mirror of
https://github.com/restic/restic.git
synced 2024-12-25 17:27:25 +00:00
33 lines
1.7 KiB
Go
33 lines
1.7 KiB
Go
// Package restorer contains code to restore data from a repository.
|
|
//
|
|
// The Restorer tries to keep the number of backend requests minimal. It does
|
|
// this by downloading all required blobs of a pack file with a single backend
|
|
// request and avoiding repeated downloads of the same pack. In addition,
|
|
// several pack files are fetched concurrently.
|
|
//
|
|
// Here is high-level pseudo-code of the how the Restorer attempts to achieve
|
|
// these goals:
|
|
//
|
|
// while there are packs to process
|
|
// choose a pack to process [1]
|
|
// get the pack from the backend or cache [2]
|
|
// write pack blobs to the files that need them [3]
|
|
// if not all pack blobs were used
|
|
// cache the pack for future use [4]
|
|
//
|
|
// Pack download and processing (steps [2] - [4]) runs on multiple concurrent
|
|
// Goroutines. The Restorer runs all steps [2]-[4] sequentially on the same
|
|
// Goroutine.
|
|
//
|
|
// Before a pack is downloaded (step [2]), the required space is "reserved" in
|
|
// the pack cache. Actual download uses single backend request to get all
|
|
// required pack blobs. This may download blobs that are not needed, but we
|
|
// assume it'll still be faster than getting individual blobs.
|
|
//
|
|
// Target files are written (step [3]) in the "right" order, first file blob
|
|
// first, then second, then third and so on. Blob write order implies that some
|
|
// pack blobs may not be immediately used, i.e. they are "out of order" for
|
|
// their respective target files. Packs with unused blobs are cached (step
|
|
// [4]). The cache has capacity limit and may purge packs before they are fully
|
|
// used, in which case the purged packs will need to be re-downloaded.
|
|
package restorer
|