[
https://issues.apache.org/jira/browse/TEZ-3998?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16657364#comment-16657364
]
ASF GitHub Bot commented on TEZ-3998:
-------------------------------------
Github user jteagles commented on a diff in the pull request:
https://github.com/apache/tez/pull/33#discussion_r226706087
--- Diff: tez-api/src/main/java/org/apache/tez/dag/api/DAG.java ---
@@ -79,16 +79,16 @@
import com.google.common.collect.Sets;
/**
- * Top level entity that defines the DAG (Directed Acyclic Graph)
representing
--- End diff --
Usually for formatting changes we submit a separate change to address the
whitespace changes to keep the logic changes separate to ease the review. Many
editors default to automatically fix trailing whitespace on save and hadoop
developers tend to disable this feature. Github allows me to hide whitespace
changes so this is not much of a big deal.
> Allow CONCURRENT edge property in DAG construction and introduce
> ConcurrentSchedulingType
> -----------------------------------------------------------------------------------------
>
> Key: TEZ-3998
> URL: https://issues.apache.org/jira/browse/TEZ-3998
> Project: Apache Tez
> Issue Type: Task
> Reporter: Yingda Chen
> Assignee: Yingda Chen
> Priority: Major
>
> This is the first task related to TEZ-3997
>
> |Note: There is no API change in this proposed change. The majority of this
> change will be lifting some existing constraints against CONCURRENT edge
> type, and addition of a VertexMangerPlugin implementation.|
>
> This includes enabling the CONCURRENT SchedulingType as a valid edge
> property, by removing all the sanity check against CONCURRENT during DAG
> construction/execution. A new VertexManagerPlugin (namely
> VertexManagerWithConcurrentInput) will be implemented for vertex with
> incoming concurrent edge(s).
> In addition, we will assume in this change that
> * A vertex *cannot* have both SEQUENTIAL and CONCURRENT incoming edges
> * No shuffle or data movement is handled by Tez framework when two vertices
> are connected through a CONCURRENT edge. Instead, runtime should be
> responsible for handling all the data-plane communications (as proposed in
> [1]).
> Note that the above assumptions are common for scenarios such as whole-DAG or
> sub-graph gang scheduling, but they may be relaxed in later implementation,
> which may allow mixture of SEQUENTIAL and CONCURRENT edges on the same vertex.
>
> Most of the (meaningful) scheduling decisions today in Tez are made based on
> the notion of (or an extended version of) source task completion. This will
> no longer be true in presence of CONCURRENT edge. Instead, events such as
> source vertex configured, or source task running will become more relevant
> when making scheduling decision for two vertices connected via a CONCURRENT
> edge. We therefore introduce a new enum *ConcurrentSchedulingType* to
> describe the “scheduling timing” for the downstream vertex in such scenarios.
> |public enum ConcurrentSchedulingType{
> /** * trigger downstream vertex tasks scheduling by "configured" event of
> upstream vertices */
> SOURCE_VERTEX_CONFIGURED,
> /** * trigger downstream vertex tasks scheduling by "running" event of
> upstream tasks */
> SOURCE_TASK_STARTED
> }|
>
> Note that in this change, we will only use SOURCE_VERTEX_CONFIGURED as the
> scheduling type, which suffice for scenarios of whole-DAG or sub-graph
> gang-scheduling, where we want (all the tasks in) the downstream vertex to be
> scheduled together with (all the tasks) in the upstream vertex. In this case,
> we can leverage the existing onVertexStateUpdated() interface of
> VextexMangerPlugin to collect relevant information to assist the scheduling
> decision, and *there is no additional API change necessary*. However, in more
> subtle case such as the parameter-server example described in Fig. 1, other
> scheduling type would be more relevant, therefore the placeholder for
> *ConcurrentSchedulingType* will be introduced in this change as part of the
> infrastructure work.
>
> Finally, since we assume that all communications between two vertices
> connected via CONCURRENT edge are handled by application runtime, a
> CONCURRENT edge will be assigned a DummyEdgeManager that basically mute all
> DME/VME handling.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
