Added ShardArchiver.py utility:

ShardArchiver is a command line utility that creates lz4
compressed tar archives from complete shards and optionally
transfers them to a remote server.

python/ShardArchiver.py

@@ -0,0 +1,150 @@
+#!/usr/bin/env python
+
+#    Copyright (c) 2018 Ripple Labs Inc.
+#
+#    Permission to use, copy, modify, and/or distribute this software for any
+#    purpose  with  or without fee is hereby granted, provided that the above
+#    copyright notice and this permission notice appear in all copies.
+#
+#    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+#    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+#    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+#    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+#    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+#    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+#    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+# Creates lz4 compressed tar archives from complete
+# shards and optinally SCP transfers to a destination
+
+import lz4.frame
+import os
+import subprocess
+import sys
+import tarfile
+
+from os import listdir, remove
+from os.path import basename, isdir, isfile, join
+
+
+def validate_args():
+    '''Validate command line arguments'''
+
+    usage = ("usage: shard_archiver <shards_directory> <output_directory>"
+             " [<indenty_file> <username> <host> <host_directory>]\n"
+             "example: shard_archiver.py /db/shards . /.ssh/id_dsa "
+             "username domain.com \\\\home\\\\archives\n")
+
+    arg_count = len(sys.argv) - 1
+    if arg_count != 2 and arg_count != 6:
+        print('Invalid number of arguments.\n')
+        print(usage)
+        sys.exit(1)
+
+    # Sanity check the shards DB path
+    if not isdir(sys.argv[1]):
+        print('Invalid shards directory.\n')
+        print(usage)
+        sys.exit(1)
+
+    # Sanity check the output path
+    if not isdir(sys.argv[2]):
+        print('Invalid output directory.\n')
+        print(usage)
+        sys.exit(1)
+
+    if arg_count > 3:
+        # Sanity check the identity file
+        if not isfile(sys.argv[3]):
+            print('Invalid identity file.\n')
+            print(usage)
+            sys.exit(1)
+
+
+def read_chunk(file_object):
+    while True:
+        data = file_object.read(16384)
+        if not data:
+            break
+        yield data
+
+
+def create_lz4(source_file, output_path):
+    src = open(source_file, mode='rb')
+    with lz4.frame.open(output_path,
+                        mode='wb',
+                        block_size=lz4.frame.BLOCKSIZE_MAX1MB,
+                        compression_level=lz4.frame.COMPRESSIONLEVEL_MAX,
+                        content_checksum=True) as f:
+        for piece in read_chunk(src):
+            f.write(piece)
+
+
+def process(args):
+    '''Process shard directory'''
+
+    shard_indexes = [d for d in listdir(args[1]) if isdir(
+        join(args[1], d)) and d.isdigit()]
+
+    for shard_index in shard_indexes:
+        tar_path = join(args[2], shard_index + '.tar')
+        lz4_path = join(args[2], shard_index + '.tar.lz4')
+
+        host = None
+        dst_path = None
+        # If host specified, check if the archive exists on it
+        if len(args) > 3:
+            host = args[4] + '@' + args[5]
+            dst_path = join(args[6], shard_index +
+                            '.tar.lz4').replace('\\', '/')
+            if subprocess.call(['ssh', '-i', args[3], host,
+                                'test -e ' + dst_path]) == 0:
+                continue
+        # Otherwise check if it exists locally
+        elif isfile(lz4_path):
+            continue
+
+        shard_dir = join(args[1], shard_index)
+
+        # A NuDB complete shard directory
+        # should have a maximum of three files
+        if len([name for name in listdir(shard_dir)
+                if isfile(join(shard_dir, name))]) > 3:
+            continue
+
+        # If a control file is present
+        # the shard is not complete
+        if isfile(join(shard_dir, 'control.txt')):
+            continue
+
+        # Verify the data file is present
+        if not isfile(join(shard_dir, 'nudb.dat')):
+            continue
+
+        # Verify the key file is present
+        if not isfile(join(shard_dir, 'nudb.key')):
+            continue
+
+        # Create tar file containing shard directory
+        if isfile(tar_path):
+            remove(tar_path)
+        with tarfile.open(tar_path, "w") as tar:
+            tar.add(shard_dir, arcname=basename(shard_dir))
+
+        # Compress the tar file
+        create_lz4(tar_path, lz4_path)
+        remove(tar_path)
+
+        # If host specified, transfer the archive to it
+        if host:
+            try:
+                subprocess.check_call(['scp', '-i', args[3], lz4_path,
+                                      "%s:%s" % (host, dst_path)])
+                remove(lz4_path)
+            except:
+                print('SCP to host failed')
+
+
+if __name__ == "__main__":
+    validate_args()
+    process(sys.argv)