Add OverlayBlobStore

Author: SwitchTV-BenBettridge

Dockerfile

@@ -1,3 +1,12 @@
+# Multistage - Builder
+FROM maven:3.6.3-jdk-11-slim as s3proxy-builder
+LABEL maintainer="Andrew Gaul <andrew@gaul.org>"
+
+COPY . /opt/s3proxy/
+WORKDIR /opt/s3proxy
+RUN  mvn package -DskipTests
+
+# Multistage - Image
 FROM openjdk:11-jre-slim
 LABEL maintainer="Andrew Gaul <andrew@gaul.org>"
 
@@ -20,6 +29,9 @@ ENV \
     S3PROXY_CORS_ALLOW_METHODS="" \
     S3PROXY_CORS_ALLOW_HEADERS="" \
     S3PROXY_IGNORE_UNKNOWN_HEADERS="false" \
+    S3PROXY_OVERLAY_BLOBSTORE="false" \
+    S3PROXY_OVERLAY_BLOBSTORE_MASK_SUFFIX="__deleted" \
+    S3PROXY_OVERLAY_BLOBSTORE_PATH="/tmp" \
     S3PROXY_ENCRYPTED_BLOBSTORE="" \
     S3PROXY_ENCRYPTED_BLOBSTORE_PASSWORD="" \
     S3PROXY_ENCRYPTED_BLOBSTORE_SALT="" \

README.md

@@ -107,6 +107,7 @@ S3Proxy can modify its behavior based on middlewares:
 * [large object mocking](https://github.com/gaul/s3proxy/wiki/Middleware-large-object-mocking)
 * [read-only](https://github.com/gaul/s3proxy/wiki/Middleware-read-only)
 * [sharded backend containers](https://github.com/gaul/s3proxy/wiki/Middleware-sharded-backend)
+* [overlay blobstore]()
 
 ## Limitations
 

src/main/java/org/gaul/s3proxy/Main.java

@@ -240,6 +240,17 @@ private static BlobStore parseMiddlewareProperties(BlobStore blobStore,
             blobStore = ReadOnlyBlobStore.newReadOnlyBlobStore(blobStore);
         }
 
+        String overlayBlobStore = properties.getProperty(
+                S3ProxyConstants.PROPERTY_OVERLAY_BLOBSTORE);
+        if("true".equalsIgnoreCase(overlayBlobStore))  {
+            System.err.println("Overlaying storage backend with local BlobStore");
+            String overlayPath = properties.getProperty(
+                    S3ProxyConstants.PROPERTY_OVERLAY_BLOBSTORE_PATH);
+            String overlayMaskSuffix = properties.getProperty(
+                    S3ProxyConstants.PROPERTY_OVERLAY_BLOBSTORE_MASK_SUFFIX);
+            blobStore = OverlayBlobStore.newOverlayBlobStore(blobStore, overlayPath, overlayMaskSuffix);
+        }
+
         ImmutableBiMap<String, String> aliases = AliasBlobStore.parseAliases(
                 properties);
         if (!aliases.isEmpty()) {