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https://issues.apache.org/jira/browse/HADOOP-15779?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gabor Bota reassigned HADOOP-15779:
-----------------------------------
Assignee: Gabor Bota
> S3guard: add inconsistency detection metrics
> --------------------------------------------
>
> Key: HADOOP-15779
> URL: https://issues.apache.org/jira/browse/HADOOP-15779
> Project: Hadoop Common
> Issue Type: Sub-task
> Components: fs/s3
> Affects Versions: 3.2.0
> Reporter: Aaron Fabbri
> Assignee: Gabor Bota
> Priority: Major
>
> S3Guard uses a trailing log of metadata changes made to an S3 bucket to add
> consistency to the eventually-consistent AWS S3 service. We should add some
> metrics that are incremented when we detect inconsistency (eventual
> consistency) in S3.
> I'm thinking at least two counters: (1) getFileStatus() (HEAD) inconsistency
> detected, and (2) listing inconsistency detected. We may want to further
> separate into categories (present / not present etc.)
> This is related to Auth. Mode and TTL work that is ongoing, so let me outline
> how I think this should all evolve:
> This should happen after HADOOP-15621 (TTL for dynamo MetadataStore), since
> that will change *when* we query both S3 and the MetadataStore (e.g. Dynamo)
> for metadata. There I suggest that:
> # Prune time is different than TTL. Prune time: "how long until
> inconsistency is no longer a problem" . TTL time "how long a MetadataStore
> entry is considered authoritative before refresh"
> # Prune expired: delete entries (when hadoop CLI prune command is run). TTL
> Expired: entries become non-authoritative.
> # Prune implemented in each MetadataStore, but TTL filtering happens in S3A.
> Once we have this, S3A will be consulting both S3 and MetadataStore depending
> on configuration and/or age of the entry in the MetadataStore. Today
> HEAD/getFileStatus() is always short-circuit (skips S3 if MetadataStore
> returns results). I think S3A should consult both when TTL is stale, and
> invoke a callback on inconsistency that increments the new metrics. For
> listing, we already are comparing both sources of truth (except when S3A auth
> mode is on and a directory is marked authoritative in MS), so it would be
> pretty simple to invoke a callback on inconsistency and bump some metrics.
> Comments / suggestions / questions welcomed.
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