3 Triggers

Visão geral

As triggers são expressões lógicas que analisam os dados coletados pelos itens e representam o estado do sistema em relação aos mesmos.

Enquanto os itens são utilizados para coletar dados, é impensável esperar que alguém tenha tempo para analisar manualmente todos os valores coletados para alertar sobre desvios e limites. O trabalho de analisar os dados deve ser deixado a cargo das expressões das trigger.

Uma expressão de trigger permite definir um limite aceitável de dados. Logo, quando o dado recebido fugir do limite aceitável a trigger será acionada, mudando seu estado para "INCIDENTE".

Uma trigger pode ter os seguintes estados:

O estado de uma trigger (a expressão) é recalculada toda vez que o Zabbix Server recebe um novo valor que afete a expressão.

Se funções baseadas em tempo (nodata(), date(), dayofmonth(), dayofweek(), time(), now()) forem utilizadas na expressão, o estado da trigger será recalculado a cada 30 segundos pelo processo de timer do Zabbix. Se forem utilizadas funções baseadas em tempo e funções normais, a trigger será recalculada quando receber um novo valour E a cada 30 segundos.

Você pode obter maiores detalhes através do manual de construção de expressões de trigger.

Calculation time

A trigger is recalculated every time Zabbix server receives a new value that is part of the expression. When a new value is received, each function that is included in the expression is recalculated (not just the one that received the new value).

Additionally, a trigger is recalculated each time when a new value is received and every 30 seconds if time-based functions are used in the expression.

Time-based functions are nodata(), date(), dayofmonth(), dayofweek(), time(), now()); they are recalculated every 30 seconds by the Zabbix history syncer process.

Evaluation period

An evaluation period is used in functions referencing the item history. It allows to specify the interval we are interested in. It can be specified as time period (30s, 10m, 1h) or as a value range (#5 - for five latest values).

The evaluation period is measured up to "now" - where "now" is the latest recalculation time of the trigger (see Calculation time above); "now" is not the "now" time of the server.

The evaluation period specifies either:

• To consider all values between "now-time period" and "now" (or, with time shift, between "now-time shift-time period" and "now-time_shift")
• To consider no more than the num count of values from the past, up to "now"
  • If there are 0 available values for the time period or num count specified - then the trigger or calculated item that uses this function becomes unsupported

Note that:

• If only a single function (referencing data history) is used in the trigger, "now" is always the latest received value. For example, if the last value was received an hour ago, the evaluation period will be regarded as up to the latest value an hour ago.
• A new trigger is calculated as soon as the first value is received (history functions); it will be calculated within 30 seconds for time-based functions. Thus the trigger will be calculated even though perhaps the set evaluation period (for example, one hour) has not yet passed since the trigger was created. The trigger will also be calculated after the first value, even though the evaluation range was set, for example, to ten latest values.