19 Éléments

Un élément est un test (métrique) de performance ou de disponibilité.

19.1 Clé de l'élément

19.1.1 Paramètes flexibles et non-flexibles

Un paramètre flexible est un paramètre qui accepte des arguments. Par exemple, vfs.fs.size[*] est un paramètre flexible. * signifie que n'importe quel caractère peut être passé en argument au paramètre. Voici des exemples de configuration valides:

• vfs.fs.size[/]
• vfs.fs.size[/opt]

19.1.2 Format de la clé

Le format de la clé de l'élément, y compris les paramètres clés, doit suivre des règles de syntaxe. L'illustration suivante représente la syntaxe supportée. Les éléments et caractères autorisé à chaque point peuvent être déterminés en suivant les lignes - "Si certains blocs peuvent être atteint par le biais de la ligne, c'est permis, sinon cela ne l'est pas" if some block can be reached through the line, it is allowed, if not - it is not allowed.

Clé d'élément

Pour construire une clé d'élément valide, on commence par spécifier le nom de la clé, ensuite on choisit ou non de renseigner un ou plusieurs paramètres comme représenté sur les deux lignes du schéma ci-dessous.

Nom de la clé

Le nom de la clé à une gamme limité de caractères autorisés. Les caractères autorisés sont:

0-9a-zA-Z_-.

Ce qui signifie:

• Tous les nombres;
• Toutes les lettres en minuscule;
• Toutes les lettres en majuscule;
• underscore "_";
• tiret "-";
• point ".";

Paramètres de la clé

Une clé d'item peut avoir plusieurs paramètres, séparés par une virgule.

Paramètre de clé individuel

Chaque paramètre de clé peut être déclaré entre guillemets, sans guillemet ou en tableau.

Un paramètre peut aussi être laissé vide, la valeur par défaut est alors utilisée. Dans les cas appropriés, un certain nombre de virgules doivent être ajoutée sur des paramètres supplémentaires sont ajoutés. Par exemple, la clé d'élément icmpping[,,200,,500] spécifie que l'intervalle entre les pings est de 200 millisecondes, le timeout - 500 millisecondes, et tous les autres paramètres sont laissés à leur valeur par défaut.

Paramètre - déclaration entre guillemet

Si le paramètre de l'élément est déclarée entre guillemets, tous les caractères Unicode sont autorisés, en incluant les guillemets qui doivent être échappées par un antislash.

Paramètre - déclaration sans guillemet

Si le paramètre de l'élément est déclarée sans guillemets, tous les caractères Unicode sont autorisés excepté les virgules (,) et les crochets (]).

Paramètre - tableau

Si le paramètre de l'élément est un tableau, il est déclaré entre crochets, où les paramètres individuels respectent les règles et syntaxe des paramètres multiples.

19.1.3 Encodages disponibles

Le paramètre "encodage" est utilisé pour spécifier l'encodage pour les traitements correspondant aux vérifications des éléments, ainsi les données récoltées ne seront pas corrompues. Pour une liste des encodages supportés (code page identifiers), veuillez consulter la documentation respective, tel que pour libiconv (Projet GNU) ou Microsoft Windows SDK documentation pour "Code Page Identifiers". Si une valeur vide pour le paramètre "encodage" est passée, ANSI avec ses extensions systèmes spécifiques (Windows) ou UTF-8 (default locale for newer Unix/Linux distributions, see your system's settings) sont utilisés par défaut.

19.2 Unsupported items

An item can become unsupported if its value can not be retrieved for some reason. Such items are still rechecked at a fixed interval, configurable in Administration section.

19.3 Supported by Platform

19.4 Zabbix Agent

List of supported parameters

WIN32-specific parameters

This section contains description of parameter supported by Zabbix WIN32 agent only.

19.5 SNMP Agent

Zabbix must be configured with SNMP support in order to be able to retrieve data provided by SNMP agents.

The following steps have to be performed in order to add monitoring of SNMP parameters:

Step 1

Create a host for the SNMP device.

Enter an IP address and a port of 161. Set the host Status to NOT MONITORED. You can use the host.SNMP template which would automatically add set of items. However, the template may not be compatible with the host.

Step 2

Find out the SNMP string of the item you want to monitor.

After creating the host, use 'snmpwalk' (part of ucd-snmp/net-snmp software which you should have installed as part of the Zabbix installation) or equivalent tool:

shell> snmpwalk <host or host IP> public

This will give you a list of SNMP strings and their last value. If it doesn't then it is possible that the SNMP 'community' is different from the standard public in which case you will need to find out what it is. You would then go through the list until you find the string you want to monitor, e.g. you wanted to monitor the bytes coming in to your switch on port 3 you would use:

interfaces.ifTable.ifEntry.ifOctetsIn.3 = Counter 32: 614794138

You should now use the snmpget command to find the OID for interfaces.ifTable.ifEntry.ifInOctets.3:

shell> snmpget -On 10.62.1.22 interfaces.ifTable.ifEntry.ifOctetsIn.3

where the last number in the string is the port number you are looking to monitor. This should give you something like the following:

.1.3.6.1.2.1.2.2.1.10.3 = Counter32: 614794138

again the last number in the OID is the port number.

3COM seem to use port numbers in the hundreds, e.g. port 1=port 101, port 3=port 103, but Cisco use regular numbers, e.g. port 3=3.

Step 3

Create an item for monitoring.

So, now go back to Zabbix and click on Items, selecting the SNMP host you created earlier. Depending on whether you used a template or not when creating your host you will have either a list of SNMP items associated with your host or just a new item box. We will work on the assumption that you are going to create the item yourself using the information you have just gathered using snmpwalk and snmpget, so enter a plain English description in the 'Description' field of the new item box. Make sure the 'Host' field has your switch/router in it and change the 'Type' field to "SNMPv1 agent". Enter the community (usually public) and enter the numeric OID that you retrieved earlier in to the 'SNMP OID' field being sure to include the leading dot, i.e. .1.3.6.1.2.1.2.2.1.10.3

Enter the 'SNMP port' as 161 and the 'Key' as something meaningful, e.g. SNMP-InOctets-Bps. Choose the Multiplier if you want one and enter an 'update interval' and 'keep history' if you want it to be different from the default. Set the 'Status' to Monitored, the 'Type of information' to Numeric (float) and the 'Store value' to DELTA (important otherwise you will get cumulative values from the SNMP device instead of the latest change).

Now save the item and go back to the hosts area of Zabbix. From here set the SNMP device to be Monitored and check in Latest data for your SNMP data!

Example 1

General example

Note that OID can be given in either numeric or string form. However, in some cases, string OID must be converted to numeric representation. Utility snmpget may be used for this purpose:

shell> snmpget -On localhost public enterprises.ucdavis.memory.memTotalSwap.0

Monitoring of SNMP parameters is possible if either -with-net-snmp or -with-ucd-snmp flag was specified while configuring Zabbix sources.

Example 2

Monitoring of Uptime

19.6 Simple checks

Simple checks are normally used for agent-less monitoring or for remote checks of services. Note that Zabbix agent is not needed for simple checks. Zabbix server is responsible for processing of simple checks (making external connections, etc).

All simple checks, except tcp and tcp_perf, accept one optional parameter:

• port - port number. If missing, standard default service port is used.

Examples of using simple checks:

ftp,155
       http
       http_perf,8080 

List of supported simple checks:

Timeout processing

Zabbix will not process a simple check longer than Timeout seconds defined in Zabbix server configuration file.

In case if Timeout time is exceeded, 2 is returned.

ICMP pings

Zabbix uses external utility fping for processing of ICMP pings. The utility is not part of Zabbix distribution and has to be additionally installed. If the utility is missing, has wrong permissions or its location does not match FpingLocation defined in configuration file, ICMP pings (icmpping, icmppingsec and icmppingloss) will not be processed.

Run these commands as user root in order to setup correct permissions:

shell> chown root:zabbix /usr/sbin/fping
       shell> chmod 710 /usr/sbin/fping
       shell> chmod ug+s /usr/sbin/fping

The default values for ICMP checks parameters:

Zabbix writes addresses to be checked to a temporary file, which is then passed to fping. If items have different parameters, only ones with identical parameters are written to a single file.

19.7 Internal checks

Internal checks allow monitoring of internals of Zabbix. Internal checks are calculated by Zabbix Server.

19.8 Aggregated checks

Aggregate checks do not require any agent running on a host being monitored. Zabbix server collects aggregate information by doing direct database queries.

Syntax of aggregate item's key

groupfunc["Host group","Item key","item func","parameter"]

Supported group functions:

Supported item functions:

Examples of keys for aggregate items:

Example 1

Total disk space of host group 'MySQL Servers'.

grpsum["MySQL Servers","vfs.fs.size[/,total]","last","0"]

Example 2

Average processor load of host group 'MySQL Servers'.

grpavg["MySQL Servers","system.cpu.load[,avg1]","last","0"]

Example 3

Average (5min) number of queries per second for host group 'MySQL Servers'

grpavg["MySQL Servers","mysql.qps","avg","300"]

19.9 External checks

External check is a check executed by Zabbix Server by running a shell script or a binary.

External checks do not require any agent running on a host being monitored.

Syntax of item's key:

script[parameters]
       * script – name of the script.
       * parameters – list of command line parameters.

If you don't want to pass your parameters to the script you may use:

script[] or
       script   <- this simplified syntax is supported starting from Zabbix 1.8.1

Zabbix server will find and execute the command in directory defined in configuration parameter ExternalScripts in zabbix_server.conf. Command will be executed as the user Zabbix server runs as, so any access permissions or environment variables should be handled in a wrapper script, if necessary, and permissions on the command should allow that user to execute it. Only commands in the specified directory are available.

First command line parameter is host name, other parameters are substituted by parameters.

Zabbix uses the standard output of the script as the value. Standard error and exit code are discarded.

Example 1

Execute script check_oracle.sh with parameters "-h 192.168.1.4". Host name 'www1.company.com'.

check_oracle.sh[-h 192.168.1.4]

Zabbix will execute:

check_oracle.sh www1.company.com -h 192.168.1.4.

19.10 SSH checks

Zabbix must be configured with SSH2 support. ::: noteimportant The minimal supported libssh2 library version is 1.0.0. :::

SSH checks are used for agent-less monitoring. Note that Zabbix agent is not needed for SSH checks.

Actual commands to be executed must be placed in the Executed script field in the item configuration. Multiple commands can be executed one after another by placing them on a new line.

19.11 Telnet checks

Telnet checks are used for agent-less monitoring. Zabbix agent is not needed for Telnet checks.

Actual commands to be executed must be placed in the Executed script field in the item configuration. Multiple commands can be executed one after another by placing them on a new line.

Till version 1.8.1, supported characters that prompt the prompt can end with:

• $
• #

Zabbix version 1.8.2 adds support for additional character:

• %

19.12 Calculated items

Calculated items is a very nice way of creating virtual data sources. Item values will be periodically calculated based on a arithmetical expression.

Resulting data will be stored in Zabbix database as for any other item - this means storing both history and trends values for fast graph generation.

To use calculated items, choose item type Calculated. You can create any key name using supported symbols. Calculation definition should be entered in the Formula field (named Expression in 1.8.1 and 1.8.2). Key is a unique identifier (per host), using allowed symbols.

A very simple expression might look like:

func(<key>|<hostname:key>,<parameter1>,<parameter2>,...)

More complex expression may use a combination of functions, operators and brackets. You could use all functions and operators supported in trigger expressions. Note that syntax is slightly different, however logic and operator precedence are exactly the same.

Supported characters for a hostname:

a..zA..Z0..9 ._-

Supported characters for a key:

a..zA..Z0..9.,_

Supported characters for a function:

a..zA..Z0..9_

Unlike trigger expressions, Zabbix processes calculated items according to item update interval, not upon receiving a new value. Also if you change item key of a referenced item, you have to update all formulas that used the old key manually.

A calculated item may become unsupported in several cases:

1. referenced item(s) not found
2. no data to calculate a function
3. division by zero
4. syntax errors

Example 1

Calculate percentage of free disk space on '/'.

Use of function last:

100*last("vfs.fs.size[/,free]")/last("vfs.fs.size[/,total]")

Zabbix will take the latest values for free and total disk spaces and calculate percentage according to the given formula.

Example 2

Calculate 10 minute average number of values processed by Zabbix.

Use of function avg:

avg("Zabbix Server:zabbix[wcache,values]",600)

Note that extensive use of calculated items with long time periods may affect performance of Zabbix Server.

Example 3

Calculate total bandwidth on eth0.

Sum of two functions:

last("net.if.in[eth0,bytes]")+last("net.if.out[eth0,bytes]")

Example 4

Calculate percentage of incoming traffic.

More complex expression:

100*last("net.if.in[eth0,bytes]")/(last("net.if.in[eth0,bytes]")+last("net.if.out[eth0,bytes]"))