One of the most common issues everyone is running into with Team Build is configuring the Drop Location.
All builds that happen through Team Build are dropped (bits are copied) to this location. Drop location is entered in the Location page of the Build Type wizard. This is essentially a shared folder on the network and needs to be available in UNC format as in \\server\share. However most users enter a path in the wizard and then any of the following three things happen
1. They forget to share the folder outResult: First build fails
2. The folder is shared out but adequate permissions are not given on itResult: First build fails
3. The folder gets unshared at some point of timeResult: Suddenly builds start failing after that
A common question is raised that both the first and second reasons of failure are a pre-requisite to starting a build, why doesn’t the Build Type wizard verify that the share exists. We could have done this but there are a couple of reasons we do not.
Firstly it could be a common scenario that the administrator is first setting up couple of Build Types and will then go and share those folders. So failing would simply hinder this process. However, this is not a very good excuse because we could have at least gone ahead verified the share and then given warnings stating that the share does not exist and the admin should share them with the correct permissions.
The main reason for not doing this verification is that scenario 2 is not easily verifiable. To undertand this let’s consider the permission required on the shared folder
1. The service account under which the Team Build Service is running on the Build Machine needs write permission on this folder
2. Other users need to have read permission on this folder so that they get to see build logs and the build itself
On the client where the Build Type is getting created through the wizard there is no information regarding the service account on the Build Machine so we cannot verify 1. This is because the admin while installing the BM could have chosen any valid account to run the service and can give explicitly and exclusive write permission to this account on the share. Moreover, user can change the Build Machine while firing the build and the service account on the new Build Machine might be a different account and that might not have permissions.
On OS’s like WinXP in addition to the sharing permission you can go to the security tab on the folders properties and apply a lot of permissions which are not accessible over the network but would make the build to fail. Take for example in share tab you give Full control to everyone and in the security for that folder you explicitly deny create folder permission. So even though our verification succeeds build will fail.
Verifying 2 does not add any value if we cannot verify 1.
Its not that we cannot verify drop location, what I tried to highlight above is that it is non-trivial. Many users think that the Wizard should just try to see if the share exists and then create and delete a file on the share to ensure it is writable. However for the reasons mentioned above this approach would just not work.