nim-dagger/codex/stores/cachestore.nim

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## Nim-Codex
## Copyright (c) 2021 Status Research & Development GmbH
## Licensed under either of
## * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
## * MIT license ([LICENSE-MIT](LICENSE-MIT))
## at your option.
## This file may not be copied, modified, or distributed except according to
## those terms.
import std/sequtils
import pkg/upraises
push: {.upraises: [].}
import std/options
import pkg/chronicles
import pkg/chronos
import pkg/libp2p
import pkg/lrucache
import pkg/questionable
import pkg/questionable/results
import ./blockstore
import ../chunker
import ../errors
export blockstore
logScope:
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topics = "codex cachestore"
type
CacheStore* = ref object of BlockStore
currentSize*: Natural # in bytes
size*: Positive # in bytes
cache: LruCache[Cid, Block]
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InvalidBlockSize* = object of CodexError
const
MiB* = 1024 * 1024 # bytes, 1 mebibyte = 1,048,576 bytes
DefaultCacheSizeMiB* = 100
DefaultCacheSize* = DefaultCacheSizeMiB * MiB # bytes
method getBlock*(self: CacheStore, cid: Cid): Future[?!Block] {.async.} =
## Get a block from the stores
##
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trace "Getting block from cache", cid
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if cid.isEmpty:
trace "Empty block, ignoring"
return success cid.emptyBlock
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if cid notin self.cache:
return failure (ref BlockNotFoundError)(msg: "Block not in cache")
try:
return success self.cache[cid]
except CatchableError as exc:
trace "Error requesting block from cache", cid, error = exc.msg
return failure exc
method hasBlock*(self: CacheStore, cid: Cid): Future[?!bool] {.async.} =
## Check if the block exists in the blockstore
##
trace "Checking CacheStore for block presence", cid
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if cid.isEmpty:
trace "Empty block, ignoring"
return true.success
return (cid in self.cache).success
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method listBlocks*(s: CacheStore, onBlock: OnBlock): Future[?!void] {.async.} =
## Get the list of blocks in the BlockStore. This is an intensive operation
##
for cid in toSeq(s.cache.keys):
await onBlock(cid)
return success()
func putBlockSync(self: CacheStore, blk: Block): bool =
let blkSize = blk.data.len # in bytes
if blkSize > self.size:
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trace "Block size is larger than cache size", blk = blkSize, cache = self.size
return false
while self.currentSize + blkSize > self.size:
try:
let removed = self.cache.removeLru()
self.currentSize -= removed.data.len
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except EmptyLruCacheError as exc:
# if the cache is empty, can't remove anything, so break and add item
# to the cache
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trace "Exception puting block to cache", exc = exc.msg
break
self.cache[blk.cid] = blk
self.currentSize += blkSize
return true
method putBlock*(self: CacheStore, blk: Block): Future[?!void] {.async.} =
## Put a block to the blockstore
##
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trace "Storing block in cache", cid = blk.cid
if blk.isEmpty:
trace "Empty block, ignoring"
return success()
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discard self.putBlockSync(blk)
return success()
method delBlock*(self: CacheStore, cid: Cid): Future[?!void] {.async.} =
## Delete a block from the blockstore
##
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trace "Deleting block from cache", cid
if cid.isEmpty:
trace "Empty block, ignoring"
return success()
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let removed = self.cache.del(cid)
if removed.isSome:
self.currentSize -= removed.get.data.len
return success()
method close*(self: CacheStore): Future[void] {.async.} =
## Close the blockstore, a no-op for this implementation
##
discard
func new*(
_: type CacheStore,
blocks: openArray[Block] = [],
cacheSize: Positive = DefaultCacheSize, # in bytes
chunkSize: Positive = DefaultChunkSize # in bytes
): CacheStore {.raises: [Defect, ValueError].} =
if cacheSize < chunkSize:
raise newException(ValueError, "cacheSize cannot be less than chunkSize")
var currentSize = 0
let
size = cacheSize div chunkSize
cache = newLruCache[Cid, Block](size)
store = CacheStore(
cache: cache,
currentSize: currentSize,
size: cacheSize)
for blk in blocks:
discard store.putBlockSync(blk)
return store