Server: data persistence

server/Dockerfile

@@ -1,6 +1,7 @@
 FROM openjdk:8-jre-alpine
 RUN mkdir /app
 COPY uhabits-server.jar /app/uhabits-server.jar
+ENV LOOP_REPO_PATH /data/
 WORKDIR /app
 CMD ["java", \
      "-server", \

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

@@ -24,11 +24,18 @@ import io.ktor.features.*
 import io.ktor.jackson.*
 import io.ktor.routing.*
 import org.isoron.uhabits.sync.*
+import org.isoron.uhabits.sync.repository.*
+import org.isoron.uhabits.sync.server.*
+import java.nio.file.*
 
 fun Application.main() = SyncApplication().apply { main() }
 
+val REPOSITORY_PATH: Path = Paths.get(System.getenv("LOOP_REPO_PATH")!!)
+
 class SyncApplication(
-    val server: AbstractSyncServer = MemorySyncServer(),
+    val server: AbstractSyncServer = RepositorySyncServer(
+        FileRepository(REPOSITORY_PATH),
+    ),
 ) {
     fun Application.main() {
         install(DefaultHeaders)

server/src/org/isoron/uhabits/sync/repository/FileRepository.kt

@@ -0,0 +1,73 @@
+/*
+ * 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.repository
+
+import org.isoron.uhabits.sync.*
+import java.io.*
+import java.nio.file.*
+
+class FileRepository(
+    private val basepath: Path,
+) : Repository {
+
+    override suspend fun put(key: String, data: SyncData) {
+        // Create directory
+        val dataPath = key.toDataPath()
+        val dataDir = dataPath.toFile()
+        dataDir.mkdirs()
+
+        // Create metadata
+        val metadataFile = dataPath.resolve("version").toFile()
+        metadataFile.outputStream().use { outputStream ->
+            PrintWriter(outputStream).use { printWriter ->
+                printWriter.print(data.version)
+            }
+        }
+
+        // Create data file
+        val dataFile = dataPath.resolve("content").toFile()
+        dataFile.outputStream().use { outputStream ->
+            PrintWriter(outputStream).use { printWriter ->
+                printWriter.print(data.content)
+            }
+        }
+    }
+
+    override suspend fun get(key: String): SyncData {
+        val dataPath = key.toDataPath()
+        val contentFile = dataPath.resolve("content").toFile()
+        val versionFile = dataPath.resolve("version").toFile()
+        if (!contentFile.exists() || !versionFile.exists()) {
+            throw KeyNotFoundException()
+        }
+        val version = versionFile.readText().trim().toLong()
+        return SyncData(version, contentFile.readText())
+    }
+
+    override suspend fun contains(key: String): Boolean {
+        val dataPath = key.toDataPath()
+        val versionFile = dataPath.resolve("version").toFile()
+        return versionFile.exists()
+    }
+
+    private fun String.toDataPath(): Path {
+        return basepath.resolve("${this.substring(0..1)}/${this.substring(2..3)}/$this")
+    }
+}

server/src/org/isoron/uhabits/sync/repository/Repository.kt

@@ -0,0 +1,46 @@
+/*
+ * 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.repository
+
+import com.sun.org.apache.xpath.internal.operations.*
+import org.isoron.uhabits.sync.*
+
+/**
+ * A class that knows how to store and retrieve a large number of [SyncData] items.
+ */
+interface Repository {
+    /**
+     * Stores a data item, under the provided key. The item can be later retrieved with [get].
+     * Replaces existing items silently.
+     */
+    suspend fun put(key: String, data: SyncData)
+
+    /**
+     * Retrieves a data item that was previously stored using [put].
+     * @throws KeyNotFoundException If no such key exists.
+     */
+    suspend fun get(key: String): SyncData
+
+    /**
+     * Returns true if the repository contains a given key.
+     */
+    suspend fun contains(key: String): Boolean
+}
+

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

@@ -17,7 +17,9 @@
  * with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-package org.isoron.uhabits.sync
+package org.isoron.uhabits.sync.server
+
+import org.isoron.uhabits.sync.*
 
 interface AbstractSyncServer {
     /**

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

@@ -17,64 +17,59 @@
  * with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
-package org.isoron.uhabits.sync
+package org.isoron.uhabits.sync.server
 
+import org.isoron.uhabits.sync.*
+import org.isoron.uhabits.sync.repository.*
 import java.util.*
 import kotlin.streams.*
 
 /**
- * An AbstractSyncServer that stores all data in memory.
+ * An AbstractSyncServer that stores all data in a [Repository].
  */
-class MemorySyncServer : AbstractSyncServer {
+class RepositorySyncServer(
-    private val db = mutableMapOf<String, SyncData>()
+    private val repo: Repository,
+) : AbstractSyncServer {
 
     override suspend fun register(): String {
-        synchronized(db) {
+        val key = generateKey()
-            val key = generateKey()
+        repo.put(key, SyncData(0, ""))
-            db[key] = SyncData(0, "")
+        return key
-            return key
-        }
     }
 
     override suspend fun put(key: String, newData: SyncData) {
-        synchronized(db) {
+        if (!repo.contains(key)) {
-            if (!db.containsKey(key)) {
+            throw KeyNotFoundException()
-                throw KeyNotFoundException()
+        }
-            }
+        val prevData = repo.get(key)
-            val prevData = db.getValue(key)
+        if (newData.version != prevData.version + 1) {
-            if (newData.version != prevData.version + 1) {
+            throw EditConflictException()
-                throw EditConflictException()
-            }
-            db[key] = newData
         }
+        repo.put(key, newData)
     }
 
     override suspend fun getData(key: String): SyncData {
-        synchronized(db) {
+        if (!repo.contains(key)) {
-            if (!db.containsKey(key)) {
+            throw KeyNotFoundException()
-                throw KeyNotFoundException()
-            }
-            return db.getValue(key)
         }
+        return repo.get(key)
     }
 
     override suspend fun getDataVersion(key: String): Long {
-        synchronized(db) {
+        if (!repo.contains(key)) {
-            if (!db.containsKey(key)) {
+            throw KeyNotFoundException()
-                throw KeyNotFoundException()
-            }
-            return db.getValue(key).version
         }
+        return repo.get(key).version
     }
 
-    private fun generateKey(): String {
+    private suspend fun generateKey(): String {
         val chars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
         while (true) {
             val key = Random().ints(64, 0, chars.length)
                 .asSequence()
                 .map(chars::get)
                 .joinToString("")
-            if (!db.containsKey(key))
+            if (!repo.contains(key))
                 return key
         }
 

server/test/org/isoron/uhabits/sync/RepositorySyncServerTest.kt

@@ -20,12 +20,16 @@
 package org.isoron.uhabits.sync
 
 import kotlinx.coroutines.*
+import org.isoron.uhabits.sync.repository.*
+import org.isoron.uhabits.sync.server.*
 import org.junit.Test
+import java.nio.file.*
 import kotlin.test.*
 
-class MemorySyncServerTest {
+class RepositorySyncServerTest {
 
-    private val server = MemorySyncServer()
+    private val tempdir = Files.createTempDirectory("db")
+    private val server = RepositorySyncServer(FileRepository(tempdir))
     private val key = runBlocking { server.register() }
 
     @Test

server/test/org/isoron/uhabits/sync/app/BaseApplicationTest.kt

@@ -20,7 +20,7 @@
 package org.isoron.uhabits.sync.app
 
 import io.ktor.application.*
-import org.isoron.uhabits.sync.*
+import org.isoron.uhabits.sync.server.*
 import org.mockito.Mockito.*
 
 open class BaseApplicationTest {

server/test/org/isoron/uhabits/sync/repository/FileRepositoryTest.kt

@@ -0,0 +1,53 @@
+/*
+ * 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/>.
+ */
+
+
+@file:Suppress("BlockingMethodInNonBlockingContext")
+
+package org.isoron.uhabits.sync.repository
+
+import kotlinx.coroutines.*
+import org.hamcrest.CoreMatchers.*
+import org.isoron.uhabits.sync.*
+import org.junit.*
+import org.junit.Assert.*
+import java.nio.file.*
+
+class FileRepositoryTest {
+
+    @Test
+    fun testUsage() = runBlocking {
+        val tempdir = Files.createTempDirectory("db")!!
+        val repo = FileRepository(tempdir)
+
+        val original = SyncData(10, "Hello world")
+        repo.put("abcdefg", original)
+
+        val metaPath = tempdir.resolve("ab/cd/abcdefg/version")
+        assertTrue("$metaPath should exist", Files.exists(metaPath))
+        assertEquals("10", metaPath.toFile().readText())
+
+        val dataPath = tempdir.resolve("ab/cd/abcdefg/content")
+        assertTrue("$dataPath should exist", Files.exists(dataPath))
+        assertEquals("Hello world", dataPath.toFile().readText())
+
+        val retrieved = repo.get("abcdefg")
+        assertThat(retrieved, equalTo(original))
+    }
+}