, it is simple to see that if the trends don't change, we are going to run out of space on June 25, 2015: