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streaming_service.go
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streaming_service.go
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package versiondb
import (
"sort"
"strings"
"sync"
abci "github.com/tendermint/tendermint/abci/types"
"github.com/cosmos/cosmos-sdk/baseapp"
"github.com/cosmos/cosmos-sdk/store/types"
sdk "github.com/cosmos/cosmos-sdk/types"
)
var _ baseapp.StreamingService = &StreamingService{}
// FlattenListener listens to the state writes and flatten them in memory.
// One listener only listens to a single storeKey.
type FlattenListener struct {
stateCache map[string]types.StoreKVPair
}
func NewFlattenListener() *FlattenListener {
return &FlattenListener{
stateCache: make(map[string]types.StoreKVPair),
}
}
func (fl *FlattenListener) OnWrite(storeKey types.StoreKey, key []byte, value []byte, delete bool) error {
fl.stateCache[string(key)] = types.StoreKVPair{
StoreKey: storeKey.Name(),
Delete: delete,
Key: key,
Value: value,
}
return nil
}
// StreamingService is a concrete implementation of StreamingService that accumulate the state changes in current block,
// writes the ordered changeset out to version storage.
type StreamingService struct {
listeners map[types.StoreKey]*FlattenListener // the listeners that will be initialized with BaseApp
versionStore VersionStore
currentBlockNumber int64 // the current block number
}
// NewStreamingService creates a new StreamingService for the provided writeDir, (optional) filePrefix, and storeKeys
func NewStreamingService(versionStore VersionStore, storeKeys []types.StoreKey) *StreamingService {
listeners := make(map[types.StoreKey]*FlattenListener, len(storeKeys))
// in this case, we are using the same listener for each Store
for _, key := range storeKeys {
listeners[key] = NewFlattenListener()
}
return &StreamingService{listeners, versionStore, 0}
}
// Listeners satisfies the baseapp.StreamingService interface
func (fss *StreamingService) Listeners() map[types.StoreKey][]types.WriteListener {
listeners := make(map[types.StoreKey][]types.WriteListener, len(fss.listeners))
for storeKey, listener := range fss.listeners {
listeners[storeKey] = []types.WriteListener{listener}
}
return listeners
}
// ListenBeginBlock satisfies the baseapp.ABCIListener interface
// It sets the currentBlockNumber.
func (fss *StreamingService) ListenBeginBlock(ctx sdk.Context, req abci.RequestBeginBlock, res abci.ResponseBeginBlock) error {
fss.currentBlockNumber = req.GetHeader().Height
return nil
}
// ListenDeliverTx satisfies the baseapp.ABCIListener interface
func (fss *StreamingService) ListenDeliverTx(ctx sdk.Context, req abci.RequestDeliverTx, res abci.ResponseDeliverTx) error {
return nil
}
// ListenEndBlock satisfies the baseapp.ABCIListener interface
// It merge the state caches of all the listeners together, and write out to the versionStore.
func (fss *StreamingService) ListenEndBlock(ctx sdk.Context, req abci.RequestEndBlock, res abci.ResponseEndBlock) error {
// sort by the storeKeys first
storeKeys := make([]types.StoreKey, 0, len(fss.listeners))
for storeKey := range fss.listeners {
storeKeys = append(storeKeys, storeKey)
}
sort.SliceStable(storeKeys, func(i, j int) bool {
return strings.Compare(storeKeys[i].Name(), storeKeys[j].Name()) < 0
})
// concat the state caches
var changeSet []types.StoreKVPair
for _, storeKey := range storeKeys {
cache := fss.listeners[storeKey].stateCache
fss.listeners[storeKey].stateCache = make(map[string]types.StoreKVPair)
// sort the cache by key
keys := make([]string, 0, len(cache))
for key := range cache {
keys = append(keys, key)
}
sort.Strings(keys)
for _, key := range keys {
changeSet = append(changeSet, cache[key])
}
}
return fss.versionStore.PutAtVersion(fss.currentBlockNumber, changeSet)
}
// Stream satisfies the baseapp.StreamingService interface
func (fss *StreamingService) Stream(wg *sync.WaitGroup) error {
return nil
}
// Close satisfies the io.Closer interface, which satisfies the baseapp.StreamingService interface
func (fss *StreamingService) Close() error {
return nil
}