server: Small fix to the BackwardsSynchronizerTask

When running the task, we replace a block when its height already exists,
this should help on the fix for #11 and #12.

server/app/com/xsn/explorer/processors/BlockOps.scala

@@ -0,0 +1,65 @@
+package com.xsn.explorer.processors
+
+import javax.inject.Inject
+
+import com.alexitc.playsonify.core.FutureApplicationResult
+import com.alexitc.playsonify.core.FutureOr.Implicits.FutureOps
+import com.xsn.explorer.data.DatabaseSeeder
+import com.xsn.explorer.data.async.{BlockFutureDataHandler, DatabaseFutureSeeder}
+import com.xsn.explorer.errors.PostgresForeignKeyViolationError
+import com.xsn.explorer.models.Transaction
+import com.xsn.explorer.models.rpc.Block
+import org.scalactic.{Bad, Good, One}
+
+import scala.concurrent.{ExecutionContext, Future}
+
+/**
+ * BlockOps is contains useful operations used for seeding the database, while these methods might be adequate to be on
+ * the [[com.xsn.explorer.services.BlockService]] class, they were added here to avoid growing that service,
+ * in any case, these methods are used by the seeding process.
+ */
+class BlockOps @Inject() (
+    databaseSeeder: DatabaseFutureSeeder,
+    blockDataHandler: BlockFutureDataHandler)(
+    implicit val ec: ExecutionContext) {
+
+  import BlockOps._
+
+  /**
+   * Creates a new block and in case of a conflict due to repeated height, the old block is replaced.
+   */
+  def createBlock(block: Block, transactions: List[Transaction]): FutureApplicationResult[Result] = {
+    val command = DatabaseSeeder.CreateBlockCommand(block, transactions)
+    databaseSeeder
+        .newBlock(command)
+        .flatMap {
+          case Good(_) => Future.successful(Good(Result.BlockCreated))
+          case Bad(One(PostgresForeignKeyViolationError("height", _))) => onRepeatedBlockHeight(block, transactions)
+          case Bad(errors) => Future.successful(Bad(errors))
+        }
+  }
+
+  private def onRepeatedBlockHeight(newBlock: Block, newTransactions: List[Transaction]): FutureApplicationResult[Result] = {
+    val result = for {
+      orphanBlock <- blockDataHandler.getBy(newBlock.height).toFutureOr
+
+      replaceCommand = DatabaseSeeder.ReplaceBlockCommand(
+        orphanBlock = orphanBlock,
+        newBlock = newBlock,
+        newTransactions = newTransactions)
+
+      _ <- databaseSeeder.replaceBlock(replaceCommand).toFutureOr
+    } yield Result.BlockReplacedByHeight
+
+    result.toFuture
+  }
+}
+
+object BlockOps {
+
+  sealed trait Result
+  object Result {
+    case object BlockCreated extends Result
+    case object BlockReplacedByHeight extends Result
+  }
+}

server/app/com/xsn/explorer/tasks/BackwardsSynchronizerTask.scala

@@ -4,11 +4,11 @@ import javax.inject.{Inject, Singleton}
 
 import com.alexitc.playsonify.core.FutureApplicationResult
 import com.alexitc.playsonify.core.FutureOr.Implicits.{FutureListOps, FutureOps, OrOps}
-import com.xsn.explorer.data.DatabaseSeeder
+import com.xsn.explorer.data.async.BlockFutureDataHandler
-import com.xsn.explorer.data.async.{BlockFutureDataHandler, DatabaseFutureSeeder}
 import com.xsn.explorer.errors.BlockNotFoundError
 import com.xsn.explorer.models.rpc.Block
 import com.xsn.explorer.models.{Blockhash, Height}
+import com.xsn.explorer.processors.BlockOps
 import com.xsn.explorer.services.{TransactionService, XSNService}
 import org.scalactic.{Bad, Good, One, Or}
 import org.slf4j.LoggerFactory
@@ -18,7 +18,7 @@ import scala.concurrent.Future
 import scala.util.control.NonFatal
 
 /**
- * As the dababse sync process is slow, it's useful to fill it using a fast server and then, release to the
+ * As the database sync process is slow, it's useful to fill it using a fast server and then, release to the
  * production server, in this case might have a database updated until block N while the SQS messages started
  * at N + X, leaving X missing blocks, this task, syncs the database from block N + X to block N.
  */
@@ -27,7 +27,7 @@ class BackwardsSynchronizerTask @Inject() (
     xsnService: XSNService,
     transactionService: TransactionService,
     blockDataHandler: BlockFutureDataHandler,
-    databaseSeeder: DatabaseFutureSeeder) {
+    blockOps: BlockOps) {
 
   private val logger = LoggerFactory.getLogger(this.getClass)
   private val lock = new Object
@@ -116,8 +116,7 @@ class BackwardsSynchronizerTask @Inject() (
       block <- xsnService.getBlock(blockhash).toFutureOr
       transactions <- block.transactions.map(transactionService.getTransaction).toFutureOr
 
-      command = DatabaseSeeder.CreateBlockCommand(block, transactions)
+      _ <- blockOps.createBlock(block, transactions).toFutureOr
-      _ <- databaseSeeder.newBlock(command).toFutureOr
       _ = logger.debug(s"Block ${block.height.int} saved")
 
       _ <- block

server/test/com/xsn/explorer/processors/BlockOpsSpec.scala

@@ -0,0 +1,51 @@
+package com.xsn.explorer.processors
+
+import com.xsn.explorer.data.anorm.dao.{BalancePostgresDAO, BlockPostgresDAO, TransactionPostgresDAO}
+import com.xsn.explorer.data.anorm.interpreters.FieldOrderingSQLInterpreter
+import com.xsn.explorer.data.anorm.{BlockPostgresDataHandler, DatabasePostgresSeeder}
+import com.xsn.explorer.data.async.{BlockFutureDataHandler, DatabaseFutureSeeder}
+import com.xsn.explorer.data.common.PostgresDataHandlerSpec
+import com.xsn.explorer.helpers.{BlockLoader, Executors, FileBasedXSNService}
+import org.scalactic.Good
+import org.scalatest.BeforeAndAfter
+import org.scalatest.concurrent.ScalaFutures
+
+class BlockOpsSpec extends PostgresDataHandlerSpec with ScalaFutures with BeforeAndAfter {
+
+  before {
+    clearDatabase()
+  }
+
+  lazy val dataHandler = new BlockPostgresDataHandler(database, new BlockPostgresDAO)
+  lazy val dataSeeder = new DatabasePostgresSeeder(
+    database,
+    new BlockPostgresDAO,
+    new TransactionPostgresDAO,
+    new BalancePostgresDAO(new FieldOrderingSQLInterpreter))
+
+  lazy val xsnService = new FileBasedXSNService
+
+  lazy val blockOps = new BlockOps(
+    new DatabaseFutureSeeder(dataSeeder)(Executors.databaseEC),
+    new BlockFutureDataHandler(dataHandler)(Executors.databaseEC))
+
+
+  val block1 = BlockLoader.get("000003fb382f6892ae96594b81aa916a8923c70701de4e7054aac556c7271ef7")
+  val block2 = BlockLoader.get("000004645e2717b556682e3c642a4c6e473bf25c653ff8e8c114a3006040ffb8")
+
+  "createBlock" should {
+    "create a new block" in {
+      whenReady(blockOps.createBlock(block1, List.empty)) { result =>
+        result mustEqual Good(BlockOps.Result.BlockCreated)
+      }
+    }
+
+    "replace a block if the height already exist" in {
+      whenReady(blockOps.createBlock(block1, List.empty)) { _.isGood mustEqual true }
+
+      whenReady(blockOps.createBlock(block2.copy(height = block1.height), List.empty)) { result =>
+        result mustEqual Good(BlockOps.Result.BlockReplacedByHeight)
+      }
+    }
+  }
+}