Integrate OpenTelemetry into OpenDC

This pull request resolves issue #91 by adopting the industry-standard OpenTelemetry standard
for collecting traces and metrics in OpenDC simulations:

* Metrics will now be exposed through OpenTelemetry's metrics API
* `opendc-telemetry` provides complementary code to support
    gathering telemetry in OpenDC.

**Breaking API Changes**
* `opendc-tracer` has been removed.
* `EventFlow` and all usages of it have been removed.
* `opendc-experiments-sc18` has been removed for now, but a 
    suitable replacement will follow soon.

1 files changed, 0 insertions, 112 deletions

diff --git a/simulator/opendc-utils/src/main/kotlin/org/opendc/utils/flow/EventFlow.kt b/simulator/opendc-utils/src/main/kotlin/org/opendc/utils/flow/EventFlow.kt
deleted file mode 100644
index 10f29f4e..00000000
--- a/simulator/opendc-utils/src/main/kotlin/org/opendc/utils/flow/EventFlow.kt
+++ /dev/null
@@ -1,112 +0,0 @@
-/*
- * Copyright (c) 2020 AtLarge Research
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in all
- * copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- */
-
-package org.opendc.utils.flow
-
-import kotlinx.coroutines.ExperimentalCoroutinesApi
-import kotlinx.coroutines.FlowPreview
-import kotlinx.coroutines.InternalCoroutinesApi
-import kotlinx.coroutines.channels.Channel
-import kotlinx.coroutines.channels.SendChannel
-import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.FlowCollector
-import kotlinx.coroutines.flow.consumeAsFlow
-
-/**
- * A [Flow] that can be used to emit events.
- */
-public interface EventFlow<T> : Flow<T> {
-    /**
-     * Emit the specified [event].
-     */
-    public fun emit(event: T)
-
-    /**
-     * Close the flow.
-     */
-    public fun close()
-}
-
-/**
- * Creates a new [EventFlow].
- */
-@Suppress("FunctionName")
-public fun <T> EventFlow(): EventFlow<T> = EventFlowImpl()
-
-/**
- * Internal implementation of the [EventFlow] class.
- */
-@OptIn(ExperimentalCoroutinesApi::class, FlowPreview::class)
-private class EventFlowImpl<T> : EventFlow<T> {
-    private var closed: Boolean = false
-    private val subscribers = mutableListOf<SendChannel<T>>()
-
-    override fun emit(event: T) {
-        if (closed) {
-            return
-        }
-
-        val it = subscribers.iterator()
-        synchronized(this) {
-            while (it.hasNext()) {
-                val chan = it.next()
-                if (chan.isClosedForSend) {
-                    it.remove()
-                } else {
-                    chan.offer(event)
-                }
-            }
-        }
-    }
-
-    override fun close() {
-        synchronized(this) {
-            closed = true
-
-            for (chan in subscribers) {
-                chan.close()
-            }
-
-            subscribers.clear()
-        }
-    }
-
-    @InternalCoroutinesApi
-    override suspend fun collect(collector: FlowCollector<T>) {
-        val channel: Channel<T>
-        synchronized(this) {
-            if (closed) {
-                return
-            }
-
-            channel = Channel(Channel.UNLIMITED)
-            subscribers.add(channel)
-        }
-        try {
-            channel.consumeAsFlow().collect(collector)
-        } finally {
-            channel.close()
-        }
-    }
-
-    override fun toString(): String = "EventFlow"
-}