merge: Move OpenTelemetry integration outside core modules (#81)

This change removes the OpenTelemetry integration from the OpenDC modules. 
Previously, we chose to integrate OpenTelemetry to provide a unified way to 
report metrics to the users.

Although this worked as expected, the overhead of the OpenTelemetry when
collecting metrics during simulation was considerable and lacked more
optimization opportunities (other than providing a separate API
implementation). Furthermore, since we were tied to OpenTelemetry's SDK
implementation, we experienced issues with throttling and registering
multiple instruments.

We will instead use another approach, where we expose the core metrics
in OpenDC via specialized interfaces (see #80) such that
access is fast and can be done without having to interface with
OpenTelemetry. In addition, we will provide an adapter to that is able
to forward these metrics to OpenTelemetry implementations, so we can
still integrate with the wider ecosystem.

## Implementation Notes :hammer_and_pick:

* Remove OpenTelemetry from "compute" modules 
* Remove OpenTelemetry from "workflow" modules 
* Remove OpenTelemetry from "FaaS" modules
* Remove OpenTelemetry from TF20 experiment 
* Remove dependency on OpenTelemetry SDK 

## External Dependencies :four_leaf_clover:

* N/A

## Breaking API Changes :warning:

* Metrics are not anymore directly exposed via OpenTelemetry. Instead, an adapter needs to be used to access the data via OpenTelemetry.

3 files changed, 12 insertions, 33 deletions

diff --git a/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/TensorFlowExperiment.kt b/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/TensorFlowExperiment.kt
index 2153a862..19236029 100644
--- a/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/TensorFlowExperiment.kt
+++ b/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/TensorFlowExperiment.kt
@@ -22,8 +22,6 @@
 
 package org.opendc.experiments.tf20
 
-import io.opentelemetry.api.metrics.MeterProvider
-import io.opentelemetry.sdk.metrics.SdkMeterProvider
 import org.opendc.experiments.tf20.core.SimTFDevice
 import org.opendc.experiments.tf20.distribute.*
 import org.opendc.experiments.tf20.keras.AlexNet
@@ -32,7 +30,6 @@ import org.opendc.harness.dsl.Experiment
 import org.opendc.harness.dsl.anyOf
 import org.opendc.simulator.compute.power.LinearPowerModel
 import org.opendc.simulator.core.runBlockingSimulation
-import org.opendc.telemetry.sdk.toOtelClock
 
 /**
  * Experiments with the TensorFlow simulation model.
@@ -49,17 +46,11 @@ public class TensorFlowExperiment : Experiment(name = "tf20") {
     private val batchSize by anyOf(16, 32, 64, 128)
 
     override fun doRun(repeat: Int): Unit = runBlockingSimulation {
-        val meterProvider: MeterProvider = SdkMeterProvider
-            .builder()
-            .setClock(clock.toOtelClock())
-            .build()
-        val meter = meterProvider.get("opendc-tf20")
-
         val envInput = checkNotNull(TensorFlowExperiment::class.java.getResourceAsStream(environmentFile))
         val def = MLEnvironmentReader().readEnvironment(envInput).first()
         val device = SimTFDevice(
-            def.uid, def.meta["gpu"] as Boolean, coroutineContext, clock, meter, def.model.cpus[0],
-            def.model.memory[0], LinearPowerModel(250.0, 60.0)
+            def.uid, def.meta["gpu"] as Boolean, coroutineContext, clock, def.model.cpus[0], def.model.memory[0],
+            LinearPowerModel(250.0, 60.0)
         )
         val strategy = OneDeviceStrategy(device)
 
diff --git a/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/core/SimTFDevice.kt b/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/core/SimTFDevice.kt
index 99948c8e..d2105196 100644
--- a/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/core/SimTFDevice.kt
+++ b/opendc-experiments/opendc-experiments-tf20/src/main/kotlin/org/opendc/experiments/tf20/core/SimTFDevice.kt
@@ -22,7 +22,6 @@
 
 package org.opendc.experiments.tf20.core
 
-import io.opentelemetry.api.metrics.Meter
 import kotlinx.coroutines.*
 import org.opendc.simulator.compute.SimBareMetalMachine
 import org.opendc.simulator.compute.SimMachine
@@ -50,7 +49,6 @@ public class SimTFDevice(
     override val isGpu: Boolean,
     context: CoroutineContext,
     clock: Clock,
-    meter: Meter,
     pu: ProcessingUnit,
     private val memory: MemoryUnit,
     powerModel: PowerModel
@@ -69,21 +67,9 @@ public class SimTFDevice(
     )
 
     /**
-     * The usage of the device.
+     * Metrics collected by the device.
      */
-    private val _usage = meter.histogramBuilder("device.usage")
-        .setDescription("The amount of device resources used")
-        .setUnit("MHz")
-        .build()
     private var _resourceUsage = 0.0
-
-    /**
-     * The power draw of the device.
-     */
-    private val _power = meter.histogramBuilder("device.power")
-        .setDescription("The power draw of the device")
-        .setUnit("W")
-        .build()
     private var _powerUsage = 0.0
     private var _energyUsage = 0.0
 
@@ -171,9 +157,7 @@ public class SimTFDevice(
         }
 
         override fun onConverge(conn: FlowConnection, now: Long) {
-            _usage.record(conn.rate)
             _resourceUsage = conn.rate
-            _power.record(machine.psu.powerDraw)
             _powerUsage = machine.powerUsage
             _energyUsage = machine.energyUsage
         }
diff --git a/opendc-experiments/opendc-experiments-tf20/src/test/kotlin/org/opendc/experiments/tf20/core/SimTFDeviceTest.kt b/opendc-experiments/opendc-experiments-tf20/src/test/kotlin/org/opendc/experiments/tf20/core/SimTFDeviceTest.kt
index 0d5fbebb..fd18a3a7 100644
--- a/opendc-experiments/opendc-experiments-tf20/src/test/kotlin/org/opendc/experiments/tf20/core/SimTFDeviceTest.kt
+++ b/opendc-experiments/opendc-experiments-tf20/src/test/kotlin/org/opendc/experiments/tf20/core/SimTFDeviceTest.kt
@@ -22,7 +22,6 @@
 
 package org.opendc.experiments.tf20.core
 
-import io.opentelemetry.api.metrics.MeterProvider
 import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.launch
 import org.junit.jupiter.api.Assertions.assertAll
@@ -41,14 +40,19 @@ import java.util.*
 internal class SimTFDeviceTest {
     @Test
     fun testSmoke() = runBlockingSimulation {
-        val meterProvider: MeterProvider = MeterProvider.noop()
-        val meter = meterProvider.get("opendc-tf20")
-
         val puNode = ProcessingNode("NVIDIA", "Tesla V100", "unknown", 1)
         val pu = ProcessingUnit(puNode, 0, 960 * 1230.0)
         val memory = MemoryUnit("NVIDIA", "Tesla V100", 877.0, 32_000)
 
-        val device = SimTFDevice(UUID.randomUUID(), isGpu = true, coroutineContext, clock, meter, pu, memory, LinearPowerModel(250.0, 100.0))
+        val device = SimTFDevice(
+            UUID.randomUUID(),
+            isGpu = true,
+            coroutineContext,
+            clock,
+            pu,
+            memory,
+            LinearPowerModel(250.0, 100.0)
+        )
 
         // Load 1 GiB into GPU memory
         device.load(1000)