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eval: add a rewrite module to handle queries with namespaces (#1675)
If configured via `atlas.eval.stream.rewrite-url`, data source URIs are sent to a rewriting service. Responses with errors are then dropped and the caller notified. Valid rewrites continue processing. Some uses, e.g. the atlas-stream case, entail updating the data sources for a flow when new subscriptions are added or existing subscriptions dropped. This will return cached rewrites for individual queries in the event the rewrite backend is unavailable. Calls will continue for the rewrite service until a successful response is received, at which point it will update the cache and forward the rewrites downstream.
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atlas-eval/src/main/scala/com/netflix/atlas/eval/stream/DataSourceRewriter.scala
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| /* | ||
| * Copyright 2014-2024 Netflix, Inc. | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package com.netflix.atlas.eval.stream | ||
|
|
||
| import com.netflix.atlas.eval.stream.Evaluator.DataSource | ||
| import com.netflix.atlas.eval.stream.Evaluator.DataSources | ||
| import com.netflix.atlas.eval.stream.HostSource.unzipIfNeeded | ||
| import com.netflix.atlas.json.Json | ||
| import com.netflix.atlas.pekko.DiagnosticMessage | ||
| import com.netflix.atlas.pekko.OpportunisticEC.ec | ||
| import com.netflix.atlas.pekko.PekkoHttpClient | ||
| import com.netflix.atlas.pekko.StreamOps | ||
| import com.netflix.spectator.api.Registry | ||
| import com.typesafe.config.Config | ||
| import com.typesafe.scalalogging.StrictLogging | ||
| import org.apache.pekko.NotUsed | ||
| import org.apache.pekko.actor.ActorSystem | ||
| import org.apache.pekko.http.scaladsl.model.ContentTypes | ||
| import org.apache.pekko.http.scaladsl.model.HttpEntity | ||
| import org.apache.pekko.http.scaladsl.model.HttpMethods | ||
| import org.apache.pekko.http.scaladsl.model.HttpRequest | ||
| import org.apache.pekko.http.scaladsl.model.StatusCodes | ||
| import org.apache.pekko.stream.scaladsl.BroadcastHub | ||
| import org.apache.pekko.stream.scaladsl.Flow | ||
| import org.apache.pekko.stream.scaladsl.Keep | ||
| import org.apache.pekko.stream.scaladsl.RetryFlow | ||
| import org.apache.pekko.stream.scaladsl.Source | ||
|
|
||
| import java.io.ByteArrayOutputStream | ||
| import java.util.concurrent.ConcurrentHashMap | ||
| import scala.concurrent.duration.DurationInt | ||
| import scala.jdk.CollectionConverters.CollectionHasAsScala | ||
| import scala.util.Failure | ||
| import scala.util.Success | ||
| import scala.util.Using | ||
|
|
||
| class DataSourceRewriter( | ||
| config: Config, | ||
| registry: Registry, | ||
| implicit val system: ActorSystem | ||
| ) extends StrictLogging { | ||
|
|
||
| private val (enabled, rewriteUrl) = { | ||
| val enabled = config.hasPath("atlas.eval.stream.rewrite-url") | ||
| val url = if (enabled) config.getString("atlas.eval.stream.rewrite-url") else "" | ||
| if (enabled) { | ||
| logger.info(s"Rewriting enabled with url: ${url}") | ||
| } else { | ||
| logger.info("Rewriting is disabled") | ||
| } | ||
| (enabled, url) | ||
| } | ||
|
|
||
| private val client = PekkoHttpClient | ||
| .create("datasource-rewrite", system) | ||
| .superPool[List[DataSource]]() | ||
|
|
||
| private val rewriteCache = new ConcurrentHashMap[String, String]() | ||
|
|
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| private val rewriteSuccess = registry.counter("atlas.eval.stream.rewrite.success") | ||
| private val rewriteFailures = registry.createId("atlas.eval.stream.rewrite.failures") | ||
| private val rewriteCacheHits = registry.counter("atlas.eval.stream.rewrite.cache", "id", "hits") | ||
|
|
||
| private val rewriteCacheMisses = | ||
| registry.counter("atlas.eval.stream.rewrite.cache", "id", "misses") | ||
|
|
||
| def rewrite( | ||
| context: StreamContext, | ||
| keepRetrying: Boolean = true | ||
| ): Flow[DataSources, DataSources, NotUsed] = { | ||
| rewrite(client, context, keepRetrying) | ||
| } | ||
|
|
||
| def rewrite( | ||
| client: SuperPoolClient, | ||
| context: StreamContext, | ||
| keepRetrying: Boolean | ||
| ): Flow[DataSources, DataSources, NotUsed] = { | ||
| if (!enabled) { | ||
| return Flow[DataSources] | ||
| } | ||
|
|
||
| val (cachedQueue, cachedSource) = StreamOps | ||
| .blockingQueue[DataSources](registry, "cachedRewrites", 1) | ||
| .toMat(BroadcastHub.sink(1))(Keep.both) | ||
| .run() | ||
| var sentCacheData = false | ||
|
|
||
| val retryFlow = RetryFlow | ||
| .withBackoff( | ||
| minBackoff = 100.milliseconds, | ||
| maxBackoff = 5.second, | ||
| randomFactor = 0.35, | ||
| maxRetries = if (keepRetrying) -1 else 0, | ||
| flow = httpFlow(client, context) | ||
| ) { | ||
| case (original, resp) => | ||
| resp match { | ||
| case Success(_) => None | ||
| case Failure(ex) => | ||
| val (request, dsl) = original | ||
| logger.debug("Retrying the rewrite request due to error", ex) | ||
| if (!sentCacheData) { | ||
| if (!cachedQueue.offer(returnFromCache(dsl))) { | ||
| // note that this should never happen. | ||
| logger.error("Unable to send cached results to queue.") | ||
| } else { | ||
| sentCacheData = true | ||
| } | ||
| } | ||
| Some(request -> dsl) | ||
| } | ||
|
|
||
| } | ||
| .watchTermination() { (_, f) => | ||
| f.onComplete { _ => | ||
| cachedQueue.complete() | ||
| } | ||
| } | ||
|
|
||
| Flow[DataSources] | ||
| .map(_.sources().asScala.toList) | ||
| .map(dsl => constructRequest(dsl) -> dsl) | ||
| .via(retryFlow) | ||
| .filter(_.isSuccess) | ||
| .map { | ||
| // reset the cached flag | ||
| sentCacheData = false | ||
| _.get | ||
| } | ||
| .merge(cachedSource) | ||
| } | ||
|
|
||
| private[stream] def httpFlow(client: SuperPoolClient, context: StreamContext) = { | ||
| Flow[(HttpRequest, List[DataSource])] | ||
| .via(client) | ||
| .flatMapConcat { | ||
| case (Success(resp), dsl) => | ||
| unzipIfNeeded(resp) | ||
| .map(_.utf8String) | ||
| .map { body => | ||
| resp.status match { | ||
| case StatusCodes.OK => | ||
| val rewrites = List.newBuilder[DataSource] | ||
| Json | ||
| .decode[List[Rewrite]](body) | ||
| .zip(dsl) | ||
| .map { | ||
| case (r, ds) => | ||
| if (!r.status.equals("OK")) { | ||
| val msg = | ||
| DiagnosticMessage.error(s"failed rewrite of ${ds.uri()}: ${r.message}") | ||
| context.dsLogger(ds, msg) | ||
| } else { | ||
| rewriteCache.put(ds.uri(), r.rewrite) | ||
| rewrites += new DataSource(ds.id, ds.step(), r.rewrite) | ||
| } | ||
| } | ||
| .toArray | ||
| // NOTE: We're assuming that the number of items returned will be the same as the | ||
| // number of uris sent to the rewrite service. If they differ, data sources may be | ||
| // mapped to IDs and steps incorrectly. | ||
| rewriteSuccess.increment() | ||
| Success(DataSources.of(rewrites.result().toArray: _*)) | ||
| case _ => | ||
| logger.error( | ||
| "Error from rewrite service. status={}, resp={}", | ||
| resp.status, | ||
| body | ||
| ) | ||
| registry | ||
| .counter( | ||
| rewriteFailures.withTags("status", resp.status.toString(), "exception", "NA") | ||
| ) | ||
| .increment() | ||
| Failure( | ||
| new RuntimeException( | ||
| s"Error from rewrite service. status=${resp.status}, resp=$body" | ||
| ) | ||
| ) | ||
| } | ||
| } | ||
| case (Failure(ex), _) => | ||
| logger.error("Failure from rewrite service", ex) | ||
| registry | ||
| .counter( | ||
| rewriteFailures.withTags("status", "0", "exception", ex.getClass.getSimpleName) | ||
| ) | ||
| .increment() | ||
| Source.single(Failure(ex)) | ||
| } | ||
| } | ||
|
|
||
| private[stream] def returnFromCache(dsl: List[DataSource]): DataSources = { | ||
| val rewrites = dsl.flatMap { ds => | ||
| val rewrite = rewriteCache.get(ds.uri()) | ||
| if (rewrite == null) { | ||
| rewriteCacheMisses.increment() | ||
| None | ||
| } else { | ||
| rewriteCacheHits.increment() | ||
| Some(new DataSource(ds.id, ds.step(), rewrite)) | ||
| } | ||
| } | ||
| DataSources.of(rewrites: _*) | ||
| } | ||
|
|
||
| private[stream] def constructRequest(dss: List[DataSource]): HttpRequest = { | ||
| val baos = new ByteArrayOutputStream | ||
| Using(Json.newJsonGenerator(baos)) { json => | ||
| json.writeStartArray() | ||
| dss.foreach(s => json.writeString(s.uri())) | ||
| json.writeEndArray() | ||
| } | ||
| HttpRequest( | ||
| uri = rewriteUrl, | ||
| method = HttpMethods.POST, | ||
| entity = HttpEntity(ContentTypes.`application/json`, baos.toByteArray) | ||
| ) | ||
| } | ||
|
|
||
| } | ||
|
|
||
| case class Rewrite(status: String, rewrite: String, original: String, message: String) |
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