Expose preferred locations config

core/src/main/scala/com/pingcap/tispark/TiConfigConst.scala

@@ -103,4 +103,6 @@ object TiConfigConst {
   // health check timeout
   val GRPC_HEALTH_CHECK_TIMEOUT = "spark.tispark.grpc.health_check_timeout_in_ms"
   val GPRC_HEALTH_CHECK_PERIOD = "spark.tispark.grpc.health_check_period_in_ms"
+  // preferred locations
+  val PREFERRED_LOCATIONS = "spark.tispark.preferred_locations"
 }

core/src/main/scala/com/pingcap/tispark/utils/TiUtil.scala

@@ -267,6 +267,11 @@ object TiUtil {
     tiConf.setHealthCheckPeriod(conf
       .get(TiConfigConst.GPRC_HEALTH_CHECK_PERIOD, TiConfiguration.DEFHealthCheckPeriod.toString)
       .toInt)
+
+    if (conf.contains(TiConfigConst.PREFERRED_LOCATIONS)) {
+      tiConf.setPreferredLocations(conf.get(TiConfigConst.PREFERRED_LOCATIONS))
+    }
+
     tiConf
   }
 

core/src/main/scala/org/apache/spark/sql/tispark/TiRDD.scala

@@ -43,6 +43,7 @@ abstract class TiRDD(
     extends RDD[InternalRow](sparkSession.sparkContext, Nil) {
 
   private lazy val partitionPerSplit = tiConf.getPartitionPerSplit
+  private lazy val preferredLocations = tiConf.getPreferredLocations
 
   protected def checkTimezone(): Unit = {
     if (!tiConf.getLocalTimeZone.equals(Converter.getLocalTimezone)) {
@@ -80,6 +81,10 @@ abstract class TiRDD(
     result.toArray
   }
 
-  override protected def getPreferredLocations(split: Partition): Seq[String] =
-    split.asInstanceOf[TiPartition].tasks.head.getHost :: Nil
+  override protected def getPreferredLocations(split: Partition): Seq[String] = {
+    if (preferredLocations.equalsIgnoreCase("host")) {
+      return split.asInstanceOf[TiPartition].tasks.head.getHost :: Nil
+    }
+    Nil
+  }
 }

docs/userguide_3.0.md

@@ -282,6 +282,7 @@ spark.sql("select t1.id,t2.id from spark_catalog.default.t t1 left join tidb_cat
 | `spark.tispark.load_tables`                     | true             | (experimental) Whether load all tables when we reload catalog cache. Disable it may cause table not find in scenarios where the table changes frequently.                                                                                                                                                                                                                                                                                           |
 | `spark.tispark.grpc.health_check_timeout_in_ms` | 2000             | The timeout of health check for TiKV and TiFlash.                                                                                                                                                                                                                                                                                                                                                                                                   |
 | `spark.tispark.grpc.health_check_period_in_ms`  | 3000             | The period duration of health check.                                                                                                                                                                                                                                                                                                                                                                                                                |
+| `spark.tispark.preferred_locations`             | ""               | The preferred locations of TiRDD partitions in TiSpark. Only `host` is available now, which takes host as preferred locations. This configuration is for forward compatibility.                                                                                                                                                                                                                                                                     |
 
 ### TLS Configuration
 

tikv-client/src/main/java/com/pingcap/tikv/TiConfiguration.java

@@ -192,6 +192,7 @@ public TiConfiguration setCertReloadIntervalInSeconds(String interval) {
   public static final int DEFHealthCheckPeriod = 3000;
   private int healthCheckTimeout = DEFHealthCheckTimeout;
   private int healthCheckPeriod = DEFHealthCheckPeriod;
+  private String preferredLocations = "";
 
   private static Long getTimeAsSeconds(String key) {
     return Utils.timeStringAsSec(key);

tikv-client/src/main/java/com/pingcap/tikv/operation/iterator/DAGIterator.java

@@ -264,6 +264,13 @@ private SelectResponse process(RegionTask regionTask) {
         }
 
         client.addResolvedLocks(startTs, resolvedLocks);
+        logger.info(
+            String.format(
+                "start coprocess request to %s in region %d with timeout %s",
+                task.getHost(),
+                region.getId(),
+                client.getTimeout()));
+
         Collection<RegionTask> tasks =
             client.coprocess(backOffer, dagRequest, ranges, responseQueue, startTs);
         if (tasks != null) {