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cs733
Commit b4502c1f authored by Sushant Mahajan's avatar Sushant Mahajan
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changed the server io to use channels for synchronized communication. Also... 

changed the server io to use channels for synchronized communication. Also added timeout for idle connection
parent 14b0a125
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Showing with 151 additions and 96 deletions
assignment1/server.go
View file @ b4502c1f
package main
import (
"bufio"
"bytes"
"fmt"
"io"
"io/ioutil"
"log"
"net"
......@@ -33,9 +33,7 @@ const (
ERR_CMD_ERR = "ERR_CMD_ERR"
ERR_NOT_FOUND = "ERR_NOT_FOUND"
ERR_VERSION = "ERR_VERSION"
//logging
LOG = true
ERR_INTERNAL = "ERR_INTERNAL"
)
type Data struct {
......@@ -75,24 +73,17 @@ func startServer() {
}
}
func read(conn net.Conn, toRead uint64) ([]byte, bool) {
buf := make([]byte, toRead)
_, err := conn.Read(buf)
if err != nil {
if err == io.EOF {
logger.Println("Client disconnected!")
return []byte{0}, false
func myRead(ch chan string, conn net.Conn) {
scanner := bufio.NewScanner(conn)
for {
if ok := scanner.Scan(); !ok {
break
} else {
temp := scanner.Text()
ch <- temp
logger.Println(temp, "$$")
}
}
n := bytes.Index(buf, []byte{0})
if n != 0 {
logger.Println("Received: ", buf[:n], string(buf[:n]))
return buf[:n-2], true
}
return []byte{0}, false
}
func write(conn net.Conn, msg string) {
......@@ -104,15 +95,17 @@ func write(conn net.Conn, msg string) {
func handleClient(conn net.Conn, table *KeyValueStore) {
defer conn.Close()
//channel for every connection for every client
ch := make(chan string)
go myRead(ch, conn)
for {
if msg, ok := read(conn, 1024); ok {
if len(msg) == 0 {
continue
}
parseInput(conn, string(msg), table)
} else {
break
msg := <-ch
logger.Println("Channel: ", msg)
if len(msg) == 0 {
continue
}
parseInput(conn, string(msg), table, ch)
}
}
......@@ -207,8 +200,14 @@ func isValid(cmd string, tokens []string, conn net.Conn) int {
return flag
}
func parseInput(conn net.Conn, msg string, table *KeyValueStore) {
func parseInput(conn net.Conn, msg string, table *KeyValueStore, ch chan string) {
tokens := strings.Fields(msg)
//general error, don't check for commands, avoid the pain
if len(tokens) > 6 {
write(conn, ERR_CMD_ERR)
return
}
var buffer bytes.Buffer
//logger.Println(tokens)
switch tokens[0] {
......@@ -216,7 +215,8 @@ func parseInput(conn net.Conn, msg string, table *KeyValueStore) {
if isValid(SET, tokens, conn) != 0 {
return
}
if ver, ok, r := performSet(conn, tokens[1:len(tokens)], table); ok {
if ver, ok, r := performSet(conn, tokens[1:len(tokens)], table, ch); ok {
debug(table)
logger.Println(ver)
if r {
buffer.Reset()
......@@ -246,6 +246,7 @@ func parseInput(conn net.Conn, msg string, table *KeyValueStore) {
buffer.WriteString(ERR_NOT_FOUND)
write(conn, buffer.String())
}
debug(table)
case GETM:
if isValid(GETM, tokens, conn) != 0 {
......@@ -270,12 +271,13 @@ func parseInput(conn net.Conn, msg string, table *KeyValueStore) {
buffer.WriteString(ERR_NOT_FOUND)
write(conn, buffer.String())
}
debug(table)
case CAS:
if isValid(CAS, tokens, conn) != 0 {
return
}
if ver, ok, r := performCas(conn, tokens[1:len(tokens)], table); r {
if ver, ok, r := performCas(conn, tokens[1:len(tokens)], table, ch); r {
if r {
switch ok {
case 0:
......@@ -300,24 +302,74 @@ func parseInput(conn net.Conn, msg string, table *KeyValueStore) {
}
}
}
debug(table)
case DELETE:
if isValid(DELETE, tokens, conn) != 0 {
return
}
if ok := performDelete(conn, tokens[1:len(tokens)], table); ok {
buffer.Reset()
buffer.WriteString(DELETED)
write(conn, buffer.String())
if ok := performDelete(conn, tokens[1:len(tokens)], table); ok == 0 {
write(conn, DELETED)
} else {
write(conn, ERR_NOT_FOUND)
}
debug(table)
default:
logger.Println("Command not found")
buffer.Reset()
buffer.WriteString(ERR_CMD_ERR)
write(conn, buffer.String())
}
}
/*
*Helper function to read value or cause timeout after 5 seconds
*parameters: channel to read data from, threshold number of bytes to read
*returns: the value string and error state
*/
func readValue(ch chan string, n uint64) ([]byte, bool) {
//now we need to read the value which should have been sent
valReadLength := uint64(0)
var v string
err := false
up := make(chan bool, 1)
//after 5 seconds passed reading value, we'll just send err to client
go func() {
time.Sleep(5 * time.Second)
up <- true
}()
//use select for the data channel and the timeout channel
for valReadLength < n {
select {
case temp := <-ch:
logger.Println("Value chunk read!")
valReadLength += uint64(len(temp))
v += temp
case <-up:
err = true
logger.Println("Oh, Oh timeout")
//write(conn, ERR_INTERNAL)
break
}
//will be true if timeout occurs
if err {
break
}
}
if err {
return []byte{0}, err
}
return []byte(v), err
}
func performSet(conn net.Conn, tokens []string, table *KeyValueStore) (uint64, bool, bool) {
func performSet(conn net.Conn, tokens []string, table *KeyValueStore, ch chan string) (uint64, bool, bool) {
k := tokens[0]
e, _ := strconv.ParseUint(tokens[1], 10, 64)
n, _ := strconv.ParseUint(tokens[2], 10, 64)
e, _ := strconv.ParseUint(tokens[1], 10, 64) //expiry time offset
n, _ := strconv.ParseUint(tokens[2], 10, 64) //numbytes
r := true
if len(tokens) == 4 && tokens[3] == NOREPLY {
......@@ -326,42 +378,36 @@ func performSet(conn net.Conn, tokens []string, table *KeyValueStore) (uint64, b
logger.Println(r)
//read value
v, ok := read(conn, n+2)
if !ok {
//error here
if v, err := readValue(ch, n); err {
write(conn, ERR_INTERNAL)
return 0, false, r
}
table.Lock()
logger.Println("Table locked")
//critical section start
var val *Data
if _, ok := table.dictionary[k]; ok {
val = table.dictionary[k]
} else {
val = new(Data)
table.dictionary[k] = val
}
ver++
val.numBytes = n
val.version = ver
if e == 0 {
val.expTime = e
} else {
val.expTime = e + uint64(time.Now().Unix())
defer table.Unlock()
table.Lock()
//critical section start
var val *Data
if _, ok := table.dictionary[k]; ok {
val = table.dictionary[k]
} else {
val = new(Data)
table.dictionary[k] = val
}
ver++
val.numBytes = n
val.version = ver
if e == 0 {
val.expTime = e
} else {
val.expTime = e + uint64(time.Now().Unix())
}
val.value = v
return val.version, true, r
}
val.value = v
table.Unlock()
logger.Println("Table unlocked")
debug(table)
return val.version, true, r
}
func performGet(conn net.Conn, tokens []string, table *KeyValueStore) (*Data, bool) {
k := tokens[0]
table.RUnlock()
defer table.RUnlock()
table.RLock()
//critical section begin
if v, ok := table.dictionary[k]; ok {
......@@ -399,7 +445,7 @@ func performGetm(conn net.Conn, tokens []string, table *KeyValueStore) (*Data, b
}
}
func performCas(conn net.Conn, tokens []string, table *KeyValueStore) (uint64, int, bool) {
func performCas(conn net.Conn, tokens []string, table *KeyValueStore, ch chan string) (uint64, int, bool) {
k := tokens[0]
e, _ := strconv.ParseUint(tokens[1], 10, 64)
ve, _ := strconv.ParseUint(tokens[2], 10, 64)
......@@ -412,43 +458,47 @@ func performCas(conn net.Conn, tokens []string, table *KeyValueStore) (uint64, i
}
//read value
v, ok := read(conn, n+2)
if !ok {
//error here
return 0, 1, r //malformed
}
defer table.Unlock()
table.Lock()
if val, ok := table.dictionary[k]; ok {
if val.version == ve {
if e == 0 {
val.expTime = e
} else {
val.expTime = e + uint64(time.Now().Unix())
if v, err := readValue(ch, n); err {
return 0, 1, r
} else {
defer table.Unlock()
table.Lock()
if val, ok := table.dictionary[k]; ok {
if val.version == ve {
if e == 0 {
val.expTime = e
} else {
val.expTime = e + uint64(time.Now().Unix())
}
val.numBytes = n
ver++
val.version = ver
val.value = v
return val.version, 0, r //key found and changed
}
val.numBytes = n
ver++
val.version = ver
val.value = v
return val.version, 0, r //key found and changed
return 0, 2, r //version mismatch
}
return 0, 2, r //version mismatch
return 0, 3, r //key not found
}
return 0, 3, r //key not found
}
func performDelete(conn net.Conn, tokens []string, table *KeyValueStore) bool {
func performDelete(conn net.Conn, tokens []string, table *KeyValueStore) int {
k := tokens[0]
logger.Println(tokens)
flag := 1
defer table.Unlock()
table.Lock()
//begin critical section
if _, ok := table.dictionary[k]; ok {
delete(table.dictionary, k)
return true
if v, ok := table.dictionary[k]; ok {
if v.expTime < uint64(time.Now().Unix()) {
flag = 1 //found but expired
} else {
flag = 0 //found not expired
}
delete(table.dictionary, k) //delete anyway as expired or needs to be deleted
return flag
}
return false
return 2 //key not found
}
func debug(table *KeyValueStore) {
......@@ -462,7 +512,12 @@ func debug(table *KeyValueStore) {
func main() {
ver = 1
if LOG {
toLog := ""
if len(os.Args) > 1 {
toLog = os.Args[1]
}
if toLog != "" {
logf, _ := os.OpenFile("serverlog.log", os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
defer logf.Close()
logger = log.New(logf, "SERVER: ", log.Ltime|log.Lshortfile)
......
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