how to convert classic build job to yaml build in AzureDevops - azure-devops

Question

We have a working classic build job in azure Devops with an self hosted agent pool. But when we tried to convert this build job to yaml method, while executing no agents are getting assigned and its hanging. Could you please correct me here if i am doing something task.
Error
"All eligible agents are disabled or offline"
below is the converted yaml file from classic build - agent job
pool:
name: MYpool
demands: maven
#Your build pipeline references an undefined variable named ‘Parameters.mavenPOMFile’. Create or edit the build pipeline for this YAML file, define the variable on the Variables tab. See https://go.microsoft.com/fwlink/?linkid=865972
steps:
- task: Maven#3
displayName: 'Maven pom.xml'
inputs:
mavenPomFile: '$(Parameters.mavenPOMFile)'
- task: CopyFiles#2
displayName: 'Copy Files to: $(build.artifactstagingdirectory)'
inputs:
SourceFolder: '$(system.defaultworkingdirectory)'
Contents: '**/*.war'
TargetFolder: '$(build.artifactstagingdirectory)'
condition: succeededOrFailed()
- task: PublishBuildArtifacts#1
displayName: 'Publish Artifact: Root'
inputs:
PathtoPublish: '$(build.artifactstagingdirectory)'
ArtifactName: Root
condition: succeededOrFailed()
- task: CopyFiles#2
displayName: 'Copy wars to build directory'
inputs:
SourceFolder: '$(build.artifactstagingdirectory)/target'
TargetFolder: '/home/myadmin/builds/$(build.buildnumber)'
- task: CopyFiles#2
displayName: 'copying docker file to Build Directory'
inputs:
SourceFolder: Admin
TargetFolder: '/home/myadmin/builds/$(build.buildnumber)'
- bash: |
# Write your commands here
mv /home/myadmin/builds/$(build.buildnumber)/mypack0.0.1.war /home/myadmin/builds/$(build.buildnumber)/ROOT.war
displayName: 'Name war file Root.war'
- task: Docker#2
displayName: 'Build the docker image'
inputs:
repository: 'mycontainerregistry.azurecr.io/myservice'
command: build
Dockerfile: '/home/myadmin/builds/$(build.buildnumber)/Dockerfile'
tags: '$(Build.BuildNumber)-DEV'
- bash: |
# Write your commands here
docker login mycontainerregistry.azurecr.io
docker push mycontainerregistry.azurecr.io/myservice:$(Build.BuildNumber)-DEV
displayName: 'Push Docker Image'
- task: CopyFiles#2
displayName: 'Copy Deployment file'
inputs:
SourceFolder: /home/myadmin/kubernetes
TargetFolder: '/home/myadmin/builds/$(build.buildnumber)'
- task: qetza.replacetokens.replacetokens-task.replacetokens#3
displayName: 'Replace image in deployment file'
inputs:
rootDirectory: '/home/myadmin/builds/$(build.buildnumber)'
targetFiles: '**/*.yml'

Answer 1

In my previous answer, I said when I wait for nearly 20-30 mins, the interface of agent will prompt below message.
In fact, this is a process which upgrade the agent to latest version automatically.
Yes, when you using YAML with private agent, the agent version must be the latest one. No matter you add the demands or not.
For our system, the agent version is a implicit demand that your agent must satisfied with the latest one when you applying it in YAML.
If it is not satisfied, it will be blocked and the agent upgrade process will be forced to be performed automatically by system after some times.
So, to execute the private agent in YAML successfully, please upgrade the agent to latest one manually.
Since what my colleague and I talked are all private to microsoft in this ticket, sorry you could not get visible on this summary. So, here I take the screenshots about it, and you can refer to it: https://imgur.com/a/4OnzHp3
We are still working on why the system prompting so confusing message like: All eligible agents are disabled or offline. And, am trying to do some contribution to let this message more clear, for example: no agents meet demands: agent version xxx.