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Nageswara Nandigam edited this page Jan 18, 2024 · 2 revisions

how auto-update works for Extension Handler?

The Daemon is tasked with ensuring the continuous operation of the Extension Handler, and Extension Handler initiation depends on the value of AutoUpdate.Enabled.

AutoUpdate.Enabled=y

  1. Daemon picks up the highest version downloaded in the VM and starts that version of the Extension Handler.
  2. The Extension Handler periodically checks for updates. Upon detection, it downloads the latest version and exits the process.

AutoUpdate.Enabled=n

  1. The Daemon picks up the version shipped with the image and starts that version of the Extension Handler.
  2. The Extension Handler does not check for updates to download the latest version.

New VMs: New VMs initially start with the shipped version. Upon startup, if a higher version is available, the Extension Handler will promptly download and Daemon will install it.

Existing VMs: Existing VMs also periodically check for Extension Handler updates. Upon detection of an update, it will be downloaded and installed.

NOTE: The version shipped with the image is managed by distro owners, and we do not have control over it.

AutoUpdate.Enabled vs AutoUpdate.UpdateToLatestVersion

Both flags are intended to control the auto-update for the Extension Handler, but there is a crucial difference in behavior:

AutoUpdate.Enabled:
If set to 'n', it will roll back to the version shipped with the image. This behavior has been historically implemented and changing it may disrupt users accustomed to this process. The flag is retained for legacy purposes. If the version shipped with the image is below 2.10.0.8, this flag will be used for the first agent update. Once the agent is updated to version 2.10.0.8 or higher, the new flag, AutoUpdate.UpdateToLatestVersion, takes effect.

AutoUpdate.UpdateToLatestVersion:
If set to 'n', it will not update to the latest version but will not roll back to the version shipped with the image. Introduced to address the need for users who want to control updates and stay on their current version until they choose to update. This flag takes effect from version 2.10.0.8 and higher.

Example, waagent --version

WALinuxAgent-2.2.53 running on ubuntu 18.04
Python: 3.8.2
Goal state agent: 2.2.53

Assuming the version shipped with the image is 2.2.53, and the latest published version is 2.10.0.8, since the initial agent version is below 2.10.0.8, it will adhere to the existing flag behavior.

AutoUpdate.Enabled=y
Update to the latest version (2.10.0.8)

AutoUpdate.Enabled=n
Roll back to the version (2.2.53)

Now, if the latest version installed on the VM is 2.10.0.8 and we publish a new version, say 2.11.0.0

AutoUpdate.Enabled=y and AutoUpdate.UpdateToLatestVersion=y
Update to the latest version (2.11.0.0)

AutoUpdate.Enabled=y and AutoUpdate.UpdateToLatestVersion=n
Stay on latest installed version on the vm (2.10.0.8)

AutoUpdate.Enabled=n and AutoUpdate.UpdateToLatestVersion=y|n
Roll back to the version (2.2.53)

This distinction allows users to have more control over updates, facilitating choices based on their preferences.

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