bundles/org.simantics.db.impl/src/org/simantics/db/impl/BlockingAsyncProcedure.java

   1 /*******************************************************************************
   2  * Copyright (c) 2018 Association for Decentralized Information Management
   3  * in Industry THTH ry.
   4  * All rights reserved. This program and the accompanying materials
   5  * are made available under the terms of the Eclipse Public License v1.0
   6  * which accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *
   9  * Contributors:
  10  *     Semantum Oy - initial API and implementation
  11  *******************************************************************************/
  12 package org.simantics.db.impl;
  13
  14 import org.simantics.db.AsyncReadGraph;
  15 import org.simantics.db.exception.DatabaseException;
  16 import org.simantics.db.impl.graph.BarrierTracing;
  17 import org.simantics.db.impl.graph.ReadGraphImpl;
  18 import org.simantics.db.impl.query.AsyncReadEntry;
  19 import org.simantics.db.impl.query.PendingTaskSupport;
  20 import org.simantics.db.procedure.AsyncProcedure;
  21
  22 public class BlockingAsyncProcedure<Result> implements AsyncProcedure<Result> {
  23
  24     private static final Object NO_RESULT = new Object();
  25
  26     public final Object key;
  27     public final ReadGraphImpl queryGraph;
  28     public final ReadGraphImpl callerGraph;
  29     public final AsyncProcedure<Result> procedure;
  30     public PendingTaskSupport pendingTaskSupport;
  31     public final boolean needsToBlock;
  32     public Object result = NO_RESULT;
  33     public Throwable exception = null;
  34
  35     private ReadGraphImpl queryGraph() {
  36         return queryGraph;
  37     }
  38
  39     public BlockingAsyncProcedure(ReadGraphImpl callerGraph, AsyncReadEntry<Result> entry, AsyncProcedure<Result> procedure, Object key, boolean needsToBlock) {
  40
  41         // A new graph for evaluating the query with correct parent and asyncBarrier
  42         queryGraph = callerGraph.withParent(entry, () -> {
  43
  44             dispatchProcedure(queryGraph(), callerGraph, entry, procedure, needsToBlock);
  45
  46         }, needsToBlock);
  47
  48         queryGraph.asyncBarrier.inc();
  49
  50         this.procedure = procedure;
  51         this.key = key;
  52         this.queryGraph.asyncBarrier.inc();
  53         this.callerGraph = callerGraph;
  54         this.needsToBlock = needsToBlock;
  55         if (BarrierTracing.BOOKKEEPING) {
  56             BarrierTracing.registerBAP(this);
  57         }
  58     }
  59
  60     @Override
  61     public void execute(AsyncReadGraph graph_, Result result) {
  62
  63         this.result = result;
  64         queryGraph.asyncBarrier.dec();
  65
  66     }
  67
  68     @Override
  69     public void exception(AsyncReadGraph graph_, Throwable t) {
  70
  71         this.exception = t;
  72         queryGraph.asyncBarrier.dec();
  73
  74     }
  75
  76     public void waitBarrier() {
  77         queryGraph.asyncBarrier.waitBarrier(key, queryGraph);
  78     }
  79
  80     public void dec() {
  81
  82         queryGraph.asyncBarrier.dec();
  83
  84     }
  85
  86     @SuppressWarnings("unchecked")
  87     public Result get() throws DatabaseException {
  88
  89         if(needsToBlock)
  90             queryGraph.asyncBarrier.waitBarrier(key, queryGraph);
  91
  92         if(exception != null) {
  93             if(exception instanceof DatabaseException) throw (DatabaseException)exception;
  94             throw new DatabaseException(exception);
  95         } else {
  96             return (Result)result;
  97         }
  98
  99     }
 100
 101     @SuppressWarnings("unchecked")
 102     public Result getResult() {
 103         return (Result)result;
 104     }
 105
 106     public Throwable getException() {
 107         return exception;
 108     }
 109
 110     @Override
 111     public String toString() {
 112         return "." + procedure;
 113     }
 114
 115     private void dispatchProcedure(ReadGraphImpl queryGraph, ReadGraphImpl parentGraph, AsyncReadEntry<Result> entry, AsyncProcedure<Result> procedure_, boolean needsToBlock) {
 116
 117         AsyncProcedure<Result> procedure = entry != null ? entry : procedure_;
 118
 119         ReadGraphImpl executeGraph = parentGraph.withParent(parentGraph.parent, null, needsToBlock);
 120         executeGraph.asyncBarrier.inc();
 121         try {
 122             if(procedure != null) {
 123                 procedure.execute(executeGraph, get());
 124             }
 125         } catch (DatabaseException e) {
 126             if(procedure != null) procedure.exception(executeGraph, e);
 127             exception = e;
 128         } catch (Throwable t) {
 129             DatabaseException dbe = new DatabaseException(t);
 130             if(procedure != null) procedure.exception(executeGraph, dbe);
 131             exception = dbe;
 132         } finally {
 133
 134             if (entry != null) {
 135                 assert(entry.isReady());
 136                 // This does not throw
 137                 entry.performFromCache(executeGraph, procedure_);
 138             }
 139
 140             executeGraph.asyncBarrier.dec();
 141             if(needsToBlock)
 142                 executeGraph.asyncBarrier.waitBarrier(procedure, executeGraph);
 143         }
 144
 145         if (BarrierTracing.BOOKKEEPING) {
 146             BarrierTracing.unregisterBAP(this);
 147         }
 148
 149     }
 150
 151 }