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DRIVERS-3479 Clarify logging truncation: Unicode code point safety and naive JSON are separate concerns #1937

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DRIVERS-3479 Clarify logging truncation: Unicode code point safety and naive JSON are separate concerns #1937

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15 changes: 9 additions & 6 deletions source/logging/logging.md
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Expand Up @@ -106,12 +106,12 @@ Drivers MUST support configuring where log messages should be output, including
Drivers MUST support configuring the maximum logged length for extended JSON documents in log messages. The unit here is
flexible and can be bytes, Unicode code points, code units, or graphemes, depending on what a driver is able to
accomplish with its language's string APIs. The default max length is 1000 of whichever unit is selected. If the chosen
unit is anything other than a Unicode code point, the driver MUST ensure that it gracefully handles cases where the
truncation length falls mid code point, by either rounding the length up or down to the closest code point boundary or
using the Unicode replacement character, to avoid producing invalid Unicode data. Drivers MUST implement truncation
naively by simply truncating the output at the required length; i.e. do not attempt to implement truncation such that
the output is still valid JSON. Truncated extended JSON MUST have a trailing ellipsis `...` appended to indicate to the
user that truncation occurred. The ellipsis MUST NOT count toward the max length.
unit is anything other than a Unicode code point, the driver MUST NOT split a Unicode code point at the truncation
boundary; instead, the driver MUST round to the nearest code point boundary or substitute the Unicode replacement
character, to avoid producing invalid Unicode data. With respect to JSON structure, drivers MUST implement truncation
naively by simply truncating the output at the required length; i.e. do not attempt to produce valid JSON after
truncation. Truncated extended JSON MUST have a trailing ellipsis `...` appended to indicate to the user that truncation
occurred. The ellipsis MUST NOT count toward the max length.

> **Fallback Implementation method**: Environment variable `MONGODB_LOG_MAX_DOCUMENT_LENGTH`. When unspecified, any
> extended JSON representation of a document which is longer than the default max length MUST be truncated to that
Expand Down Expand Up @@ -403,6 +403,9 @@ on individual clients or for particular namespaces.

## Changelog

- 2026-05-13: Clarify truncation requirements: Unicode code point safety and naive JSON truncation are separate concerns
that do not contradict each other.

- 2024-03-06: Migrated from reStructuredText to Markdown.

- 2022-11-16: Add policy on severity level for log messages corresponding to driver exceptions.
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