Increment in _work directory

Question

What causes the folder name under \'_work\' to change on a Private Agent?

We are currently using _work/10/s etc. It has used this for the last few builds, but what would

Answer 1

There is SourceRootMapping folder in the working folder and there are Mappings.json and SourceFolder.json files (SourceRootMapping{guid} folder{build definition id} folder\sourceFolder.json) in this folder.

Mappings.json:

{
  "lastBuildFolderCreatedOn": "05/16/2018 13:20:06 +08:00",
  "lastBuildFolderNumber": 2
}

A SourceFolder.json:

{
  "build_artifactstagingdirectory": "1\\a",
  "agent_builddirectory": "1",
  "collectionUrl": "https://XXX.visualstudio.com/",
  "definitionName": "a",
  "fileFormatVersion": 3,
  "lastRunOn": "05/16/2018 13:18:06 +08:00",
  "repositoryType": "TfsGit",
  "lastMaintenanceAttemptedOn": "",
  "lastMaintenanceCompletedOn": "",
  "build_sourcesdirectory": "1\\s",
  "common_testresultsdirectory": "1\\TestResults",
  "collectionId": "21136b22-dbe8-4fae-a111-3f8c5b0fed9b",
  "definitionId": "285",
  "hashKey": "d2545895fec8eea22c60ecc24f6593a986106b80",
  "repositoryUrl": "https://starain.visualstudio.com/Scrum2017/_git/cppbase",
  "system": "build"
}

So, it’s easy to find that the VSTS agent increase the folder number per to Mappings.json and SourceFolder.json file is used to mapping build definition and its corresponding working folder.