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kinesis.go
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kinesis.go
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/*
* The MIT License (MIT)
*
* Copyright (c) 2014 Niek J. Sanders
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
*/
package gokinesis
import (
"bufio"
"bytes"
"encoding/json"
"fmt"
"os"
)
// RecordConsumer interface must be implemented by Go KCL consumers and then
// invoked using Run(). Only a single RecordConsumer should ever be Run() since
// it depends on stdin/stdout for the MultiLangDaemon control protocol.
type RecordConsumer interface {
// Init is called before record processing with the shardId.
Init(string) error
// ProcessRecords is called for each batch of records to be processed.
ProcessRecords([]*KclRecord, *Checkpointer) error
// Shutdown is called before termination.
Shutdown(ShutdownType, *Checkpointer) error
}
// ShutdownType indicates whether we have a graceful or zombie shutdown.
type ShutdownType int
const (
unknownShutdown ShutdownType = iota
// GracefulShutdown means checkpoint should be called.
GracefulShutdown
// ZombieShutdown means checkpoint may NOT be called. Another record
// processor may own the shard now.
ZombieShutdown
)
// Run talks to the local KCL MultiLangDaemon using a request/reply protocol
// over stdin/stdout.
func Run(c RecordConsumer) {
checkpointer := &Checkpointer{true}
for {
// read next daemon request
req := getAction()
if req == nil {
break
}
// dispatch based on action
var err error
switch {
case req.Action == "processRecords":
err = c.ProcessRecords(req.Records, checkpointer)
case req.Action == "initialize":
err = c.Init(*req.ShardID)
case req.Action == "shutdown":
shutdownType := GracefulShutdown
if req.Reason == nil || *req.Reason == "ZOMBIE" {
checkpointer.isAllowed = false
shutdownType = ZombieShutdown
}
err = c.Shutdown(shutdownType, checkpointer)
default:
err = fmt.Errorf("Unsupported KCL action: %s", req.Action)
}
if err != nil {
fmt.Fprintf(os.Stderr, "%s\n", err)
os.Exit(1)
}
// respond with ack
fmt.Printf("\n{\"action\": \"status\", \"responseFor\": \"%s\"}\n", req.Action)
}
}
// Checkpointer marks a consumers progress.
type Checkpointer struct {
// isAllowed controls whether checkpointing triggers a panic.
isAllowed bool
}
// CheckpointAll marks all consumed messages as processed.
func (cp *Checkpointer) CheckpointAll() error {
msg := "\n{\"action\": \"checkpoint\", \"checkpoint\": null}\n"
return cp.doCheckpoint(msg)
}
// CheckpointSeq marks messages up to sequence number as processed.
func (cp *Checkpointer) CheckpointSeq(seqNum string) error {
msg := fmt.Sprintf("\n{\"action\": \"checkpoint\", \"checkpoint\": \"%s\"}\n", seqNum)
return cp.doCheckpoint(msg)
}
// CheckpointAll marks all consumed messages as processed.
func (cp *Checkpointer) CheckpointAllV2() error {
msg := "\n{\"action\": \"checkpoint\", \"sequenceNumber\": null, \"subSequenceNumber\": null}\n"
return cp.doCheckpoint(msg)
}
// CheckpointSeq marks messages up to sequence number as processed.
func (cp *Checkpointer) CheckpointSeqV2(seqNum string) error {
msg := fmt.Sprintf("\n{\"action\": \"checkpoint\", \"sequenceNumber\": \"%s\", \"subSequenceNumber\": null}\n", seqNum)
return cp.doCheckpoint(msg)
}
func (cp *Checkpointer) doCheckpoint(msg string) error {
if !cp.isAllowed {
panic("attempted to checkpoint on ZOMBIE termination")
}
// send checkpoint req
fmt.Print(msg)
// receive checkpoint ack
ack := getAction()
// exit on fatal, error out on retryable
if ack == nil {
fmt.Fprintf(os.Stderr, "Received EOF rather than checkpoint ack\n")
os.Exit(1)
} else if ack.Action != "checkpoint" {
fmt.Fprintf(os.Stderr, "Received invalid checkpoint ack: %s\n", ack.Action)
os.Exit(1)
} else if ack.Error != nil {
return fmt.Errorf(*ack.Error)
}
// success
return nil
}
// KclRecord is an individual kinesis record. Note that the body is always
// base64 encoded.
type KclRecord struct {
DataB64 string `json:"data"`
PartitionKey string `json:"partitionKey"`
SequenceNumber string `json:"sequenceNumber"`
}
// KclAction is a request from the local KCL daemon.
type KclAction struct {
Action string `json:"action"`
ShardID *string `json:"shardId"`
Records []*KclRecord `json:"records"`
Reason *string `json:"reason"`
Error *string `json:"error"`
}
// getAction reads a request from the KCL MultiLangDaemon.
func getAction() *KclAction {
bio := bufio.NewReader(os.Stdin)
var buffer bytes.Buffer
for {
linePart, hasMoreInLine, err := bio.ReadLine()
if err != nil {
panic("Unable to read line from stdin " + err.Error())
}
buffer.Write(linePart)
if hasMoreInLine == false {
break
}
}
var req KclAction
err := json.Unmarshal(buffer.Bytes(), &req)
if err != nil {
fmt.Fprintf(os.Stderr, "Could not understand line read from input: %s\n", buffer.String())
}
return &req
}