Implement and test SwapJobImpl

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/application/config/Config.java

@@ -4,12 +4,16 @@ import com.google.gson.Gson;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import uk.ac.ic.wlgitbridge.application.exception.ConfigFileException;
+import uk.ac.ic.wlgitbridge.bridge.swap.job.SwapJobConfig;
+import uk.ac.ic.wlgitbridge.bridge.swap.store.SwapStoreConfig;
 import uk.ac.ic.wlgitbridge.snapshot.base.JSONSource;
 import uk.ac.ic.wlgitbridge.util.Instance;
 
+import javax.annotation.Nullable;
 import java.io.FileReader;
 import java.io.IOException;
 import java.io.Reader;
+import java.util.Optional;
 
 /**
  * Created by Winston on 05/12/14.
@@ -36,7 +40,12 @@ public class Config implements JSONSource {
     private String apiBaseURL;
     private String postbackURL;
     private String serviceName;
+    @Nullable
     private Oauth2 oauth2;
+    @Nullable
+    private SwapStoreConfig swapStore;
+    @Nullable
+    private SwapJobConfig swapJob;
 
     public Config(String configFilePath) throws ConfigFileException,
                                                 IOException {
@@ -134,6 +143,14 @@ public class Config implements JSONSource {
         return oauth2;
     }
 
+    public Optional<SwapStoreConfig> getSwapStore() {
+        return Optional.ofNullable(swapStore);
+    }
+
+    public Optional<SwapJobConfig> getSwapJob() {
+        return Optional.ofNullable(swapJob);
+    }
+
     private JsonElement getElement(JsonObject configObject, String name) {
         JsonElement element = configObject.get(name);
         if (element == null) {

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/Bridge.java

@@ -9,10 +9,9 @@ import uk.ac.ic.wlgitbridge.bridge.resource.ResourceCache;
 import uk.ac.ic.wlgitbridge.bridge.resource.UrlResourceCache;
 import uk.ac.ic.wlgitbridge.bridge.snapshot.NetSnapshotAPI;
 import uk.ac.ic.wlgitbridge.bridge.snapshot.SnapshotAPI;
-import uk.ac.ic.wlgitbridge.bridge.swap.SwapJob;
-import uk.ac.ic.wlgitbridge.bridge.swap.SwapJobConfig;
-import uk.ac.ic.wlgitbridge.bridge.swap.SwapJobImpl;
-import uk.ac.ic.wlgitbridge.bridge.swap.SwapStore;
+import uk.ac.ic.wlgitbridge.bridge.swap.job.SwapJob;
+import uk.ac.ic.wlgitbridge.bridge.swap.job.SwapJobConfig;
+import uk.ac.ic.wlgitbridge.bridge.swap.store.SwapStore;
 import uk.ac.ic.wlgitbridge.data.CandidateSnapshot;
 import uk.ac.ic.wlgitbridge.data.ProjectLockImpl;
 import uk.ac.ic.wlgitbridge.data.filestore.GitDirectoryContents;
@@ -31,7 +30,6 @@ import uk.ac.ic.wlgitbridge.snapshot.push.exception.*;
 import uk.ac.ic.wlgitbridge.util.Log;
 
 import java.io.IOException;
-import java.time.Duration;
 import java.util.*;
 
 /**
@@ -56,7 +54,7 @@ public class Bridge {
             RepoStore repoStore,
             DBStore dbStore,
             SwapStore swapStore,
-            SwapJobConfig swapJobConfig
+            Optional<SwapJobConfig> swapJobConfig
     ) {
         ProjectLock lock = new ProjectLockImpl((int threads) ->
                 Log.info("Waiting for " + threads + " projects...")
@@ -66,7 +64,7 @@ public class Bridge {
                 repoStore,
                 dbStore,
                 swapStore,
-                new SwapJobImpl(
+                SwapJob.fromConfig(
                         swapJobConfig,
                         lock,
                         repoStore,
@@ -108,8 +106,8 @@ public class Bridge {
         Log.info("Bye");
     }
 
-    public void startSwapJob(Duration interval) {
-        swapJob.start(interval);
+    public void startSwapJob() {
+        swapJob.start();
     }
 
     /* TODO: Remove these when WLBridged is moved into RepoStore */

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/db/DBStore.java

@@ -24,6 +24,8 @@ public interface DBStore {
 
     String getOldestUnswappedProject();
 
+    int getNumUnswappedProjects();
+
     /**
      * Sets the last accessed time for the given project name.
      * @param projectName the project's name

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/db/sqlite/SqliteDBStore.java

@@ -86,6 +86,11 @@ public class SqliteDBStore implements DBStore {
         return query(new GetOldestProjectName());
     }
 
+    @Override
+    public int getNumUnswappedProjects() {
+        return query(new GetNumUnswappedProjects());
+    }
+
     @Override
     public void setLastAccessedTime(
             String projectName,

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/db/sqlite/query/GetNumUnswappedProjects.java

@@ -0,0 +1,31 @@
+package uk.ac.ic.wlgitbridge.bridge.db.sqlite.query;
+
+import uk.ac.ic.wlgitbridge.bridge.db.sqlite.SQLQuery;
+
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+/**
+ * Created by winston on 24/08/2016.
+ */
+public class GetNumUnswappedProjects implements SQLQuery<Integer> {
+
+    private static final String GET_NUM_UNSWAPPED_PROJECTS =
+            "SELECT COUNT(*)\n" +
+            "    FROM `swap_table`\n" +
+            "    WHERE `last_accessed` IS NOT NULL";
+
+    @Override
+    public String getSQL() {
+        return GET_NUM_UNSWAPPED_PROJECTS;
+    }
+
+    @Override
+    public Integer processResultSet(ResultSet resultSet) throws SQLException {
+        while (resultSet.next()) {
+            return resultSet.getInt("COUNT(*)");
+        }
+        throw new IllegalStateException("Count always returns results");
+    }
+
+}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/lock/LockGuard.java

@@ -0,0 +1,10 @@
+package uk.ac.ic.wlgitbridge.bridge.lock;
+
+/**
+ * Created by winston on 24/08/2016.
+ */
+public interface LockGuard extends AutoCloseable {
+
+    void close();
+
+}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/lock/ProjectLock.java

@@ -4,9 +4,17 @@ package uk.ac.ic.wlgitbridge.bridge.lock;
  * Created by winston on 20/08/2016.
  */
 public interface ProjectLock {
+
     void lockAll();
 
     void lockForProject(String projectName);
 
     void unlockForProject(String projectName);
+
+    /* RAII hahaha */
+    default LockGuard lockGuard(String projectName) {
+        lockForProject(projectName);
+        return () -> unlockForProject(projectName);
+    }
+
 }

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/repo/FSRepoStore.java

@@ -58,9 +58,12 @@ public class FSRepoStore implements RepoStore {
     }
 
     @Override
-    public InputStream bzip2Project(String projectName) throws IOException {
+    public InputStream bzip2Project(
+            String projectName,
+            long[] sizePtr
+    ) throws IOException {
         Preconditions.checkArgument(Project.isValidProjectName(projectName));
-        return Tar.bz2.zip(getDotGitForProject(projectName));
+        return Tar.bz2.zip(getDotGitForProject(projectName), sizePtr);
     }
 
     @Override

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/repo/RepoStore.java

@@ -25,7 +25,16 @@ public interface RepoStore {
      * IOException if the project doesn't exist. The returned stream is a copy
      * of the original .git directory, which must be deleted using remove().
      */
-    InputStream bzip2Project(String projectName) throws IOException;
+    InputStream bzip2Project(
+            String projectName,
+            long[] sizePtr
+    ) throws IOException;
+
+    default InputStream bzip2Project(
+            String projectName
+    ) throws IOException {
+        return bzip2Project(projectName, null);
+    }
 
     void remove(String projectName) throws IOException;
 
@@ -36,6 +45,9 @@ public interface RepoStore {
      * @param projectName the name of the project, e.g. abc123
      * @param dataStream the data stream containing the bzipped contents.
      */
-    void unbzip2Project(String projectName, InputStream dataStream) throws IOException;
+    void unbzip2Project(
+            String projectName,
+            InputStream dataStream
+    ) throws IOException;
 
 }

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/SwapJob.java

@@ -1,14 +0,0 @@
-package uk.ac.ic.wlgitbridge.bridge.swap;
-
-import java.time.Duration;
-
-/**
- * Created by winston on 20/08/2016.
- */
-public interface SwapJob {
-
-    void start(Duration interval);
-
-    void stop();
-
-}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/SwapJobConfig.java

@@ -1,33 +0,0 @@
-package uk.ac.ic.wlgitbridge.bridge.swap;
-
-/**
- * Created by winston on 23/08/2016.
- */
-public class SwapJobConfig {
-
-    public static final SwapJobConfig DEFAULT =
-            new SwapJobConfig(1, 1, 2);
-
-    private final int minProjects;
-    private final long lowGiB;
-    private final long highGiB;
-
-    public SwapJobConfig(int minProjects, long lowGiB, long highGiB) {
-        this.minProjects = minProjects;
-        this.lowGiB = lowGiB;
-        this.highGiB = highGiB;
-    }
-
-    public int getMinProjects() {
-        return minProjects;
-    }
-
-    public long getLowGiB() {
-        return lowGiB;
-    }
-
-    public long getHighGiB() {
-        return highGiB;
-    }
-
-}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/SwapJobImpl.java

@@ -1,73 +0,0 @@
-package uk.ac.ic.wlgitbridge.bridge.swap;
-
-import uk.ac.ic.wlgitbridge.bridge.db.DBStore;
-import uk.ac.ic.wlgitbridge.bridge.lock.ProjectLock;
-import uk.ac.ic.wlgitbridge.bridge.repo.RepoStore;
-import uk.ac.ic.wlgitbridge.util.Log;
-
-import java.time.Duration;
-import java.util.Timer;
-import java.util.concurrent.atomic.AtomicInteger;
-
-/**
- * Created by winston on 20/08/2016.
- */
-public class SwapJobImpl implements SwapJob {
-
-    private final int minProjects;
-    private final long lowGiB;
-    private final long highGiB;
-
-    private final ProjectLock lock;
-    private final RepoStore repoStore;
-    private final SwapStore swapStore;
-    private final DBStore dbStore;
-
-    private final Timer timer;
-
-    final AtomicInteger swaps;
-
-    public SwapJobImpl(
-            SwapJobConfig cfg,
-            ProjectLock lock,
-            RepoStore repoStore,
-            DBStore dbStore,
-            SwapStore swapStore
-    ) {
-        minProjects = cfg.getMinProjects();
-        lowGiB = cfg.getLowGiB();
-        highGiB = cfg.getHighGiB();
-        this.lock = lock;
-        this.repoStore = repoStore;
-        this.swapStore = swapStore;
-        this.dbStore = dbStore;
-        timer = new Timer();
-        swaps = new AtomicInteger(0);
-    }
-
-    @Override
-    public void start(Duration interval) {
-        timer.scheduleAtFixedRate(
-                uk.ac.ic.wlgitbridge.util.Timer.makeTimerTask(this::doSwap),
-                0,
-                interval.toMillis()
-        );
-    }
-
-    @Override
-    public void stop() {
-        timer.cancel();
-    }
-
-    private void doSwap() {
-        Log.info("Running {}th swap", swaps.getAndIncrement());
-        while (repoStore.totalSize() > lowGiB) {
-            doEvict();
-        }
-    }
-
-    private void doEvict() {
-        dbStore.getOldestUnswappedProject();
-    }
-
-}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/SwapStore.java

@@ -1,21 +0,0 @@
-package uk.ac.ic.wlgitbridge.bridge.swap;
-
-import java.io.IOException;
-import java.io.InputStream;
-
-/**
- * Created by winston on 20/08/2016.
- */
-public interface SwapStore {
-
-    void upload(
-            String projectName,
-            InputStream uploadStream,
-            long contentLength
-    ) throws IOException;
-
-    InputStream openDownloadStream(String projectName);
-
-    void remove(String projectName);
-
-}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/job/NoopSwapJob.java

@@ -0,0 +1,30 @@
+package uk.ac.ic.wlgitbridge.bridge.swap.job;
+
+import java.io.IOException;
+
+/**
+ * Created by winston on 24/08/2016.
+ */
+public class NoopSwapJob implements SwapJob {
+
+    @Override
+    public void start() {
+
+    }
+
+    @Override
+    public void stop() {
+
+    }
+
+    @Override
+    public void evict(String projName) throws IOException {
+
+    }
+
+    @Override
+    public void restore(String projName) throws IOException {
+
+    }
+
+}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/job/SwapJob.java

@@ -0,0 +1,42 @@
+package uk.ac.ic.wlgitbridge.bridge.swap.job;
+
+import uk.ac.ic.wlgitbridge.bridge.db.DBStore;
+import uk.ac.ic.wlgitbridge.bridge.lock.ProjectLock;
+import uk.ac.ic.wlgitbridge.bridge.repo.RepoStore;
+import uk.ac.ic.wlgitbridge.bridge.swap.store.SwapStore;
+
+import java.io.IOException;
+import java.util.Optional;
+
+/**
+ * Created by winston on 20/08/2016.
+ */
+public interface SwapJob {
+
+    static SwapJob fromConfig(
+            Optional<SwapJobConfig> cfg,
+            ProjectLock lock,
+            RepoStore repoStore,
+            DBStore dbStore,
+            SwapStore swapStore
+    ) {
+        if (cfg.isPresent()) {
+            return new SwapJobImpl(
+                    cfg.get(),
+                    lock,
+                    repoStore,
+                    dbStore,
+                    swapStore
+            );
+        }
+        return new NoopSwapJob();
+    }
+
+    void start();
+
+    void stop();
+
+    void evict(String projName) throws IOException;
+
+    void restore(String projName) throws IOException;
+}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/job/SwapJobConfig.java

@@ -0,0 +1,44 @@
+package uk.ac.ic.wlgitbridge.bridge.swap.job;
+
+/**
+ * Created by winston on 23/08/2016.
+ */
+public class SwapJobConfig {
+
+    public static final SwapJobConfig DEFAULT =
+            new SwapJobConfig(1, 1, 2, 3600000);
+
+    private final int minProjects;
+    private final int lowGiB;
+    private final int highGiB;
+    private final long intervalMillis;
+
+    public SwapJobConfig(
+            int minProjects,
+            int lowGiB,
+            int highGiB,
+            long intervalMillis
+    ) {
+        this.minProjects = minProjects;
+        this.lowGiB = lowGiB;
+        this.highGiB = highGiB;
+        this.intervalMillis = intervalMillis;
+    }
+
+    public int getMinProjects() {
+        return minProjects;
+    }
+
+    public int getLowGiB() {
+        return lowGiB;
+    }
+
+    public int getHighGiB() {
+        return highGiB;
+    }
+
+    public long getIntervalMillis() {
+        return intervalMillis;
+    }
+
+}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/job/SwapJobImpl.java

@@ -0,0 +1,163 @@
+package uk.ac.ic.wlgitbridge.bridge.swap.job;
+
+import com.google.api.client.repackaged.com.google.common.base.Preconditions;
+import uk.ac.ic.wlgitbridge.bridge.db.DBStore;
+import uk.ac.ic.wlgitbridge.bridge.lock.LockGuard;
+import uk.ac.ic.wlgitbridge.bridge.lock.ProjectLock;
+import uk.ac.ic.wlgitbridge.bridge.repo.RepoStore;
+import uk.ac.ic.wlgitbridge.bridge.swap.store.SwapStore;
+import uk.ac.ic.wlgitbridge.util.Log;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.sql.Timestamp;
+import java.time.Duration;
+import java.time.LocalDateTime;
+import java.util.Timer;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * Created by winston on 20/08/2016.
+ */
+public class SwapJobImpl implements SwapJob {
+
+    private static final long GiB = (1l << 30);
+
+    int minProjects;
+    long lowWatermarkBytes;
+    long highWatermarkBytes;
+    Duration interval;
+
+    private final ProjectLock lock;
+    private final RepoStore repoStore;
+    private final DBStore dbStore;
+    private final SwapStore swapStore;
+
+    private final Timer timer;
+
+    final AtomicInteger swaps;
+
+    public SwapJobImpl(
+            SwapJobConfig cfg,
+            ProjectLock lock,
+            RepoStore repoStore,
+            DBStore dbStore,
+            SwapStore swapStore
+    ) {
+        this(
+                cfg.getMinProjects(),
+                GiB * cfg.getLowGiB(),
+                GiB * cfg.getHighGiB(),
+                Duration.ofMillis(cfg.getIntervalMillis()),
+                lock,
+                repoStore,
+                dbStore,
+                swapStore
+        );
+    }
+
+    SwapJobImpl(
+            int minProjects,
+            long lowWatermarkBytes,
+            long highWatermarkBytes,
+            Duration interval,
+            ProjectLock lock,
+            RepoStore repoStore,
+            DBStore dbStore,
+            SwapStore swapStore
+    ) {
+        this.minProjects = minProjects;
+        this.lowWatermarkBytes = lowWatermarkBytes;
+        this.highWatermarkBytes = highWatermarkBytes;
+        this.interval = interval;
+        this.lock = lock;
+        this.repoStore = repoStore;
+        this.dbStore = dbStore;
+        this.swapStore = swapStore;
+        timer = new Timer();
+        swaps = new AtomicInteger(0);
+    }
+
+    @Override
+    public void start() {
+        timer.scheduleAtFixedRate(
+                uk.ac.ic.wlgitbridge.util.Timer.makeTimerTask(this::doSwap),
+                0,
+                interval.toMillis()
+        );
+    }
+
+    @Override
+    public void stop() {
+        timer.cancel();
+    }
+
+    private void doSwap() {
+        Log.info("Running swap number {}", swaps.get() + 1);
+        long totalSize = repoStore.totalSize();
+        Log.info("Size is {}/{} (high)", totalSize, highWatermarkBytes);
+        if (totalSize < highWatermarkBytes) {
+            Log.info("No need to swap.");
+            swaps.incrementAndGet();
+            return;
+        }
+        int numProjects = dbStore.getNumProjects();
+        while (
+                (totalSize = repoStore.totalSize()) > lowWatermarkBytes &&
+                (numProjects = dbStore.getNumUnswappedProjects()) > minProjects
+        ) {
+            try {
+                evict(dbStore.getOldestUnswappedProject());
+            } catch (IOException e) {
+                Log.warn("Exception while swapping, giving up", e);
+            }
+        }
+        if (totalSize > lowWatermarkBytes) {
+            Log.warn(
+                    "Finished swapping, but total size is still too high."
+            );
+        }
+        Log.info(
+                "Size: {}/{} (low), " +
+                        "{} (high), " +
+                        "projects on disk: {}/{}, " +
+                        "min projects on disk: {}",
+                totalSize,
+                lowWatermarkBytes,
+                highWatermarkBytes,
+                numProjects,
+                dbStore.getNumProjects(),
+                minProjects
+        );
+        swaps.incrementAndGet();
+    }
+
+    @Override
+    public void evict(String projName) throws IOException {
+        Preconditions.checkNotNull(projName);
+        Log.info("Evicting project: {}", projName);
+        try (LockGuard __ = lock.lockGuard(projName)) {
+            long[] sizePtr = new long[1];
+            InputStream bzipped = repoStore.bzip2Project(projName, sizePtr);
+            swapStore.upload(projName, bzipped, sizePtr[0]);
+            dbStore.setLastAccessedTime(projName, null);
+            repoStore.remove(projName);
+        }
+        Log.info("Evicted project: {}", projName);
+    }
+
+    @Override
+    public void restore(String projName) throws IOException {
+        try (LockGuard __ = lock.lockGuard(projName)) {
+            repoStore.unbzip2Project(
+                    projName,
+                    swapStore.openDownloadStream(projName)
+            );
+            dbStore.setLastAccessedTime(
+                    projName,
+                    Timestamp.valueOf(LocalDateTime.now())
+            );
+        }
+    }
+
+}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/InMemorySwapStore.java → services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/store/InMemorySwapStore.java

@@ -1,4 +1,4 @@
-package uk.ac.ic.wlgitbridge.bridge.swap;
+package uk.ac.ic.wlgitbridge.bridge.swap.store;
 
 import org.apache.commons.io.IOUtils;
 

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/store/NoopSwapStore.java

@@ -0,0 +1,35 @@
+package uk.ac.ic.wlgitbridge.bridge.swap.store;
+
+import java.io.ByteArrayInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+
+/**
+ * Created by winston on 24/08/2016.
+ */
+public class NoopSwapStore implements SwapStore {
+
+    public NoopSwapStore(SwapStoreConfig config) {
+
+    }
+
+    @Override
+    public void upload(
+            String projectName,
+            InputStream uploadStream,
+            long contentLength
+    ) throws IOException {
+
+    }
+
+    @Override
+    public InputStream openDownloadStream(String projectName) {
+        return new ByteArrayInputStream(new byte[0]);
+    }
+
+    @Override
+    public void remove(String projectName) {
+
+    }
+
+}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/S3SwapStore.java → services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/store/S3SwapStore.java

@@ -1,4 +1,4 @@
-package uk.ac.ic.wlgitbridge.bridge.swap;
+package uk.ac.ic.wlgitbridge.bridge.swap.store;
 
 import com.amazonaws.auth.BasicAWSCredentials;
 import com.amazonaws.services.s3.AmazonS3;
@@ -16,7 +16,15 @@ public class S3SwapStore implements SwapStore {
 
     private final String bucketName;
 
-    public S3SwapStore(
+    public S3SwapStore(SwapStoreConfig cfg) {
+        this(
+                cfg.getAwsAccessKey(),
+                cfg.getAwsSecret(),
+                cfg.getS3BucketName()
+        );
+    }
+
+    S3SwapStore(
             String accessKey,
             String secret,
             String bucketName

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/store/SwapStore.java

@@ -0,0 +1,43 @@
+package uk.ac.ic.wlgitbridge.bridge.swap.store;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Optional;
+import java.util.function.Function;
+
+/**
+ * Created by winston on 20/08/2016.
+ */
+public interface SwapStore {
+
+    Map<String, Function<SwapStoreConfig, SwapStore>> swapStores =
+            new HashMap<String, Function<SwapStoreConfig, SwapStore>>() {
+
+                {
+                    put("noop", NoopSwapStore::new);
+                    put("s3", S3SwapStore::new);
+                }
+
+            };
+
+    static SwapStore fromConfig(
+            Optional<SwapStoreConfig> cfg
+    ) {
+        SwapStoreConfig cfg_ = cfg.orElse(SwapStoreConfig.NOOP);
+        String type = cfg_.getType();
+        return swapStores.get(type).apply(cfg_);
+    }
+
+    void upload(
+            String projectName,
+            InputStream uploadStream,
+            long contentLength
+    ) throws IOException;
+
+    InputStream openDownloadStream(String projectName);
+
+    void remove(String projectName);
+
+}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/bridge/swap/store/SwapStoreConfig.java

@@ -0,0 +1,63 @@
+package uk.ac.ic.wlgitbridge.bridge.swap.store;
+
+/**
+ * Created by winston on 24/08/2016.
+ */
+public class SwapStoreConfig {
+
+    public static final SwapStoreConfig NOOP = new SwapStoreConfig(
+            "noop",
+            null,
+            null,
+            null
+    );
+
+    private String type;
+    private String awsAccessKey;
+    private String awsSecret;
+    private String s3BucketName;
+
+    public SwapStoreConfig() {}
+
+    public SwapStoreConfig(
+            String awsAccessKey,
+            String awsSecret,
+            String s3BucketName
+    ) {
+        this(
+                "s3",
+                awsAccessKey,
+                awsSecret,
+                s3BucketName
+        );
+    }
+
+    SwapStoreConfig(
+            String type,
+            String awsAccessKey,
+            String awsSecret,
+            String s3BucketName
+    ) {
+        this.type = type;
+        this.awsAccessKey = awsAccessKey;
+        this.awsSecret = awsSecret;
+        this.s3BucketName = s3BucketName;
+    }
+
+    public String getType() {
+        return type;
+    }
+
+    public String getAwsAccessKey() {
+        return awsAccessKey;
+    }
+
+    public String getAwsSecret() {
+        return awsSecret;
+    }
+
+    public String getS3BucketName() {
+        return s3BucketName;
+    }
+
+}

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/server/GitBridgeServer.java

@@ -13,8 +13,7 @@ import uk.ac.ic.wlgitbridge.bridge.db.DBStore;
 import uk.ac.ic.wlgitbridge.bridge.db.sqlite.SqliteDBStore;
 import uk.ac.ic.wlgitbridge.bridge.repo.FSRepoStore;
 import uk.ac.ic.wlgitbridge.bridge.repo.RepoStore;
-import uk.ac.ic.wlgitbridge.bridge.swap.SwapJobConfig;
-import uk.ac.ic.wlgitbridge.bridge.swap.SwapStore;
+import uk.ac.ic.wlgitbridge.bridge.swap.store.SwapStore;
 import uk.ac.ic.wlgitbridge.git.exception.InvalidRootDirectoryPathException;
 import uk.ac.ic.wlgitbridge.git.servlet.WLGitServlet;
 import uk.ac.ic.wlgitbridge.snapshot.base.SnapshotAPIRequest;
@@ -25,7 +24,6 @@ import javax.servlet.DispatcherType;
 import javax.servlet.Filter;
 import javax.servlet.ServletException;
 import java.io.File;
-import java.io.InputStream;
 import java.net.BindException;
 import java.nio.file.Paths;
 import java.util.EnumSet;
@@ -47,7 +45,9 @@ public class GitBridgeServer {
     private String rootGitDirectoryPath;
     private String apiBaseURL;
 
-    public GitBridgeServer(Config config) throws ServletException, InvalidRootDirectoryPathException {
+    public GitBridgeServer(
+            Config config
+    ) throws ServletException, InvalidRootDirectoryPathException {
         org.eclipse.jetty.util.log.Log.setLog(new NullLogger());
         this.port = config.getPort();
         this.rootGitDirectoryPath = config.getRootGitDirectory();
@@ -57,31 +57,19 @@ public class GitBridgeServer {
                         repoStore.getRootDirectory().getAbsolutePath()
                 ).resolve(".wlgb").resolve("wlgb.db").toFile()
         );
-        SwapStore swapStore = new SwapStore() {
-            @Override
-            public void upload(String projectName, InputStream uploadStream, long contentLength) {
-
-            }
-
-            @Override
-            public InputStream openDownloadStream(String projectName) {
-                return null;
-            }
-
-            @Override
-            public void remove(String projectName) {
-
-            }
-        };
+        SwapStore swapStore = SwapStore.fromConfig(config.getSwapStore());
         bridgeAPI = Bridge.make(
                 repoStore,
                 dbStore,
                 swapStore,
-                SwapJobConfig.DEFAULT
+                config.getSwapJob()
         );
         jettyServer = new Server(port);
         configureJettyServer(config);
-        SnapshotAPIRequest.setBasicAuth(config.getUsername(), config.getPassword());
+        SnapshotAPIRequest.setBasicAuth(
+                config.getUsername(),
+                config.getPassword()
+        );
         apiBaseURL = config.getAPIBaseURL();
         SnapshotAPIRequest.setBaseURL(apiBaseURL);
         Util.setServiceName(config.getServiceName());
@@ -115,7 +103,9 @@ public class GitBridgeServer {
         }
     }
 
-    private void configureJettyServer(Config config) throws ServletException, InvalidRootDirectoryPathException {
+    private void configureJettyServer(
+            Config config
+    ) throws ServletException, InvalidRootDirectoryPathException {
         HandlerCollection handlers = new HandlerList();
         handlers.addHandler(initApiHandler());
         handlers.addHandler(initGitHandler(config));
@@ -135,16 +125,28 @@ public class GitBridgeServer {
         return api;
     }
 
-    private Handler initGitHandler(Config config) throws ServletException, InvalidRootDirectoryPathException {
-        final ServletContextHandler servletContextHandler = new ServletContextHandler(ServletContextHandler.SESSIONS);
+    private Handler initGitHandler(
+            Config config
+    ) throws ServletException, InvalidRootDirectoryPathException {
+        final ServletContextHandler servletContextHandler =
+                new ServletContextHandler(ServletContextHandler.SESSIONS);
         if (config.isUsingOauth2()) {
             Filter filter = new Oauth2Filter(config.getOauth2());
-            servletContextHandler.addFilter(new FilterHolder(filter), "/*", EnumSet.of(DispatcherType.REQUEST));
+            servletContextHandler.addFilter(
+                    new FilterHolder(filter),
+                    "/*",
+                    EnumSet.of(DispatcherType.REQUEST)
+            );
         }
         servletContextHandler.setContextPath("/");
         servletContextHandler.addServlet(
                 new ServletHolder(
-                        new WLGitServlet(servletContextHandler, bridgeAPI, rootGitDirectoryPath)),
+                        new WLGitServlet(
+                                servletContextHandler,
+                                bridgeAPI,
+                                rootGitDirectoryPath
+                        )
+                ),
                 "/*"
         );
         return servletContextHandler;
@@ -152,7 +154,9 @@ public class GitBridgeServer {
 
     private Handler initResourceHandler() {
         ResourceHandler resourceHandler = new FileHandler(bridgeAPI);
-        resourceHandler.setResourceBase(new File(rootGitDirectoryPath, ".wlgb/atts").getAbsolutePath());
+        resourceHandler.setResourceBase(
+                new File(rootGitDirectoryPath, ".wlgb/atts").getAbsolutePath()
+        );
         return resourceHandler;
     }
 }

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/util/Tar.java

@@ -23,11 +23,21 @@ public class Tar {
 
         public static InputStream zip(
                 File fileOrDir
+        ) throws IOException {
+            return zip(fileOrDir, null);
+        }
+
+        public static InputStream zip(
+                File fileOrDir,
+                long[] sizePtr
         ) throws IOException {
             ByteArrayOutputStream target = new ByteArrayOutputStream();
             try (OutputStream bzip2 = new BZip2CompressorOutputStream(target)) {
                 tarTo(fileOrDir, bzip2);
             }
+            if (sizePtr != null) {
+                sizePtr[0] = target.size();
+            }
             return target.toInputStream();
         }
 
@@ -60,7 +70,6 @@ public class Tar {
                     Paths.get(fileOrDir.getParentFile().getAbsolutePath()),
                     fileOrDir
             );
-            tout.close();
         }
     }
 

services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/BridgeTest.java

@@ -7,10 +7,8 @@ import uk.ac.ic.wlgitbridge.bridge.lock.ProjectLock;
 import uk.ac.ic.wlgitbridge.bridge.repo.RepoStore;
 import uk.ac.ic.wlgitbridge.bridge.resource.ResourceCache;
 import uk.ac.ic.wlgitbridge.bridge.snapshot.SnapshotAPI;
-import uk.ac.ic.wlgitbridge.bridge.swap.SwapJob;
-import uk.ac.ic.wlgitbridge.bridge.swap.SwapStore;
-
-import java.time.Duration;
+import uk.ac.ic.wlgitbridge.bridge.swap.job.SwapJob;
+import uk.ac.ic.wlgitbridge.bridge.swap.store.SwapStore;
 
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;
@@ -52,9 +50,9 @@ public class BridgeTest {
 
     @Test
     public void shutdownStopsSwapJob() {
-        bridge.startSwapJob(Duration.ofSeconds(1));
+        bridge.startSwapJob();
         bridge.doShutdown();
-        verify(swapJob).start(Duration.ofSeconds(1));
+        verify(swapJob).start();
         verify(swapJob).stop();
     }
 

services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/db/sqlite/SqliteDBStoreTest.java

@@ -132,4 +132,19 @@ public class SqliteDBStoreTest {
         assertEquals("older", dbStore.getOldestUnswappedProject());
     }
 
+    @Test
+    public void testGetNumUnswappedProjects() {
+        dbStore.setLatestVersionForProject("asdf", 1);
+        dbStore.setLastAccessedTime(
+                "asdf",
+                Timestamp.valueOf(LocalDateTime.now())
+        );
+        assertEquals(1, dbStore.getNumUnswappedProjects());
+        dbStore.setLastAccessedTime(
+                "asdf",
+                null
+        );
+        assertEquals(0, dbStore.getNumUnswappedProjects());
+    }
+
 }

services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/db/sqlite/update/delete/DeleteFilesForProjectSQLUpdateTest.java

@@ -7,8 +7,18 @@ public class DeleteFilesForProjectSQLUpdateTest {
 
     @Test
     public void testGetSQL() {
-        DeleteFilesForProjectSQLUpdate update = new DeleteFilesForProjectSQLUpdate("projname", "path1", "path2");
-        assertEquals("DELETE FROM `url_index_store` WHERE `project_name` = ? AND path IN (?, ?);\n", update.getSQL());
+        DeleteFilesForProjectSQLUpdate update =
+                new DeleteFilesForProjectSQLUpdate(
+                        "projname",
+                        "path1",
+                        "path2"
+                );
+        assertEquals(
+                "DELETE FROM `url_index_store` " +
+                        "WHERE `project_name` = ? " +
+                        "AND path IN (?, ?);\n",
+                update.getSQL()
+        );
     }
 
 }

services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/repo/FSRepoStoreTest.java

@@ -21,6 +21,20 @@ import static org.junit.Assert.assertEquals;
  */
 public class FSRepoStoreTest {
 
+    public static File makeTempRepoDir(
+            TemporaryFolder tmpFolder,
+            String name
+    ) throws IOException {
+        File tmp = tmpFolder.newFolder(name);
+        Path rootdir = Paths.get(
+                "src/test/resources/uk/ac/ic/wlgitbridge/"
+                        + "bridge/repo/FSRepoStoreTest/rootdir"
+        );
+        FileUtils.copyDirectory(rootdir.toFile(), tmp);
+        Files.renameAll(tmp, "DOTgit", ".git");
+        return tmp;
+    }
+
     private FSRepoStore repoStore;
     private File original;
 
@@ -28,13 +42,7 @@ public class FSRepoStoreTest {
     public void setup() throws IOException {
         TemporaryFolder tmpFolder = new TemporaryFolder();
         tmpFolder.create();
-        File tmp = tmpFolder.newFolder("repostore");
-        Path rootdir = Paths.get(
-                "src/test/resources/uk/ac/ic/wlgitbridge/"
-                        + "bridge/repo/FSRepoStoreTest/rootdir"
-        );
-        FileUtils.copyDirectory(rootdir.toFile(), tmp);
-        Files.renameAll(tmp, "DOTgit", ".git");
+        File tmp = makeTempRepoDir(tmpFolder, "rootdir");
         original = tmpFolder.newFolder("original");
         FileUtils.copyDirectory(tmp, original);
         repoStore = new FSRepoStore(tmp.getAbsolutePath());

services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/swap/SwapJobImplTest.java

@@ -1,58 +0,0 @@
-package uk.ac.ic.wlgitbridge.bridge.swap;
-
-import org.junit.Before;
-import org.junit.Test;
-import uk.ac.ic.wlgitbridge.bridge.db.DBStore;
-import uk.ac.ic.wlgitbridge.bridge.lock.ProjectLock;
-import uk.ac.ic.wlgitbridge.bridge.repo.RepoStore;
-
-import java.time.Duration;
-
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertTrue;
-import static org.mockito.Mockito.mock;
-
-/**
- * Created by winston on 20/08/2016.
- */
-public class SwapJobImplTest {
-
-    private SwapJobImpl swapJob;
-
-    private ProjectLock lock;
-    private RepoStore repoStore;
-    private DBStore dbStore;
-    private SwapStore swapStore;
-
-    @Before
-    public void setup() {
-        lock = mock(ProjectLock.class);
-        repoStore = mock(RepoStore.class);
-        dbStore = mock(DBStore.class);
-        swapStore = mock(SwapStore.class);
-        swapJob = new SwapJobImpl(
-                SwapJobConfig.DEFAULT,
-                lock,
-                repoStore,
-                dbStore,
-                swapStore
-        );
-    }
-
-    @Test
-    public void startingTimerAlwaysCausesASwap() {
-        assertEquals(0, swapJob.swaps.get());
-        swapJob.start(Duration.ofHours(1));
-        while (swapJob.swaps.get() <= 0);
-        assertTrue(swapJob.swaps.get() > 0);
-    }
-
-    @Test
-    public void swapsHappenEveryInterval() {
-        assertEquals(0, swapJob.swaps.get());
-        swapJob.start(Duration.ofMillis(1));
-        while (swapJob.swaps.get() <= 1);
-        assertTrue(swapJob.swaps.get() > 1);
-    }
-
-}

services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/swap/job/SwapJobImplTest.java

@@ -0,0 +1,119 @@
+package uk.ac.ic.wlgitbridge.bridge.swap.job;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+import uk.ac.ic.wlgitbridge.bridge.db.DBStore;
+import uk.ac.ic.wlgitbridge.bridge.db.sqlite.SqliteDBStore;
+import uk.ac.ic.wlgitbridge.bridge.lock.ProjectLock;
+import uk.ac.ic.wlgitbridge.bridge.repo.FSRepoStore;
+import uk.ac.ic.wlgitbridge.bridge.repo.FSRepoStoreTest;
+import uk.ac.ic.wlgitbridge.bridge.repo.RepoStore;
+import uk.ac.ic.wlgitbridge.bridge.swap.store.InMemorySwapStore;
+import uk.ac.ic.wlgitbridge.bridge.swap.store.SwapStore;
+import uk.ac.ic.wlgitbridge.data.ProjectLockImpl;
+
+import java.io.IOException;
+import java.sql.Timestamp;
+import java.time.Duration;
+import java.time.LocalDateTime;
+import java.time.temporal.ChronoUnit;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Created by winston on 20/08/2016.
+ */
+public class SwapJobImplTest {
+
+    private SwapJobImpl swapJob;
+
+    private ProjectLock lock;
+    private RepoStore repoStore;
+    private DBStore dbStore;
+    private SwapStore swapStore;
+
+    @Before
+    public void setup() throws IOException {
+        TemporaryFolder tmpFolder = new TemporaryFolder();
+        tmpFolder.create();
+        lock = new ProjectLockImpl();
+        repoStore = new FSRepoStore(
+                FSRepoStoreTest.makeTempRepoDir(
+                        tmpFolder,
+                        "repostore"
+                ).getAbsolutePath()
+        );
+        dbStore = new SqliteDBStore(tmpFolder.newFile());
+        dbStore.setLatestVersionForProject("proj1", 0);
+        dbStore.setLatestVersionForProject("proj2", 0);
+        dbStore.setLastAccessedTime(
+                "proj1",
+                Timestamp.valueOf(LocalDateTime.now())
+        );
+        dbStore.setLastAccessedTime(
+                "proj2",
+                Timestamp.valueOf(
+                        LocalDateTime.now().minus(1, ChronoUnit.SECONDS)
+                )
+        );
+        swapStore = new InMemorySwapStore();
+        swapJob = new SwapJobImpl(
+                1,
+                15000,
+                30000,
+                Duration.ofMillis(100),
+                lock,
+                repoStore,
+                dbStore,
+                swapStore
+        );
+    }
+
+    @Test
+    public void startingTimerAlwaysCausesASwap() {
+        swapJob.lowWatermarkBytes = 16384;
+        swapJob.interval = Duration.ofHours(1);
+        assertEquals(0, swapJob.swaps.get());
+        swapJob.start();
+        while (swapJob.swaps.get() <= 0);
+        assertTrue(swapJob.swaps.get() > 0);
+    }
+
+    @Test
+    public void swapsHappenEveryInterval() {
+        swapJob.lowWatermarkBytes = 16384;
+        assertEquals(0, swapJob.swaps.get());
+        swapJob.start();
+        while (swapJob.swaps.get() <= 1);
+        assertTrue(swapJob.swaps.get() > 1);
+    }
+
+    @Test
+    public void noProjectsGetSwappedWhenUnderHighWatermark() {
+        swapJob.highWatermarkBytes = 65536;
+        assertEquals(2, dbStore.getNumUnswappedProjects());
+        swapJob.start();
+        while (swapJob.swaps.get() < 1);
+        assertEquals(2, dbStore.getNumUnswappedProjects());
+    }
+
+    @Test
+    public void correctProjGetSwappedWhenOverHighWatermark(
+    ) throws IOException {
+        swapJob.lowWatermarkBytes = 16384;
+        assertEquals(2, dbStore.getNumUnswappedProjects());
+        assertEquals("proj2", dbStore.getOldestUnswappedProject());
+        swapJob.start();
+        while (swapJob.swaps.get() < 1);
+        assertEquals(1, dbStore.getNumUnswappedProjects());
+        assertEquals("proj1", dbStore.getOldestUnswappedProject());
+        swapJob.restore("proj2");
+        int numSwaps = swapJob.swaps.get();
+        while (swapJob.swaps.get() <= numSwaps);
+        assertEquals(1, dbStore.getNumUnswappedProjects());
+        assertEquals("proj2", dbStore.getOldestUnswappedProject());
+    }
+
+}

services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/swap/InMemorySwapStoreTest.java → services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/swap/store/InMemorySwapStoreTest.java

@@ -1,9 +1,10 @@
-package uk.ac.ic.wlgitbridge.bridge.swap;
+package uk.ac.ic.wlgitbridge.bridge.swap.store;
 
 import org.apache.commons.io.IOUtils;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
+import uk.ac.ic.wlgitbridge.bridge.swap.store.InMemorySwapStore;
 
 import java.io.ByteArrayInputStream;
 import java.io.IOException;
@@ -51,7 +52,8 @@ public class InMemorySwapStoreTest {
     }
 
     @Test
-    public void uploadingForTheSameProjectOverwritesTheFile() throws IOException {
+    public void uploadingForTheSameProjectOverwritesTheFile(
+    ) throws IOException {
         byte[] proj1Contents = "helloproj1".getBytes();
         byte[] proj1NewContents = "goodbyeproj1".getBytes();
         swapStore.upload(

services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/swap/S3SwapStoreTest.java → services/git-bridge/src/test/java/uk/ac/ic/wlgitbridge/bridge/swap/store/S3SwapStoreTest.java

@@ -1,4 +1,4 @@
-package uk.ac.ic.wlgitbridge.bridge.swap;
+package uk.ac.ic.wlgitbridge.bridge.swap.store;
 
 import org.junit.Before;
 

services/git-bridge/src/test/resources/logback-test.xml

@@ -1,7 +1,7 @@
 <configuration>
     <!-- Log everything (subject to logger and root levels set below) to stdout. -->
-    <appender name="tempfile" class="ch.qos.logback.core.FileAppender">
-        <file>${java.io.tmpdir}/git-bridge-test.log</file>
+    <appender name="stderr" class="ch.qos.logback.core.ConsoleAppender">
+        <target>System.err</target>
         <encoder>
             <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level [%thread] %logger{0}: %msg%n</pattern>
         </encoder>
@@ -12,6 +12,6 @@
 
     <!-- The root log level determines how much our dependencies put in the logs. -->
     <root level="WARN">
-        <appender-ref ref="tempfile" />
+        <appender-ref ref="stderr" />
     </root>
 </configuration>