Not having a skew caused an issue where:
1. Uplink calls "begin segment", where segment isn't committed to the
database.
2. Uplink stores piece X to the storage node A with timestamp 1.
3. Satellite runs garbage collection with timestamp 2.
4. Satellite sends retain request to storage node A with timestamp 2.
5. Storage node A deletes piece X, because 1 < 2.
6. Uplink calls "commit segment" with storage node A in it.
7. Download of segment fails, because A doesn't have piece X.
In production this is not an issue since the MaxTimeSkew is 72h by
default.
Change-Id: Id87ca3ddc44103dcd85d031b1367168c014b8e7b
* nicer flags
* fix concurrency
* add concurrent workers
* initialize things
* fix tests
* close retain service
* ensure we don't have workers working on the same satellite
* ensure things compile
* fix other compilation issues:
* concurrency changes
ran this with `go test -count=1000` and it passed all of them.
- we add a closed channel so that we can select on it with
context cancellation.
- we put a once in so we only close the channel once.
- every time the queue/running state changes, we have to broadcast
because we may want to wake up N pending Wait calls or other
concurrent workers.
- because we broadcast, we don't need to do the polling in Wait
anymore.
- ensure Run doesn't start multiple times so that we don't have
to worry about concurrent Close with multiple Runs.
- hold the lock while we start workers so that a concurrent Close
with Run can't decide that there's nothing started and exit
and then have Run start things.
- make sure to poll the closed/context channels through loops
or at the start of Run calls in case Close happens first.
- these polls should be under a mutex because they have a default
case which makes it possible to schedule such that Close hasn't
executed the channel close so it starts more work.
- cancel a local Run context when it's going to exit to make sure
that any retainPieces calls have a canceled context.
- hopefully enough comments to both check my work and help readers
digest what's going on.
Change-Id: Ida0e226a7e01e8ae64fa2c59dd5a84b04bccfbd7
* use the retain error class
Change-Id: I1511eaef135f98afd57b878e997e4c8a0d11cafc
* concurrency fixes again
- forgot to update the gc test to use the old Wait api.
- we need to drop the lock while we wait for the workers
to exit, because they may be blocked on the condition
variable
- additionally, we need to broadcast when we close the
signal channel because the state changed: they want
to wake up and exit.
Change-Id: I4204699792275260cd912f29aa73720f7d9b14b5
* undo my misguided rename
Change-Id: I6baffe1eb0434e260212c485bbcc01bed3250881
* remove pollInterval
* format paragraph more nicely
* move skew calculation into retain pieces
Add retain service on storagenode. This service runs retain jobs that have been queued by the storagenodes. Rather than running retain jobs during the grpc Retain() call, the grpc call queues a retain job to the retain service and returns immediately afterwards, removing a significant bottleneck in garbage collection.
Deprecate the pieceinfo database, and start storing piece info as a header to
piece files. Institute a "storage format version" concept allowing us to handle
pieces stored under multiple different types of storage. Add a piece_expirations
table which will still be used to track expiration times, so we can query it, but
which should be much smaller than the pieceinfo database would be for the
same number of pieces. (Only pieces with expiration times need to be stored in piece_expirations, and we don't need to store large byte blobs like the serialized
order limit, etc.) Use specialized names for accessing any functionality related
only to dealing with V0 pieces (e.g., `store.V0PieceInfo()`). Move SpaceUsed-
type functionality under the purview of the piece store. Add some generic
interfaces for traversing all blobs or all pieces. Add lots of tests.
* Added a gc package at satellite/gc, which contains the gc.Service, which runs garbage collection integrated with the metainfoloop, and the gc PieceTracker, which implements the metainfo loop Observer interface and stores all of the filters (about which pieces are good) for each node.
* Added a gc config located at satellite/gc/service.go (loop disabled by default in release)
* Creates bloom filters with pieces to be retained inside the metainfo loop
* Sends RetainRequests (or filters with good piece ids) to all storage nodes.
