gb vendor fetch github.com/matrix-org/naffka

main
Mark Haines 2017-08-15 16:06:09 +01:00
parent 2071387f3c
commit 0d894e3da5
7 changed files with 577 additions and 0 deletions

6
vendor/manifest vendored
View File

@ -101,6 +101,12 @@
"revision": "768a8767051a4aca7f5e41f912954ae04d5f1efb", "revision": "768a8767051a4aca7f5e41f912954ae04d5f1efb",
"branch": "master" "branch": "master"
}, },
{
"importpath": "github.com/matrix-org/naffka",
"repository": "https://github.com/matrix-org/naffka",
"revision": "d28656e34f96a8eeaab53e3b7678c9ce14af5786",
"branch": "master"
},
{ {
"importpath": "github.com/matrix-org/util", "importpath": "github.com/matrix-org/util",
"repository": "https://github.com/matrix-org/util", "repository": "https://github.com/matrix-org/util",

View File

@ -0,0 +1,5 @@
# naffka
Single in-process implementation of the [sarama golang kafka](https://github.com/Shopify/sarama) APIs.
It's like Kafka, but a bit [naff](https://www.collinsdictionary.com/dictionary/english/naff).

View File

@ -0,0 +1,5 @@
#! /bin/bash
DOT_GIT="$(dirname $0)/../.git"
ln -s "../../hooks/pre-commit" "$DOT_GIT/hooks/pre-commit"

View File

@ -0,0 +1,24 @@
#! /bin/bash
set -eu
golint ./...
misspell -error .
# gofmt doesn't exit with an error code if the files don't match the expected
# format. So we have to run it and see if it outputs anything.
if gofmt -l -s . 2>&1 | read
then
echo "Error: not all code had been formatted with gofmt."
echo "Fixing the following files"
gofmt -s -w -l .
echo
echo "Please add them to the commit"
git status --short
exit 1
fi
ineffassign .
go tool vet --all --shadow .
gocyclo -over 16 .
go test -timeout 5s . ./...

View File

@ -0,0 +1,91 @@
package naffka
import (
"fmt"
"sync"
)
// A MemoryDatabase stores the message history as arrays in memory.
// It can be used to run unit tests.
// If the process is stopped then any messages that haven't been
// processed by a consumer are lost forever.
type MemoryDatabase struct {
topicsMutex sync.Mutex
topics map[string]*memoryDatabaseTopic
}
type memoryDatabaseTopic struct {
messagesMutex sync.Mutex
messages []Message
}
func (t *memoryDatabaseTopic) addMessages(msgs []Message) error {
t.messagesMutex.Lock()
defer t.messagesMutex.Unlock()
if int64(len(t.messages)) != msgs[0].Offset {
return fmt.Errorf("message offset %d is not immediately after the previous offset %d", msgs[0].Offset, len(t.messages))
}
t.messages = append(t.messages, msgs...)
return nil
}
// getMessages returns the current messages as a slice.
// This slice will have it's own copy of the length field so won't be affected
// by adding more messages in addMessages.
// The slice will share the same backing array with the slice we append new
// messages to. It is safe to read the messages in the backing array since we
// only append to the slice. It is not safe to write or append to the returned
// slice.
func (t *memoryDatabaseTopic) getMessages() []Message {
t.messagesMutex.Lock()
defer t.messagesMutex.Unlock()
return t.messages
}
func (m *MemoryDatabase) getTopic(topicName string) *memoryDatabaseTopic {
m.topicsMutex.Lock()
defer m.topicsMutex.Unlock()
result := m.topics[topicName]
if result == nil {
result = &memoryDatabaseTopic{}
if m.topics == nil {
m.topics = map[string]*memoryDatabaseTopic{}
}
m.topics[topicName] = result
}
return result
}
// StoreMessages implements Database
func (m *MemoryDatabase) StoreMessages(topic string, messages []Message) error {
if err := m.getTopic(topic).addMessages(messages); err != nil {
return err
}
return nil
}
// FetchMessages implements Database
func (m *MemoryDatabase) FetchMessages(topic string, startOffset, endOffset int64) ([]Message, error) {
messages := m.getTopic(topic).getMessages()
if endOffset > int64(len(messages)) {
return nil, fmt.Errorf("end offset %d out of range %d", endOffset, len(messages))
}
if startOffset >= endOffset {
return nil, fmt.Errorf("start offset %d greater than or equal to end offset %d", startOffset, endOffset)
}
if startOffset < -1 {
return nil, fmt.Errorf("start offset %d less than -1", startOffset)
}
return messages[startOffset+1 : endOffset], nil
}
// MaxOffsets implements Database
func (m *MemoryDatabase) MaxOffsets() (map[string]int64, error) {
m.topicsMutex.Lock()
defer m.topicsMutex.Unlock()
result := map[string]int64{}
for name, t := range m.topics {
result[name] = int64(len(t.getMessages())) - 1
}
return result, nil
}

View File

@ -0,0 +1,360 @@
package naffka
import (
"fmt"
"log"
"sync"
"time"
sarama "gopkg.in/Shopify/sarama.v1"
)
// Naffka is an implementation of the sarama kafka API designed to run within a
// single go process. It implements both the sarama.SyncProducer and the
// sarama.Consumer interfaces. This means it can act as a drop in replacement
// for kafka for testing or single instance deployment.
type Naffka struct {
db Database
topicsMutex sync.Mutex
topics map[string]*topic
}
// New creates a new Naffka instance.
func New(db Database) (*Naffka, error) {
n := &Naffka{db: db, topics: map[string]*topic{}}
maxOffsets, err := db.MaxOffsets()
if err != nil {
return nil, err
}
for topicName, offset := range maxOffsets {
n.topics[topicName] = &topic{
topicName: topicName,
nextOffset: offset + 1,
}
}
return n, nil
}
// A Message is used internally within naffka to store messages.
// It is converted to a sarama.ConsumerMessage when exposed to the
// public APIs to maintain API compatibility with sarama.
type Message struct {
Offset int64
Key []byte
Value []byte
Timestamp time.Time
}
func (m *Message) consumerMessage(topic string) *sarama.ConsumerMessage {
return &sarama.ConsumerMessage{
Topic: topic,
Offset: m.Offset,
Key: m.Key,
Value: m.Value,
Timestamp: m.Timestamp,
}
}
// A Database is used to store naffka messages.
// Messages are stored so that new consumers can access the full message history.
type Database interface {
// StoreMessages stores a list of messages.
// Every message offset must be unique within each topic.
// Messages must be stored monotonically and contiguously for each topic.
// So for a given topic the message with offset n+1 is stored after the
// the message with offset n.
StoreMessages(topic string, messages []Message) error
// FetchMessages fetches all messages with an offset greater than but not
// including startOffset and less than but not including endOffset.
// The range of offsets requested must not overlap with those stored by a
// concurrent StoreMessages. The message offsets within the requested range
// are contigous. That is FetchMessage("foo", n, m) will only be called
// once the messages between n and m have been stored by StoreMessages.
// Every call must return at least one message. That is there must be at
// least one message between the start and offset.
FetchMessages(topic string, startOffset, endOffset int64) ([]Message, error)
// MaxOffsets returns the maximum offset for each topic.
MaxOffsets() (map[string]int64, error)
}
// SendMessage implements sarama.SyncProducer
func (n *Naffka) SendMessage(msg *sarama.ProducerMessage) (partition int32, offset int64, err error) {
err = n.SendMessages([]*sarama.ProducerMessage{msg})
return msg.Partition, msg.Offset, err
}
// SendMessages implements sarama.SyncProducer
func (n *Naffka) SendMessages(msgs []*sarama.ProducerMessage) error {
byTopic := map[string][]*sarama.ProducerMessage{}
for _, msg := range msgs {
byTopic[msg.Topic] = append(byTopic[msg.Topic], msg)
}
var topicNames []string
for topicName := range byTopic {
topicNames = append(topicNames, topicName)
}
now := time.Now()
topics := n.getTopics(topicNames)
for topicName := range byTopic {
if err := topics[topicName].send(now, byTopic[topicName]); err != nil {
return err
}
}
return nil
}
func (n *Naffka) getTopics(topicNames []string) map[string]*topic {
n.topicsMutex.Lock()
defer n.topicsMutex.Unlock()
result := map[string]*topic{}
for _, topicName := range topicNames {
t := n.topics[topicName]
if t == nil {
// If the topic doesn't already exist then create it.
t = &topic{db: n.db, topicName: topicName}
n.topics[topicName] = t
}
result[topicName] = t
}
return result
}
// Topics implements sarama.Consumer
func (n *Naffka) Topics() ([]string, error) {
n.topicsMutex.Lock()
defer n.topicsMutex.Unlock()
var result []string
for topic := range n.topics {
result = append(result, topic)
}
return result, nil
}
// Partitions implements sarama.Consumer
func (n *Naffka) Partitions(topic string) ([]int32, error) {
// Naffka stores a single partition per topic, so this always returns a single partition ID.
return []int32{0}, nil
}
// ConsumePartition implements sarama.Consumer
func (n *Naffka) ConsumePartition(topic string, partition int32, offset int64) (sarama.PartitionConsumer, error) {
if partition != 0 {
return nil, fmt.Errorf("Unknown partition ID %d", partition)
}
topics := n.getTopics([]string{topic})
return topics[topic].consume(offset), nil
}
// HighWaterMarks implements sarama.Consumer
func (n *Naffka) HighWaterMarks() map[string]map[int32]int64 {
n.topicsMutex.Lock()
defer n.topicsMutex.Unlock()
result := map[string]map[int32]int64{}
for topicName, topic := range n.topics {
result[topicName] = map[int32]int64{
0: topic.highwaterMark(),
}
}
return result
}
// Close implements sarama.SyncProducer and sarama.Consumer
func (n *Naffka) Close() error {
return nil
}
const channelSize = 1024
type partitionConsumer struct {
topic *topic
messages chan *sarama.ConsumerMessage
// Whether the consumer is ready for new messages or whether it
// is catching up on historic messages.
// Reads and writes to this field are proctected by the topic mutex.
ready bool
}
// AsyncClose implements sarama.PartitionConsumer
func (c *partitionConsumer) AsyncClose() {
}
// Close implements sarama.PartitionConsumer
func (c *partitionConsumer) Close() error {
// TODO: Add support for performing a clean shutdown of the consumer.
return nil
}
// Messages implements sarama.PartitionConsumer
func (c *partitionConsumer) Messages() <-chan *sarama.ConsumerMessage {
return c.messages
}
// Errors implements sarama.PartitionConsumer
func (c *partitionConsumer) Errors() <-chan *sarama.ConsumerError {
// TODO: Add option to pass consumer errors to an errors channel.
return nil
}
// HighWaterMarkOffset implements sarama.PartitionConsumer
func (c *partitionConsumer) HighWaterMarkOffset() int64 {
return c.topic.highwaterMark()
}
// block writes the message to the consumer blocking until the consumer is ready
// to add the message to the channel. Once the message is successfully added to
// the channel it will catch up by pulling historic messsages from the database.
func (c *partitionConsumer) block(cmsg *sarama.ConsumerMessage) {
c.messages <- cmsg
c.catchup(cmsg.Offset)
}
// catchup reads historic messages from the database until the consumer has caught
// up on all the historic messages.
func (c *partitionConsumer) catchup(fromOffset int64) {
for {
// First check if we have caught up.
caughtUp, nextOffset := c.topic.hasCaughtUp(c, fromOffset)
if caughtUp {
return
}
// Limit the number of messages we request from the database to be the
// capacity of the channel.
if nextOffset > fromOffset+int64(cap(c.messages)) {
nextOffset = fromOffset + int64(cap(c.messages))
}
// Fetch the messages from the database.
msgs, err := c.topic.db.FetchMessages(c.topic.topicName, fromOffset, nextOffset)
if err != nil {
// TODO: Add option to write consumer errors to an errors channel
// as an alternative to logging the errors.
log.Print("Error reading messages: ", err)
// Wait before retrying.
// TODO: Maybe use an exponentional backoff scheme here.
// TODO: This timeout should take account of all the other goroutines
// that might be doing the same thing. (If there are a 10000 consumers
// then we don't want to end up retrying every millisecond)
time.Sleep(10 * time.Second)
continue
}
if len(msgs) == 0 {
// This should only happen if the database is corrupted and has lost the
// messages between the requested offsets.
log.Fatalf("Corrupt database returned no messages between %d and %d", fromOffset, nextOffset)
}
// Pass the messages into the consumer channel.
// Blocking each write until the channel has enough space for the message.
for i := range msgs {
c.messages <- msgs[i].consumerMessage(c.topic.topicName)
}
// Update our the offset for the next loop iteration.
fromOffset = msgs[len(msgs)-1].Offset
}
}
type topic struct {
db Database
topicName string
mutex sync.Mutex
consumers []*partitionConsumer
nextOffset int64
}
func (t *topic) send(now time.Time, pmsgs []*sarama.ProducerMessage) error {
var err error
// Encode the message keys and values.
msgs := make([]Message, len(pmsgs))
for i := range msgs {
if pmsgs[i].Key != nil {
msgs[i].Key, err = pmsgs[i].Key.Encode()
if err != nil {
return err
}
}
if pmsgs[i].Value != nil {
msgs[i].Value, err = pmsgs[i].Value.Encode()
if err != nil {
return err
}
}
pmsgs[i].Timestamp = now
msgs[i].Timestamp = now
}
// Take the lock before assigning the offsets.
t.mutex.Lock()
defer t.mutex.Unlock()
offset := t.nextOffset
for i := range msgs {
pmsgs[i].Offset = offset
msgs[i].Offset = offset
offset++
}
// Store the messages while we hold the lock.
err = t.db.StoreMessages(t.topicName, msgs)
if err != nil {
return err
}
t.nextOffset = offset
// Now notify the consumers about the messages.
for i := range msgs {
cmsg := msgs[i].consumerMessage(t.topicName)
for _, c := range t.consumers {
if c.ready {
select {
case c.messages <- cmsg:
default:
// The consumer wasn't ready to receive a message because
// the channel buffer was full.
// Fork a goroutine to send the message so that we don't
// block sending messages to the other consumers.
c.ready = false
go c.block(cmsg)
}
}
}
}
return nil
}
func (t *topic) consume(offset int64) *partitionConsumer {
t.mutex.Lock()
defer t.mutex.Unlock()
c := &partitionConsumer{
topic: t,
}
// Handle special offsets.
if offset == sarama.OffsetNewest {
offset = t.nextOffset
}
if offset == sarama.OffsetOldest {
offset = -1
}
c.messages = make(chan *sarama.ConsumerMessage, channelSize)
t.consumers = append(t.consumers, c)
// Start catching up on historic messages in the background.
go c.catchup(offset)
return c
}
func (t *topic) hasCaughtUp(c *partitionConsumer, offset int64) (bool, int64) {
t.mutex.Lock()
defer t.mutex.Unlock()
// Check if we have caught up while holding a lock on the topic so there
// isn't a way for our check to race with a new message being sent on the topic.
if offset+1 == t.nextOffset {
// We've caught up, the consumer can now receive messages as they are
// sent rather than fetching them from the database.
c.ready = true
return true, t.nextOffset
}
return false, t.nextOffset
}
func (t *topic) highwaterMark() int64 {
t.mutex.Lock()
defer t.mutex.Unlock()
return t.nextOffset
}

View File

@ -0,0 +1,86 @@
package naffka
import (
"testing"
"time"
sarama "gopkg.in/Shopify/sarama.v1"
)
func TestSendAndReceive(t *testing.T) {
naffka, err := New(&MemoryDatabase{})
if err != nil {
t.Fatal(err)
}
producer := sarama.SyncProducer(naffka)
consumer := sarama.Consumer(naffka)
const topic = "testTopic"
const value = "Hello, World"
c, err := consumer.ConsumePartition(topic, 0, sarama.OffsetOldest)
if err != nil {
t.Fatal(err)
}
message := sarama.ProducerMessage{
Value: sarama.StringEncoder(value),
Topic: topic,
}
if _, _, err = producer.SendMessage(&message); err != nil {
t.Fatal(err)
}
var result *sarama.ConsumerMessage
select {
case result = <-c.Messages():
case _ = <-time.NewTimer(10 * time.Second).C:
t.Fatal("expected to receive a message")
}
if string(result.Value) != value {
t.Fatalf("wrong value: wanted %q got %q", value, string(result.Value))
}
select {
case result = <-c.Messages():
t.Fatal("expected to only receive one message")
default:
}
}
func TestDelayedReceive(t *testing.T) {
naffka, err := New(&MemoryDatabase{})
if err != nil {
t.Fatal(err)
}
producer := sarama.SyncProducer(naffka)
consumer := sarama.Consumer(naffka)
const topic = "testTopic"
const value = "Hello, World"
message := sarama.ProducerMessage{
Value: sarama.StringEncoder(value),
Topic: topic,
}
if _, _, err = producer.SendMessage(&message); err != nil {
t.Fatal(err)
}
c, err := consumer.ConsumePartition(topic, 0, sarama.OffsetOldest)
if err != nil {
t.Fatal(err)
}
var result *sarama.ConsumerMessage
select {
case result = <-c.Messages():
case _ = <-time.NewTimer(10 * time.Second).C:
t.Fatal("expected to receive a message")
}
if string(result.Value) != value {
t.Fatalf("wrong value: wanted %q got %q", value, string(result.Value))
}
}