Merge pull request #65 from TimWSpence/non-safepointing-text-render

Non safepointing text render

Author: hamnis

prometheus-metrics/src/main/scala/org/http4s/metrics/prometheus/NonSafepointingStringWriter.scala

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2018 http4s.org
+ *
+ * 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 org.http4s.metrics.prometheus
+
+import java.io.Writer
+
+/** This should be equivalent to [[java.io.StringWriter]] but uses
+  * a [[java.lang.StringBuilder]] rather than a [[java.lang.StringBuffer]]
+  * and consequently is not synchronized
+  */
+private[prometheus] class NonSafepointingStringWriter extends Writer {
+
+  private[this] val buf: StringBuilder = new StringBuilder()
+
+  override def write(str: String): Unit = {
+    buf.append(str)
+    ()
+  }
+
+  override def write(buff: Array[Char]): Unit = {
+    buf.append(buff)
+    ()
+  }
+
+  override def write(i: Int): Unit = {
+    buf.append(i.toChar)
+    ()
+  }
+
+  override def write(str: String, start: Int, limit: Int): Unit = write(str.slice(start, limit))
+
+  override def write(buff: Array[Char], start: Int, limit: Int): Unit = write(
+    buff.slice(start, limit)
+  )
+
+  override def append(c: Char): Writer = {
+    buf.append(c)
+    this
+  }
+
+  override def append(cs: CharSequence): Writer = {
+    buf.append(cs)
+    this
+  }
+
+  override def append(cs: CharSequence, start: Int, limit: Int): Writer =
+    // Replicating behaviour of StringWriter ¯\_(ツ)_/¯
+    if (cs == null) append("null")
+    else
+      append(cs.subSequence(start, limit))
+
+  override def flush(): Unit = ()
+
+  override def close(): Unit = ()
+
+  override def toString(): String = buf.toString()
+
+}

prometheus-metrics/src/main/scala/org/http4s/metrics/prometheus/PrometheusExportService.scala

@@ -25,8 +25,6 @@ import org.http4s.Uri.Path
 import org.http4s._
 import org.http4s.syntax.all._
 
-import java.io.StringWriter
-
 /*
  * PrometheusExportService Contains an HttpService
  * ready to be scraped by Prometheus, paired
@@ -54,7 +52,7 @@ object PrometheusExportService {
   def generateResponse[F[_]: Sync](collectorRegistry: CollectorRegistry): F[Response[F]] =
     Sync[F]
       .delay {
-        val writer = new StringWriter
+        val writer = new NonSafepointingStringWriter()
         TextFormat.write004(writer, collectorRegistry.metricFamilySamples)
         writer.toString
       }

prometheus-metrics/src/test/scala/org/http4s/metrics/prometheus/PrometheusExportServiceSuite.scala

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2018 http4s.org
+ *
+ * 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 org.http4s.metrics.prometheus
+
+import cats.effect._
+import munit.CatsEffectSuite
+import org.http4s.client.dsl.io._
+import org.http4s.dsl.io._
+import org.http4s.implicits._
+
+class PrometheusExportServiceSuite extends CatsEffectSuite {
+
+  test("Returns Prometheus-format") {
+    PrometheusExportService.build[IO].use { svc =>
+      svc.routes.orNotFound
+        .run(GET(uri"/metrics"))
+        .flatMap(resp => resp.as[String])
+        .flatMap { resp =>
+          IO {
+            val lines = resp.linesIterator.toList
+            // Assortment of lines that should appear in the output as a sanity check
+            assert(clue(lines).contains("# TYPE jvm_memory_pool_allocated_bytes_total counter"))
+            assert(clue(lines).contains("# HELP jvm_threads_daemon Daemon thread count of a JVM"))
+            assert(clue(lines).contains("# HELP process_open_fds Number of open file descriptors."))
+            assert(clue(lines).contains("# TYPE process_open_fds gauge"))
+          }
+        }
+    }
+  }
+
+}