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ReplicatedJournal.scala
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ReplicatedJournal.scala
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package com.evolutiongaming.kafka.journal.eventual
import cats.effect.Resource
import cats.effect.syntax.all._
import cats.syntax.all._
import cats.{Applicative, Monad, ~>}
import com.evolutiongaming.catshelper.{BracketThrowable, Log, MeasureDuration, MonadThrowable}
import com.evolutiongaming.kafka.journal._
import com.evolutiongaming.skafka.Topic
import com.evolutiongaming.smetrics.MetricsHelper._
import com.evolutiongaming.smetrics._
import scala.collection.immutable.SortedSet
import scala.concurrent.duration.FiniteDuration
/** Write-only implementation of a journal stored to eventual storage, i.e.
* Cassandra.
*
* This class is used to replicate events read from Kafka, hence the name.
*
* It follows a hierarchical structure, i.e., roughly speaking, it is
* a factory of topic-specific [[ReplicatedTopicJournal]] instances.
*
* @see [[EventualJournal]] for a read-only counterpart of this class.
*/
trait ReplicatedJournal[F[_]] {
/** Select list of kafka topics previously saved into eventual storage */
def topics: F[SortedSet[Topic]]
/** Create a topic-specific write-only journal */
def journal(topic: Topic): Resource[F, ReplicatedTopicJournal[F]]
}
object ReplicatedJournal {
private sealed abstract class Empty
def empty[F[_] : Applicative]: ReplicatedJournal[F] = new Empty with ReplicatedJournal[F] {
def topics = SortedSet.empty[Topic].pure[F]
def journal(topic: Topic) = {
ReplicatedTopicJournal
.empty[F]
.pure[F]
.toResource
}
}
private sealed abstract class MapK
private sealed abstract class WithLog
private sealed abstract class WithMetrics
private sealed abstract class WithEnhanceError
implicit class ReplicatedJournalOps[F[_]](val self: ReplicatedJournal[F]) extends AnyVal {
def mapK[G[_]](
f: F ~> G)(implicit
B: BracketThrowable[F],
GT: BracketThrowable[G]
): ReplicatedJournal[G] = new MapK with ReplicatedJournal[G] {
def topics = f(self.topics)
def journal(topic: Topic) = {
self
.journal(topic)
.map { _.mapK(f) }
.mapK(f)
}
}
def withLog(
log: Log[F])(implicit
F: Monad[F],
measureDuration: MeasureDuration[F]
): ReplicatedJournal[F] = new WithLog with ReplicatedJournal[F] {
def topics = {
for {
d <- MeasureDuration[F].start
r <- self.topics
d <- d
_ <- log.debug(s"topics in ${ d.toMillis }ms, r: ${ r.mkString(",") }")
} yield r
}
def journal(topic: Topic) = {
self
.journal(topic)
.map { _.withLog(topic, log) }
}
}
def withMetrics(
metrics: Metrics[F])(implicit
F: Monad[F],
measureDuration: MeasureDuration[F]
): ReplicatedJournal[F] = new WithMetrics with ReplicatedJournal[F] {
def topics = {
for {
d <- MeasureDuration[F].start
r <- self.topics
d <- d
_ <- metrics.topics(d)
} yield r
}
def journal(topic: Topic) = {
self
.journal(topic)
.map { _.withMetrics(topic, metrics) }
}
}
def enhanceError(implicit F: MonadThrowable[F]): ReplicatedJournal[F] = {
def journalError[A](msg: String, cause: Throwable) = {
JournalError(s"ReplicatedJournal.$msg failed with $cause", cause)
}
new WithEnhanceError with ReplicatedJournal[F] {
def topics = {
self
.topics
.adaptError { case a => journalError(s"topics", a) }
}
def journal(topic: Topic) = {
self
.journal(topic)
.map { _.enhanceError(topic) }
.adaptError { case a => journalError(s"journal, topic: $topic", a) }
}
}
}
def toFlat(implicit F: BracketThrowable[F]): ReplicatedJournalFlat[F] = ReplicatedJournalFlat(self)
}
trait Metrics[F[_]] {
def topics(latency: FiniteDuration): F[Unit]
def offsetsGet(latency: FiniteDuration): F[Unit]
def offsetsUpdate(topic: Topic, latency: FiniteDuration): F[Unit]
def offsetsCreate(topic: Topic, latency: FiniteDuration): F[Unit]
def append(topic: Topic, latency: FiniteDuration, events: Int): F[Unit]
def delete(topic: Topic, latency: FiniteDuration): F[Unit]
def purge(topic: Topic, latency: FiniteDuration): F[Unit]
}
object Metrics {
def empty[F[_] : Applicative]: Metrics[F] = const(().pure[F])
def const[F[_]](unit: F[Unit]): Metrics[F] = {
class Const
new Const with Metrics[F] {
def topics(latency: FiniteDuration) = unit
def offsetsGet(latency: FiniteDuration) = unit
def offsetsUpdate(topic: Topic, latency: FiniteDuration) = unit
def offsetsCreate(topic: Topic, latency: FiniteDuration) = unit
def append(topic: Topic, latency: FiniteDuration, events: Int) = unit
def delete(topic: Topic, latency: FiniteDuration) = unit
def purge(topic: Topic, latency: FiniteDuration) = unit
}
}
def of[F[_] : Monad](
registry: CollectorRegistry[F],
prefix: String = "replicated_journal"
): Resource[F, Metrics[F]] = {
val latencySummary = registry.summary(
name = s"${ prefix }_latency",
help = "Journal call latency in seconds",
quantiles = Quantiles.Default,
labels = LabelNames("type"))
val topicLatencySummary = registry.summary(
name = s"${ prefix }_topic_latency",
help = "Journal topic call latency in seconds",
quantiles = Quantiles.Default,
labels = LabelNames("topic", "type"))
val eventsSummary = registry.summary(
name = s"${ prefix }_events",
help = "Number of events saved",
quantiles = Quantiles.Empty,
labels = LabelNames("topic"))
for {
latencySummary <- latencySummary
topicLatencySummary <- topicLatencySummary
eventsSummary <- eventsSummary
} yield {
def observeTopicLatency(name: String, topic: Topic, latency: FiniteDuration) = {
topicLatencySummary
.labels(topic, name)
.observe(latency.toNanos.nanosToSeconds)
}
def observeLatency(name: String, latency: FiniteDuration) = {
latencySummary
.labels(name)
.observe(latency.toNanos.nanosToSeconds)
}
class Main
new Main with Metrics[F] {
def topics(latency: FiniteDuration) = {
observeLatency(name = "topics", latency = latency)
}
def offsetsGet(latency: FiniteDuration): F[Unit] = {
observeLatency(name = "offsets.get", latency = latency)
}
def offsetsUpdate(topic: Topic, latency: FiniteDuration) = {
observeLatency(name = "offsets.update", latency = latency)
}
def offsetsCreate(topic: Topic, latency: FiniteDuration) = {
observeLatency(name = "offsets.create", latency = latency)
}
def append(topic: Topic, latency: FiniteDuration, events: Int) = {
for {
_ <- eventsSummary.labels(topic).observe(events.toDouble)
_ <- observeTopicLatency(name = "append", topic = topic, latency = latency)
} yield {}
}
def delete(topic: Topic, latency: FiniteDuration) = {
observeTopicLatency(name = "delete", topic = topic, latency = latency)
}
def purge(topic: Topic, latency: FiniteDuration) = {
observeTopicLatency(name = "purge", topic = topic, latency = latency)
}
}
}
}
}
}