README
¶
WAL: Write Ahead Log
How data travels?
- Application Buffer or Library Buffer: at this point data lives in application address space.
- Kernel Buffer: Kernel page cache where data can live for a non fixed time.
- Storage Device Cache:
- Stable Storage:
How data travels in MDB?
When data is written to the network socket it is read by the server in buffer i.e. application memory. The server already has a file stream opened(WAL file).
Installation
Example
// Start a new WAL
walObj, err = wal.Open(/path/to/wal/dir)
// Open the existing latest WAL
walObj, err = wal.Open(/path/to/wal/dir)
// Write to WAL
err := walObj.Write([]byte("some data"))
// Read opened WAL file:
rChan := db.rWalObj.Read()
for record := range rChan {
// do something with the data here
}
- Close the opened WAL:
db.rWalObj.Close()
Documentation
¶
Index ¶
Constants ¶
This section is empty.
Variables ¶
View Source
var ( // ErrWalNotFound no recovery log found. Possible reason first db run. ErrWalNotFound = errors.New("WAL: WAL recovery log not found") // ErrInvalidPath raised when passed path doesn't exists ErrInvalidPath = errors.New("WAL: Invalid directory") // ErrInvalidSeq is raised when a missing sequence is found in wal file. // Wal recovery should stop here. ErrInvalidSeq = errors.New("WAL: Invalid sequence found while recovering. Abort") // ErrInvalidWalData is raised while validating each record with it's hash. Wal // recovery should stop here. ErrInvalidWalData = errors.New("WAL: Invalid data found while recovering. Abort") ErrBadWalName = errors.New("WAL: Bad wal name") )
Functions ¶
func CalculateHash ¶
CalculateHash returns the crc32 value for data
Types ¶
type Record ¶
Record stores individual db command record. Each record contains complete data about a command.
Source Files
Click to show internal directories.
Click to hide internal directories.