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kinesis-cli.go
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kinesis-cli.go
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/*
kinesis-cli is a command line interface tool for interacting with AWS kinesis.
To install:
go get github.com/sendgridlabs/go-kinesis/kinesis-cli
To build:
cd $GOPATH/src/github.com/sendgridlabs/go-kinesis/kinesis-cli; go build
To use:
run ./kinesis-cli to see the usage.
*/
package main
import (
"bufio"
"encoding/json"
"fmt"
"math/big"
"os"
"strconv"
"strings"
// "github.com/sendgridlabs/go-kinesis"
"github.com/sendgridlabs/go-kinesis"
)
const HELP = `Usage: ./kinesis-cli <command> [<arg>, ...]
(Note: expects $AWS_ACCESS_KEY, $AWS_SECRET_KEY and $AWS_REGION_NAME to be set)
Commands:
create <streamName> [<# shards>]
delete <streamName>
describe <streamName> [<exclusive start shardId> <limit>]
split <streamName> <shardId> [<hash key>]
merge <streamName> <shardId> <adjacent shardId>
`
var EMPTY_STRING = ""
var EMPTY_INT = -1
var DEFAULT_NUM_SHARDS = 1
func create(args []string) {
streamName := getArg(args, 0, "stream name", nil)
numShards := getIntArg(args, 1, "stream name", &DEFAULT_NUM_SHARDS)
if !confirm(fmt.Sprintf("create stream '%s' with %d shard(s)", streamName, numShards)) {
fmt.Println("Create canceled.")
return
}
if err := newClient().CreateStream(streamName, numShards); err != nil {
die(false, "Error creating shard: %s", err)
}
}
func delete(args []string) {
streamName := getArg(args, 0, "stream name", nil)
if !confirm("delete stream '" + streamName + "'") {
fmt.Println("Delete canceled.")
return
}
if err := newClient().DeleteStream(streamName); err != nil {
die(false, "Error deleting shard: %s", err)
}
}
func describe(args []string) {
streamName := getArg(args, 0, "stream name", nil)
exclusiveStartShardId := getArg(args, 1, "exclusive start shard id", &EMPTY_STRING)
limit := getIntArg(args, 2, "limit", &EMPTY_INT)
streamDesc := describeStream(streamName, exclusiveStartShardId, limit)
prettyBytes, err := json.MarshalIndent(streamDesc, "", " ")
if err != nil {
die(false, "Error marshaling response: %s", err)
}
fmt.Println(string(prettyBytes))
}
func split(args []string) {
streamName := getArg(args, 0, "stream name", nil)
shardId := getArg(args, 1, "shard id", nil)
newStartHash := getArg(args, 2, "starting hash", &EMPTY_STRING)
if newStartHash == "" {
newStartHash = askForShardStartHash(streamName, shardId)
}
if !confirm(fmt.Sprintf("split shard %s at hash key %s", shardId, newStartHash)) {
fmt.Println("Split canceled.")
return
}
requestArgs := kinesis.NewArgs()
requestArgs.Add("StreamName", streamName)
requestArgs.Add("ShardToSplit", shardId)
requestArgs.Add("NewStartingHashKey", newStartHash)
if err := newClient().SplitShard(requestArgs); err != nil {
die(false, "Error splitting shard: %s", err)
}
}
func merge(args []string) {
streamName := getArg(args, 0, "stream name", nil)
shardId := getArg(args, 1, "shard id", nil)
adjacentShardId := getArg(args, 2, "adjacent shard id", nil)
requestArgs := kinesis.NewArgs()
requestArgs.Add("StreamName", streamName)
requestArgs.Add("ShardToMerge", shardId)
requestArgs.Add("AdjacentShardToMerge", adjacentShardId)
if !confirm(fmt.Sprintf("merge shards %s and %s", shardId, adjacentShardId)) {
fmt.Println("Merge canceled.")
return
}
if err := newClient().MergeShards(requestArgs); err != nil {
die(false, "Error merging shards: %s", err)
}
}
func main() {
if len(os.Args) < 2 {
die(true, "Error: no command specified.")
}
if os.Getenv(kinesis.AccessEnvKey) == "" ||
os.Getenv(kinesis.SecretEnvKey) == "" {
fmt.Printf("WARNING: %s and/or %s environment variables not set. Will "+
"attempt to fetch credentials from metadata server.\n",
kinesis.AccessEnvKey, kinesis.SecretEnvKey)
}
if os.Getenv(kinesis.RegionEnvName) == "" {
fmt.Printf("WARNING: %s not set.\n", kinesis.RegionEnvName)
}
switch os.Args[1] {
case "create":
create(os.Args[2:])
case "delete":
delete(os.Args[2:])
case "describe":
describe(os.Args[2:])
case "split":
split(os.Args[2:])
case "merge":
merge(os.Args[2:])
default:
die(true, "Error: unknown command '%s'", os.Args[1])
}
}
//
// Command line helper functions
//
func die(printHelp bool, format string, args ...interface{}) {
if printHelp {
fmt.Print(HELP)
}
fmt.Printf(format, args...)
fmt.Println("")
os.Exit(1)
}
func confirm(action string) bool {
prompt := fmt.Sprintf("Are you sure you want to %s?\n[y/N]: ", action)
s := readString(prompt, "")
return strings.ToLower(s) == "y"
}
func readString(prompt string, defaultStr string) string {
fmt.Print(prompt)
reader := bufio.NewReader(os.Stdin)
result, err := reader.ReadString('\n')
if err != nil {
die(false, "Error reading input: %s", err)
}
if result = strings.TrimSpace(result); result == "" {
return defaultStr
}
return result
}
func getArg(specified []string, index int, name string, def *string) string {
if index < len(specified) {
return specified[index]
}
if def == nil {
die(true, "Error: %s is required.", name)
}
return *def
}
func getIntArg(specified []string, index int, name string, def *int) int {
var argStr string
if def != nil {
defStr := strconv.Itoa(*def)
argStr = getArg(specified, index, name, &defStr)
} else {
argStr = getArg(specified, index, name, nil)
}
intArg, err := strconv.Atoi(argStr)
if err != nil {
die(false, "Error parsing %s as integer: %s\n%s", name, argStr, err)
}
return intArg
}
//
// Big int (for 128-bit start/end hash keys) helper functions
//
// Takes two large base 10 numeric strings a and b, and returns (a + b)/2
func getMiddle(lowStr, highStr string) *big.Int {
low := bigIntFromStr(lowStr, 10)
high := bigIntFromStr(highStr, 10)
if low.Cmp(high) != -1 {
die(false, "Error: %s is not smaller than %s", lowStr, highStr)
}
middle := new(big.Int)
middle = middle.Div(middle.Add(low, high), big.NewInt(2))
return middle
}
// Takes two large base 10 numeric strings low and high and returns low < x < high.
func isBetween(lowStr, highStr, xStr string) bool {
low := bigIntFromStr(lowStr, 10)
high := bigIntFromStr(highStr, 10)
x := bigIntFromStr(xStr, 10)
return x.Cmp(low) == 1 && x.Cmp(high) == -1
}
func bigIntFromStr(s string, base int) *big.Int {
result := new(big.Int)
result, success := result.SetString(s, 10)
if !success {
die(false, "Error: cannot create big int from string '%s'", s)
}
return result
}
//
// Kinesis helper functions
//
func newClient() kinesis.KinesisClient {
auth, _ := kinesis.NewAuthFromEnv()
return kinesis.New(auth, kinesis.NewRegionFromEnv())
}
func askForShardStartHash(streamName, shardId string) string {
// Figure out a sensible default value for a split hash key.
shardDesc := describeShard(streamName, shardId)
if shardDesc == nil {
die(false, "Error: No shard found with id %s", shardId)
}
existingStart, existingEnd := shardDesc.HashKeyRange.StartingHashKey, shardDesc.HashKeyRange.EndingHashKey
newStartHash := getMiddle(existingStart, existingEnd).String()
prompt := fmt.Sprintf("Shard's current hash key range (%s - %s)\nDefault (even split) key: %s\nType new key or press [enter] to choose default: ",
existingStart, existingEnd, newStartHash)
newStartHash = readString(prompt, newStartHash)
if !isBetween(existingStart, existingEnd, newStartHash) {
die(false, "New starting hash '%s' is not within shard's current range.", newStartHash)
}
return newStartHash
}
func describeShard(streamName, shardId string) *kinesis.DescribeStreamShards {
describeResponse := describeStream(streamName, "", -1)
for _, shard := range describeResponse.StreamDescription.Shards {
if shard.ShardId == shardId {
return &shard
}
}
return nil
}
func describeStream(streamName, exclusiveStartShardId string, limit int) *kinesis.DescribeStreamResp {
var response *kinesis.DescribeStreamResp
done := false
for !done {
requestArgs := kinesis.NewArgs()
requestArgs.Add("StreamName", streamName)
if exclusiveStartShardId != "" {
requestArgs.Add("ExclusiveStartShardId", exclusiveStartShardId)
}
if limit > 0 {
requestArgs.Add("Limit", limit)
}
curResponse, err := newClient().DescribeStream(requestArgs)
if err != nil {
die(false, "Error describing stream: %s", err)
}
if response == nil {
response = curResponse
} else {
shards := response.StreamDescription.Shards
for _, shard := range curResponse.StreamDescription.Shards {
shards = append(shards, shard)
if len(shards) >= limit {
done = true
break
}
exclusiveStartShardId = shard.ShardId
limit--
}
}
done = done || !response.StreamDescription.HasMoreShards
}
return response
}