Hey Joel, thanks for chiming in! Regarding dependencies - while it's possible to provide pluggable interfaces, the issue I'm concerned about is conflicting versions of transitive dependencies at runtime. For example, I used a java agent that had a different version of snakeyaml, and it ended up breaking C*'s startup sequence [1]. I suggest putting external modules on separate threads with their own classpath to avoid this issue.
I think there's quite a bit of overlap between the two desires expressed in this thread, even though they achieve very different results. I personally can't see myself using something that treats an object store as cold storage where SSTables are moved (implying they weren't there before), and I've expressed my concerns with this, but other folks seem to want it and that's OK. I feel very strongly that treating local storage as a cache with the full dataset on object store is a better approach, but ultimately different people have different priorities. Either way, stuff is moved to object store at some point, and pulled to the local disk on demand. I am *firmly* of the position that this CEP should not exclude the local storage as cache option, and should be accounted for in the design. Jon [1] https://issues.apache.org/jira/browse/CASSANDRA-19663 On Thu, Mar 6, 2025 at 10:31 AM Joel Shepherd <sheph...@amazon.com> wrote: > On 3/6/2025 7:16 AM, Jon Haddad wrote: > > Assuming everything else is identical, might not matter for S3. However, > not every object store has a filesystem mount. > > Regarding sprawling dependencies, we can always make the provider specific > libraries available as a separate download and put them on their own thread > with a separate class path. I think in JVM dtest does this already. > Someone just started asking about IAM for login, it sounds like a similar > problem. > > That was me. :-) Cassandra's auth already has fairly well defined > interfaces and a plug-in mechanism, so it's easy to vend alternative auth > solutions without polluting the main project's dependency graph, at > build-time anyway. A similar approach could be beneficial for CEP-36, > particularly (IMO) for cold-storage purposes. I suspect decoupling > pluggable alternate channel proxies for cold storage from configurable > alternate channel proxies for redirecting data locally to free up space, > migrate to a different storage device, etc., would make both easier. The > CEP seems to be trying to do both, but they smell like pretty different > goals to me. > > Thanks -- Joel. > > > On Thu, Mar 6, 2025 at 12:53 AM Benedict <bened...@apache.org> wrote: > >> I think another way of saying what Stefan may be getting at is what does >> a library give us that an appropriately configured mount dir doesn’t? >> >> We don’t want to treat S3 the same as local disk, but this can be >> achieved easily with config. Is there some other benefit of direct >> integration? Well defined exceptions if we need to distinguish cases is one >> that maybe springs to mind but perhaps there are others? >> >> >> On 6 Mar 2025, at 08:39, Štefan Miklošovič <smikloso...@apache.org> >> wrote: >> >> >> >> That is cool but this still does not show / explain how it would look >> like when it comes to dependencies needed for actually talking to storages >> like s3. >> >> Maybe I am missing something here and please explain when I am mistaken >> but If I understand that correctly, for talking to s3 we would need to use >> a library like this, right? (1). So that would be added among Cassandra >> dependencies? Hence Cassandra starts to be biased against s3? Why s3? Every >> time somebody comes up with a new remote storage support, that would be >> added to classpath as well? How are these dependencies going to play with >> each other and with Cassandra in general? Will all these storage >> provider libraries for arbitrary clouds be even compatible with Cassandra >> licence-wise? >> >> I am sorry I keep repeating these questions but this part of that I just >> don't get at all. >> >> We can indeed add an API for this, sure sure, why not. But for people who >> do not want to deal with this at all and just be OK with a FS mounted, why >> would we block them doing that? >> >> (1) >> https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-s3/pom.xml >> >> On Wed, Mar 5, 2025 at 3:28 PM Mick Semb Wever <m...@apache.org> wrote: >> >>> . >>> >>> >>> It’s not an area where I can currently dedicate engineering effort. But >>>> if others are interested in contributing a feature like this, I’d see it as >>>> valuable for the project and would be happy to collaborate on >>>> design/architecture/goals. >>>> >>> >>> >>> Jake mentioned 17 months ago a custom FileSystemProvider we could offer. >>> >>> None of us at DataStax has gotten around to providing that, but to >>> quickly throw something over the wall this is it: >>> >>> https://github.com/datastax/cassandra/blob/main/src/java/org/apache/cassandra/io/storage/StorageProvider.java >>> >>> (with a few friend classes under o.a.c.io.util) >>> >>> We then have a RemoteStorageProvider, private in another repo, that >>> implements that and also provides the RemoteFileSystemProvider that Jake >>> refers to. >>> >>> Hopefully that's a start to get people thinking about CEP level details, >>> while we get a cleaned abstract of RemoteStorageProvider and friends to >>> offer. >>> >>>
