org.apache.flink.compiler.deadlockdetect

Class DeadlockPreventer

java.lang.Object

org.apache.flink.compiler.deadlockdetect.DeadlockPreventer

All Implemented Interfaces:

Visitor<PlanNode>

public class DeadlockPreventer
extends Object
implements Visitor<PlanNode>

Certain pipelined flows may lead to deadlocks, in which case we need to make sure the pipelines are broken or made elastic enough to prevent that. This is only relevat to pipelined data flows where one operator has more than one consumers (successors in the flow). Most cases are caught by the general logic that deals with branching/joining flows. The following cases need additional checks: (source1) ------ (join) \ / \ / \/ /\ / \ / \ (source2) ------(join) Since both sources pipeline their data into a build and a probe side, they get stalled by the back pressure from the probe side (which waits for the build side to complete) and never finish the build side. We can model dependencies of pipelined / materialized connections and do a reguar cyclic dependencies check to detect such situations. Pipelined connections have a dependency from sender to receiver, non-pipelined (fully dammed) connections have a dependency from receiver to sender.

Constructor Summary

Constructors

Constructor and Description
DeadlockPreventer()

Method Summary

Modifier and Type	Method and Description
boolean	hasDeadlock(List<? extends PlanNode> sinks) Creates new DeadlockGraph from plan and checks for cycles
void	postVisit(PlanNode visitable)
boolean	preVisit(PlanNode visitable)
void	resolveDeadlocks(List<? extends PlanNode> sinks)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DeadlockPreventer

public DeadlockPreventer()

Method Detail

resolveDeadlocks

public void resolveDeadlocks(List<? extends PlanNode> sinks)

hasDeadlock

public boolean hasDeadlock(List<? extends PlanNode> sinks)

Creates new DeadlockGraph from plan and checks for cycles

preVisit

public boolean preVisit(PlanNode visitable)

Specified by:

preVisit in interface Visitor<PlanNode>

postVisit

public void postVisit(PlanNode visitable)

Specified by:

postVisit in interface Visitor<PlanNode>