[GitHub] [hive] okumin commented on a change in pull request #1744: HIVE-24485: Make the slow-start behavior tunable

[GitBox <gi...@apache.org>]

okumin commented on a change in pull request #1744:
URL: https://github.com/apache/hive/pull/1744#discussion_r571351354



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File path: ql/src/java/org/apache/hadoop/hive/ql/parse/GenTezUtils.java
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@@ -81,6 +82,12 @@ public static ReduceWork createReduceWork(
     boolean isAutoReduceParallelism =
         context.conf.getBoolVar(HiveConf.ConfVars.TEZ_AUTO_REDUCER_PARALLELISM);
 
+    float slowStartMaxSrcFraction = context.conf.getFloat(
+        ShuffleVertexManager.TEZ_SHUFFLE_VERTEX_MANAGER_MAX_SRC_FRACTION,
+        ShuffleVertexManager.TEZ_SHUFFLE_VERTEX_MANAGER_MAX_SRC_FRACTION_DEFAULT);
+    float slowStartMinSrcFraction = context.conf.getFloat(
+        ShuffleVertexManager.TEZ_SHUFFLE_VERTEX_MANAGER_MIN_SRC_FRACTION,
+        ShuffleVertexManager.TEZ_SHUFFLE_VERTEX_MANAGER_MIN_SRC_FRACTION_DEFAULT);

Review comment:
       I wonder if we should add new parameters and use them instead of ones defined in ShuffleVertexManager.
   Looking through this class, it would be consistent to introduce new parameters and use `TEZ_SHUFFLE_VERTEX_MANAGER_{MIN, MAX}_SRC_FRACTION` only in `DagUtils.java`.
   However, Hive on Tez can access `TEZ_SHUFFLE_VERTEX_MANAGER_{MIN, MAX}_SRC_FRACTION` in other cases. So I thought it might be also confusing to have two methods to tweak slow-start behavior, one is for auto-reduce parallelism and the other one is for all other cases.
   https://github.com/apache/tez/blob/73bcabd2bca2536bf4f3673443a8dcdaaf79a4eb/tez-dag/src/main/java/org/apache/tez/dag/app/dag/impl/VertexImpl.java#L2893-L2897
   
   My ideas are
   - use `TEZ_SHUFFLE_VERTEX_MANAGER_{MIN, MAX}_SRC_FRACTION`
   - add params for auto parallelism, like `TEZ_AUTO_REDUCER_PARALLELISM_{MIN, MAX}_SRC_FRACTION`, and use them only for auto parallelism
   - add params to configure slow-start behavior, like `TEZ_SLOW_START_{MIN, MAX}_SRC_FRACTION`, and use it for all cases, meaning Hive on Tez ignores `TEZ_SHUFFLE_VERTEX_MANAGER_{MIN, MAX}_SRC_FRACTION` configured by a user




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