icinga2/doc/4.1-configuration-syntax.md

Configuration Syntax

Object Definition

Icinga 2 features an object-based configuration format. You can define new objects using the object keyword:

object Host "host1.example.org" {
  display_name = "host1"

  address = "192.168.0.1"
  address6 = "::1"
}

In general you need to write each statement on a new line. Expressions started with {, ( and [ extend until the matching closing brace and can be broken up into multiple lines.

Alternatively you can write multiple statements in a single line by separating them with a semi-colon:

object Host "host1.example.org" {
  display_name = "host1"

  address = "192.168.0.1"; address6 = "::1"
}

Each object is uniquely identified by its type (Host) and name (host1.example.org). Some types have composite names, e.g. the Service type which uses the host_name attribute and the name you specified to generate its object name.

Exclamation marks (!) are not permitted in object names.

Objects can contain a comma-separated list of property declarations. Instead of commas semi-colons may also be used. The following data types are available for property values:

Expressions

The following expressions can be used in the right-hand side of dictionary values.

Numeric Literals

A floating-point number.

Example:

-27.3

Duration Literals

Similar to floating-point numbers except for the fact that they support suffixes to help with specifying time durations.

Example:

2.5m

Supported suffixes include ms (milliseconds), s (seconds), m (minutes), h (hours) and d (days).

Duration literals are converted to seconds by the config parser and are treated like numeric literals.

String Literals

A string.

Example:

"Hello World!"

Certain characters need to be escaped. The following escape sequences are supported:

Character	Escape sequence
"	\"
\	\\
<TAB>	\t
<CARRIAGE-RETURN>	\r
<LINE-FEED>	\n
<BEL>	\b
<FORM-FEED>	\f

In addition to these pre-defined escape sequences you can specify arbitrary ASCII characters using the backslash character (\) followed by an ASCII character in octal encoding.

Multi-line String Literals

Strings spanning multiple lines can be specified by enclosing them in {{{ and }}}.

Example.

{{{This
is
a multi-line
string.}}}

Unlike in ordinary strings special characters do not have to be escaped in multi-line string literals.

Boolean Literals

The keywords true and false are equivalent to 1 and 0 respectively.

Null Value

The null keyword can be used to specify an empty value.

Dictionary

An unordered list of key-value pairs. Keys must be unique and are compared in a case-insensitive manner.

Individual key-value pairs must be separated from each other with a comma. The comma after the last key-value pair is optional.

Example:

{
  address = "192.168.0.1"
  port = 443
}

Identifiers may not contain certain characters (e.g. space) or start with certain characters (e.g. digits). If you want to use a dictionary key that is not a valid identifier you can put the key in double quotes.

Setting a dictionary key to null causes the key and its value to be removed from the dictionary.

Array

An ordered list of values.

Individual array elements must be separated from each other with a comma. The comma after the last element is optional.

Example:

[ "hello", 42 ]

An array may simultaneously contain values of different types, such as strings and numbers.

Operators

The following operators are supported in expressions:

Operator	Examples (Result)	Description
!	!"Hello" (false), !false (true)	Logical negation of the operand
~	~true (false)	Bitwise negation of the operand

•    | 1 + 3 (4), "hello " + "world" ("hello world") | Adds two numbers; concatenates strings
  

•    | 3 - 1 (2)                                     | Subtracts two numbers
  

•    | 5m * 10 (3000)                                | Multiplies two numbers
  

/ | 5m / 5 (60) | Divides two numbers & | 7 & 3 (3) | Binary AND | | 2 | 3 (3) | Binary OR < | 3 < 5 (true) | Less than

   | 3 > 5 (false)                                 | Greater than

<= | 3 <= 3 (true) | Less than or equal

= | 3 >= 3 (true) | Greater than or equal << | 4 << 8 (1024) | Left shift

  | 1024 >> 4 (64)                                | Right shift

== | "hello" == "hello" (true), 3 == 5 (false) | Equal to != | "hello" != "world" (true), 3 != 3 (false) | Not equal to in | "foo" in [ "foo", "bar" ] (true) | Element contained in array !in | "foo" !in [ "bar", "baz" ] (true) | Element not contained in array () | (3 + 3) * 5 | Groups sub-expressions

Constants may be used in expressions:

const MyCheckInterval = 10m

...

{
  check_interval = MyCheckInterval / 2.5
}

Function Calls

Functions can be called using the () operator:

const MyGroups = [ "test1", "test" ]

{
  check_interval = len(MyGroups) * 1m
}

Function	Description
regex(pattern, text)	Returns true if the regex pattern matches the text, false otherwise.
match(pattern, text)	Returns true if the wildcard pattern matches the text, false otherwise.
len(value)	Returns the length of the value, i.e. the number of elements for an array or dictionary, or the length of the string in bytes.
union(array, array, ...)	Returns an array containing all unique elements from the specified arrays.
intersection(array, array, ...)	Returns an array containing all unique elements which are common to all specified arrays.
string(value)	Converts the value to a string.
number(value)	Converts the value to a number.
bool(value)	Converts to value to a bool.
log(value)	Writes a message to the log. Non-string values are converted to a JSON string.
log(severity, facility, value)	Writes a message to the log. severity can be one of LogDebug, LogInformation, LogWarning and LogCritical. Non-string values are converted to a JSON string.
exit(integer)	Terminates the application.

Dictionary Operators

In addition to the = operator shown above a number of other operators to manipulate dictionary elements are supported. Here's a list of all available operators:

Operator =

Sets a dictionary element to the specified value.

Example:

{
  a = 5,
  a = 7
}

In this example a has the value 7 after both instructions are executed.

Operator +=

The += operator is a shortcut. The following expression:

{
  a = [ "hello" ]
  a += [ "world" ]
}

is equivalent to:

{
  a = [ "hello" ]
  a = a + [ "world" ]
}

Operator -=

The -= operator is a shortcut. The following expression:

{
  a = 10
  a -= 5
}

is equivalent to:

{
  a = 10
  a = a - 5
}

Operator *=

The *= operator is a shortcut. The following expression:

{
  a = 60
  a *= 5
}

is equivalent to:

{
  a = 60
  a = a * 5
}

Operator /=

The /= operator is a shortcut. The following expression:

{
  a = 300
  a /= 5
}

is equivalent to:

{
  a = 300
  a = a / 5
}

Indexer

The indexer syntax provides a convenient way to set dictionary elements.

Example:

{
  hello.key = "world"
}

Example (alternative syntax):

{
  hello["key"] = "world"
}

This is equivalent to writing:

{
  hello += {
    key = "world"
  }
}

Template Imports

Objects can import attributes from other objects.

Example:

template Host "default-host" {
  vars.color = "red"
}

template Host "test-host" {
  import "default-host"

  vars.color = "blue"
}

object Host "localhost" {
  import "test-host"

  address = "127.0.0.1"
  address6 = "::1"
}

The default-host and test-host objects are marked as templates using the template keyword. Unlike ordinary objects templates are not instantiated at run-time. Parent objects do not necessarily have to be templates, however in general they are.

The vars dictionary for the localhost object contains all three custom attributes and the custom attribute color has the value "blue".

Parent objects are resolved in the order they're specified using the import keyword.

Constants

Global constants can be set using the const keyword:

const VarName = "some value"

Once defined a constant can be access from any file. Constants cannot be changed once they are set.

Apply

The apply keyword can be used to create new objects which are associated with another group of objects. Applying group membership for objects can be done in a similar way using group apply

apply Service "ping" to Host {
  import "generic-service"

  check_command = "ping4"

  assign where host.name == "localhost"
}

In this example the assign where condition is a boolean expression which is evaluated for all objects of type Host and a new service with name "ping" is created for each matching host.

The to keyword and the target type may be omitted if there is only target type, e.g. for the Service type.

Depending on the object type used in the apply expression additional local variables may be available for use in the where condition:

Source Type	Target Type	Variables
Service	Host	host
Dependency	Host	host
Dependency	Service	host, service
Notification	Host	host
Notification	Service	host, service
ScheduledDowntime	Host	host
ScheduledDowntime	Service	host, service

Any valid config attribute can be accessed using the host and service variables. For example, host.address would return the value of the host's "address" attribute - or null if that attribute isn't set.

Group Membership Apply

The apply keyword can be used for groups too. Instead of creating a new object (for example a new HostGroup object for every matching Host) it will create the group object only once and add the membership for the matching rule object.

apply HostGroup "www" to Host {
  display_name = "Web Server"

  assign where match("*www*", host.name)
}

In this example the assign where condition is a boolean expression which is evaluated for all object of type Host. A new host group with name "www" is created and each matching host is added to this host group.

Depending on the group object type used in the apply expression additional local variables may be available for use in the where condition:

Source Type	Target Type	Variables
HostGroup	Host	host
ServiceGroup	Service	host, service
UserGroup	User	user

Any valid config attribute can be accessed using the host, service and user variables. For example, user.vars.sla would return the value of the user's custom attribute "sla" - or null if that attribute isn't set.

Boolean Values

The assign where and ignore where statements, the !, && and || operators as well as the bool() function convert their arguments to a boolean value based on the following rules:

Description	Example Value	Boolean Value
Empty value	null	false
Zero	0	false
Non-zero integer	-23945	true
Empty string	""	false
Non-empty string	"Hello"	true
Empty array	[]	false
Non-empty array	[ "Hello" ]	true
Empty dictionary	{}	false
Non-empty dictionary	{ key = "value" }	true

Comments

The Icinga 2 configuration format supports C/C++-style and shell-style comments.

Example:

/*
 This is a comment.
 */
object Host "localhost" {
  check_interval = 30 // this is also a comment.
  retry_interval = 15 # yet another comment
}

Includes

Other configuration files can be included using the include directive. Paths must be relative to the configuration file that contains the include directive.

Example:

include "some/other/file.conf"
include "conf.d/*.conf"

Wildcard includes are not recursive.

Icinga also supports include search paths similar to how they work in a C/C++ compiler:

include <itl/itl.conf>

Note the use of angle brackets instead of double quotes. This causes the config compiler to search the include search paths for the specified file. By default $PREFIX/share/icinga2 is included in the list of search paths. Additional include search paths can be added using command-line options.

Wildcards are not permitted when using angle brackets.

Recursive Includes

The include_recursive directive can be used to recursively include all files in a directory which match a certain pattern.

Example:

include_recursive "conf.d", "*.conf"
include_recursive "templates"

The first parameter specifies the directory from which files should be recursively included.

The file names need to match the pattern given in the second parameter. When no pattern is specified the default pattern "*.conf" is used.

Library directive

The library directive can be used to manually load additional libraries. Libraries can be used to provide additional object types and functions.

Example:

library "snmphelper"