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Merge branch 'main' into houseme/test/scanner-heal-v2-w20
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@@ -7,6 +7,16 @@ On-Demand Migration (ODM) attaches an external S3-compatible **source bucket** t
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The module is on by default (rustfs/backlog#2163); set `RUSTFS_ON_DEMAND_MIGRATION_ENABLED=false` on every node to turn it off (`rustfs/src/module_switches.rs`). With the switch off, the runtime never intervenes on a read and the admin `PUT` route refuses with `OnDemandMigrationDisabled`. Reads of the configuration and of the status endpoint keep working while the switch is off, so a disabled deployment can still be inspected. The switch only decides whether the module may act at all: a bucket with no `on-demand-migration.json` is never resolved by the runtime and makes no source call, so turning the module on changes nothing for buckets you have not configured.
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## List continuation token rollout
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`RUSTFS_ON_DEMAND_MIGRATION_LIST_V2_TOKENS` defaults to `false`; unset or invalid boolean values also keep it off. It controls only whether a v1 listing may first issue a v2 continuation token after an empty truncated merged page. Every node with this reader support accepts existing v2 tokens and continues their budget even with the switch off. Ordinary pages that consume an object or common prefix retain the original v1 token shape.
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Leave the switch off while deploying v2 reader support to every node that can receive a continuation request, including nodes behind other load-balancer routes. Then set it to `true` in each node's environment and restart those nodes to enable issuance. A v1-only binary rejects v2 with `400 InvalidArgument` before the source-error policy runs; neither `not_found` nor turning off list-through makes that old reader compatible. With issuance still off, a new v1 chain retains the existing limitation: an empty source cursor cycle spanning requests can continue indefinitely. The default rollout does not claim to fix that chain until issuance is enabled.
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An active v2 budget rejects the sixteenth consecutive merged page that consumes no new object/common prefix and reaches no new end-of-list state. The first fifteen empty pages can be resumed; with the existing two-fetch-per-side limit, that interval costs at most 32 fetches per side, including the failing request. A key, common prefix, or a newly exhausted side on the sixteenth request succeeds and resets the budget. A side that was already exhausted does not reset it again. This is a resource bound, not proof of a cursor cycle: an unusually long but valid empty source-page chain also reaches the limit. Tokens are unsigned base64 JSON, so this budget applies to clients that continue with the returned token unchanged; replaying or editing a token can reset it, and it is not a malicious-client defense or a global request quota. The two-fetch-per-side request limit and existing source rate limiter still apply. A source failure follows `policy.source_error`: `propagate` returns `424 SourceUnavailable` with `invalid_pagination`; `not_found` returns the fetched local listing with `x-rustfs-on-demand-migration-list: local_only`. A blocking local-side failure returns `InternalError`, without silently discarding local entries.
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For rollback, first turn issuance off on every node. Keep v2-capable readers available for outstanding v2 chains: switching issuance off does not erase their budgets, and tokens have no expiration that proves those chains have drained. Route those continuations to compatible readers or have clients explicitly restart their listings before restoring v1-only binaries. Restarting a listing is a new scan and can repeat entries. Do not roll back readers while assuming the issuance switch makes existing v2 tokens disappear.
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## Positioning
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| Capability | Direction | What it moves | Where the authoritative copy is | When to use it instead |
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