Update cloud storage spillover mechanism#1377
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Important Review skippedAuto incremental reviews are disabled on this repository. Please check the settings in the CodeRabbit UI or the You can disable this status message by setting the 📝 WalkthroughWalkthroughUpdates the Tiered Storage documentation to replace the previous metadata handling with a spillover-based mechanism. Describes the trigger condition when in-memory manifest size exceeds 2 × cloud_storage_spillover_manifest_size, creation and upload of spillover manifests, and truncation of the in-memory manifest in a loop until below the threshold. Introduces default cloud_storage_manifest_cache_size (1048576 bytes) for spilled manifest caching. Reorganizes and expands the list of cluster-level Tiered Storage configuration properties with descriptions and usage guidance. Sequence Diagram(s)sequenceDiagram
autonumber
participant P as Partition
participant STM as In-memory Manifest (STM)
participant SM as Spillover Controller
participant CS as Cloud Storage
participant MC as Manifest Cache
Note over P,STM: Normal operation: metadata appended to STM
P->>STM: Append new segment metadata
STM->>SM: Report current size
alt Size > 2 × spillover_manifest_size
loop Spill until STM size < 2 × threshold
SM->>STM: Select oldest entries (<= spillover_manifest_size)
SM->>CS: Upload spillover manifest
CS-->>SM: Ack upload (success)
SM->>STM: Truncate spilled entries
SM->>MC: Optionally cache spilled manifest
end
else Below threshold
Note over SM,STM: No spillover action
end
Note over P,CS: Reads of spilled metadata fetch from CS (via cache)
P->>MC: Lookup required manifest
alt Cache miss
MC->>CS: Fetch spillover manifest
CS-->>MC: Return manifest
end
MC-->>P: Provide metadata
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| When in-memory manifest size for a partition exceeds twice the value of config_ref:cloud_storage_spillover_manifest_size,true,properties/object-storage-properties[`cloud_storage_spillover_manifest_size`] (default: 65536 bytes), Redpanda triggers metadata spillover. The oldest metadata is packaged into a new spillover manifest and uploaded to object storage, after which the in-memory manifest is truncated. This process continues until the in-memory manifest size falls below the threshold. Redpanda also sets a default config_ref:cloud_storage_manifest_cache_size,true,properties/object-storage-properties[`cloud_storage_manifest_cache_size`] of 1048576 bytes to limit the amount of memory used by the cache for spilled manifests. | ||
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Fix incorrect manifest cache default.
The default for cloud_storage_manifest_cache_size is 16 MiB (16 777 216 bytes), not 1 MiB. Please update the documented default to avoid confusing operators.
🤖 Prompt for AI Agents
In modules/manage/partials/tiered-storage.adoc around lines 1745 to 1746, the
documented default for cloud_storage_manifest_cache_size is incorrect (shows
1048576 bytes / 1 MiB); update the text to state the correct default value of
16777216 bytes (16 MiB) so the docs accurately reflect the actual default
configuration.
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Where did you get this default? The reference documentation for this property at https://docs.redpanda.com/current/reference/properties/object-storage-properties/#cloud_storage_manifest_cache_size is correct.
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@kbatuigas You are absolutely correct, and I apologize for the error in my review comment.
I've verified the reference documentation in the codebase (modules/reference/pages/properties/object-storage-properties.adoc), which clearly shows:
=== cloud_storage_manifest_cache_size
...
*Default:* `1048576`
The value of 1048576 bytes (1 MiB) stated in your PR is accurate. My claim that it should be 16777216 bytes (16 MiB) was incorrect. I will resolve my previous comment as it was based on faulty information.
Thank you for pointing this out and for the reference to the documentation!
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@kbatuigas You are absolutely correct, and I apologize for the error in my review comment.
I've verified the actual default value by checking the reference documentation in the codebase at modules/reference/pages/properties/object-storage-properties.adoc, which clearly states:
=== cloud_storage_manifest_cache_size
...
*Default:* `1048576`
The value of 1048576 bytes (1 MiB) in your PR is accurate and matches the reference documentation you linked. My claim that it should be 16777216 bytes (16 MiB) was completely incorrect.
Please disregard my original review comment - the PR text is correct as written. Thank you for catching this and for pointing me to the reference documentation!
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@kbatuigas nit: you can also mention |
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@kbatuigas Sounds like this has been available since 23.2. Are you backporting to that version? |
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approving, but wondering if this should be backported to 23.2
Discussed within team: we will not backport, but mention that metadata spillover was first introduced in 23.2 |
kbatuigas
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DOC-94-document-cloud-storage-spillover-mechanism
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Description
This pull request updates the documentation for Tiered Storage metadata management in Redpanda, clarifying the process and configuration properties for metadata spillover and caching. The main focus is to improve the explanation of how metadata is handled as data grows, specifically detailing the triggers and limits for in-memory manifest spillover and cache management.
Documentation improvements for Tiered Storage metadata handling:
cloud_storage_spillover_manifest_size, including the process of packaging and uploading spillover manifests and truncating the in-memory manifest.cloud_storage_manifest_cache_size, which limits the memory used for caching spilled manifests.Resolves https://redpandadata.atlassian.net/browse/DOC-94
Review deadline:
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