[jira] [Commented] (HDDS-6682) Validate Bucket ID of bucket associated with in-flight requests.

["István Fajth (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDDS-6682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17678442#comment-17678442 ] 

István Fajth commented on HDDS-6682:
------------------------------------

Hi, this one hit my eye based on the PR, let me add some thoughts here:

The original intent with the RequestFeatureValidator concept was described in HDDS-6427 as:
{quote}
After a few rounds of discussions we came up with an idea to implement pluggable pre and post validation hooks for request processing, that can help us to either right away reject a specific query from an old client, or if the response contains something that the client can understand, give us the possibility to re-write the regular response to a form that the old client can understand, or at least give the old client a specific error message that says why the request fails.
Similarly, the system should have the possibility to adjust the request coming from the old clients if it is possible, so that the request can be served.
{quote}
So we decided to have a fail-fast or mend things on the fly if possible approach, it was never about verifying whether the request should be executed when it arrives to the actual request processing, that part has its own responsibility to check the current state, while the validator itself is an addition to handle certain cases - that we can handle - as the first and last thing we do during request processing.

Based on this I think we should add logic to the corresponding validateAndUpdateCache methods, to reject the request if the current state requires rejection, and we should not add extra logic to the outermost layer of request processing.
This means that if the request should work on FSO bucket, and the bucket in the meantime was deleted and recreated as non-FSO, then drop the request in validateAndUpdateCache, also this means that if the client is old and can not understand FSO, drop the request in validateAndUpdateCache, and so on...

Grabbing the bucket id on every request, and validate it on all the write requests seems to have a negative performance impact as well, so probably we would like to avoid that, but for me this does not seem to be the real reason to do not do it this way, the real reason is that it feels bad to compare bucket ids, as even though the attached PR solves the race condition for cases where the bucket id changes due to parallel operations, but are we sure we do not have other combination of parallel request execution(s) where the bucket id does not change, but the execution of the validateAndUpdateCache results in operations that are running even though they should not?

> Validate Bucket ID of bucket associated with in-flight requests.
> ----------------------------------------------------------------
>
>                 Key: HDDS-6682
>                 URL: https://issues.apache.org/jira/browse/HDDS-6682
>             Project: Apache Ozone
>          Issue Type: Sub-task
>            Reporter: Jyotinder Singh
>            Assignee: Jyotinder Singh
>            Priority: Major
>              Labels: pull-request-available
>
> In high concurrency scenarios (which will become more common once we introduced prefix-based locking), there is a possibility of the following race condition:
> Take for instance the following scenario and 3 concurrent write requests:
> Bucket {{vol/buck1}} exists with {{LEGACY}} layout.
> {*}Request 1{*}: {{CreateKey}} by an older client (pre- bucket layout) on a bucket {{{}vol/buck1{}}}.
> {*}Request 2{*}: {{DeleteBucket}} by a new client on the bucket {{{}vol/buck1{}}}.
> {*}Request 3{*}: {{CreateBucket}} by a new client on the bucket {{vol/buck1}} with layout {{{}FILE_SYSTEM_OPTIMIZED{}}}.
> Let's say that these requests are processed in the following order:
>  # {{Request 1}} is picked up by one of the threads, which proceeds to run the {{PRE_PROCESS}} validations on this request. The validator we are interested in is called {{{}blockCreateKeyWithBucketLayoutFromOldClient{}}}. This validator will make sure that the bucket associated with this request is a {{LEGACY}} bucket - which is the pre-defined behavior in the case of old client/new cluster interactions since we do not want an old client operating on buckets using a new metadata layout.
> One thing to know here is that at this stage, the OM does not hold a bucket lock (which only happens inside the {{updateAndValidateCache}} method associated with the write request's handler class).
>  # While {{Request 1}} was being processed, another thread was processing {{{}Request 2{}}}. Let's say `Request2' managed to get hold of the bucket lock and successfully completed the bucket deletion.
>  # Now before {{Request 1}} got a chance to acquire the bucket lock, {{Request 3}} manages to acquire it. It proceeds with the bucket creation and creates a new bucket {{vol/buck1}} with {{FILE_SYSTEM_OPTIMIZED}} bucket layout.
>  # Finally, {{Request 1}} is able to acquire the bucket lock and proceeds to enter its {{validateAndUpdateCache}} method. However, even though it is able to find the bucket it is looking for, this is not the same bucket that was validated in its pre-processing hook. This new bucket has the same name, but a different bucket layout. The request ends up modifying a bucket that it should not be allowed to touch.
> This race condition can lead to undefined behavior of the Ozone cluster, where older clients might be modifying information they do not understand.
> This PR aims to add bucket ID validation to the request processing flow, which would make sure that the bucket that ends up being processed is the same one that was validated.



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