# Language Reference ## 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 character and can be broken up into multiple lines. Alternatively you can write multiple statements on a single line by separating them with a semicolon: 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 semicolons may also be used. The following data types are available for property values: All objects have at least the following attributes: Attribute | Description ---------------------|----------------------------- name | The name of the object. This attribute can be modified in the object definition to override the name specified with the `object` directive. type | The type of the object. ## Expressions The following expressions can be used on the right-hand side of assignments. ### 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 used to denote truth values. ### 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-sensitive manner. Individual key-value pairs must either be comma-separated or on separate lines. 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 enclose the key in double quotes. ### Array An ordered list of values. Individual array elements must be comma-separated. 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. The operators are by descending precedence. Operator | Precedence | Examples (Result) | Description ---------|------------|-----------------------------------------------|-------------------------------- () | 1 | (3 + 3) * 5 | Groups sub-expressions () | 1 | Math.random() | Calls a function [] | 1 | a[3] | Array subscript . | 1 | a.b | Element access ! | 2 | !"Hello" (false), !false (true) | Logical negation of the operand ~ | 2 | ~true (false) | Bitwise negation of the operand + | 2 | +3 | Unary plus - | 2 | -3 | Unary minus * | 3 | 5m * 10 (3000) | Multiplies two numbers / | 3 | 5m / 5 (60) | Divides two numbers % | 3 | 17 % 12 (5) | Remainder after division + | 4 | 1 + 3 (4), "hello " + "world" ("hello world") | Adds two numbers; concatenates strings - | 4 | 3 - 1 (2) | Subtracts two numbers << | 5 | 4 << 8 (1024) | Left shift >> | 5 | 1024 >> 4 (64) | Right shift < | 6 | 3 < 5 (true) | Less than > | 6 | 3 > 5 (false) | Greater than <= | 6 | 3 <= 3 (true) | Less than or equal >= | 6 | 3 >= 3 (true) | Greater than or equal in | 7 | "foo" in [ "foo", "bar" ] (true) | Element contained in array !in | 7 | "foo" !in [ "bar", "baz" ] (true) | Element not contained in array == | 8 | "hello" == "hello" (true), 3 == 5 (false) | Equal to != | 8 | "hello" != "world" (true), 3 != 3 (false) | Not equal to & | 9 | 7 & 3 (3) | Binary AND ^ | 10 | 17 ^ 12 (29) | Bitwise XOR | | 11 | 2 | 3 (3) | Binary OR && | 13 | true && false (false), 3 && 7 (7), 0 && 7 (0) | Logical AND || | 14 | true || false (true), 0 || 7 (7)| Logical OR = | 12 | a = 3 | Assignment => | 15 | x => x * x (function with arg x) | Lambda, for loop ### Function Calls Functions can be called using the `()` operator: const MyGroups = [ "test1", "test" ] { check_interval = len(MyGroups) * 1m } A list of available functions is available in the [Library Reference](21-library-reference.md#library-reference) chapter. ## Assignments In addition to the `=` operator shown above a number of other operators to manipulate attributes are supported. Here's a list of all available operators: ### Operator = Sets an attribute 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" } } If the `hello` attribute does not already have a value it is automatically initialized to an empty dictionary. ## Template Imports Objects can import attributes from other objects. Example: template Host "default-host" { vars.colour = "red" } template Host "test-host" { import "default-host" vars.colour = "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 `colour` 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 accessed from any file. Constants cannot be changed once they are set. Icinga 2 provides a number of special global constants. Some of them can be overridden using the `--define` command line parameter: Variable |Description --------------------|------------------- PrefixDir |**Read-only.** Contains the installation prefix that was specified with cmake -DCMAKE_INSTALL_PREFIX. Defaults to "/usr/local". SysconfDir |**Read-only.** Contains the path of the sysconf directory. Defaults to PrefixDir + "/etc". ZonesDir |**Read-only.** Contains the path of the zones.d directory. Defaults to SysconfDir + "/zones.d". LocalStateDir |**Read-only.** Contains the path of the local state directory. Defaults to PrefixDir + "/var". RunDir |**Read-only.** Contains the path of the run directory. Defaults to LocalStateDir + "/run". PkgDataDir |**Read-only.** Contains the path of the package data directory. Defaults to PrefixDir + "/share/icinga2". StatePath |**Read-write.** Contains the path of the Icinga 2 state file. Defaults to LocalStateDir + "/lib/icinga2/icinga2.state". ObjectsPath |**Read-write.** Contains the path of the Icinga 2 objects file. Defaults to LocalStateDir + "/cache/icinga2/icinga2.debug". PidPath |**Read-write.** Contains the path of the Icinga 2 PID file. Defaults to RunDir + "/icinga2/icinga2.pid". Vars |**Read-write.** Contains a dictionary with global custom attributes. Not set by default. NodeName |**Read-write.** Contains the cluster node name. Set to the local hostname by default. UseVfork |**Read-write.** Whether to use vfork(). Only available on *NIX. Defaults to true. AttachDebugger |**Read-write.** Whether to attach a debugger when Icinga 2 crashes. Defaults to false. RunAsUser |**Read-write.** Defines the user the Icinga 2 daemon is running as. Used in the `init.conf` configuration file. RunAsGroup |**Read-write.** Defines the group the Icinga 2 daemon is running as. Used in the `init.conf` configuration file. ## Apply The `apply` keyword can be used to create new objects which are associated with another group of objects. 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. [Expression operators](20-language-reference.md#expression-operators) may be used in `assign where` conditions. The `to` keyword and the target type may be omitted if there is only one 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 Assign Group objects can be assigned to specific member objects using the `assign where` and `ignore where` conditions. object HostGroup "linux-servers" { display_name = "Linux Servers" assign where host.vars.os == "Linux" } In this example the `assign where` condition is a boolean expression which is evaluated for all objects of the type `Host`. Each matching host is added as member to the host group with the name "linux-servers". Membership exclusion can be controlled using the `ignore where` condition. [Expression operators](20-language-reference.md#expression-operators) may be used in `assign where` and `ignore where` conditions. Source Type | Variables ------------------|-------------- HostGroup | host ServiceGroup | host, service UserGroup | user ## Boolean Values The `assign where`, `ignore where`, `if` and `while` statements, the `!` operator 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 For a list of supported expression operators for `assign where` and `ignore where` statements, see [expression operators](20-language-reference.md#expression-operators). ## 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 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/include is included in the list of search paths. Additional include search paths can be added using [command-line options](8-cli-commands.md#config-include-path). 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. ## Zone Includes The `include_zones` recursively includes all subdirectories for the given path. In addition to that it sets the `zone` attribute for all objects created in these subdirectories to the name of the subdirectory. Example: include_zones "etc", "zones.d", "*.conf" include_zones "puppet", "puppet-zones" The first parameter specifies a tag name for this directive. Each `include_zones` invocation should use a unique tag name. When copying the zones' configuration files Icinga uses the tag name as the name for the destination directory in `/var/lib/icinga2/api/config`. The second parameter specifies the directory which contains the subdirectories. The file names need to match the pattern given in the third 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" ## Functions Functions can be defined using the `function` keyword. Example: function multiply(a, b) { return a * b } When encountering the `return` keyword further execution of the function is terminated and the specified value is supplied to the caller of the function: log(multiply(3, 5)) In this example the `multiply` function we declared earlier is invoked with two arguments (3 and 5). The function computes the product of those arguments and makes the result available to the function's caller. When no value is supplied for the `return` statement the function returns `null`. Functions which do not have a `return` statement have their return value set to the value of the last expression which was performed by the function. For example, we could have also written our `multiply` function like this: function multiply(a, b) { a * b } Anonymous functions can be created by omitting the name in the function definition. The resulting function object can be used like any other value: var fn = function() { 3 } fn() /* Returns 3 */ ## Lambda Expressions Functions can also be declared using the alternative lambda syntax. Example: f = (x) => x * x Multiple statements can be used by putting the function body into braces: f = (x) => { log("Lambda called") x * x } Just like with ordinary functions the return value is the value of the last statement. For lambdas which take exactly one argument the braces around the arguments can be omitted: f = x => x * x ## Abbreviated Lambda Syntax Lambdas which take no arguments can also be written using the abbreviated lambda syntax. Example: f = {{ 3 }} This creates a new function which returns the value 3. ## Variable Scopes When setting a variable Icinga checks the following scopes in this order whether the variable already exists there: * Local Scope * `this` Scope * Global Scope The local scope contains variables which only exist during the invocation of the current function, object or apply statement. Local variables can be declared using the `var` keyword: function multiply(a, b) { var temp = a * b return temp } Each time the `multiply` function is invoked a new `temp` variable is used which is in no way related to previous invocations of the function. When setting a variable which has not previously been declared as local using the `var` keyword the `this` scope is used. The `this` scope refers to the current object which the function or object/apply statement operates on. object Host "localhost" { check_interval = 5m } In this example the `this` scope refers to the "localhost" object. The `check_interval` attribute is set for this particular host. You can explicitly access the `this` scope using the `this` keyword: object Host "localhost" { var check_interval = 5m /* This explicitly specifies that the attribute should be set * for the host, if we had omitted `this.` the (poorly named) * local variable `check_interval` would have been modified instead. */ this.check_interval = 1m } Similarly the keywords `locals` and `globals` are available to access the local and global scope. Functions also have a `this` scope. However unlike for object/apply statements the `this` scope for a function is set to whichever object was used to invoke the function. Here's an example: hm = { h_word = null function init(word) { h_word = word } } /* Let's invoke the init() function */ hm.init("hello") We're using `hm.init` to invoke the function which causes the value of `hm` to become the `this` scope for this function call. ## Closures By default `function`s, `object`s and `apply` rules do not have access to variables declared outside of their scope (except for global variables). In order to access variables which are defined in the outer scope the `use` keyword can be used: function MakeHelloFunction(name) { return function() use(name) { log("Hello, " + name) } } In this case a new variable `name` is created inside the inner function's scope which has the value of the `name` function argument. Alternatively a different value for the inner variable can be specified: function MakeHelloFunction(name) { return function() use (greeting = "Hello, " + name) { log(greeting) } } ## Conditional Statements Sometimes it can be desirable to only evaluate statements when certain conditions are met. The if/else construct can be used to accomplish this. Example: a = 3 if (a < 5) { a *= 7 } else if (a > 10) { a *= 5 } else { a *= 2 } An if/else construct can also be used in place of any other value. The value of an if/else statement is the value of the last statement which was evaluated for the branch which was taken: a = if (true) { log("Taking the 'true' branch") 7 * 3 } else { log("Taking the 'false' branch") 9 } This example prints the log message "Taking the 'true' branch" and the `a` variable is set to 21 (7 * 3). The value of an if/else construct is null if the condition evaluates to false and no else branch is given. ## While Loops The `while` statement checks a condition and executes the loop body when the condition evaluates to `true`. This is repeated until the condition is no longer true. Example: var num = 5 while (num > 5) { log("Test") num -= 1 } The `continue` and `break` keywords can be used to control how the loop is executed: The `continue` keyword skips over the remaining expressions for the loop body and begins the next loop evaluation. The `break` keyword breaks out of the loop. ## For Loops The `for` statement can be used to iterate over arrays and dictionaries. Example: var list = [ "a", "b", "c" ] for (item in list) { log("Item: " + item) } The loop body is evaluated once for each item in the array. The variable `item` is declared as a local variable just as if the `var` keyword had been used. Iterating over dictionaries can be accomplished in a similar manner: var dict = { a = 3, b = 7 } for (key => value in dict) { log("Key: " + key + ", Value: " + value) } The `continue` and `break` keywords can be used to control how the loop is executed: The `continue` keyword skips over the remaining expressions for the loop body and begins the next loop evaluation. The `break` keyword breaks out of the loop. ## Exceptions Built-in commands may throw exceptions to signal errors such as invalid arguments. User scripts can throw exceptions using the `throw` keyword. Example: throw "An error occurred." There is currently no way for scripts to catch exceptions. ## Types All values have a static type. The `typeof` function can be used to determine the type of a value: typeof(3) /* Returns an object which represents the type for numbers */ The following built-in types are available: Type | Examples | Description -----------|-------------------|------------------------ Number | 3.7 | A numerical value. Boolean | true, false | A boolean value. String | "hello" | A string. Array | [ "a", "b" ] | An array. Dictionary | { a = 3 } | A dictionary. Depending on which libraries are loaded additional types may become available. The `icinga` library implements a whole bunch of other types, e.g. Host, Service, CheckCommand, etc. Each type has an associated type object which describes the type's semantics. These type objects are made available using global variables which match the type's name: /* This logs 'true' */ log(typeof(3) == Number) The type object's `prototype` property can be used to find out which methods a certain type supports: /* This returns: ["find","len","lower","replace","split","substr","to_string","upper"] */ keys(String.prototype) ## Reserved Keywords These keywords are reserved and must not be used as constants or custom attributes. object template include include_recursive library null true false const var this use apply to where import assign ignore function return for if else in You can escape reserved keywords using the `@` character. The following example tries to set `vars.include` which references a reserved keyword and generates an error: [2014-09-15 17:24:00 +0200] critical/config: Location: /etc/icinga2/conf.d/hosts/localhost.conf(13): vars.sla = "24x7" /etc/icinga2/conf.d/hosts/localhost.conf(14): /etc/icinga2/conf.d/hosts/localhost.conf(15): vars.include = "some cmdb export field" ^^^^^^^ /etc/icinga2/conf.d/hosts/localhost.conf(16): } /etc/icinga2/conf.d/hosts/localhost.conf(17): Config error: in /etc/icinga2/conf.d/hosts/localhost.conf: 15:8-15:14: syntax error, unexpected include (T_INCLUDE), expecting T_IDENTIFIER [2014-09-15 17:24:00 +0200] critical/config: 1 errors, 0 warnings. You can escape the `include` keyword by prefixing it with an additional `@` character: object Host "localhost" { import "generic-host" address = "127.0.0.1" address6 = "::1" vars.os = "Linux" vars.sla = "24x7" vars.@include = "some cmdb export field" }