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Subject [GitHub] [spark] gaborgsomogyi commented on a change in pull request #24922: [SPARK-28120][SS] Rocksdb state storage implementation
Date Wed, 04 Sep 2019 13:56:31 GMT
gaborgsomogyi commented on a change in pull request #24922: [SPARK-28120][SS]  Rocksdb state
storage implementation
URL: https://github.com/apache/spark/pull/24922#discussion_r319845206
 
 

 ##########
 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/RocksDbStateStoreProvider.scala
 ##########
 @@ -0,0 +1,642 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.execution.streaming.state;
+
+import java.io._
+import java.util
+import java.util.Locale
+
+import scala.collection.JavaConverters._
+import scala.util.control.NonFatal
+
+import org.apache.commons.io.FileUtils
+import org.apache.hadoop.conf.Configuration
+import org.apache.hadoop.fs._
+
+import org.apache.spark.{SparkConf, SparkEnv}
+import org.apache.spark.internal.Logging
+import org.apache.spark.io.FileUtility
+import org.apache.spark.sql.catalyst.expressions.UnsafeRow
+import org.apache.spark.sql.execution.streaming.CheckpointFileManager
+import org.apache.spark.sql.types.StructType
+import org.apache.spark.util.Utils
+
+private[sql] class RocksDbStateStoreProvider extends StateStoreProvider with Logging {
+
+  /* Internal fields and methods */
+  @volatile private var stateStoreId_ : StateStoreId = _
+  @volatile private var keySchema: StructType = _
+  @volatile private var valueSchema: StructType = _
+  @volatile private var storeConf: StateStoreConf = _
+  @volatile private var hadoopConf: Configuration = _
+  @volatile private var numberOfVersionsToRetain: Int = _
+  @volatile private var localDirectory: String = _
+
+  /*
+   * Additional configurations related to rocksDb. This will capture all configs in
+   * SQLConf that start with `spark.sql.streaming.stateStore.rocksDb`
+   */
+  @volatile private var rocksDbConf: Map[String, String] = Map.empty[String, String]
+
+  private lazy val baseDir: Path = stateStoreId.storeCheckpointLocation()
+  private lazy val fm = CheckpointFileManager.create(baseDir, hadoopConf)
+  private lazy val sparkConf = Option(SparkEnv.get).map(_.conf).getOrElse(new SparkConf)
+
+  private case class StoreFile(version: Long, path: Path, isSnapshot: Boolean)
+
+  import WALUtils._
+
+  /** Implementation of [[StateStore]] API which is backed by RocksDB and HDFS */
+  class RocksDbStateStore(val version: Long) extends StateStore with Logging {
+
+    /** Trait and classes representing the internal state of the store */
+    trait STATE
+
+    case object LOADED extends STATE
+
+    case object UPDATING extends STATE
+
+    case object COMMITTED extends STATE
+
+    case object ABORTED extends STATE
+
+    private val newVersion = version + 1
+    @volatile private var state: STATE = LOADED
+    private val finalDeltaFile: Path = deltaFile(baseDir, newVersion)
+    private lazy val deltaFileStream = fm.createAtomic(finalDeltaFile, overwriteIfPossible
= true)
+    private lazy val compressedStream = compressStream(deltaFileStream, sparkConf)
+
+    override def id: StateStoreId = RocksDbStateStoreProvider.this.stateStoreId
+
+    var rocksDbWriteInstance: OptimisticTransactionDbInstance = null
+
+    /*
+     * numEntriesInDb and bytesUsedByDb are estimated value
+     * due to the nature of RocksDB implementation.
+     * see https://github.com/facebook/rocksdb/wiki/RocksDB-FAQ for more details
+     */
+    var numEntriesInDb: Long = 0L
+    var bytesUsedByDb: Long = 0L
+
+    private def initTransaction(): Unit = {
+      if (state == LOADED && rocksDbWriteInstance == null) {
+        logDebug(s"Creating Transactional DB for batch $version")
+        rocksDbWriteInstance = new OptimisticTransactionDbInstance(
+          keySchema,
+          valueSchema,
+          newVersion.toString,
+          rocksDbConf)
+        rocksDbWriteInstance.open(rocksDbPath)
+        state = UPDATING
+        rocksDbWriteInstance.startTransactions()
+      }
+    }
+
+    override def get(key: UnsafeRow): UnsafeRow = {
+      initTransaction()
+      rocksDbWriteInstance.get(key)
+    }
+
+    override def put(key: UnsafeRow, value: UnsafeRow): Unit = {
+      initTransaction()
+      verify(state == UPDATING, s"Cannot put after already committed or aborted")
+      val keyCopy = key.copy()
+      val valueCopy = value.copy()
+      rocksDbWriteInstance.put(keyCopy, valueCopy)
+      writeUpdateToDeltaFile(compressedStream, keyCopy, valueCopy)
+    }
+
+    override def remove(key: UnsafeRow): Unit = {
+      initTransaction()
+      verify(state == UPDATING, "Cannot remove after already committed or aborted")
+      rocksDbWriteInstance.remove(key)
+      writeRemoveToDeltaFile(compressedStream, key)
+    }
+
+    override def getRange(
+        start: Option[UnsafeRow],
+        end: Option[UnsafeRow]): Iterator[UnsafeRowPair] = {
+      verify(state == UPDATING, "Cannot getRange after already committed or aborted")
+      iterator()
+    }
+
+    /** Commit all the updates that have been made to the store, and return the new version.
*/
+    override def commit(): Long = {
+      initTransaction()
+      verify(state == UPDATING, s"Cannot commit after already committed or aborted")
+      try {
+        synchronized {
+          rocksDbWriteInstance.commit(Some(getCheckpointPath(newVersion)))
+          finalizeDeltaFile(compressedStream)
+        }
+        state = COMMITTED
+        numEntriesInDb = rocksDbWriteInstance.getApproxEntriesInDb()
+        bytesUsedByDb = numEntriesInDb * (keySchema.defaultSize + valueSchema.defaultSize)
+        newVersion
+      } catch {
+        case NonFatal(e) =>
+          throw new IllegalStateException(s"Error committing version $newVersion into $this",
e)
+      } finally {
+        storeMap.remove(version)
+        close()
+      }
+    }
+
+    /*
+     * Abort all the updates made on this store. This store will not be usable any more.
+     */
+    override def abort(): Unit = {
+      // This if statement is to ensure that files are deleted only if there are changes
to the
+      // StateStore. We have two StateStores for each task, one which is used only for reading,
and
+      // the other used for read+write. We don't want the read-only to delete state files.
+      try {
+        if (state == UPDATING) {
+          state = ABORTED
+          synchronized {
+            rocksDbWriteInstance.abort()
+            cancelDeltaFile(compressedStream, deltaFileStream)
+          }
+          logInfo(s"Aborted version $newVersion for $this")
+        } else {
+          state = ABORTED
+        }
+      } catch {
+        case NonFatal(e) =>
+          throw new IllegalStateException(s"Error aborting version $newVersion into $this",
e)
+      } finally {
+        storeMap.remove(version)
+        close()
+      }
+    }
+
+    def close(): Unit = {
+      if (rocksDbWriteInstance != null) {
+        rocksDbWriteInstance.close()
+        rocksDbWriteInstance = null
+      }
+    }
+
+    /*
+     * Get an iterator of all the store data.
+     * This can be called only after committing all the updates made in the current thread.
+     */
+    override def iterator(): Iterator[UnsafeRowPair] = {
+      state match {
+        case UPDATING =>
+          logDebug("state = updating using transaction DB")
+          // We need to use current db to read uncommitted transactions
+          rocksDbWriteInstance.iterator(closeDbOnCompletion = false)
+
+        case LOADED | ABORTED =>
+          // use check-pointed db for previous version
+          logDebug(s"state = loaded/aborted using check-pointed DB with version $version")
+          if (version == 0) {
+            Iterator.empty
+          } else {
+            val path = getCheckpointPath(version)
+            val r: RocksDbInstance =
+              new RocksDbInstance(keySchema, valueSchema, version.toString, rocksDbConf)
+            r.open(path, readOnly = true)
+            r.iterator(closeDbOnCompletion = true)
+          }
+        case COMMITTED =>
+          logDebug(s"state = committed using check-pointed DB with version $newVersion")
+          // use check-pointed db for current updated version
+          val path = getCheckpointPath(newVersion)
+          val r: RocksDbInstance =
+            new RocksDbInstance(keySchema, valueSchema, newVersion.toString, rocksDbConf)
+          r.open(path, readOnly = true)
+          r.iterator(closeDbOnCompletion = true)
+
+        case _ => Iterator.empty
+      }
+    }
+
+    override def metrics: StateStoreMetrics = {
+      val metricsFromProvider: Map[String, Long] = getMetricsForProvider()
+      val customMetrics = metricsFromProvider.flatMap {
+        case (name, value) =>
+          // just allow searching from list cause the list is small enough
+          supportedCustomMetrics.find(_.name == name).map(_ -> value)
+      }
+      StateStoreMetrics(Math.max(numEntriesInDb, 0), Math.max(bytesUsedByDb, 0), customMetrics)
+    }
+
+    /*
+     * Whether all updates have been committed
+     */
+    override def hasCommitted: Boolean = {
+      state == COMMITTED
+    }
+
+    override def toString(): String = {
+      s"RocksDbStateStore[id=(op=${id.operatorId},part=${id.partitionId}),dir=$baseDir]"
+    }
+
+  }
+
+  /*
+   * Initialize the provider with more contextual information from the SQL operator.
+   * This method will be called first after creating an instance of the StateStoreProvider
by
+   * reflection.
+   *
+   * @param stateStoreId    Id of the versioned StateStores that this provider will generate
+   * @param keySchema       Schema of keys to be stored
+   * @param valueSchema     Schema of value to be stored
+   * @param keyIndexOrdinal Optional column (represent as the ordinal of the field in keySchema)
by
+   *                        which the StateStore implementation could index the data.
+   * @param storeConfs      Configurations used by the StateStores
+   * @param hadoopConf      Hadoop configuration that could be used by StateStore
+   *                        to save state data
+   */
+  override def init(
+      stateStoreId: StateStoreId,
+      keySchema: StructType,
+      valueSchema: StructType,
+      keyIndexOrdinal: Option[Int], // for sorting the data by their keys
+      storeConfs: StateStoreConf,
+      hadoopConf: Configuration): Unit = {
+    this.stateStoreId_ = stateStoreId
+    this.keySchema = keySchema
+    this.valueSchema = valueSchema
+    this.storeConf = storeConfs
+    this.hadoopConf = hadoopConf
+    this.numberOfVersionsToRetain = storeConfs.maxVersionsToRetainInMemory
+    fm.mkdirs(baseDir)
+    this.rocksDbConf = storeConf.confs
 
 Review comment:
   Let me explain my point. If we take an example like `RocksDbInstance.scala` it contains
implementation detail about how to get specific parameter values, like [this](https://github.com/apache/spark/pull/24922/files#diff-1d0920add5494799c03eed9682fe7bfbR199-R203).
In this scenario it's bad that `RocksDbInstance` defines what is the default etc. This can
be extracted to `RocksDbStateStoreConf` class which can inherit all the behavior from `StateStoreConf`.
If it's applied then the implementation would look this this: `conf.blockSizeInKB`. As mentioned
in my previous comment `ConfigBuilder` can be used and together with this change the code
would be less coupled. Something like this:
   
   Possibility1.
   ```
   class RocksDbStateStoreConf(@transient private val stateStoreConf: StateStoreConf)
     extends StateStoreConf {
   ...
     val blockSizeInKB: Int = stateStoreConf.sqlConf.blockSizeInKB
   ...
   }
   ```
   
   Possibility2.
   ```
   class RocksDbStateStoreConf(@transient private val sqlConf: SQLConf)
     extends Serializable {
   ...
     val blockSizeInKB: Int = sqlConf.blockSizeInKB
   ...
   }
   ```
   Haven't spent too much time which one is better but I've the feeling the first one is easier.
Feel free to evaluate and suggest better option if you've something.
   

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