CycleCloud Cluster Template File Parsing

CycleCloud resolves parameter values and performs logical evaluation of functions.

Parameter Types

CycleCloud handles several basic types of parameters. In most cases, it handles them as expected:

Attribute = foo      # string
Attribute = 1        # integer
Attribute = 1.1      # double
Attribute = false    # boolean
Attribute = foo, bar # string[]

To be more explicit, string values can be surrounded by double quotes (for example, Attribute = "foo"). This syntax is useful when a value looks like a number but should be interpreted as a string, such as version numbers. Set Boolean values to the bare tokens true or false (case-insensitive). CycleCloud interprets comma-separated values as lists, and it interprets elements using the same rules as previously described.

Parameter Value Evaluation

CycleCloud directly interprets parameter values that use the $ or ${} notation.

MyAttribute = $MyParameter
MyAttribute2 = ${MyParameter2}
MyAttributeList = $Param1, $Param2

Functions that use parameters

The CycleCloud template parser can do math and ternary logic analysis, as shown in the following example.

MaxCoreCount = ${HyperthreadedCoreCount/2}
SubnetId = ${ifThenElse($Autoscale, $BurstSubnet, $FixedSubnet)}
JetpackPlatform = ${imageselect == "windows" ? "windows" : "centos-7"}

Available functions

Note

This list isn't comprehensive, but it covers some of the most commonly used functions.

ifThenElse

Acts as a ternary operator. Returns one of two values given an expression that evaluates to true or false.

Syntax:

ifThenElse(predicate, trueValue, falseValue)

Arguments:

Name	Required	Description
predicate	yes	An expression that evaluates to true or false.
trueValue	yes	The value to use when predicate evaluates to true.
falseValue	yes	The value to use when predicate evaluates to false.

ifUndefined

If the result of evaluating a given expression is undefined, returns a different value. Otherwise, it simply returns the result.

Syntax:

ifUndefined(expression, value)

Arguments:

Name	Required	Description
expression	yes	The expression to evaluate.
value	yes	The value to return when expression evaluates to undefined.

regexp

Performs a regular expression match on the given string. Returns true if there's a match, and false otherwise.

Syntax:

regexp(pattern, target, [options])

Arguments:

Name	Required	Description
pattern	yes	A Java-style regular expression.
target	yes	The input string.
options	no	Options to use when evaluating the regular expression. For more details, see Java's regular expression flags on java.util.regex.Pattern.

regexps

Performs regular expression substitution on the given string and returns the new string.

Syntax:

regexps(pattern, target, substitution, [options])

Arguments:

Name	Required	Description
pattern	yes	A Java-style regular expression that matches the string to substitute.
target	yes	The input string.
substitution	yes	The new string to substitute in place of the part of target that matches the regular expression.
options	no	Options to use when evaluating the regular expression. For more details, see Java's regular expression flags on java.util.regex.Pattern.

size

Returns the length of a given string.

Syntax:

size(string)

Arguments:

Name	Required	Description
string	yes	The string to check.

strjoin

Concatenates multiple strings together with a separator.

Syntax:

strjoin(separator, strings)

Arguments:

Name	Required	Description
separator	yes	A string separator to put between strings.
strings	yes	A list of strings to concatenate. You can also provide the strings as separate arguments: strjoin(separator, string1, string2, string3...)

substr

Returns part of a string from the start index to the end index (or the end of the string if you don't provide an end index).

Syntax:

substr(string, startIndex, [endIndex])

Arguments:

Name	Required	Description
string	yes	The input string.
startIndex	yes	The start index to use.
endIndex	no	An optional end index.

trim

Removes all whitespace characters from the start and end of a string and returns the result.

Syntax:

trim(string)

Arguments:

Name	Required	Description
string	yes	The string to trim.

Available operators

Operator	Definition
-, +, /, *	arithmetic
<, <=, >=, >	comparators
==, !=	equality evaluators
&&, ||	compound boolean operators

Special ClusterName Variable

The ${ClusterName} variable always exists. CycleCloud evaluates this variable to the name of the CycleCloud cluster.

EmailAddress = ${strcat("myuser", "@", ClusterName)}
ResourceId = ${ClusterName}-00-resource

Relative Time

CycleCloud interprets back-ticks around time duration as relative time. It supports seconds, minutes, and days.

ThrottleCapacityTime=`10m` 
Attribute1=`30s`
Attribute2=`7d`