Download all groups that changed between the previous and current cache

This makes us behave like a standard client that only keeps a single
copy of each group in its cache. This ensures we can at least detect
(crc32, version) collisions for a particular group, rather than silently
skipping colliding cached groups.

A disadvantage is that more bandwidth usage is required, especially if
the download is interrupted.

Signed-off-by: Graham <gpe@openrs2.org>

archive/src/main/kotlin/org/openrs2/archive/cache/CacheDownloader.kt

@@ -24,7 +24,16 @@ public class CacheDownloader @Inject constructor(
         try {
             suspendCoroutine<Unit> { continuation ->
                 val bootstrap = bootstrapFactory.createBootstrap(group)
-                val handler = Js5ChannelHandler(bootstrap, game.id, hostname, port, build, continuation, importer)
+                val handler = Js5ChannelHandler(
+                    bootstrap,
+                    game.id,
+                    hostname,
+                    port,
+                    build,
+                    game.previousMasterIndexId,
+                    continuation,
+                    importer
+                )
 
                 bootstrap.handler(Js5ChannelInitializer(handler))
                     .connect(hostname, port)

archive/src/main/kotlin/org/openrs2/archive/cache/CacheImporter.kt

@@ -169,9 +169,10 @@ public class CacheImporter @Inject constructor(
         uncompressed: ByteBuf,
         gameId: Int,
         build: Int,
+        previousId: Int?,
         timestamp: Instant,
         name: String,
-    ): List<ByteBuf?> {
+    ): Pair<Int, List<ByteBuf?>> {
         return database.execute { connection ->
             prepare(connection)
 
@@ -199,17 +200,28 @@ public class CacheImporter @Inject constructor(
                 overwrite = true
             )
 
+            /*
+             * In order to defend against (crc32, version) collisions, we only
+             * use a cached index if its checksum/version haven't changed
+             * between the previously downloaded version of the cache and the
+             * current version. This emulates the behaviour of a client always
+             * using the latest version of the cache - so if there is a
+             * collision, real players of the game would experience problems.
+             */
             connection.prepareStatement(
                 """
                 SELECT c.data
                 FROM master_index_archives a
-                LEFT JOIN containers c ON c.crc32 = a.crc32
-                LEFT JOIN indexes i ON i.version = a.version AND i.container_id = c.id
+                LEFT JOIN master_index_archives a2 ON a2.master_index_id = ? AND a2.archive_id = a.archive_id AND
+                    a2.crc32 = a.crc32 AND a2.version = a.version
+                LEFT JOIN containers c ON c.crc32 = a2.crc32
+                LEFT JOIN indexes i ON i.version = a2.version AND i.container_id = c.id
                 WHERE a.master_index_id = ?
                 ORDER BY a.archive_id ASC
             """.trimIndent()
             ).use { stmt ->
-                stmt.setInt(1, id)
+                stmt.setObject(1, previousId, Types.INTEGER)
+                stmt.setInt(2, id)
 
                 stmt.executeQuery().use { rows ->
                     val indexes = mutableListOf<ByteBuf?>()
@@ -224,7 +236,7 @@ public class CacheImporter @Inject constructor(
                         }
 
                         indexes.filterNotNull().forEach(ByteBuf::retain)
-                        return@execute indexes
+                        return@execute Pair(id, indexes)
                     } finally {
                         indexes.filterNotNull().forEach(ByteBuf::release)
                     }
@@ -237,7 +249,8 @@ public class CacheImporter @Inject constructor(
         archive: Int,
         index: Js5Index,
         buf: ByteBuf,
-        uncompressed: ByteBuf
+        uncompressed: ByteBuf,
+        previousMasterIndexId: Int?
     ): List<Int> {
         return database.execute { connection ->
             prepare(connection)
@@ -273,22 +286,33 @@ public class CacheImporter @Inject constructor(
             }
 
             /*
-             * We deliberately ignore groups with truncated versions here and
-             * re-download them, just in case there's a (crc32, truncated version)
-             * collision.
+             * In order to defend against (crc32, version) collisions, we only
+             * use a cached group if its checksum/version haven't changed
+             * between the previously downloaded version of the cache and the
+             * current version. This emulates the behaviour of a client always
+             * using the latest version of the cache - so if there is a
+             * collision, real players of the game would experience problems.
+             *
+             * We never use cached groups with a truncated version, as these
+             * are even more likely to be prone to collisions.
              */
             connection.prepareStatement(
                 """
                 SELECT t.group_id
                 FROM tmp_groups t
-                LEFT JOIN groups g ON g.archive_id = ? AND g.group_id = t.group_id AND g.version = t.version AND
-                    NOT g.version_truncated
-                LEFT JOIN containers c ON c.id = g.container_id AND c.crc32 = t.crc32
+                LEFT JOIN master_index_valid_indexes i ON i.master_index_id = ? AND
+                    i.archive_id = ?
+                LEFT JOIN index_groups ig ON ig.container_id = i.container_id AND ig.group_id = t.group_id AND
+                    ig.crc32 = t.crc32 AND ig.version = t.version
+                LEFT JOIN groups g ON g.archive_id = i.archive_id AND g.group_id = ig.group_id AND
+                    g.version = ig.version AND NOT g.version_truncated
+                LEFT JOIN containers c ON c.id = g.container_id AND c.crc32 = ig.crc32
                 WHERE g.container_id IS NULL
                 ORDER BY t.group_id ASC
             """.trimIndent()
             ).use { stmt ->
-                stmt.setInt(1, archive)
+                stmt.setObject(1, previousMasterIndexId, Types.INTEGER)
+                stmt.setInt(2, archive)
 
                 stmt.executeQuery().use { rows ->
                     val groups = mutableListOf<Int>()
@@ -770,6 +794,21 @@ public class CacheImporter @Inject constructor(
         }
     }
 
+    public suspend fun setMasterIndexId(gameId: Int, masterIndexId: Int) {
+        database.execute { connection ->
+            connection.prepareStatement(
+                """
+                UPDATE games SET master_index_id = ? WHERE id = ?
+            """.trimIndent()
+            ).use { stmt ->
+                stmt.setInt(1, masterIndexId)
+                stmt.setInt(2, gameId)
+
+                stmt.execute()
+            }
+        }
+    }
+
     public companion object {
         public const val BATCH_SIZE: Int = 1024
     }

archive/src/main/kotlin/org/openrs2/archive/cache/Js5ChannelHandler.kt

@@ -35,6 +35,7 @@ public class Js5ChannelHandler(
     private val hostname: String,
     private val port: Int,
     private var build: Int,
+    private val previousMasterIndexId: Int?,
     private val continuation: Continuation<Unit>,
     private val importer: CacheImporter,
     private val masterIndexFormat: MasterIndexFormat = MasterIndexFormat.VERSIONED,
@@ -44,6 +45,7 @@ public class Js5ChannelHandler(
     private val maxBuild = build + maxBuildAttempts
     private val inFlightRequests = mutableSetOf<Js5Request.Group>()
     private val pendingRequests = ArrayDeque<Js5Request.Group>()
+    private var currentMasterIndexId: Int = 0
     private var masterIndex: Js5MasterIndex? = null
     private lateinit var indexes: Array<Js5Index?>
     private val groups = mutableListOf<CacheImporter.Group>()
@@ -155,6 +157,10 @@ public class Js5ChannelHandler(
         }
 
         if (complete) {
+            runBlocking {
+                importer.setMasterIndexId(gameId, currentMasterIndexId)
+            }
+
             ctx.close()
             continuation.resume(Unit)
         }
@@ -164,14 +170,15 @@ public class Js5ChannelHandler(
         Js5Compression.uncompress(buf.slice()).use { uncompressed ->
             masterIndex = Js5MasterIndex.read(uncompressed.slice(), masterIndexFormat)
 
-            val rawIndexes = runBlocking {
             val name = "Downloaded from $hostname:$port"
+            val (id, rawIndexes) = runBlocking {
                 importer.importMasterIndexAndGetIndexes(
                     masterIndex!!,
                     buf,
                     uncompressed,
                     gameId,
                     build,
+                    previousMasterIndexId,
                     timestamp = Instant.now(),
                     name
                 )
@@ -189,6 +196,8 @@ public class Js5ChannelHandler(
             } finally {
                 rawIndexes.filterNotNull().forEach(ByteBuf::release)
             }
+
+            currentMasterIndexId = id
         }
     }
 
@@ -207,7 +216,7 @@ public class Js5ChannelHandler(
             }
 
             val groups = runBlocking {
-                importer.importIndexAndGetMissingGroups(archive, index, buf, uncompressed)
+                importer.importIndexAndGetMissingGroups(archive, index, buf, uncompressed, previousMasterIndexId)
             }
             for (group in groups) {
                 request(archive, group)

archive/src/main/kotlin/org/openrs2/archive/game/Game.kt

@@ -4,5 +4,6 @@ public data class Game(
     public val id: Int,
     public val hostname: String?,
     public val port: Int?,
-    public val build: Int?
+    public val build: Int?,
+    public val previousMasterIndexId: Int?
 )

archive/src/main/kotlin/org/openrs2/archive/game/GameDatabase.kt

@@ -12,7 +12,7 @@ public class GameDatabase @Inject constructor(
         return database.execute { connection ->
             connection.prepareStatement(
                 """
-                SELECT id, hostname, port, build
+                SELECT id, hostname, port, build, master_index_id
                 FROM games
                 WHERE name = ?
             """.trimIndent()
@@ -37,7 +37,12 @@ public class GameDatabase @Inject constructor(
                         build = null
                     }
 
-                    return@execute Game(id, hostname, port, build)
+                    var masterIndexId: Int? = rows.getInt(5)
+                    if (rows.wasNull()) {
+                        masterIndexId = null
+                    }
+
+                    return@execute Game(id, hostname, port, build, masterIndexId)
                 }
             }
         }

archive/src/main/resources/org/openrs2/archive/V1__init.sql

@@ -108,6 +108,8 @@ CREATE TABLE master_indexes (
     UNIQUE (container_id, format)
 );
 
+ALTER TABLE games ADD COLUMN master_index_id INT NULL REFERENCES master_indexes (id);
+
 CREATE TABLE master_index_archives (
     master_index_id INTEGER NOT NULL REFERENCES master_indexes (id),
     archive_id uint1 NOT NULL,