Incremental API and disk format for task caching

build-caching/pom.xml

@@ -23,6 +23,13 @@
             <version>0.15.0</version>
         </dependency>
 
+        <!-- JSON serialization -->
+        <dependency>
+            <groupId>com.google.code.gson</groupId>
+            <artifactId>gson</artifactId>
+            <version>2.8.6</version>
+        </dependency>
+
         <!-- Test -->
         <dependency>
             <groupId>junit</groupId>

build-caching/src/main/java/com/vertispan/j2cl/build/BuildService.java

@@ -1,7 +1,6 @@
 package com.vertispan.j2cl.build;
 
 import com.vertispan.j2cl.build.impl.CollectedTaskInputs;
-import com.vertispan.j2cl.build.task.BuildLog;
 import com.vertispan.j2cl.build.task.OutputTypes;
 import com.vertispan.j2cl.build.task.TaskFactory;
 

build-caching/src/main/java/com/vertispan/j2cl/build/ChangedCachedPath.java

@@ -0,0 +1,36 @@
+package com.vertispan.j2cl.build;
+
+import com.vertispan.j2cl.build.task.CachedPath;
+
+import java.nio.file.Path;
+import java.util.Optional;
+
+/**
+ * Implementation of the ChangedCachedPath interface.
+ */
+public class ChangedCachedPath implements com.vertispan.j2cl.build.task.ChangedCachedPath {
+    private final ChangeType type;
+    private final Path sourcePath;
+    private final CachedPath newIfAny;
+
+    public ChangedCachedPath(ChangeType type, Path sourcePath, CachedPath newPath) {
+        this.type = type;
+        this.sourcePath = sourcePath;
+        this.newIfAny = newPath;
+    }
+
+    @Override
+    public ChangeType changeType() {
+        return type;
+    }
+
+    @Override
+    public Path getSourcePath() {
+        return sourcePath;
+    }
+
+    @Override
+    public Optional<Path> getNewAbsolutePath() {
+        return Optional.ofNullable(newIfAny).map(CachedPath::getAbsolutePath);
+    }
+}

build-caching/src/main/java/com/vertispan/j2cl/build/DefaultDiskCache.java

@@ -29,28 +29,8 @@ public DefaultDiskCache(File cacheDir, Executor executor) throws IOException {
     }
 
     @Override
-    protected Path taskDir(CollectedTaskInputs inputs) {
-        String projectName = inputs.getProject().getKey();
-        Murmur3F hash = new Murmur3F();
-
-        hash.update(inputs.getTaskFactory().getClass().toString().getBytes(StandardCharsets.UTF_8));
-        hash.update(inputs.getTaskFactory().getTaskName().getBytes(StandardCharsets.UTF_8));
-        hash.update(inputs.getTaskFactory().getVersion().getBytes(StandardCharsets.UTF_8));
-
-        for (Input input : inputs.getInputs()) {
-            input.updateHash(hash);
-        }
-
-        for (Map.Entry<String, String> entry : inputs.getUsedConfigs().entrySet()) {
-            hash.update(entry.getKey().getBytes(StandardCharsets.UTF_8));
-            if (entry.getValue() == null) {
-                hash.update(0);
-            } else {
-                hash.update(entry.getValue().getBytes(StandardCharsets.UTF_8));
-            }
-        }
-
-        return cacheDir.toPath().resolve(projectName.replaceAll("[^\\-_a-zA-Z0-9.]", "-")).resolve(hash.getValueHexString() + "-" + inputs.getTaskFactory().getOutputType());
+    protected Path taskDir(String projectName, String hashString, String outputType) {
+        return cacheDir.toPath().resolve(projectName.replaceAll("[^\\-_a-zA-Z0-9.]", "-")).resolve(hashString + "-" + outputType);
     }
 
     @Override
@@ -72,4 +52,9 @@ protected Path logFile(Path taskDir) {
     protected Path outputDir(Path taskDir) {
         return taskDir.resolve("results");
     }
+
+    @Override
+    protected Path cacheSummary(Path taskDir) {
+        return taskDir.resolve("cacheSummary.json");
+    }
 }

build-caching/src/main/java/com/vertispan/j2cl/build/DiskCache.java

@@ -1,30 +1,32 @@
 package com.vertispan.j2cl.build;
 
+import com.google.gson.GsonBuilder;
 import com.vertispan.j2cl.build.impl.CollectedTaskInputs;
 import com.vertispan.j2cl.build.task.CachedPath;
 import io.methvin.watcher.PathUtils;
 import io.methvin.watcher.hashing.FileHash;
 import io.methvin.watcher.hashing.FileHasher;
+import io.methvin.watcher.hashing.Murmur3F;
 import io.methvin.watchservice.MacOSXListeningWatchService;
 import io.methvin.watchservice.WatchablePath;
 
 import java.io.File;
 import java.io.IOException;
 import java.io.UncheckedIOException;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.WatchService;
 import java.nio.file.*;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.nio.file.attribute.FileTime;
 import java.time.Instant;
-import java.time.temporal.TemporalAmount;
-import java.time.temporal.TemporalUnit;
 import java.util.*;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Executor;
+import java.util.stream.Collectors;
 
 /**
- * Manages the cached task inputs and outputs.
+ * Manages the cached task inputs and outputs, without direct knowledge of the project or task apis.
  */
 public abstract class DiskCache {
     private static final boolean IS_MAC = System.getProperty("os.name").toLowerCase().contains("mac");
@@ -38,6 +40,10 @@ public CacheResult(Path taskDir) {
             this.taskDir = taskDir;
         }
 
+        public Path taskDir() {
+            return taskDir;
+        }
+
         public Path logFile() {
             //TODO finish building a logger that will write to this
             return DiskCache.this.logFile(taskDir);
@@ -54,6 +60,10 @@ public TaskOutput output() {
             return taskOutput;
         }
 
+        public Path cachedSummary() {
+            return DiskCache.this.cacheSummary(taskDir);
+        }
+
         public void markSuccess() {
             markFinished(this);
             runningTasks.remove(taskDir);
@@ -237,7 +247,9 @@ public Path getAbsolutePath() {
             return absoluteParent.resolve(sourcePath);
         }
 
-        @Override
+        /**
+         * Internal API, as this is not at this time used by any caller.
+         */
         public FileHash getHash() {
             return hash;
         }
@@ -340,16 +352,57 @@ private void deleteRecursively(Path path) throws IOException {
         }
     }
 
-    protected abstract Path taskDir(CollectedTaskInputs inputs);
+    private String taskSummaryContents(CollectedTaskInputs inputs) {
+        TaskSummaryDiskFormat src = new TaskSummaryDiskFormat();
+        src.setProjectKey(inputs.getProject().getKey());
+        src.setOutputType(inputs.getTaskFactory().getOutputType());
+        src.setTaskImpl(inputs.getTaskFactory().getClass().getName());
+        src.setTaskImplVersion(inputs.getTaskFactory().getVersion());
+
+        src.setInputs(inputs.getInputs().stream()
+                .map(Input::makeDiskFormat)
+                .collect(Collectors.groupingBy(i -> i.getProjectKey() + "-" + i.getOutputType()))
+                .values().stream()
+                .map(list -> {
+                    TaskSummaryDiskFormat.InputDiskFormat result = new TaskSummaryDiskFormat.InputDiskFormat();
+                    result.setProjectKey(list.get(0).getProjectKey());
+                    result.setOutputType(list.get(0).getOutputType());
+
+                    result.setFileHashes(
+                            list.stream().flatMap(i -> i.getFileHashes().entrySet().stream())
+                                    .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue, (left, right) -> {
+                                        if (left.equals(right)) {
+                                            return left;
+                                        }
+                                        throw new IllegalStateException("Two hashes for one file! " + left + " vs " + right);
+                                    }))
+                    );
+
+                    return result;
+                })
+                .collect(Collectors.toUnmodifiableList()));
+
+        src.setConfigs(inputs.getUsedConfigs());
+
+        return new GsonBuilder().serializeNulls().setPrettyPrinting().create().toJson(src);
+    }
+
+    protected abstract Path taskDir(String projectName, String hashString, String outputType);
+
     protected abstract Path successMarker(Path taskDir);
     protected abstract Path failureMarker(Path taskDir);
     protected abstract Path logFile(Path taskDir);
     protected abstract Path outputDir(Path taskDir);
+    protected abstract Path cacheSummary(Path taskDir);
 
     interface Listener {
+        /** Ready for the current listener to do the work */
         void onReady(CacheResult result);
+        /** Someone else did it, but failed for some reason, not re-runnable */
         void onFailure(CacheResult result);
+        /** Someone else tried to do it, but ran into an error, possibly recoverable if we try again */
         void onError(Throwable throwable);
+        /** Someone else finished it, successfully, notify listeners */
         void onSuccess(CacheResult result);
     }
     public class PendingCacheResult implements Cancelable {
@@ -431,7 +484,14 @@ private synchronized void failure() {
      */
     public void waitForTask(CollectedTaskInputs taskDetails, Listener listener) {
         assert taskDetails.getInputs().stream().allMatch(Input::hasContents);
-        final Path taskDir = taskDir(taskDetails);
+
+        Murmur3F murmur3F = new Murmur3F();
+        byte[] taskSummaryContents = taskSummaryContents(taskDetails).getBytes(StandardCharsets.UTF_8);
+        murmur3F.update(taskSummaryContents);
+        String hashString = murmur3F.getValueHexString();
+
+        final Path taskDir = taskDir(taskDetails.getProject().getKey(), hashString, taskDetails.getTaskFactory().getOutputType());
+
         PendingCacheResult cancelable = new PendingCacheResult(taskDir, listener);
         taskFutures.computeIfAbsent(taskDir, ignore -> Collections.newSetFromMap(new ConcurrentHashMap<>())).add(cancelable);
         try {
@@ -449,6 +509,7 @@ public void waitForTask(CollectedTaskInputs taskDetails, Listener listener) {
                 // caller can begin work right away
                 Files.createDirectory(outputDir);
                 Files.createFile(logFile(taskDir));
+                Files.write(cacheSummary(taskDir), taskSummaryContents);
                 cancelable.ready();
                 return;
             }
@@ -546,4 +607,13 @@ public void markFailed(CacheResult failedResult) {
         }
     }
 
+    public Optional<CacheResult> getCacheResult(Path taskDir) {
+        if (Files.exists(taskDir) || Files.exists(successMarker(taskDir))) {
+            CacheResult result = new CacheResult(taskDir);
+            knownOutputs.computeIfAbsent(taskDir, this::makeOutput);
+            return Optional.of(result);
+        }
+        return Optional.empty();
+    }
+
 }

build-caching/src/main/java/com/vertispan/j2cl/build/Input.java

@@ -1,8 +1,7 @@
 package com.vertispan.j2cl.build;
 
-import io.methvin.watcher.hashing.Murmur3F;
+import com.vertispan.j2cl.build.task.ChangedCachedPath;
 
-import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.nio.file.PathMatcher;
 import java.util.*;
@@ -18,10 +17,29 @@
  * interested in, and take the hash of the hashes to represent
  */
 public class Input implements com.vertispan.j2cl.build.task.Input {
+    public interface BuildSpecificChanges {
+        List<? extends ChangedCachedPath> compute();
+        static BuildSpecificChanges memoize(BuildSpecificChanges changes) {
+            return new BuildSpecificChanges() {
+                private List<ChangedCachedPath> results;
+                @Override
+                public List<ChangedCachedPath> compute() {
+                    if (results == null) {
+                        List<? extends ChangedCachedPath> computed = changes.compute();
+                        assert computed != null;
+                        results = new ArrayList<>(computed);
+                    }
+
+                    return results;
+                }
+            };
+        }
+    }
     private final Project project;
     private final String outputType;
 
     private TaskOutput contents;
+    private BuildSpecificChanges buildSpecificChanges;
 
     public Input(Project project, String outputType) {
         this.project = project;
@@ -66,6 +84,13 @@ public Collection<DiskCache.CacheEntry> getFilesAndHashes() {
                     .collect(Collectors.toUnmodifiableList());
         }
 
+        @Override
+        public Collection<? extends ChangedCachedPath> getChanges() {
+            return wrapped.getChanges().stream()
+                    .filter(entry -> Arrays.stream(filters).anyMatch(f -> f.matches(entry.getSourcePath())))
+                    .collect(Collectors.toUnmodifiableList());
+        }
+
         @Override
         public com.vertispan.j2cl.build.task.Project getProject() {
             return wrapped.getProject();
@@ -103,17 +128,37 @@ public void setCurrentContents(TaskOutput contents) {
     /**
      * Internal API.
      *
-     * Updates the given hash object with the filtered file inputs - their paths and their
-     * hashes, so that if files are moved or changed we change the hash value, but we don't
-     * re-hash each file every time we ask.
+     * Once a task is finished, we can let it be used by other tasks as an input. In
+     * order for those tasks to execute incrementally, each particular Input must
+     * only have changed relative to the last time that its owner task ran successfully.
+     * Instead of being set all at once, this is re-assigned before each task actually
+     * executes.
      */
-    public void updateHash(Murmur3F hash) {
-        for (DiskCache.CacheEntry fileAndHash : getFilesAndHashes()) {
-            hash.update(fileAndHash.getSourcePath().toString().getBytes(StandardCharsets.UTF_8));
-            hash.update(fileAndHash.getHash().asBytes());
-        }
+    public void setBuildSpecificChanges(BuildSpecificChanges buildSpecificChanges) {
+        this.buildSpecificChanges = BuildSpecificChanges.memoize(buildSpecificChanges);
     }
 
+    /**
+     * Internal API.
+     *
+     * Creates a simple payload that describes this input, so it can be written to disk.
+     */
+    public TaskSummaryDiskFormat.InputDiskFormat makeDiskFormat() {
+        TaskSummaryDiskFormat.InputDiskFormat out = new TaskSummaryDiskFormat.InputDiskFormat();
+
+        out.setProjectKey(getProject().getKey());
+        out.setOutputType(getOutputType());
+
+        out.setFileHashes(getFilesAndHashes().stream().collect(Collectors.toMap(
+                e -> e.getSourcePath().toString(),
+                e -> e.getHash().asString()
+        )));
+
+        return out;
+    }
+
+
+
     @Override
     public Project getProject() {
         return project;
@@ -139,6 +184,14 @@ public Collection<DiskCache.CacheEntry> getFilesAndHashes() {
         return contents.filesAndHashes();
     }
 
+    @Override
+    public Collection<? extends ChangedCachedPath> getChanges() {
+        if (buildSpecificChanges == null) {
+            throw new NullPointerException("Changes not yet provided " + this);
+        }
+        return buildSpecificChanges.compute();
+    }
+
     @Override
     public String toString() {
         return "Input{" +