How do I fix incorrect checksums in my Nexus repository?

Question

Some of the artifacts in my local Nexus repository don't have the correct checksum. For example (wrong checksum):

cat central/org/codehaus/plexus/plexus-compiler-api/1.8/plexus-compiler-api-1.8.pom.sha1 95f3332c2bbace129da501424f297e47dd0e976b

vs (correct checksum):

sha1sum central/org/codehaus/plexus/plexus-compiler-api/1.8/plexus-compiler-api-1.8.pom 4c2947f7e2d09b6e13da34292d897c564f1f9828

It looks like I have a few artifacts in my repository that were downloaded when this bug was active.

Maven Central has the correct checksum (4c29...) now, but the checksums in my local Nexus repository remain stale. I don't know how to get my local repository to verify and / or re-download the correct checksum from central.

What is the correct way of fixing my local repository. There aren't too many artifacts with this problem, so I think I could (by hand) verify they still exist in central and delete them from my local repository. They should get re-cached with the correct checksums. Is there a better way?

Update:

I've looked at this more and I'm almost positive I know what the source of my problem is. One of the artifacts I'm having trouble with is this one (plexus-compiler-api:1.8):

In my repository, both the .pom and .pom.sha1 are timestamped as 29-Mar-2010. At central, the .pom is timestamped as 29-Mar-2010 while the .pom.sha1 is timestamped as 21-Apr-2010. I was reading about Nexus maintenance. I assume that, on 21-Apr-2010, Maven Central rebuilt metadata and verified checksums which fixed the incorrect .sha1 for the plexus-compiler-api:1.8 artifact.

According to the Sonatype link above, I should be able to expire the caches for Maven Central and have my local installation pull new copies of anything with newer timestamps than the originally cached artifacts. However, based on the behavior I've observed, I think it's only checking timestamps for artifact files, not checksum files.

As far as my local Nexus repository is concerned, I have the most recent version of the artifact (29-Mar-2010), so there's no need to re-download anything.

I've noticed my version of Nexus is quite old (1.5 vs 1.9.1), so I'll try updating and see if the newer version does a better job of expiring caches. If not, I'll probably see what the Sonatype guys think (maybe it's a bug?).

Answer 1

Nope, what you face is the defined behaviour of Nexus and Maven.

First, expiring caches does not delete anything from local cache of Nexus, it just marks them "old". The effect of marking items as "old" is shown on next incoming request asking for those same artifacts (if never asked for, the "old" artifacts just sits there). Meaning, expire cache alone will not cause Nexus to download remotely changed (newer) files. Nexus never downloads on it's own (if we leave out the index from this discussion). You have to force a client (Maven) ask for them – and that will result following chain of action: "cache content old", remote change detection and finally re-download and caching of the new file.

Next, what happens here is that Maven, since artifact (the JAR file) is not changed, not even asks for checksum file either, hence nothing "triggers" the "old" marked checksum refetch on Nexus side. Other to note, if we talk about released artifact (and Maven Central does contains released artifacts only), Maven will never re-check them, unless they are not present in local repository (once brought into local repository, Maven will never try to refetch them). Meaning, you need to remove them from local repository to be sure that Maven will ask for them from Nexus, and finally, that Nexus will detect the checksum file changes on remote and do what you actually want.

Re-download should happen, for example if you nuke your Maven's local repository and rebuild with a clean/empty one. In this case, Maven should ask for both, JAR artifact and checksum file – but from your description it's not clear how did you (or did you?) invoke Maven after expiring caches on Nexus.

Try this:

a) run expire caches on Nexus "Maven Central" proxy repository

b) nuke local repository (or just redirect it to a new clean folder by tampering ~/.m2/settings.xml

c) make Maven build your project, and it should refetch both, the JAR and checksum files (by using empty/nuked local repository)

Hope this explains some of the stuff you wrote.

Reference to JIRA issue discussing same thing.