Matrix builds for multi-platform in Jenkins - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a matrix build with two platforms.

Jenkins

matrix {
    axes {
        axis {
            name 'PLATFORM'
            values [1]
        }
    }
}

Drag options to blanks, or click blank then click option'

A['linux', 'windows']

B'linux windows'

Clinux, windows

D'linux', 'windows'

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around platform names

Using spaces instead of commas to separate values

The values field expects a list of strings separated by commas and enclosed in quotes.

2fill in blank

medium

Complete the code to run a shell command in the matrix build.

Jenkins

steps {
    sh '[1]'
}

Drag options to blanks, or click blank then click option'

Aecho Hello from $PLATFORM

Bprint Hello from $PLATFORM

Cecho Hello from PLATFORM

Decho 'Hello from PLATFORM'

Attempts:

3 left

💡 Hint

Common Mistakes

Using print instead of echo

Not using the $ sign before PLATFORM

The sh step runs shell commands. To use the matrix variable, use $PLATFORM inside the command.

3fill in blank

hard

Fix the error in the matrix axis definition.

Jenkins

matrix {
    axes {
        axis {
            name [1]
            values 'linux', 'windows'
        }
    }
}

Drag options to blanks, or click blank then click option'

A"PLATFORM"

B'PLATFORM'

CPLATFORM

Dplatform

Attempts:

3 left

💡 Hint

Common Mistakes

Not quoting the axis name

Using double quotes inconsistently

The name must be a quoted string. Single quotes are preferred in Jenkinsfiles.

4fill in blank

hard

Fill both blanks to define a matrix with OS and JDK versions.

Jenkins

matrix {
    axes {
        axis {
            name [1]
            values 'linux', 'windows'
        }
        axis {
            name [2]
            values 'jdk8', 'jdk11'
        }
    }
}

Drag options to blanks, or click blank then click option'

A'OS'

B'JDK'

C'PLATFORM'

D'JAVA_VERSION'

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent or unclear axis names

Not quoting the axis names

The first axis is commonly named OS for operating system, and the second axis JDK for Java versions.

5fill in blank

hard

Fill all three blanks to run a shell command using both matrix variables.

Jenkins

steps {
    sh 'echo Building on [1] with [2] and version [3]'
}

Drag options to blanks, or click blank then click option'

A$OS

B$JDK

C$JAVA_VERSION

D$PLATFORM

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing variable names or forgetting the $ sign

Using undefined variable names

Use $OS and $JDK for the first two variables, and $JAVA_VERSION for the version variable in the shell command.

Practice

1. What is the main purpose of using a matrix build in Jenkins for multi-platform projects?

easy

A. To run the same build steps on multiple platform combinations automatically

B. To run only one build on a single platform

C. To manually select which platform to build on

D. To speed up builds by skipping tests

Solution

1. Step 1: Understand matrix build concept

   A matrix build runs the same steps on different combinations of variables like OS and architecture.

2. Step 2: Identify the purpose for multi-platform

   This allows testing and building on all required platforms automatically without manual intervention.

3. Final Answer:

   To run the same build steps on multiple platform combinations automatically -> Option A

4. Quick Check:

   Matrix build = multi-platform automatic runs [OK]

Hint: Matrix builds run all platform combos automatically [OK]

Common Mistakes:

• Thinking matrix builds run only on one platform
• Confusing matrix with manual selection
• Assuming matrix skips tests

2. Which syntax correctly defines two axes named os and arch in a Jenkins matrix build?

easy

A. matrix { axis name='os' values='linux,windows'; axis name='arch' values='x86,arm' }

B. matrix { os: ['linux', 'windows'], arch: ['x86', 'arm'] }

C. axes { axis('os', ['linux', 'windows']); axis('arch', ['x86', 'arm']) }

D. axes { axis { name 'os'; values 'linux', 'windows' } axis { name 'arch'; values 'x86', 'arm' } }

Solution

1. Step 1: Recall Jenkins matrix axes syntax

   Jenkins uses axes { axis { name '...' ; values '...' } } blocks to define axes.

2. Step 2: Match syntax with options

   axes { axis { name 'os'; values 'linux', 'windows' } axis { name 'arch'; values 'x86', 'arm' } } matches the correct syntax with two axis blocks inside axes.

3. Final Answer:

   axes { axis { name 'os'; values 'linux', 'windows' } axis { name 'arch'; values 'x86', 'arm' } } -> Option D

4. Quick Check:

   Correct axis syntax = axes { axis { name 'os'; values 'linux', 'windows' } axis { name 'arch'; values 'x86', 'arm' } } [OK]

Hint: Use axes { axis { name; values } } for matrix axes [OK]

Common Mistakes:

• Using incorrect matrix or axis syntax
• Mixing JSON-like syntax instead of Groovy
• Missing semicolons or braces

3. Given this Jenkins matrix snippet:

axes {
  axis {
    name 'os'
    values 'linux', 'windows'
  }
  axis {
    name 'arch'
    values 'x86', 'arm'
  }
}
stages {
  stage('Build') {
    steps {
      echo "Building on ${os} for ${arch}"
    }
  }
}

How many total build combinations will Jenkins run?

medium

A. 6

B. 2

C. 4

D. 8

Solution

1. Step 1: Count values in each axis

   Axis 'os' has 2 values: linux, windows. Axis 'arch' has 2 values: x86, arm.

2. Step 2: Calculate total combinations

   Total combinations = 2 (os) * 2 (arch) = 4.

3. Final Answer:

   4 -> Option C

4. Quick Check:

   2 OS * 2 arch = 4 builds [OK]

Hint: Multiply axis values count for total combinations [OK]

Common Mistakes:

• Adding instead of multiplying axis values
• Counting only one axis
• Misreading axis values count

4. You wrote this matrix build snippet but Jenkins fails with an error:

axes {
  axis {
    name 'os'
    values 'linux', 'windows'
  }
  axis {
    name 'arch'
    value 'x86', 'arm'
  }
}

What is the error and how to fix it?

medium

A. Typo: use 'values' instead of 'value' in second axis

B. Missing quotes around 'x86' and 'arm'

C. Axes block should be named 'matrix' not 'axes'

D. Use commas instead of spaces between values

Solution

1. Step 1: Identify syntax error in axis definition

   The second axis uses 'value' instead of the correct 'values' keyword.

2. Step 2: Correct the keyword

   Change 'value' to 'values' to fix the syntax error and allow multiple values.

3. Final Answer:

   Typo: use 'values' instead of 'value' in second axis -> Option A

4. Quick Check:

   Axis keyword must be 'values' [OK]

Hint: Check for 'values' keyword spelling in axes [OK]

Common Mistakes:

• Using 'value' instead of 'values'
• Forgetting commas between values
• Misnaming axes block

5. You want to run a matrix build on OS (linux, windows) and arch (x86, arm), but only run the 'arm' builds on agents labeled 'arm-node'. How do you configure the matrix to achieve this?

hard

A. Set agent { label 'arm-node' } globally for all builds

B. Use agent { label "${arch == 'arm' ? 'arm-node' : ''}" } inside the matrix

C. Add when { expression { arch == 'arm' } } to skip arm builds

D. Use exclude { axis { name 'arch'; value 'arm' } } to remove arm builds

Solution

1. Step 1: Understand agent labeling per axis value

   You want 'arm' builds to run only on 'arm-node' labeled agents, others on default.

2. Step 2: Use conditional label assignment in agent block

   Using agent { label "${arch == 'arm' ? 'arm-node' : ''}" } assigns 'arm-node' label only for arm builds.

3. Final Answer:

   Use agent { label "${arch == 'arm' ? 'arm-node' : ''}" } inside the matrix -> Option B

4. Quick Check:

   Conditional agent label = Use agent { label "${arch == 'arm' ? 'arm-node' : ''}" } inside the matrix [OK]

Hint: Use conditional label in agent block for selective platforms [OK]

Common Mistakes:

• Setting global agent label affecting all builds
• Skipping arm builds instead of assigning correct agent
• Excluding arm builds instead of targeting agent