![]() ![]() Rolling file is a single file, but continuously replaced with new content. Than discard the old file if present and continue rename sequence from step ‘delete old file’ Rolling file new file (under its name before rename).We need plan B with Volume copy, without closing them. TODO this does not work on windows with memory mapped files. But rename operation must be finished and synced to disk. use #move in atomic or non-atomic way.synchronize and close new file, release its c marker.There should be fallback option, when we can not close file Volume, but copy content between Volumes.Sometimes handle is not released even after JVM exit, and OS restart is required. MappedByteBuffer handle is not released until GC or cleaner hack. Opened memory mapped file on Windows can not be renamed.#move is atomic, but it might fail in some cases.MapDB needs file move to be atomic, and supported in range variety of platforms. The ‘new file’ replaces old file and has its name changed. ![]() The ‘old file’ is file which is being replaced, it will be deleted before File Rename. Store is recreated in new file, and old file is replaced with new content. File Renameįile Rename is used in StoreDirect compaction. Or user can remove marker file and try his luck. In this case main file should be discarded and recreated from original data source. If there is an crash, recovery sequence will find marker file, assume that main file was not closed correctly and will refuse to open it. In that case marker file stays while the main file is opened for write. If file was not closed, it most likely becomes corrupted and MapDB will refuse to reopen in.įile Create sequence is also used for temporary file without crash protection. Compared to File Create this file is opened continuously and only closed on system shutdown. Temporary file in MapDB is write-able file without crash protection (usually by write-ahead-log). In case of failure throw an data corruption exception. check if marker file exists, fail if it exists.TODO we should check for pending File Rename operations here.open main file and lock it, fail if main file does not exist.In case of recovery, or when file is being opened, follow this sequence: fill main file with content, write checksums.create marker file with File.createNewFile().MapDB needs file population to be atomic, and uses uses. File CreateĮmpty file creation is atomic operation, but populating file with content is not. Marker files have the same name as main file, but with. Those are empty files created and deleted using atomic filesystem API. To ensure crash resistance and atomicity MapDB relies on marker files. That means file operations are atomic (they either succeed or fail without side effects). If file operation did not finished it reverts everything into last stable state. In case of crash there is recovery operation after restart. File operationsįile operations (such as file create, rename or sync) must be atomic and must survive system crash. This chapter is storage specification for MapDB files. ![]()
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