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consumer.go
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consumer.go
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package main
import (
"fmt"
"log"
"math/rand"
"time"
"github.com/garyburd/redigo/redis"
)
const (
//Max number or ms for processing message
MAX_RAND_PROCESS_TIME = 1000
MODE_UNKNOWN = iota
MODE_GENERATOR
MODE_CONSUMER
)
type (
Message string
//Message with error
BadMessage struct {
msg Message
err string
}
ProcessedMessage struct {
duration time.Duration
msg Message
worker int
}
Consumer struct {
pool *redis.Pool
queue string
errQueue string
in chan Message
out chan ProcessedMessage
bad chan BadMessage
maxGoroutines int
stop chan struct{}
isActive bool
}
)
//String representation of BadMessage
func (b *BadMessage) String() string {
return fmt.Sprintf("m:%q e:%q", b.msg, b.err)
}
//Create new Consumer struct
func NewConsumer(p *redis.Pool, q string, eq string, mg int) *Consumer {
return &Consumer{
pool: p,
queue: q,
errQueue: eq,
in: make(chan Message),
out: make(chan ProcessedMessage),
bad: make(chan BadMessage),
maxGoroutines: mg,
stop: make(chan struct{}),
}
}
//Redis message listner
func (c *Consumer) Process(in chan Message, out chan ProcessedMessage) {
c.in = in
c.out = out
for i := 1; i <= c.maxGoroutines; i++ {
go c.RunWorker(i)
}
log.Printf("%d workers started.\n", c.maxGoroutines)
c.isActive = true
pc := c.pool.Get()
defer pc.Close()
defer func(c *Consumer) {
log.Printf("%d workers stopped.\n", c.maxGoroutines)
}(c)
defer c.Close()
for {
select {
case <-c.stop:
//dirty hack, should wait before closing c.out
//while switching from consumer to generator mode
time.Sleep(time.Second)
c.stop <- struct{}{}
return
default:
msg, err := pc.Do("BRPOP", c.queue, 0)
if err != nil {
log.Println("messages: unable to get from redis:", err)
return
}
v, err := redis.Values(msg, err)
LogIf(err)
s, err := redis.String(v[1], err)
LogIf(err)
c.in <- Message(s)
}
}
}
//Runs message consuming
func (c *Consumer) Start() {
in := make(chan Message)
out := make(chan ProcessedMessage)
bad := make(chan BadMessage)
if !c.Ping() {
close(out)
c.out = out
return
}
go c.ProcessErrors(bad)
go c.Process(in, out)
go func(cc *Consumer) {
for {
select {
case <-cc.out:
}
}
}(c)
}
//Stops all workers
func (c *Consumer) Stop() {
if !c.IsActive() {
return
}
c.stop <- struct{}{}
<-c.stop
}
//Makes primary work for random milliseconds.
func (c *Consumer) RunWorker(wid int) {
r := rand.New(rand.NewSource(time.Now().UnixNano()))
processTime := time.Duration(r.Intn(MAX_RAND_PROCESS_TIME))
for m := range c.in {
if prob() {
c.bad <- BadMessage{msg: m, err: fmt.Sprintf("Error code %d", processTime)}
} else {
time.Sleep(time.Millisecond * processTime)
c.out <- ProcessedMessage{duration: processTime, msg: m, worker: wid}
}
}
}
//Closes working channels
func (c *Consumer) Close() {
if !c.IsActive() {
return
}
close(c.bad)
close(c.in)
close(c.out)
c.isActive = false
}
//Get bad messages from chan and call PushError
func (c *Consumer) ProcessErrors(bad chan BadMessage) {
pc := c.pool.Get()
defer pc.Close()
c.bad = bad
for b := range c.bad {
_, err := pc.Do("LPUSH", c.errQueue, b.String())
if err != nil {
log.Println("errors: unable to push to redis:", err)
}
}
}
//Returns consumer state
func (c *Consumer) IsActive() bool {
return c.isActive
}
//Pings Redis
func (c *Consumer) Ping() bool {
pc := c.pool.Get()
defer pc.Close()
p, err := pc.Do("PING")
if err != nil {
return false
}
return p == "PONG"
}