eval: preserve presentation meta for trace graph (Netflix#1638)

Map back to normal graph URI and generate the config to
support consistent presentation metadata behavior.

atlas-eval/src/main/scala/com/netflix/atlas/eval/stream/ExprInterpreter.scala

@@ -56,6 +56,7 @@ class ExprInterpreter(config: Config) {
 
   private val hostRewriter = new HostRewriter(config.getConfig("atlas.eval.host-rewrite"))
 
+  /** Evaluate a normal Atlas Graph URI and produce and graph config. */
   def eval(uri: Uri): GraphConfig = {
     val graphCfg = grapher.toGraphConfig(uri)
 
@@ -71,6 +72,26 @@ class ExprInterpreter(config: Config) {
     graphCfg.copy(query = rewritten.mkString(","), parsedQuery = Success(rewritten))
   }
 
+  /**
+    * Evaluate a time series URI. This could be an normal Atlas Graph URI or a trace
+    * time series URI. If a non-time series URI is passed in the result will be None.
+    */
+  def evalTimeSeries(uri: Uri): Option[GraphConfig] = {
+    determineExprType(uri) match {
+      case ExprType.TIME_SERIES       => Some(eval(uri))
+      case ExprType.TRACE_TIME_SERIES => Some(eval(toGraphUri(uri)))
+      case _                          => None
+    }
+  }
+
+  /** Convert a trace time series URI to a normal graph URI for generating the config. */
+  private def toGraphUri(uri: Uri): Uri = {
+    val ts = evalTraceTimeSeries(uri)
+    val newExpr = ts.map(_.expr).mkString(",")
+    val newQuery = uri.query().filterNot(_._1 == "q").prepended("q" -> newExpr)
+    uri.withQuery(Uri.Query(newQuery*))
+  }
+
   /**
     * Check that data expressions are supported. The streaming path doesn't support
     * time shifts, filters, and integral. The filters and integral are excluded because

atlas-eval/src/main/scala/com/netflix/atlas/eval/stream/FinalExprEval.scala

@@ -102,25 +102,23 @@ private[stream] class FinalExprEval(exprInterpreter: ExprInterpreter)
 
         // Compute the new set of expressions
         recipients = sources
-          .filter { s =>
-            exprInterpreter.determineExprType(Uri(s.uri)).isTimeSeriesType
-          }
           .flatMap { s =>
             try {
-              val graphCfg = exprInterpreter.eval(Uri(s.uri))
-              val exprs = graphCfg.exprs
-              // Reuse the previous evaluated expression if available. States for the stateful
-              // expressions are maintained in an IdentityHashMap so if the instances change
-              // the state will be reset.
-              exprs.map { e =>
-                val paletteName =
-                  if (graphCfg.flags.presentationMetadataEnabled) {
-                    val axis = e.axis.getOrElse(0)
-                    Some(graphCfg.flags.axisPalette(graphCfg.settings, axis))
-                  } else {
-                    None
-                  }
-                previous.getOrElse(e, e) -> ExprInfo(s.id, paletteName)
+              exprInterpreter.evalTimeSeries(Uri(s.uri)).toList.flatMap { graphCfg =>
+                val exprs = graphCfg.exprs
+                // Reuse the previous evaluated expression if available. States for the stateful
+                // expressions are maintained in an IdentityHashMap so if the instances change
+                // the state will be reset.
+                exprs.map { e =>
+                  val paletteName =
+                    if (graphCfg.flags.presentationMetadataEnabled) {
+                      val axis = e.axis.getOrElse(0)
+                      Some(graphCfg.flags.axisPalette(graphCfg.settings, axis))
+                    } else {
+                      None
+                    }
+                  previous.getOrElse(e, e) -> ExprInfo(s.id, paletteName)
+                }
               }
             } catch {
               case e: Exception =>

atlas-eval/src/test/scala/com/netflix/atlas/eval/stream/EvaluatorSuite.scala

@@ -789,6 +789,6 @@ class EvaluatorSuite extends FunSuite {
       "synthetic://test/traces/graph?q=name,cpu,:eq,nf.app,foo,:eq,:and&step=1ms&numStepIntervals=5"
     val future = Source.fromPublisher(evaluator.createPublisher(uri)).runWith(Sink.seq)
     val result = Await.result(future, scala.concurrent.duration.Duration.Inf)
-    assertEquals(result.size, 5)
+    assertEquals(result.size, 10)
   }
 }

atlas-eval/src/test/scala/com/netflix/atlas/eval/stream/FinalExprEvalSuite.scala

@@ -762,4 +762,60 @@ class FinalExprEvalSuite extends FunSuite {
     assertEquals(ts.styleMetadata.get.color, Color.RED)
     assertEquals(ts.styleMetadata.get.lineStyle, LineStyle.STACK)
   }
+
+  test("trace time series: aggregate with single datapoint per group") {
+    val expr = DataExpr.Sum(Query.Equal("name", "rps"))
+    val tags = Map("name" -> "rps")
+    val input = List(
+      sources(ds("a", s"http://atlas/traces/graph?q=app,foo,:eq,$expr,:span-time-series")),
+      group(0),
+      group(1, AggrDatapoint(0, step, expr, "i-1", tags, 42.0)),
+      group(2, AggrDatapoint(0, step, expr, "i-1", tags, 43.0)),
+      group(3, AggrDatapoint(0, step, expr, "i-1", tags, 44.0))
+    )
+
+    val output = run(input)
+
+    val timeseries = output.filter(isTimeSeries)
+    assertEquals(timeseries.size, 4)
+    val expectedTimeseries = List(Double.NaN, 42.0, 43.0, 44.0)
+    timeseries.zip(expectedTimeseries).foreach {
+      case (env, expectedValue) =>
+        assertEquals(env.id, "a")
+        val ts = env.message.asInstanceOf[TimeSeriesMessage]
+        checkValue(ts, expectedValue)
+    }
+
+    val dataRateMsgs = output.filter(isEvalDataRate).filter(_.id == "a")
+    assert(dataRateMsgs.size == 3)
+    val expectedSizes = Array(
+      Array(
+        EvalDataSize(1, Map(expr.toString -> 1)),
+        EvalDataSize(1, Map(expr.toString -> 1)),
+        EvalDataSize(1)
+      ),
+      Array(
+        EvalDataSize(1, Map(expr.toString -> 1)),
+        EvalDataSize(1, Map(expr.toString -> 1)),
+        EvalDataSize(1)
+      ),
+      Array(
+        EvalDataSize(1, Map(expr.toString -> 1)),
+        EvalDataSize(1, Map(expr.toString -> 1)),
+        EvalDataSize(1)
+      )
+    )
+    dataRateMsgs.zipWithIndex.foreach(envAndIndex => {
+      val rate = getAsEvalDataRate(envAndIndex._1)
+      val i = envAndIndex._2
+      checkRate(
+        rate,
+        60000 * (i + 1),
+        60000,
+        expectedSizes(i)(0),
+        expectedSizes(i)(1),
+        expectedSizes(i)(2)
+      )
+    })
+  }
 }