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copy.go
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copy.go
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package main
import (
"sync"
"time"
"github.com/aws/aws-sdk-go/service/dynamodb"
"github.com/sirupsen/logrus"
"golang.org/x/time/rate"
)
const (
maxBatchSize = 25
)
func (state *syncState) copyTable()(error) {
logger.WithFields(logrus.Fields{
"Source Table": state.tableConfig.SrcTable,
"Destination Table": state.tableConfig.DstTable,
}).Debug("Starting copying of tables")
err := state.readAndWrite()
return err
}
func (state *syncState) readAndWrite() error {
var writerWG, readerWG sync.WaitGroup
writeWorkers := state.tableConfig.CopyLoad.WriteWorkers
readWorkers := state.tableConfig.CopyLoad.ReadWorkers
scannedItems := make(chan []map[string]*dynamodb.AttributeValue)
quitCopy := make(chan error)
writerWG.Add(writeWorkers)
lim := rate.Limit(state.tableConfig.CopyLoad.WriteQPS)
rl := rate.NewLimiter(lim, int(state.tableConfig.CopyLoad.WriteQPS))
for i := 0; i < writeWorkers; i++ {
go state.writeTable(scannedItems, &writerWG, i, rl)
}
readerWG.Add(readWorkers)
for i := 0; i < readWorkers; i++ {
go state.readTable(scannedItems, &readerWG, i, quitCopy)
}
checkError:
for {
select {
case err := <-quitCopy:
if err != nil {
return err
} else {
break checkError
}
}
}
readerWG.Wait()
close(scannedItems)
writerWG.Wait()
logger.WithFields(logrus.Fields{
"Source Table": state.tableConfig.SrcTable,
"Destination Table": state.tableConfig.DstTable,
}).Info("Finished copying dynamodb tables")
return nil
}
func (state *syncState) writeTable(itemsChan chan []map[string]*dynamodb.AttributeValue,
writerWG *sync.WaitGroup, id int, rl *rate.Limiter) {
defer writerWG.Done()
var writeBatchSize int64
var reqCapacity float64
writeRequest := make(map[string][]*dynamodb.WriteRequest, 0)
dst := state.tableConfig.DstTable
if maxBatchSize > state.tableConfig.CopyLoad.WriteQPS {
writeBatchSize = state.tableConfig.CopyLoad.WriteQPS
} else {
writeBatchSize = maxBatchSize
}
for {
items, more := <-itemsChan
if !more {
logger.WithFields(logrus.Fields{"Id": id}).Info("Write worker finished")
return
}
for _, item := range items {
requestSize := len(writeRequest[dst])
if int64(requestSize) == writeBatchSize {
consumedCapacity := state.processBatch(writeRequest, rl, reqCapacity, id, writeBatchSize)
reqCapacity = 0
for _, each := range consumedCapacity {
reqCapacity += *each.CapacityUnits
}
writeRequest[dst] = []*dynamodb.WriteRequest{{
PutRequest: &dynamodb.PutRequest{Item: item},
}}
} else {
writeRequest[dst] = append(writeRequest[dst], &dynamodb.WriteRequest{
PutRequest: &dynamodb.PutRequest{Item: item},
})
}
}
// Process items left over (if any)
// More items may have been left over because len(items) % writeBatchSize != 0
if len(writeRequest[dst]) > 0 {
state.processBatch(writeRequest, rl, reqCapacity, id, writeBatchSize)
writeRequest = make(map[string][]*dynamodb.WriteRequest, 0)
}
}
}
func (state *syncState) processBatch(
batch map[string][]*dynamodb.WriteRequest,
rl *rate.Limiter, reqCapacity float64,
id int, writeBatchSize int64) []*dynamodb.ConsumedCapacity {
logger.WithFields(logrus.Fields{"Id": id}).Info("Trying to acquire write permits")
r := rl.ReserveN(time.Now(), int(reqCapacity))
if !r.OK() {
r = rl.ReserveN(time.Now(), int(writeBatchSize))
}
time.Sleep(r.Delay())
logger.WithFields(logrus.Fields{"Id": id, "Req Capacity": reqCapacity}).Info("Acquired permits")
consumedCapacity := make([]*dynamodb.ConsumedCapacity, 0)
i := 0
for len(batch) > 0 {
output, _ := batchWrite(batch, state.dstStreamListener.dynamo)
consumedCapacity = append(consumedCapacity, output.ConsumedCapacity...)
if output.UnprocessedItems != nil {
backoff(i, "BatchWrite")
i++
}
batch = output.UnprocessedItems
}
return consumedCapacity
}
func (state *syncState) readTable(
itemsChan chan []map[string]*dynamodb.AttributeValue,
readerWG *sync.WaitGroup, id int, quitCopy chan error) {
defer readerWG.Done()
lastEvaluatedKey := make(map[string]*dynamodb.AttributeValue, 0)
for {
result, err := scanTable(state.tableConfig.SrcTable, id, state.tableConfig.CopyLoad.ReadWorkers,
lastEvaluatedKey, state.srcStreamListener.dynamo)
if err != nil {
logger.WithFields(logrus.Fields{
"Table": state.tableConfig.SrcTable,
"Error": err,
}).Error("Failed to scan table")
quitCopy <- err
}
lastEvaluatedKey = result.LastEvaluatedKey
itemsChan <- result.Items
if len(lastEvaluatedKey) == 0 {
logger.WithFields(logrus.Fields{
"Table": state.tableConfig.SrcTable,
}).Info("Read worker finished")
quitCopy <- nil
return
}
}
}