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docs: storage: dead-letter-queue: document new config parameter #2575

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docs: storage: dead-letter-queue: document new config parameter
eschabell May 18, 2026
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docs: storage: config: yaml: service-section: added new config parameter
eschabell May 18, 2026
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1 change: 1 addition & 0 deletions administration/configuring-fluent-bit/yaml/service-section.md
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| `storage.max_chunks_up` | Sets the number of chunks that can be `up` in memory for input plugins that use filesystem storage. | `128` |
| `storage.metrics` | If `http_server` option is enabled in the main `service` section, this option registers a new endpoint where internal metrics of the storage layer can be consumed. For more details, see [Monitoring](../../monitoring.md). Possible values: `off` or `on`. | `off` |
| `storage.path` | Sets a location to store streams and chunks of data. If this parameter isn't set, input plugins can't use filesystem buffering. | _none_ |
| `storage.rejected.limit` | Sets the maximum total size of the dead letter queue. Accepts size values such as `100M` or `1G`. When the limit is reached, new rejected chunks are skipped and a warning is logged. If not set, the DLQ size is unlimited. | _none_ |

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[FluentBit.Acronyms] Spell out 'DLQ', if it's unfamiliar to the audience.

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{"message": "[FluentBit.Acronyms] Spell out 'DLQ', if it's unfamiliar to the audience.", "location": {"path": "administration/configuring-fluent-bit/yaml/service-section.md", "range": {"start": {"line": 56, "column": 228}}}, "severity": "INFO"}
| `storage.rejected.path` | Sets the subdirectory name under `storage.path` for storing rejected chunks in the dead letter queue. | `rejected` |
| `storage.sync` | Configures the synchronization mode used to store data in the file system. Using `full` increases the reliability of the filesystem buffer and ensures that data is guaranteed to be synced to the filesystem even if Fluent Bit crashes. On Linux, `full` corresponds with the `MAP_SYNC` option for [memory mapped files](https://man7.org/linux/man-pages/man2/mmap.2.html). Possible values: `normal`, `full`. | `normal` |
| `storage.trim_files` | If enabled, Fluent Bit trims chunk files in the filesystem to reclaim disk space after data is flushed. Possible values: `off` or `on`. | `off` |
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12 changes: 12 additions & 0 deletions administration/dead-letter-queue.md
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storage.rejected.path: rejected
```

## Limit DLQ size

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{"message": "[FluentBit.Acronyms] Spell out 'DLQ', if it's unfamiliar to the audience.", "location": {"path": "administration/dead-letter-queue.md", "range": {"start": {"line": 25, "column": 10}}}, "severity": "INFO"}

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{"message": "[FluentBit.Headings] 'Limit DLQ size' should use sentence-style capitalization.", "location": {"path": "administration/dead-letter-queue.md", "range": {"start": {"line": 25, "column": 4}}}, "severity": "INFO"}

To prevent the dead letter queue from growing unbounded, set `storage.rejected.limit` in the `service` section. When the total size of rejected chunks reaches this limit, Fluent Bit skips copying additional chunks and logs a warning. Accepts size values such as `100M` or `1G`. If not set, the DLQ size is unlimited.

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[FluentBit.Acronyms] Spell out 'DLQ', if it's unfamiliar to the audience.

Raw Output:
{"message": "[FluentBit.Acronyms] Spell out 'DLQ', if it's unfamiliar to the audience.", "location": {"path": "administration/dead-letter-queue.md", "range": {"start": {"line": 27, "column": 295}}}, "severity": "INFO"}

```yaml
service:
storage.path: /var/log/flb-storage/
storage.keep.rejected: on
storage.rejected.path: rejected
storage.rejected.limit: 500M
```

## Format

Each dead letter queue file is named using this format:
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