S3C-35 Refactoring of bucketfile (S3 file metadata backend)

The changes allow bucketfile to use a new API in Arsenal to
communicate with a remote leveldb database, containing sublevels for
bucket storage. Metadata is still stored on a local levelDB server,
but it should now be easy to move the storage logic in a new daemon
running on a remote server, and it should be robust.

Instead of relying on the existing implementation of multilevel, it
uses client/server wrappers around a new level-net communication
protocol and API in Arsenal based on socket.io to exchange messages.

It shall be compatible with the existing metadata since it still uses
the core sublevel module for the storage logic, only the RPC procotol
has changed.

Test done:

 - put a few 100s of files in different S3 subdirectories
 - list directories and subdirectories
 - get/delete files
 - multi-part upload
 - introduce random connection errors (tcpkill) to check robustness
   and automatic reconnection

config.json

@@ -36,5 +36,9 @@
     },
     "healthChecks": {
         "allowFrom": ["127.0.0.1/8", "::1"]
+    },
+    "metadataDaemon": {
+        "host": "localhost",
+        "port": 9990
     }
 }

init.js

@@ -6,61 +6,11 @@ const fs = require('fs');
 const os = require('os');
 
 const async = require('async');
-const uuid = require('node-uuid');
 
 const constants = require('./constants').default;
 const config = require('./lib/Config.js').default;
 const logger = require('./lib/utilities/logger.js').logger;
-
-let ioctl;
-try {
-    ioctl = require('ioctl');
-} catch (err) {
-    logger.warn('ioctl dependency is unavailable. skipping...');
-}
-
-function _setDirSyncFlag(path) {
-    const GETFLAGS = 2148034049;
-    const SETFLAGS = 1074292226;
-    const FS_DIRSYNC_FL = 65536;
-    const buffer = Buffer.alloc(8, 0);
-    const pathFD = fs.openSync(path, 'r');
-    const status = ioctl(pathFD, GETFLAGS, buffer);
-    assert.strictEqual(status, 0);
-    const currentFlags = buffer.readUIntLE(0, 8);
-    const flags = currentFlags | FS_DIRSYNC_FL;
-    buffer.writeUIntLE(flags, 0, 8);
-    const status2 = ioctl(pathFD, SETFLAGS, buffer);
-    assert.strictEqual(status2, 0);
-    fs.closeSync(pathFD);
-    const pathFD2 = fs.openSync(path, 'r');
-    const confirmBuffer = Buffer.alloc(8, 0);
-    ioctl(pathFD2, GETFLAGS, confirmBuffer);
-    assert.strictEqual(confirmBuffer.readUIntLE(0, 8),
-        currentFlags | FS_DIRSYNC_FL, 'FS_DIRSYNC_FL not set');
-    logger.info('FS_DIRSYNC_FL set');
-    fs.closeSync(pathFD2);
-}
-
-function printUUID(metadataPath) {
-    const uuidFile = `${metadataPath}/uuid`;
-
-    try {
-        fs.accessSync(uuidFile, fs.F_OK | fs.R_OK);
-    } catch (e) {
-        if (e.code === 'ENOENT') {
-            const v = uuid.v4();
-            const fd = fs.openSync(uuidFile, 'w');
-            fs.writeSync(fd, v.toString());
-            fs.closeSync(fd);
-        } else {
-            throw e;
-        }
-    }
-
-    const uuidValue = fs.readFileSync(uuidFile);
-    logger.info(`This deployment's identifier is ${uuidValue}`);
-}
+const storageUtils = require('arsenal').storage.utils;
 
 // If neither data nor metadata is using the file backend,
 // there is no need to init
@@ -71,18 +21,15 @@ if (config.backends.data !== 'file' && config.backends.data !== 'multiple' &&
 }
 
 const dataPath = config.filePaths.dataPath;
-const metadataPath = config.filePaths.metadataPath;
 
 fs.accessSync(dataPath, fs.F_OK | fs.R_OK | fs.W_OK);
-fs.accessSync(metadataPath, fs.F_OK | fs.R_OK | fs.W_OK);
 const warning = 'WARNING: Synchronization directory updates are not ' +
     'supported on this platform. Newly written data could be lost ' +
     'if your system crashes before the operating system is able to ' +
     'write directory updates.';
-if (os.type() === 'Linux' && os.endianness() === 'LE' && ioctl) {
+if (os.type() === 'Linux' && os.endianness() === 'LE') {
     try {
-        _setDirSyncFlag(dataPath);
-        _setDirSyncFlag(metadataPath);
+        storageUtils.setDirSyncFlag(dataPath);
     } catch (err) {
         logger.warn(warning, { error: err.stack });
     }
@@ -105,5 +52,4 @@ async.eachSeries(subDirs, (subDirName, next) => {
  err => {
      assert.strictEqual(err, null, `Error creating data files ${err}`);
      logger.info('Init complete.  Go forth and store data.');
-     printUUID(metadataPath);
  });

lib/Config.js

@@ -269,6 +269,20 @@ class Config {
             }
         }
 
+        if (config.metadataDaemon) {
+            this.metadataDaemon = {};
+            assert.strictEqual(
+                typeof config.metadataDaemon.host, 'string',
+                'bad config: metadata daemon host must be a string');
+            this.metadataDaemon.host = config.metadataDaemon.host;
+
+            assert(Number.isInteger(config.metadataDaemon.port)
+                   && config.metadataDaemon.port > 0,
+                   'bad config: metadata daemon port must be a ' +
+                   'positive integer');
+            this.metadataDaemon.port = config.metadataDaemon.port;
+        }
+
         if (process.env.ENABLE_LOCAL_CACHE) {
             this.localCache = defaultLocalCache;
         }