CycleCloud Cluster Template File Parsing

CycleCloud is able to resolve parameter values and perform logical evaluation of functions.

Parameter Types

CycleCloud handles several basic types of parameters. In most cases, it will handle 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 may be useful in the case where a value looks like a number but should be interpreted as a string (version numbers, for example). Boolean values can be set to the bare tokens true or false (case-insensitive). Comma-separated values are interpreted as lists, and elements are in turn interpreted using the same rules as above.

Parameter Value Evaluation

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

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

Functions using Parameters

The CycleCloud template parser is able to perform math and do ternary logic analysis as seen below.

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

Available functions:

Note

This list is not comprehensive, but covers some of the most commonly-used functions.

ifThenElse

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

Syntax:

ifThenElse(predicate, trueValue, falseValue)

Arguments:

Name	Required	Description
predicate	yes	An expression which 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 instead. Otherwise 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 and returns true if there was a match, 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. See Java's regular expression flags on java.util.regex.Pattern for more details.

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 which matches the string to substitute.
target	yes	The input string.
substitution	yes	The new string to substitute in place of the part of target which matches the regular expression.
options	no	Options to use when evaluating the regular expression. See Java's regular expression flags on java.util.regex.Pattern for more details.

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 using a separator.

Syntax:

strjoin(separator, strings)

Arguments:

Name	Required	Description
separator	yes	A string separator to append between strings.
strings	yes	A list of strings to concatenate. May also be specified as a variable number of function 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 no end index is given).

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

One variable always provided is ${ClusterName}. This is evaluated 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; supporting second, minute and day.

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