Connect with predecessors requires more details in connection slot

Connect with predecessors requires more details in connection slot

https://github.com/apache/incubator-wayang/blob/d859a97d43a8c3c3c964150eaff8f3833e41ea75/wayang-api/wayang-api-rest/src/main/java/org/apache/wayang/api/rest/server/spring/decoder/WayangPlanBuilder.java#L134

```java

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* to you under the Apache License, Version 2.0 (the
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* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
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* See the License for the specific language governing permissions and
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*/

package org.apache.wayang.api.rest.server.spring.decoder;

import com.google.protobuf.InvalidProtocolBufferException;
import org.apache.wayang.api.python.function.WrappedPythonFunction;
import org.apache.wayang.basic.operators.MapPartitionsOperator;
import org.apache.wayang.basic.operators.TextFileSink;
import org.apache.wayang.basic.operators.TextFileSource;
import org.apache.wayang.basic.operators.UnionAllOperator;
import org.apache.wayang.commons.serializable.OperatorProto;
import org.apache.wayang.commons.serializable.PlanProto;
import org.apache.wayang.commons.serializable.WayangPlanProto;
import org.apache.wayang.core.api.WayangContext;
import org.apache.wayang.core.api.exception.WayangException;
import org.apache.wayang.core.function.MapPartitionsDescriptor;
import org.apache.wayang.core.plan.wayangplan.OperatorBase;
import org.apache.wayang.core.plan.wayangplan.WayangPlan;
import org.apache.wayang.java.Java;
import org.apache.wayang.spark.Spark;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.*;
import java.util.stream.Collectors;
import java.util.Base64;

public class WayangPlanBuilder {

private WayangPlan wayangPlan;
private WayangContext wayangContext;

public WayangPlanBuilder(FileInputStream planFile){
try {

WayangPlanProto plan = WayangPlanProto.parseFrom(planFile);

this.wayangContext = buildContext(plan);
this.wayangPlan = buildPlan(plan);

} catch (IOException e) {
e.printStackTrace();
}
}

public WayangPlanBuilder(String writtenPlan){

System.out.println(writtenPlan);
byte[] message = Base64.getDecoder().decode(writtenPlan);
System.out.println(message);

try {
WayangPlanProto plan = WayangPlanProto.parseFrom(message);

this.wayangContext = buildContext(plan);
this.wayangPlan = buildPlan(plan);
} catch (InvalidProtocolBufferException e) {
e.printStackTrace();
}

}

private WayangContext buildContext(WayangPlanProto plan){

WayangContext ctx = new WayangContext();
// plan.getContext().getPlatformsList().forEach(platform -> {
// if (platform.getNumber() == 0)
// ctx.with(Java.basicPlugin());
// else if (platform.getNumber() == 1)
// ctx.with(Spark.basicPlugin());
// });
ctx.with(Spark.basicPlugin());

return ctx;
}

private WayangPlan buildPlan(WayangPlanProto plan){

System.out.println(plan);

PlanProto planProto = plan.getPlan();
LinkedList protoList = new LinkedList<>();
planProto.getSourcesList().forEach(protoList::addLast);

Map operators = new HashMap<>();
List sinks = new ArrayList<>();
while(! protoList.isEmpty()) {

OperatorProto proto = protoList.pollFirst();

/* Checking if protoOperator can be connected to the current WayangPlan*/
boolean processIt;
if(proto.getType().equals("source")) processIt = true;

else {
/* Checking if ALL predecessors were already processed */
processIt = true;
for(String predecessor : proto.getPredecessorsList()){
if (!operators.containsKey(predecessor)) {
processIt = false;
break;
}
}
}

/* Operators should not be processed twice*/
if(operators.containsKey(proto.getId())) processIt = false;

if(processIt) {

/* Create and store Wayang operator */
OperatorBase operator = createOperatorByType(proto);
operators.put(proto.getId(), operator);

/*TODO Connect with predecessors requires more details in connection slot*/
int order = 0;
for (String pre_id : proto.getPredecessorsList()) {

OperatorBase predecessor = operators.get(pre_id);
/* Only works without replicate topology */
predecessor.connectTo(0, operator, order);
order++;

if(proto.getType().toLowerCase().contains("sink")){
sinks.add(operator);
//if(!sinks.contains(operator)) {
// sinks.add(operator);
//}
}
}

/*List of OperatorProto successors
* They will be added to the protoList
* nevertheless they must be processed only if the parents are in operators list */
List listSuccessors = planProto.getOperatorsList()
.stream()
.filter(t -> proto.getSuccessorsList().contains(t.getId()))
.collect(Collectors.toList());
for (OperatorProto successor : listSuccessors){
if(!protoList.contains(successor)){
protoList.addLast(successor);
}
}

List sinkSuccessors = planProto.getSinksList()
.stream()
.filter(t -> proto.getSuccessorsList().contains(t.getId()))
.collect(Collectors.toList());
for (OperatorProto successor : sinkSuccessors){
if(!protoList.contains(successor)){
protoList.addLast(successor);
}
}

} else {

/* In case we cannot process it yet, It must be added again at the end*/
protoList.addLast(proto);
}
}

WayangPlan wayangPlan = new WayangPlan(sinks.get(0));
return wayangPlan;
}

public OperatorBase createOperatorByType(OperatorProto operator){

switch(operator.getType()){
case "TextFileSource":
try {
String source_path = operator.getPath();
URL url = new File(source_path).toURI().toURL();
return new TextFileSource(url.toString());
} catch (MalformedURLException e) {
e.printStackTrace();
}
break;
case "TextFileSink":
try {
String sink_path = operator.getPath();
URL url = new File(sink_path).toURI().toURL();
return new TextFileSink(
url.toString(),
String.class
);

} catch (MalformedURLException e) {
e.printStackTrace();
}
break;
case "MapPartitionOperator":
return new MapPartitionsOperator<>(
new MapPartitionsDescriptor(
new WrappedPythonFunction(
l -> l,
operator.getUdf()
),
String.class,
String.class
)
);

case "union":
return new UnionAllOperator(
String.class
);

}

throw new WayangException("Operator Type not supported "+operator.getType());
}

public WayangContext getWayangContext() {
return wayangContext;
}

public WayangPlan getWayangPlan() {
return wayangPlan;
}
}

```

968f82f6dab0e9e1d3ede6303836f9e65e3d9304

Start in wayang-api/wayang-api-rest/src/main/java/org/apache/wayang/api/rest/server/spring/decoder/WayangPlanBuilder.java at the predecessor-processing loop and inspect OperatorBase.connectTo. Determine which connection-slot details are required for predecessor relationships, including the noted replicate-topology limitation. Done means plans with predecessor connections are built successfully without relying on the current incomplete slot handling.

Written by the indexing model from the issue text.