[tycho-user] Nexus p2 unzip plugin: Read lock during ZIP transfer to pro

[Irene Wang <iwang@xxxxxxxxxx>]

Hello,

Hopefully, this is the correct list to ask about an issue with the Nexus 
p2 unzip plugin. We're using version 0.15.0-SNAPSHOT of the p2 unzip 
plugin with instances of Nexus Pro 2.14.2-01. We are having problems 
with blocked read access to a ZIP artifact (and its corresponding p2 
unzip virtual path) while that ZIP artifact is being transferred to a 
regular Maven proxy repository. This blocked read issue does not occur 
when there is no p2 unzip virtual repository sourcing the repository.

On our main Nexus instance, we have a Maven repository (A) with a p2 
virtual repository (A') that sources repository A.
On another "mirror" Nexus server, we have a Maven proxy repository (B) 
of the same repository A.

The symptom is that whenever a ZIP artifact is published to A and the 
proxy repository B has requested that ZIP artifact before the p2 
unzipped version on A' is requested, both the original artifact on A and 
and the virtual artifact on A' are unreadable until the replication of 
the ZIP from A to B is complete (keeps attempting to load until the 
request times out). Once the transfer of the ZIP to the proxy repository 
B is finished, all paths on A, A' and B become accessible. The expected 
behaviour is that A and A' on the main instance would still be readable 
during the transfer of the ZIP to the proxy repository B. Again, this 
locking only happens when a p2 unzip virtual repository A' is configured 
with its source as A.

As our "mirror" Nexus is located in another geographical region, the 
transfer of ZIP artifacts from A to B can take quite some time, and in 
the meantime, the corresponding artifacts cannot be requested on the 
main Nexus, whether in ZIP (A) or p2 unzip (A') format.

Would anyone have any insight into a locking mechanism specific to the 
p2 unzip plugin that could explain what we're seeing, and if so, would 
there be a workaround or fix?

Thanks very much in advance,

Irene