Struct okaywal::Configuration

pub struct Configuration<M> {
    pub file_manager: M,
    pub directory: PathId,
    pub preallocate_bytes: u32,
    pub checkpoint_after_bytes: u64,
    pub buffer_bytes: usize,
    pub version_info: Arc<Vec<u8>>,
}

A WriteAheadLog configuration.

Fields

file_manager: M

The file manager to use for storing data.

Typically this is [StdFileManager].

directory: PathId

The directory to store the log files in.

preallocate_bytes: u32

The number of bytes each log file should be preallocated with. Log files may grow to be larger than this size if needed.

checkpoint_after_bytes: u64

After this many bytes have been written to the active log file, begin a checkpointing process. This number should be less than preallocate_bytes to try to ensure the checkpointing process happens before the preallocated space is fully exhausted. If this amount is too close to the preallocation amount, an entry being written may need to extend the file which is a slow operation.

buffer_bytes: usize

The number of bytes to use for the in-memory buffer when reading and writing from the log.

version_info: Arc<Vec<u8>>

An arbitrary chunk of bytes that is stored in the log files. Limited to 255 bytes. This can be used for any purpose, but the design inspiration was to allow detection of what format or version of a format the data was inside of the log without needing to parse the entries.

Implementations

impl Configuration<StdFileManager>

pub fn default_for<P: AsRef<Path>>(path: P) -> Self

Returns the default configuration for a given directory.

This currently is:

• preallocate_bytes: 1 megabyte
• checkpoint_after_bytes: 768 kilobytes
• buffer_bytes: 16 kilobytes

impl<M> Configuration<M>where M: FileManager,

pub fn default_with_manager<P: AsRef<Path>>(path: P, file_manager: M) -> Self

Returns the default configuration for a given directory and file manager.

This currently is:

• preallocate_bytes: 1 megabyte
• checkpoint_after_bytes: 768 kilobytes
• buffer_bytes: 16 kilobytes

pub fn preallocate_bytes(self, bytes: u32) -> Self

Sets the number of bytes to preallocate for each segment file. Returns self.

Preallocating disk space allows for more consistent performance. This number should be large enough to allow batching multiple entries into one checkpointing operation.

pub fn checkpoint_after_bytes(self, bytes: u64) -> Self

Sets the number of bytes written required to begin a checkpoint operation. Returns self.

This value should be smaller than preallocate_bytes to ensure checkpoint operations begin before too much data is written in a log entry. If more data is written before a checkpoint occurs, the segment will grow to accommodate the extra data, but that write will not be as fast due to needing to allocate more space from the filesystem to perform the write.

pub fn buffer_bytes(self, bytes: usize) -> Self

Sets the number of bytes to use for internal buffers when reading and writing data to the log. Returns self.

pub fn open<Manager: LogManager<M>>( self, manager: Manager ) -> Result<WriteAheadLog<M>>

Opens the log using the provided log manager with this configuration.

Trait Implementations

impl<M: Clone> Clone for Configuration<M>

fn clone(&self) -> Configuration<M>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<M: Debug> Debug for Configuration<M>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Configuration<StdFileManager>

fn default() -> Self

Returns the “default value” for a type.