* feat(backends/s3): add warmup support before repacks and restores
This commit introduces basic support for transitioning pack files stored
in cold storage to hot storage on S3 and S3-compatible providers.
To prevent unexpected behavior for existing users, the feature is gated
behind new flags:
- `s3.enable-restore`: opt-in flag (defaults to false)
- `s3.restore-days`: number of days for the restored objects to remain
in hot storage (defaults to `7`)
- `s3.restore-timeout`: maximum time to wait for a single restoration
(default to `1 day`)
- `s3.restore-tier`: retrieval tier at which the restore will be
processed. (default to `Standard`)
As restoration times can be lengthy, this implementation preemptively
restores selected packs to prevent incessant restore-delays during
downloads. This is slightly sub-optimal as we could process packs
out-of-order (as soon as they're transitioned), but this would really
add too much complexity for a marginal gain in speed.
To maintain simplicity and prevent resources exhautions with lots of
packs, no new concurrency mechanisms or goroutines were added. This just
hooks gracefully into the existing routines.
**Limitations:**
- Tests against the backend were not written due to the lack of cold
storage class support in MinIO. Testing was done manually on
Scaleway's S3-compatible object storage. If necessary, we could
explore testing with LocalStack or mocks, though this requires further
discussion.
- Currently, this feature only warms up before restores and repacks
(prune/copy), as those are the two main use-cases I came across.
Support for other commands may be added in future iterations, as long
as affected packs can be calculated in advance.
- The feature is gated behind a new alpha `s3-restore` feature flag to
make it explicit that the feature is still wet behind the ears.
- There is no explicit user notification for ongoing pack restorations.
While I think it is not necessary because of the opt-in flag, showing
some notice may improve usability (but would probably require major
refactoring in the progress bar which I didn't want to start). Another
possibility would be to add a flag to send restores requests and fail
early.
See https://github.com/restic/restic/issues/3202
* ui: warn user when files are warming up from cold storage
* refactor: remove the PacksWarmer struct
It's easier to handle multiple handles in the backend directly, and it
may open the door to reducing the number of requests made to the backend
in the future.
The Test method was only used in exactly one place, namely when trying
to create a new repository it was used to check whether a config file
already exists.
Use a combination of Stat() and IsNotExist() instead.
The ioutil functions are deprecated since Go 1.17 and only wrap another
library function. Thus directly call the underlying function.
This commit only mechanically replaces the function calls.
This enables the backends to request the calculation of a
backend-specific hash. For the currently supported backends this will
always be MD5. The hash calculation happens as early as possible, for
pack files this is during assembly of the pack file. That way the hash
would even capture corruptions of the temporary pack file on disk.
This can be used to check how large a backup is or validate exclusions.
It does not actually write any data to the underlying backend. This is
implemented as a simple overlay backend that accepts writes without
forwarding them, passes through reads, and generally does the minimal
necessary to pretend that progress is actually happening.
Fixes#1542
Example usage:
$ restic -vv --dry-run . | grep add
new /changelog/unreleased/issue-1542, saved in 0.000s (350 B added)
modified /cmd/restic/cmd_backup.go, saved in 0.000s (16.543 KiB added)
modified /cmd/restic/global.go, saved in 0.000s (0 B added)
new /internal/backend/dry/dry_backend_test.go, saved in 0.000s (3.866 KiB added)
new /internal/backend/dry/dry_backend.go, saved in 0.000s (3.744 KiB added)
modified /internal/backend/test/tests.go, saved in 0.000s (0 B added)
modified /internal/repository/repository.go, saved in 0.000s (20.707 KiB added)
modified /internal/ui/backup.go, saved in 0.000s (9.110 KiB added)
modified /internal/ui/jsonstatus/status.go, saved in 0.001s (11.055 KiB added)
modified /restic, saved in 0.131s (25.542 MiB added)
Would add to the repo: 25.892 MiB
