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[#1523] writecache: Simplify logic

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1. Remove in-memory cache. It doesn't persist objects and if we want
   more speed, `NoSync` option can be used for the bolt DB.
2. Put to the metabase in a synchronous fashion. This considerably
   simplifies overall logic and plays nicely with the metabase bolt DB
   batch settings.

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>
This commit is contained in:
Evgenii Stratonikov 2022-07-07 15:52:40 +03:00 • committed by fyrchik
parent 4176b2a1bc
commit ddaed283e9
9 changed files with 140 additions and 328 deletions
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18
pkg/local_object_storage/writecache/mode.go
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@ -23,13 +23,6 @@ func (c *cache) SetMode(m mode.Mode) error {
return nil
}
if !c.readOnly() {
// Because modeMtx is taken no new objects will arrive an all other modifying
// operations are completed.
// 1. Persist objects already in memory on disk.
c.persistMemoryCache()
}
if c.db != nil {
if err := c.db.Close(); err != nil {
return fmt.Errorf("can't close write-cache database: %w", err)
@ -37,13 +30,10 @@ func (c *cache) SetMode(m mode.Mode) error {
c.db = nil
}
// 2. Suspend producers to ensure there are channel send operations in fly.
// metaCh and directCh can be populated either during Put or in background memory persist thread.
// Former possibility is eliminated by taking `modeMtx` mutex and
// latter by explicit persist in the previous step.
// flushCh is populated by `flush` with `modeMtx` is also taken.
// Thus all producers are shutdown and we only need to wait until all channels are empty.
for len(c.metaCh) != 0 || len(c.directCh) != 0 || len(c.flushCh) != 0 {
// Suspend producers to ensure there are channel send operations in fly.
// flushCh is populated by `flush` with `modeMtx` taken, thus waiting until it is empty
// guarantees that there are no in-fly operations.
for len(c.flushCh) != 0 {
c.log.Info("waiting for channels to flush")
time.Sleep(time.Second)
}