Add server metrics

server/build.gradle

@@ -61,6 +61,9 @@ dependencies {
     implementation "io.ktor:ktor-html-builder:$ktor_version"
     implementation "io.ktor:ktor-jackson:$ktor_version"
     implementation "org.jetbrains:kotlin-css-jvm:1.0.0-pre.31-kotlin-1.2.41"
+    implementation "io.prometheus:simpleclient:0.9.0"
+    implementation "io.prometheus:simpleclient_httpserver:0.9.0"
+    implementation "io.prometheus:simpleclient_hotspot:0.9.0"
     testImplementation "io.ktor:ktor-server-tests:$ktor_version"
     testImplementation "org.mockito:mockito-core:2.+"
 }

server/src/org/isoron/uhabits/sync/app/MetricsModule.kt

@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2016-2020 Alinson Santos Xavier <git@axavier.org>
+ *
+ * This file is part of Loop Habit Tracker.
+ *
+ * Loop Habit Tracker is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by the
+ * Free Software Foundation, either version 3 of the License, or (at your
+ * option) any later version.
+ *
+ * Loop Habit Tracker is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package org.isoron.uhabits.sync.app
+
+import io.ktor.application.*
+import io.ktor.http.*
+import io.ktor.response.*
+import io.ktor.routing.*
+import io.prometheus.client.*
+import io.prometheus.client.exporter.common.*
+import io.prometheus.client.hotspot.*
+import java.io.*
+
+
+fun Routing.metrics(app: SyncApplication) {
+    // Register JVM metrics
+    DefaultExports.initialize()
+
+    get("/metrics") {
+        val writer = StringWriter()
+        TextFormat.write004(
+            writer,
+            CollectorRegistry.defaultRegistry.filteredMetricFamilySamples(setOf<String>()),
+        )
+        call.respond(HttpStatusCode.OK, writer.toString())
+    }
+}

server/src/org/isoron/uhabits/sync/app/SyncApplication.kt

@@ -47,6 +47,7 @@ class SyncApplication(
             registration(this@SyncApplication)
             storage(this@SyncApplication)
             links(this@SyncApplication)
+            metrics(this@SyncApplication)
         }
     }
 }

server/src/org/isoron/uhabits/sync/server/RepositorySyncServer.kt

@@ -19,6 +19,7 @@
 
 package org.isoron.uhabits.sync.server
 
+import io.prometheus.client.*
 import org.isoron.uhabits.sync.*
 import org.isoron.uhabits.sync.links.*
 import org.isoron.uhabits.sync.repository.*
@@ -32,13 +33,21 @@ class RepositorySyncServer(
     private val linkManager: LinkManager = LinkManager(),
 ) : AbstractSyncServer {
 
+    private val requestsCounter: Counter = Counter.build()
+        .name("requests_total")
+        .help("Total number of requests")
+        .labelNames("method")
+        .register()
+
     override suspend fun register(): String {
+        requestsCounter.labels("register").inc()
         val key = generateKey()
         repo.put(key, SyncData(0, ""))
         return key
     }
 
     override suspend fun put(key: String, newData: SyncData) {
+        requestsCounter.labels("put").inc()
         if (!repo.contains(key)) {
             throw KeyNotFoundException()
         }
@@ -50,6 +59,7 @@ class RepositorySyncServer(
     }
 
     override suspend fun getData(key: String): SyncData {
+        requestsCounter.labels("getData").inc()
         if (!repo.contains(key)) {
             throw KeyNotFoundException()
         }
@@ -57,6 +67,7 @@ class RepositorySyncServer(
     }
 
     override suspend fun getDataVersion(key: String): Long {
+        requestsCounter.labels("getDataVersion").inc()
         if (!repo.contains(key)) {
             throw KeyNotFoundException()
         }
@@ -64,10 +75,12 @@ class RepositorySyncServer(
     }
 
     override suspend fun registerLink(syncKey: String): Link {
+        requestsCounter.labels("registerLink").inc()
         return linkManager.register(syncKey)
     }
 
     override suspend fun getLink(id: String): Link {
+        requestsCounter.labels("getLink").inc()
         return linkManager.get(id)
     }