TAS Notifications-UI Errand fails with: CNB 'detector' could not be executed: exit status 20

Products

• VMware Tanzu Application Service for VMs

Issue/Introduction

When attempting to run TAS errands using TAS 4.0+, it may fail with:
 

Detect failed: CNB `detector` could not be executed: exit status 20 /tmp/buildpacks/2a80bad2491d9964595f72c47aacea29/bin/detect: line 5: cd: /tmp/app/: No such file or directory NoAppDetectedError - An app was not successfully detected by any available buildpack FAILED

This has been observed happening with the TAS Notifications UI errand, but it may happen for others also.

Environment

Product Version: 4.0

Resolution

The problem is caused due to the ordering of the buildpacks. When you run cf buildpacks:

The buildpack used by the notifications app is:

go_buildpack 23 true false go_buildpack-cached-cflinuxfs4-v1.10.10.zip cflinuxfs4

However, the problem happens when this buildpack is placed in a higher position on the list:

web_servers_cnb_beta 16 true false web-servers-cnb-buildpack-cflinuxfs4-v0.5.0.zip cflinuxfs4

In this case, the notifications app tries to push with the web_servers_cnb_beta buildpack instead, which causes the app to fail.

To resolve this, you'll need to move the go_buildpack to be above the web_servers_cnb_beta buildpack. This command should swap them:

cf update-buildpack web_servers_cnb_beta -s cflinuxfs4 -i <number>

(Replacing <number> with a position lower than the go buildpack)

The notifications errand should then succeed.