Implements a new special generation counter value (UINT64_MAX) that
allows clients to assert that a file should NOT exist when performing
operations.
Primary use case: Atomic "create-if-not-exists" operations
When combined with TOASTY_WRITE_CREATE_IF_MISSING flag:
- File doesn't exist → server creates file and writes (SUCCESS)
- File exists → gen_match fails → BADGEN error (prevents overwrite)
This enables race-condition-free file creation where you want to
create a NEW file or fail if it already exists.
Key changes:
- Added MISSING_FILE_GENERATION constant to file_tree.h
- Updated gen_match() to return false when checking existing entities
against MISSING_FILE_GENERATION
- Modified file_tree_delete_entity() to succeed (no-op) when file is
missing and MISSING_FILE_GENERATION is specified (idempotent delete)
- Modified file_tree_write() to validate against the new value
- Added documentation in metadata_server.c explaining how
MISSING_FILE_GENERATION works WITH CREATE_IF_MISSING
- Updated protocol documentation in PROTOCOL.txt
- Added comprehensive feature documentation in MISSING_FILE_GENERATION.md
Additional use cases:
- Idempotent delete operations (delete only if not already gone)
- Detecting unexpected file creation in validation/testing scenarios
The implementation is backward compatible and type-safe. Files are
never assigned MISSING_FILE_GENERATION as their actual generation value.
Adds support for truncating files after write operations, enabling proper
HTTP PUT semantics where the entire file content should be replaced.
Implementation:
- Added TOASTY_WRITE_TRUNCATE_AFTER flag (0x02) to ToastyFS API
- Updated file_tree_write() to accept truncate_after parameter:
* When true, sets file size to exactly offset+length
* Removes chunks beyond the new file size
* Marks removed chunks for garbage collection
- Metadata server extracts and passes truncate flag to file_tree_write()
- WAL replay passes false for truncate_after (already handled in original write)
- Web proxy PUT now uses both CREATE_IF_MISSING and TRUNCATE_AFTER flags
- Updated documentation in PROTOCOL.txt, DESIGN.txt, and web/DESIGN.txt
Benefits:
- Proper HTTP PUT semantics (replace entire file content)
- Efficient: single write operation truncates and updates file
- Works with both sync and async APIs
- Garbage collection automatically removes orphaned chunks
Adds support for automatically creating files when write operations target
non-existent files. This is essential for REST PUT operations which should
be able to create new resources.
Implementation:
- Added TOASTY_WRITE_CREATE_IF_MISSING flag to ToastyFS API header
- Updated toasty_write() and toasty_begin_write() to accept flags parameter
- Client sends write flags in MESSAGE_TYPE_WRITE message to metadata server
- Metadata server parses flags and handles file auto-creation atomically:
* When write fails with FILETREE_NOENT and flag is set
* Logs creation to WAL for crash consistency
* Creates file with default 4096-byte chunk size
* Retries write with newly created file's generation tag
- Updated web proxy PUT handler to use TOASTY_WRITE_CREATE_IF_MISSING
- Updated examples and simulation client for new API signature
Benefits:
- Works for both sync and async APIs
- Single round trip (atomic server-side operation)
- Prevents race conditions
- Proper WAL logging ensures crash consistency
Claudeandcozis