Improve performance of currentVersion by caching

src/main/groovy/pl/allegro/tech/build/axion/release/infrastructure/DryRepository.groovy

@@ -20,6 +20,11 @@ class DryRepository implements ScmRepository {
         this.delegateRepository = delegateRepository
     }
 
+    @Override
+    String id() {
+        return delegateRepository.id();
+    }
+
     @Override
     void fetchTags(ScmIdentity identity, String remoteName) {
         log("fetching tags from remote")

src/main/groovy/pl/allegro/tech/build/axion/release/infrastructure/DummyRepository.groovy

@@ -21,6 +21,11 @@ class DummyRepository implements ScmRepository {
         logger.quiet("Couldn't perform $commandName command on uninitialized repository")
     }
 
+    @Override
+    String id() {
+        return "DummyRepository"
+    }
+
     @Override
     void fetchTags(ScmIdentity identity, String remoteName) {
         log('fetch tags')

src/main/groovy/pl/allegro/tech/build/axion/release/infrastructure/git/ScmCache.java

@@ -0,0 +1,106 @@
+package pl.allegro.tech.build.axion.release.infrastructure.git;
+
+import groovy.lang.Tuple2;
+import org.eclipse.jgit.api.Git;
+import org.eclipse.jgit.api.errors.GitAPIException;
+import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.revwalk.RevCommit;
+import org.eclipse.jgit.revwalk.RevWalk;
+import pl.allegro.tech.build.axion.release.domain.scm.ScmException;
+import pl.allegro.tech.build.axion.release.domain.scm.ScmRepository;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Provides cached version for some operations on {@link ScmRepository}
+ */
+public class ScmCache {
+
+    /**
+     * Since this cache is statis and Gradle Demon might keep JVM process in background for a long
+     * time, we have to put some TTL for cached values.
+     */
+    private static final long INVALIDATE_AFTER_MILLIS = 1000 * 60;
+
+    private static final ScmCache CACHE = new ScmCache();
+
+    public static ScmCache getInstance() {
+        return CACHE;
+    }
+
+    private ScmCache() { }
+
+    private final Map<String, CachedState> cache = new HashMap<>();
+
+    synchronized void invalidate(ScmRepository repository) {
+        cache.remove(repository.id());
+    }
+
+    public synchronized boolean checkUncommittedChanges(ScmRepository repository) {
+        CachedState state = retrieveCachedStateFor(repository);
+        if (state.hasUncommittedChanges == null) {
+            state.hasUncommittedChanges = repository.checkUncommittedChanges();
+        }
+        return state.hasUncommittedChanges;
+    }
+
+    synchronized List<Tuple2<Ref, RevCommit>> parsedTagList(ScmRepository repository, Git git, RevWalk walker) throws GitAPIException {
+        CachedState state = retrieveCachedStateFor(repository);
+        if (state.tags == null) {
+            List<Tuple2<Ref, RevCommit>> list = new ArrayList<>();
+            for (Ref tag : git.tagList().call()) {
+                try {
+                    list.add(new Tuple2<>(tag, walker.parseCommit(tag.getObjectId())));
+                } catch (IOException e) {
+                    throw new ScmException(e);
+                }
+            }
+            state.tags = list;
+        }
+        return state.tags;
+    }
+
+    private CachedState retrieveCachedStateFor(ScmRepository scmRepository) {
+        String key = scmRepository.id();
+        String currentHeadRevision = scmRepository.currentPosition().getRevision();
+        long currentTime = System.currentTimeMillis();
+        CachedState state = cache.get(key);
+        if (state == null) {
+            state = new CachedState(currentHeadRevision);
+            cache.put(key, state);
+        } else {
+            if (!currentHeadRevision.equals(state.headRevision) || (state.createTimestamp + INVALIDATE_AFTER_MILLIS) < currentTime) {
+                state = new CachedState(currentHeadRevision);
+                cache.put(key, state);
+            }
+        }
+        return state;
+    }
+
+    /**
+     * Helper object holding cached values per SCM repository
+     */
+    private static class CachedState {
+
+        final long createTimestamp;
+
+        /**
+         * HEAD revision of repo for which this cache was created. Cache has to be invalidated
+         * if HEAD changes.
+         */
+        final String headRevision;
+
+        Boolean hasUncommittedChanges;
+
+        List<Tuple2<Ref, RevCommit>> tags;
+
+        CachedState(String headRevision) {
+            createTimestamp = System.currentTimeMillis();
+            this.headRevision = headRevision;
+        }
+    }
+}

src/main/java/pl/allegro/tech/build/axion/release/domain/VersionResolver.java

@@ -7,6 +7,7 @@
 import pl.allegro.tech.build.axion.release.domain.scm.ScmPosition;
 import pl.allegro.tech.build.axion.release.domain.scm.ScmRepository;
 import pl.allegro.tech.build.axion.release.domain.scm.TaggedCommits;
+import pl.allegro.tech.build.axion.release.infrastructure.git.ScmCache;
 
 import java.util.regex.Pattern;
 
@@ -55,7 +56,7 @@ public VersionContext resolveVersion(VersionProperties versionProperties, TagPro
             versions.onReleaseTag,
             versions.onNextVersionTag,
             versions.noTagsFound,
-            repository.checkUncommittedChanges()
+            ScmCache.getInstance().checkUncommittedChanges(repository)
         );
 
         VersionFactory.FinalVersion finalVersion = versionFactory.createFinalVersion(scmState, versions.current);

src/main/java/pl/allegro/tech/build/axion/release/domain/scm/ScmRepository.java

@@ -5,6 +5,8 @@
 
 public interface ScmRepository {
 
+    String id();
+
     void fetchTags(ScmIdentity identity, String remoteName);
 
     void tag(String tagName);

src/main/java/pl/allegro/tech/build/axion/release/infrastructure/git/GitRepository.java

@@ -1,5 +1,6 @@
 package pl.allegro.tech.build.axion.release.infrastructure.git;
 
+import groovy.lang.Tuple2;
 import org.eclipse.jgit.api.*;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.eclipse.jgit.api.errors.NoHeadException;
@@ -9,13 +10,15 @@
 import org.eclipse.jgit.revwalk.RevSort;
 import org.eclipse.jgit.revwalk.RevWalk;
 import org.eclipse.jgit.transport.*;
+import org.eclipse.jgit.util.FS;
 import pl.allegro.tech.build.axion.release.domain.logging.ReleaseLogger;
 import pl.allegro.tech.build.axion.release.domain.scm.*;
 
 import java.io.File;
 import java.io.IOException;
 import java.net.URISyntaxException;
 import java.util.*;
+import java.util.function.Supplier;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 import java.util.stream.StreamSupport;
@@ -33,7 +36,8 @@ public class GitRepository implements ScmRepository {
     public GitRepository(ScmProperties properties) {
         try {
             this.repositoryDir = properties.getDirectory();
-            this.jgitRepository = Git.open(repositoryDir);
+            RepositoryCache.FileKey key = RepositoryCache.FileKey.lenient(repositoryDir, FS.DETECTED);
+            this.jgitRepository = Git.wrap(RepositoryCache.open(key, true));
             this.properties = properties;
         } catch (RepositoryNotFoundException exception) {
             throw new ScmRepositoryUnavailableException(exception);
@@ -51,6 +55,11 @@ public GitRepository(ScmProperties properties) {
 
     }
 
+    @Override
+    public String id() {
+        return repositoryDir.getAbsolutePath();
+    }
+
     /**
      * This fetch method behaves like git fetch, meaning it only fetches thing without merging.
      * As a result, any fetched tags will not be visible via GitRepository tag listing methods
@@ -93,6 +102,7 @@ public void tag(final String tagName) {
 
             if (!isOnExistingTag) {
                 jgitRepository.tag().setName(tagName).call();
+                ScmCache.getInstance().invalidate(this);
             } else {
                 logger.debug("The head commit " + headId + " already has the tag " + tagName + ".");
             }
@@ -109,6 +119,7 @@ private ObjectId head() throws IOException {
     public void dropTag(String tagName) {
         try {
             jgitRepository.tagDelete().setTags(GIT_TAG_PREFIX + tagName).call();
+            ScmCache.getInstance().invalidate(this);
         } catch (GitAPIException e) {
             throw new ScmException(e);
         }
@@ -139,7 +150,9 @@ public ScmPushResult push(ScmIdentity identity, ScmPushOptions pushOptions, bool
 
     private Iterable<PushResult> callPush(PushCommand pushCommand) {
         try {
-            return pushCommand.call();
+            Iterable<PushResult> result = pushCommand.call();
+            ScmCache.getInstance().invalidate(this);
+            return result;
         } catch (GitAPIException e) {
             throw new ScmException(e);
         }
@@ -204,6 +217,7 @@ public void commit(List<String> patterns, String message) {
             }
 
             jgitRepository.commit().setMessage(message).call();
+            ScmCache.getInstance().invalidate(this);
         } catch (GitAPIException | IOException e) {
             throw new ScmException(e);
         }
@@ -331,39 +345,36 @@ private List<TagsOnCommit> taggedCommitsInternal(Pattern pattern, String maybeSi
                 startingCommit = headId;
             }
 
-
             RevWalk walk = walker(startingCommit);
-            if (!inclusive) {
-                walk.next();
-            }
 
-            Map<String, List<String>> allTags = tagsMatching(pattern, walk);
-
-            RevCommit currentCommit;
-            List<String> currentTagsList;
-            for (currentCommit = walk.next(); currentCommit != null; currentCommit = walk.next()) {
-                currentTagsList = allTags.get(currentCommit.getId().getName());
-
-                if (currentTagsList != null) {
-                    TagsOnCommit taggedCommit = new TagsOnCommit(
-                        currentCommit.getId().name(),
-                        currentTagsList
-                    );
-                    taggedCommits.add(taggedCommit);
-
-                    if (stopOnFirstTag) {
-                        break;
+            try {
+                if (!inclusive) {
+                    walk.next();
+                }
+                Map<String, List<String>> allTags = tagsMatching(pattern, walk);
+                if (stopOnFirstTag) {
+                    // stopOnFirstTag needs to get latest tag, therefore the order does matter
+                    // order is given by walking the repository commits. this can be slower in some
+                    // situations than returning all tagged commits
+                    RevCommit currentCommit;
+                    for (currentCommit = walk.next(); currentCommit != null; currentCommit = walk.next()) {
+                        List<String> tagList = allTags.get(currentCommit.getId().getName());
+                        if (tagList != null) {
+                            TagsOnCommit taggedCommit = new TagsOnCommit(currentCommit.getId().name(), tagList);
+                            taggedCommits.add(taggedCommit);
+                            break;
+                        }
                     }
-
+                } else {
+                    // order not needed, we can just return all tagged commits
+                    allTags.forEach((key, value) -> taggedCommits.add(new TagsOnCommit(key, value)));
                 }
-
+            } finally {
+                walk.dispose();
             }
-
-            walk.dispose();
         } catch (IOException | GitAPIException e) {
             throw new ScmException(e);
         }
-
         return taggedCommits;
     }
 
@@ -380,27 +391,17 @@ private RevWalk walker(ObjectId startingCommit) throws IOException {
     }
 
     private Map<String, List<String>> tagsMatching(Pattern pattern, RevWalk walk) throws GitAPIException {
-        List<Ref> tags = jgitRepository.tagList().call();
+        List<Tuple2<Ref, RevCommit>> parsedTagList = ScmCache.getInstance().parsedTagList(this, jgitRepository, walk);
 
-        return tags.stream()
-            .map(tag -> new TagNameAndId(
-                tag.getName().substring(GIT_TAG_PREFIX.length()),
-                parseCommitSafe(walk, tag.getObjectId())
-            ))
+        return parsedTagList.stream()
+            .map(pair -> new TagNameAndId(
+                pair.getFirst().getName().substring(GIT_TAG_PREFIX.length()),
+                pair.getSecond().getName()))
             .filter(t -> pattern.matcher(t.name).matches())
             .collect(
                 HashMap::new,
                 (m, t) -> m.computeIfAbsent(t.id, (s) -> new ArrayList<>()).add(t.name),
-                HashMap::putAll
-            );
-    }
-
-    private String parseCommitSafe(RevWalk walk, AnyObjectId commitId) {
-        try {
-            return walk.parseCommit(commitId).getName();
-        } catch (IOException e) {
-            throw new ScmException(e);
-        }
+                HashMap::putAll);
     }
 
     private final static class TagNameAndId {