The document outlines the execution hierarchy, variables, tasks, agents, and trigger types in a YAML pipeline for Azure DevOps. It highlights categories for tasks, the functionality of agents and pools, and various methods for triggering builds, including CI, PR, scheduled, and build completion triggers. Additionally, it discusses integrations with Azure Cloud, available extensions, and resources for further reading.

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Execution Hierarchy
1. Execution hierarchy in a YAML pipeline:
• YAML Pipeline
• Stages: [stage1, stage2,… stagen]
• Jobs:[job1, job2,… jobn]
• Steps: [task1, task2,… taskn]
2. Every pipeline has at least one stage & one job even if you don’t explicitly define them.
3. By default, everything executes sequentially*, in the orderdefined.
4. Conditional execution is possible.
5. Dependencies can be explicitly specified.
1. Parallelization, fan-in, fan-out scenarios possible.

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Variables
1. Predefined Variables:
• Agent variables | Build variables |System variables
2. $(var): CustomVariables, in orderof priority:
• Job-level | Stage-level |Root (pipeline) level | Queue-time
3. Using variables in scripts:
1. Batch/Cmd: %VARIABLE_NAME%
2. PowerShell: $env:VARIABLE_NAME
3. Bash: $VARIABLE_NAME
4. Secret Variables can be set at pipeline level using the web editor.
5. Variable Groups allow reuse ofvariablesacross multiple pipelines.
• Variable groupscan loadsecret variablesfrom AzureKeyVault.

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Tasks
1. Task Categories
1. Tool Tasks
2. Build Tasks
3. Test Tasks
4. Package Tasks
5. Deploy Tasks
6. Utility Tasks
2. All built-in tasks areopen-sourced on github.
3. Possible to develop a custom task.
4. Important Considerations:
1. Task versions
2. Task inputs (control options)
3. Task short forms(e.g. - script: is ashort formof –task: @CmdLine@2).

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DEMO

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Agents & Agent Pools
1. YAML pipeline jobsrun on agents (Microsoft-hosted orself-hosted).
2. Agent pools available bydefault:
• Azure Pipelines: Pool forMicrosoft-hosted agents
• Ubuntu | MacOS | Windows Server |Windows Server Core
• Default: Pool for self-hosted agents.
• Linux | MacOS |Windows
3. You can add more pools (with self-hosted agents) if needed.

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Trigger Types
1. CITriggers
• Triggerwhenever a push is made tospecific branches or aspecific tag is pushed.
• Possible tobatch CIbuilds.
• Use [skip ci]in commit message toskip triggering.
• Specific file paths can be included orexcluded (wildcards aresupported).
2. PRTriggers
• Only supported for GitHub andBitbucket Cloud
• Use branch policies with build validation for AzureRepos (git).
3. Scheduled Triggers
• CRON Expression based triggers for periodic builds/deployments
4. Build Completion Triggers
• Not yet supported in YAML pipelines.
• Once YAMLpipeline created, use classic editor tospecify build completion trigger.
5. NOTE: Can’t use variables in triggers (variables areevaluated only after triggerfires).

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Miscellaneous
1. Environments: “dev”,“staging”,“production” etc.
1. Deployment jobs: Special jobs with lifecycle hooks androllback actions.
2. Approvals
2. Build Labels
3. Service hooks / notifications
4. Parallel Jobs
1. Microsoft-hosted pools:
1. Public projects: 10 free parallel-jobs. No monthly time limits.
2. Private projects: 1 free parallel-job. Limited to30 hrs/month.
2. Self-hosted pools:
1. Public projects: Unlimited parallel jobs.
2. Private projects: 1 free parallel job.

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Integrations With AzureCloud
1. Service Connections
• Connect to Azureusing Service Principal or ManagedIdentity.
2. Built-in Deployment Tasks
• Deploy IaaS,PaaS, serverless, containerized workloads directly toAzure.
3. Microsoft Hosted Agents
• Comes pre-installed with AzureCLI,AzurePowerShell cmdlets &Azure SDKs
4. AzureDevOps Extension for AzureCLI
• az extension add--name azure-devops

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Extensions and Marketplace
1. Extensions for AzureDevOps
1. CodeSearch
2. AWS Tools
2. Extensions for Visual Studio Code
1. AzureTools (pack ofextensions)
2. AzureRepos
3. Extensions for Visual Studio

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FurtherReading
1. AzurePipelines Documentation:
• Expressions
• Hosted Agents
• Predefined Variables
• Service Connections
• Tasks (github)
• Tasks (reference)
• YAMLSchema
• Awesome AzureDevOps Resources