diff --git a/packetary/tests/test_packetary.py b/packetary/library/__init__.py
similarity index 75%
rename from packetary/tests/test_packetary.py
rename to packetary/library/__init__.py
index 7970569..60d4f22 100644
--- a/packetary/tests/test_packetary.py
+++ b/packetary/library/__init__.py
@@ -15,17 +15,6 @@
 #    under the License.
 
 
-"""
-test_packetary
-----------------------------------
+import eventlet
 
-Tests for `packetary` module.
-"""
-
-from packetary.tests import base
-
-
-class TestPacketary(base.TestCase):
-
-    def test_something(self):
-        pass
+eventlet.monkey_patch()
diff --git a/packetary/library/checksum.py b/packetary/library/checksum.py
new file mode 100644
index 0000000..7243389
--- /dev/null
+++ b/packetary/library/checksum.py
@@ -0,0 +1,82 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright 2015 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import functools
+import hashlib
+
+
+class _HashComposite(object):
+    """Combines several hash methods."""
+
+    def __init__(self, hash_objects):
+        self.hash_objects = hash_objects
+
+    def update(self, data):
+        """Updates the hash objects with the string arg.
+
+        For more details see doc of hashlib.update.
+        """
+        for o in self.hash_objects:
+            o.update(data)
+
+    def hexdigest(self):
+        """Returns the list of appropriate hexdigests of hash_objects.
+
+        For more details see doc of hashlib.hexdigest.
+        """
+        return [o.hexdigest() for o in self.hash_objects]
+
+
+def _new_composite(methods):
+    """Creates new composite method."""
+
+    def wrapper():
+        return _HashComposite([x() for x in methods])
+    return wrapper
+
+
+def _checksum(method):
+    """Makes function to calculate checksum for stream."""
+    @functools.wraps(method)
+    def calculate(stream, chunksize=16 * 1024):
+        """Calculates checksum for binary stream.
+
+        :param stream: file-like object opened in binary mode.
+        :return: the checksum of content in terms of method.
+        """
+
+        s = method()
+        while True:
+            chunk = stream.read(chunksize)
+            if not chunk:
+                break
+            s.update(chunk)
+        return s.hexdigest()
+    return calculate
+
+
+md5 = _checksum(hashlib.md5)
+
+sha1 = _checksum(hashlib.sha1)
+
+sha256 = _checksum(hashlib.sha256)
+
+
+def composite(*methods):
+    """Calculate several checksum at one time."""
+    return _checksum(_new_composite(
+        [getattr(hashlib, x) for x in methods]
+    ))
diff --git a/packetary/library/connections.py b/packetary/library/connections.py
new file mode 100644
index 0000000..6d42fd4
--- /dev/null
+++ b/packetary/library/connections.py
@@ -0,0 +1,280 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright 2015 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import logging
+import os
+import six
+import six.moves.http_client as http_client
+import six.moves.urllib.request as urllib_request
+import six.moves.urllib_error as urllib_error
+import time
+
+from packetary.library.streams import StreamWrapper
+
+
+logger = logging.getLogger(__package__)
+
+
+RETRYABLE_ERRORS = (http_client.HTTPException, IOError)
+
+
+class RangeError(urllib_error.URLError):
+    pass
+
+
+class RetryableRequest(urllib_request.Request):
+    offset = 0
+    retries_left = 1
+    start_time = 0
+
+
+class ResumableResponse(StreamWrapper):
+    """The http-response wrapper to add resume ability.
+
+    Allows to resume read from same position if connection is lost.
+    """
+
+    def __init__(self, request, response, opener):
+        """Initialises.
+
+        :param request: the original http request
+        :param response: the original http response
+        :param opener: the instance of urllib.OpenerDirector
+        """
+        super(ResumableResponse, self).__init__(response)
+        self.request = request
+        self.opener = opener
+
+    def read_chunk(self, chunksize):
+        """Overrides super class method."""
+        while 1:
+            try:
+                chunk = self.stream.read(chunksize)
+                self.request.offset += len(chunk)
+                return chunk
+            except RETRYABLE_ERRORS as e:
+                response = self.opener.error(
+                    self.request.get_type(), self.request,
+                    self.stream, 502, six.text_type(e), self.stream.info()
+                )
+                self.stream = response.stream
+
+
+class RetryHandler(urllib_request.BaseHandler):
+    """urllib Handler to add ability for retrying on server errors."""
+
+    @staticmethod
+    def http_request(request):
+        """Initialises http request."""
+        logger.debug("start request: %s", request.get_full_url())
+        if request.offset > 0:
+            request.add_header('Range', 'bytes=%d-' % request.offset)
+        request.start_time = time.time()
+        return request
+
+    def http_response(self, request, response):
+        """Wraps response in a ResumableResponse.
+
+        Checks that partial request completed successfully.
+        """
+        # the server should response partial content if range is specified
+        logger.debug(
+            "finish request: %s - %d (%s), duration - %d ms.",
+            request.get_full_url(), response.getcode(), response.msg,
+            int((time.time() - request.start_time) * 1000)
+        )
+        if request.offset > 0 and response.getcode() != 206:
+            raise RangeError("Server does not support ranges.")
+        return ResumableResponse(request, response, self.parent)
+
+    def http_error(self, req, fp, code, msg, hdrs):
+        """Checks error code and retries request if it is allowed."""
+        if code >= 500 and req.retries_left > 0:
+            req.retries_left -= 1
+            logger.warning(
+                "fail request: %s - %d(%s), retries left - %d.",
+                req.get_full_url(), code, msg, req.retries_left
+            )
+            return self.parent.open(req)
+
+    https_request = http_request
+    https_response = http_response
+
+
+class Connection(object):
+    """Helper class to deal with streams."""
+
+    def __init__(self, opener, retries_num):
+        """Initializes.
+
+        :param opener: the instance of urllib.OpenerDirector
+        :param retries_num: the number of allowed retries
+        """
+        self.opener = opener
+        self.retries_num = retries_num
+
+    def make_request(self, url, offset=0):
+        """Makes new http request.
+
+        :param url: the remote file`s url
+        :param offset: the number of bytes from begin, that will be skipped
+        :return: The new http request
+        """
+
+        if url.startswith("/"):
+            url = "file://" + url
+
+        request = RetryableRequest(url)
+        request.retries_left = self.retries_num
+        request.offset = offset
+        return request
+
+    def open_stream(self, url, offset=0):
+        """Opens remote file for streaming.
+
+        :param url: the remote file`s url
+        :param offset: the number of bytes from begin, that will be skipped
+        """
+
+        request = self.make_request(url, offset)
+        while 1:
+            try:
+                return self.opener.open(request)
+            except (RangeError, urllib_error.HTTPError):
+                raise
+            except RETRYABLE_ERRORS as e:
+                if request.retries_left <= 0:
+                    raise
+                request.retries_left -= 1
+                logger.exception(
+                    "Failed to open url - %s: %s. retries left - %d.",
+                    url, six.text_type(e), request.retries_left
+                )
+
+    def retrieve(self, url, filename, offset=0):
+        """Downloads remote file.
+
+        :param url: the remote file`s url
+        :param filename: the file`s name, that includes path on local fs
+        :param offset: the number of bytes from begin, that will be skipped
+        """
+
+        self._ensure_dir_exists(filename)
+        fd = os.open(filename, os.O_CREAT | os.O_WRONLY)
+        try:
+            self._copy_stream(fd, url, offset)
+        except RangeError:
+            if offset == 0:
+                raise
+            logger.warning(
+                "Failed to resume download, starts from begin: %s", url
+            )
+            self._copy_stream(fd, url, 0)
+        finally:
+            os.fsync(fd)
+            os.close(fd)
+
+    @staticmethod
+    def _ensure_dir_exists(dst):
+        """Checks that directory exists and creates otherwise."""
+        target_dir = os.path.dirname(dst)
+        try:
+            os.makedirs(target_dir)
+        except OSError as e:
+            if e.errno != 17:
+                raise
+
+    def _copy_stream(self, fd, url, offset):
+        """Copies remote file to local.
+
+        :param fd: the file`s descriptor
+        :param url: the remote file`s url
+        :param offset: the number of bytes from begin, that will be skipped
+        """
+
+        source = self.open_stream(url, offset)
+        os.ftruncate(fd, offset)
+        os.lseek(fd, offset, os.SEEK_SET)
+        chunk_size = 16 * 1024
+        while 1:
+            chunk = source.read(chunk_size)
+            if not chunk:
+                break
+            os.write(fd, chunk)
+
+
+class ConnectionContext(object):
+    """Helper class acquire and release connection within context."""
+    def __init__(self, connection, on_exit):
+        self.connection = connection
+        self.on_exit = on_exit
+
+    def __enter__(self):
+        return self.connection
+
+    def __exit__(self, *_):
+        self.on_exit(self.connection)
+
+
+class ConnectionsPool(object):
+    """Controls the number of simultaneously opened connections."""
+
+    MIN_CONNECTIONS_COUNT = 1
+
+    def __init__(self, count=0, proxy=None, secure_proxy=None, retries_num=0):
+        """Initialises.
+
+        :param count: the number of allowed simultaneously connections
+        :param proxy: the url of proxy for http-connections
+        :param secure_proxy: the url of proxy for https-connections
+        :param retries_num: the number of allowed retries
+        """
+        if proxy:
+            proxies = {
+                "http": proxy,
+                "https": secure_proxy or proxy,
+            }
+        else:
+            proxies = None
+
+        opener = urllib_request.build_opener(
+            RetryHandler(),
+            urllib_request.ProxyHandler(proxies)
+        )
+
+        limit = max(count, self.MIN_CONNECTIONS_COUNT)
+        connections = six.moves.queue.Queue()
+        while limit > 0:
+            connections.put(Connection(opener, retries_num))
+            limit -= 1
+
+        self.free = connections
+
+    def get(self, timeout=None):
+        """Gets the free connection.
+
+        Blocks in case if there is no free connections.
+
+        :param timeout: the timeout in seconds to wait.
+            by default infinity waiting.
+        """
+        return ConnectionContext(
+            self.free.get(timeout=timeout), self._release
+        )
+
+    def _release(self, connection):
+        """Puts back connection to free connections."""
+        self.free.put(connection)
diff --git a/packetary/library/executor.py b/packetary/library/executor.py
new file mode 100644
index 0000000..7e708d1
--- /dev/null
+++ b/packetary/library/executor.py
@@ -0,0 +1,82 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright 2015 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from __future__ import with_statement
+
+import logging
+import six
+
+from eventlet.greenpool import GreenPool
+
+
+logger = logging.getLogger(__package__)
+
+
+class AsynchronousSection(object):
+    """Allows calling function asynchronously with waiting on exit."""
+
+    MIN_POOL_SIZE = 1
+
+    def __init__(self, size=0, ignore_errors_num=0):
+        """Initialises.
+
+        :param size: the max number of parallel tasks
+        :param ignore_errors_num:
+               number of errors which does not stop the execution
+        """
+
+        self.executor = GreenPool(max(size, self.MIN_POOL_SIZE))
+        self.ignore_errors_num = ignore_errors_num
+        self.errors = 0
+        self.tasks = set()
+
+    def __enter__(self):
+        self.errors = 0
+        return self
+
+    def __exit__(self, etype, *_):
+        self.wait(etype is not None)
+
+    def execute(self, func, *args, **kwargs):
+        """Calls function asynchronously."""
+        if 0 <= self.ignore_errors_num < self.errors:
+            raise RuntimeError("Too many errors.")
+
+        gt = self.executor.spawn(func, *args, **kwargs)
+        self.tasks.add(gt)
+        gt.link(self.on_complete)
+
+    def on_complete(self, gt):
+        """Callback to handle task completion."""
+
+        try:
+            gt.wait()
+        except Exception as e:
+            self.errors += 1
+            logger.exception("Task failed: %s", six.text_type(e))
+        finally:
+            self.tasks.discard(gt)
+
+    def wait(self, ignore_errors=False):
+        """Waits until all tasks will be completed.
+
+        Do not use directly, will be called from context manager.
+        """
+        self.executor.waitall()
+        if not ignore_errors and self.errors > 0:
+            raise RuntimeError(
+                "Operations completed with errors. See log for more details."
+            )
diff --git a/packetary/library/streams.py b/packetary/library/streams.py
new file mode 100644
index 0000000..558a27b
--- /dev/null
+++ b/packetary/library/streams.py
@@ -0,0 +1,125 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright 2015 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import zlib
+
+
+class StreamWrapper(object):
+    """Helper class to implement stream wrappers.
+
+    It is base-class for Streamers,
+    that provides functionality to transform stream on the fly.
+    The wrapped stream may return data more that required,
+    the extra read data will be kept in the internal buffer till
+    next read.
+    """
+
+    CHUNK_SIZE = 1024
+
+    def __init__(self, stream):
+        """Initializes.
+
+        :param stream: file-like object opened in binary mode.
+        """
+        self.stream = stream
+        self.unread_tail = b""
+
+    def __getattr__(self, item):
+        return getattr(self.stream, item)
+
+    def _read_tail(self):
+        tmp = self.unread_tail
+        self.unread_tail = b""
+        return tmp
+
+    def _align_chunk(self, chunk, size):
+        self.unread_tail = chunk[size:]
+        return chunk[:size]
+
+    def read_chunk(self, chunksize):
+        """Overrides this method to change default behaviour."""
+        return self.stream.read(chunksize)
+
+    def read(self, size=-1):
+        result = self._read_tail()
+        if size < 0:
+            while True:
+                chunk = self.read_chunk(self.CHUNK_SIZE)
+                if not chunk:
+                    break
+                result += chunk
+        else:
+            if len(result) > size:
+                result = self._align_chunk(result, size)
+            size -= len(result)
+            while size > 0:
+                chunk = self.read_chunk(max(self.CHUNK_SIZE, size))
+                if not chunk:
+                    break
+                if len(chunk) > size:
+                    chunk = self._align_chunk(chunk, size)
+                size -= len(chunk)
+                result += chunk
+        return result
+
+    def readline(self):
+        pos = self.unread_tail.find(b"\n")
+        if pos >= 0:
+            line = self._align_chunk(self.unread_tail, pos + 1)
+        else:
+            line = self._read_tail()
+            while True:
+                chunk = self.read_chunk(self.CHUNK_SIZE)
+                if not chunk:
+                    break
+                pos = chunk.find(b"\n")
+                if pos >= 0:
+                    line += self._align_chunk(chunk, pos + 1)
+                    break
+                line += chunk
+        return line
+
+    def readlines(self):
+        while True:
+            line = self.readline()
+            if not line:
+                break
+            yield line
+
+    def __iter__(self):
+        return self.readlines()
+
+
+class GzipDecompress(StreamWrapper):
+    """The decompress stream."""
+
+    def __init__(self, stream):
+        super(GzipDecompress, self).__init__(stream)
+        # Magic parameter makes zlib module understand gzip header
+        # http://stackoverflow.com/questions/1838699/how-can-i-decompress-a-gzip-stream-with-zlib
+        # This works on cpython and pypy, but not jython.
+        self.decompress = zlib.decompressobj(16 + zlib.MAX_WBITS)
+
+    def read_chunk(self, chunksize):
+        if self.decompress.unconsumed_tail:
+            return self.decompress.decompress(
+                self.decompress.unconsumed_tail, chunksize
+            )
+
+        chunk = self.stream.read(chunksize)
+        if not chunk:
+            return self.decompress.flush()
+        return self.decompress.decompress(chunk, chunksize)
diff --git a/packetary/tests/test_checksums.py b/packetary/tests/test_checksums.py
new file mode 100644
index 0000000..8060e00
--- /dev/null
+++ b/packetary/tests/test_checksums.py
@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright 2015 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import six
+
+from packetary.library import checksum
+from packetary.tests import base
+
+
+class TestChecksum(base.TestCase):
+    def test_checksum(self):
+        stream = six.BytesIO(b"line1\nline2\nline3\n")
+        checksums = {
+            checksum.md5: "cc3d5ed5fda53dfa81ea6aa951d7e1fe",
+            checksum.sha1: "8c84f6f36dd2230d3e9c954fa436e5fda90b1957",
+            checksum.sha256: "66663af9c7aa341431a8ee2ff27b72"
+                             "abd06c9218f517bb6fef948e4803c19e03"
+        }
+        for chunksize in (8, 256):
+            for algo, expected in six.iteritems(checksums):
+                stream.seek(0)
+                self.assertEqual(
+                    expected, algo(stream, chunksize)
+                )
+
+    def test_composite(self):
+        stream = six.BytesIO(b"line1\nline2\nline3\n")
+        result = checksum.composite('md5', 'sha1', 'sha256')(stream)
+        self.assertEqual(
+            [
+                "cc3d5ed5fda53dfa81ea6aa951d7e1fe",
+                "8c84f6f36dd2230d3e9c954fa436e5fda90b1957",
+                "66663af9c7aa341431a8ee2ff27b72"
+                "abd06c9218f517bb6fef948e4803c19e03"
+            ],
+            result
+        )
diff --git a/packetary/tests/test_connections.py b/packetary/tests/test_connections.py
new file mode 100644
index 0000000..33d4ef2
--- /dev/null
+++ b/packetary/tests/test_connections.py
@@ -0,0 +1,249 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright 2015 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import mock
+import six
+import time
+
+from packetary.library import connections
+from packetary.tests import base
+
+
+class TestConnectionsPool(base.TestCase):
+    def test_get_connection(self):
+        pool = connections.ConnectionsPool(count=2)
+        self.assertEqual(2, pool.free.qsize())
+        with pool.get():
+            self.assertEqual(1, pool.free.qsize())
+        self.assertEqual(2, pool.free.qsize())
+
+    def _check_proxies(self, pool, http_proxy, https_proxy):
+        with pool.get() as c:
+            for h in c.opener.handlers:
+                if isinstance(h, connections.urllib_request.ProxyHandler):
+                    self.assertEqual(
+                        (http_proxy, https_proxy),
+                        (h.proxies["http"], h.proxies["https"])
+                    )
+                    break
+            else:
+                self.fail("ProxyHandler should be in list of handlers.")
+
+    def test_set_proxy(self):
+        pool = connections.ConnectionsPool(count=1, proxy="http://localhost")
+        self._check_proxies(pool, "http://localhost", "http://localhost")
+        pool = connections.ConnectionsPool(
+            proxy="http://localhost", secure_proxy="https://localhost")
+        self._check_proxies(pool, "http://localhost", "https://localhost")
+
+    def test_reliability(self):
+        pool = connections.ConnectionsPool(count=0, retries_num=2)
+        self.assertEqual(1, pool.free.qsize())
+        with pool.get() as c:
+            self.assertEqual(2, c.retries_num)
+            for h in c.opener.handlers:
+                if isinstance(h, connections.RetryHandler):
+                    break
+            else:
+                self.fail("RetryHandler should be in list of handlers.")
+
+
+class TestConnection(base.TestCase):
+    def setUp(self):
+        super(TestConnection, self).setUp()
+        self.connection = connections.Connection(mock.MagicMock(), 2)
+
+    def test_make_request(self):
+        request = self.connection.make_request("/test/file", 0)
+        self.assertIsInstance(request, connections.RetryableRequest)
+        self.assertEqual("file:///test/file", request.get_full_url())
+        self.assertEqual(0, request.offset)
+        self.assertEqual(2, request.retries_left)
+        request2 = self.connection.make_request("http://server/path", 100)
+        self.assertEqual("http://server/path", request2.get_full_url())
+        self.assertEqual(100, request2.offset)
+
+    def test_open_stream(self):
+        self.connection.open_stream("/test/file")
+        self.assertEqual(1, self.connection.opener.open.call_count)
+        args = self.connection.opener.open.call_args[0]
+        self.assertIsInstance(args[0], connections.RetryableRequest)
+        self.assertEqual(2, args[0].retries_left)
+
+    @mock.patch("packetary.library.connections.logger")
+    def test_retries_on_io_error(self, logger):
+        self.connection.opener.open.side_effect = [
+            IOError("I/O error"),
+            mock.MagicMock()
+        ]
+        self.connection.open_stream("/test/file")
+        self.assertEqual(2, self.connection.opener.open.call_count)
+        logger.exception.assert_called_with(
+            "Failed to open url - %s: %s. retries left - %d.",
+            "/test/file", "I/O error", 1
+        )
+
+        self.connection.opener.open.side_effect = IOError("I/O error")
+        with self.assertRaises(IOError):
+            self.connection.open_stream("/test/file")
+        logger.exception.assert_called_with(
+            "Failed to open url - %s: %s. retries left - %d.",
+            "/test/file", "I/O error", 0
+        )
+
+    def test_raise_other_errors(self):
+        self.connection.opener.open.side_effect = \
+            connections.urllib_error.HTTPError("", 500, "", {}, None)
+
+        with self.assertRaises(connections.urllib_error.URLError):
+            self.connection.open_stream("/test/file")
+
+        self.assertEqual(1, self.connection.opener.open.call_count)
+
+    @mock.patch("packetary.library.connections.os")
+    def test_retrieve_from_offset(self, os):
+        os.path.mkdirs.side_effect = OSError(17, "")
+        os.open.return_value = 1
+        response = mock.MagicMock()
+        self.connection.opener.open.return_value = response
+        response.read.side_effect = [b"test", b""]
+        self.connection.retrieve("/file/src", "/file/dst", 10)
+        os.lseek.assert_called_once_with(1, 10, os.SEEK_SET)
+        os.ftruncate.assert_called_once_with(1, 10)
+        self.assertEqual(1, os.write.call_count)
+        os.fsync.assert_called_once_with(1)
+        os.close.assert_called_once_with(1)
+
+    @mock.patch.multiple(
+        "packetary.library.connections",
+        logger=mock.DEFAULT,
+        os=mock.DEFAULT
+    )
+    def test_retrieve_from_offset_fail(self, os, logger):
+        os.path.mkdirs.side_effect = OSError(17, "")
+        os.open.return_value = 1
+        response = mock.MagicMock()
+        self.connection.opener.open.side_effect = [
+            connections.RangeError("error"), response
+        ]
+        response.read.side_effect = [b"test", b""]
+        self.connection.retrieve("/file/src", "/file/dst", 10)
+        logger.warning.assert_called_once_with(
+            "Failed to resume download, starts from begin: %s",
+            "/file/src"
+        )
+        os.lseek.assert_called_once_with(1, 0, os.SEEK_SET)
+        os.ftruncate.assert_called_once_with(1, 0)
+        self.assertEqual(1, os.write.call_count)
+        os.fsync.assert_called_once_with(1)
+        os.close.assert_called_once_with(1)
+
+
+@mock.patch("packetary.library.connections.logger")
+class TestRetryHandler(base.TestCase):
+    def setUp(self):
+        super(TestRetryHandler, self).setUp()
+        self.handler = connections.RetryHandler()
+        self.handler.add_parent(mock.MagicMock())
+
+    def test_start_request(self, logger):
+        request = mock.MagicMock()
+        request.offset = 0
+        request.get_full_url.return_value = "/file/test"
+        request = self.handler.http_request(request)
+        request.start_time <= time.time()
+        logger.debug.assert_called_with("start request: %s", "/file/test")
+        request.offset = 1
+        request = self.handler.http_request(request)
+        request.add_header.assert_called_once_with('Range', 'bytes=1-')
+
+    def test_handle_response(self, logger):
+        request = mock.MagicMock()
+        request.offset = 0
+        request.start_time.__rsub__.return_value = 0.01
+        request.get_full_url.return_value = "/file/test"
+        response = mock.MagicMock()
+        response.getcode.return_value = 200
+        response.msg = "test"
+        r = self.handler.http_response(request, response)
+        self.assertIsInstance(r, connections.ResumableResponse)
+        logger.debug.assert_called_with(
+            "finish request: %s - %d (%s), duration - %d ms.",
+            "/file/test", 200, "test", 10
+        )
+
+    def test_handle_partial_response(self, _):
+        request = mock.MagicMock()
+        request.offset = 1
+        request.get_full_url.return_value = "/file/test"
+        response = mock.MagicMock()
+        response.getcode.return_value = 200
+        response.msg = "test"
+        with self.assertRaises(connections.RangeError):
+            self.handler.http_response(request, response)
+        response.getcode.return_value = 206
+        self.handler.http_response(request, response)
+
+    def test_error(self, logger):
+        request = mock.MagicMock()
+        request.get_full_url.return_value = "/test"
+        request.retries_left = 1
+        self.handler.http_error(
+            request, mock.MagicMock(), 500, "error", mock.MagicMock()
+        )
+        logger.warning.assert_called_with(
+            "fail request: %s - %d(%s), retries left - %d.",
+            "/test", 500, "error", 0
+        )
+        self.handler.http_error(
+            request, mock.MagicMock(), 500, "error", mock.MagicMock()
+        )
+        self.handler.parent.open.assert_called_once_with(request)
+
+
+class TestResumeableResponse(base.TestCase):
+    def setUp(self):
+        super(TestResumeableResponse, self).setUp()
+        self.request = mock.MagicMock()
+        self.opener = mock.MagicMock()
+        self.stream = mock.MagicMock()
+
+    def test_resume_read(self):
+        self.request.offset = 0
+        response = connections.ResumableResponse(
+            self.request,
+            self.stream,
+            self.opener
+        )
+        self.stream.read.side_effect = [
+            b"chunk1", IOError(), b"chunk2", b""
+        ]
+        self.opener.error.return_value = response
+        data = response.read()
+        self.assertEqual(b"chunk1chunk2", data)
+        self.assertEqual(12, self.request.offset)
+        self.assertEqual(1, self.opener.error.call_count)
+
+    def test_read(self):
+        self.request.offset = 0
+        response = connections.ResumableResponse(
+            self.request,
+            six.BytesIO(b"line1\nline2\nline3\n"),
+            self.opener
+        )
+        self.assertEqual(
+            b"line1\nline2\nline3\n", response.read()
+        )
diff --git a/packetary/tests/test_executor.py b/packetary/tests/test_executor.py
new file mode 100644
index 0000000..59d036e
--- /dev/null
+++ b/packetary/tests/test_executor.py
@@ -0,0 +1,64 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright 2015 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import mock
+import threading
+import time
+
+from packetary.library import executor
+from packetary.tests import base
+
+
+def _raise_value_error(*_):
+    raise ValueError("error")
+
+
+@mock.patch("packetary.library.executor.logger")
+class TestAsynchronousSection(base.TestCase):
+    def setUp(self):
+        super(TestAsynchronousSection, self).setUp()
+        self.results = []
+
+    def test_isolation(self, _):
+        section1 = executor.AsynchronousSection()
+        section2 = executor.AsynchronousSection()
+        event = threading.Event()
+        section1.execute(event.wait)
+        section2.execute(time.sleep, 0)
+        section2.wait()
+        event.set()
+        section1.wait()
+
+    def test_ignore_errors(self, logger):
+        section = executor.AsynchronousSection(ignore_errors_num=1)
+        section.execute(_raise_value_error)
+        section.execute(time.sleep, 0)
+        section.wait(ignore_errors=True)
+        self.assertEqual(1, section.errors)
+        logger.exception.assert_called_with(
+            "Task failed: %s", "error"
+        )
+
+    def test_fail_if_too_many_errors(self, _):
+        section = executor.AsynchronousSection(ignore_errors_num=0)
+        section.execute(_raise_value_error)
+        section.wait(ignore_errors=True)
+        with self.assertRaisesRegexp(RuntimeError, "Too many errors"):
+            section.execute(time.sleep, 0)
+
+        with self.assertRaisesRegexp(
+                RuntimeError, "Operations completed with errors"):
+            section.wait(ignore_errors=False)
diff --git a/packetary/tests/test_streams.py b/packetary/tests/test_streams.py
new file mode 100644
index 0000000..77fc956
--- /dev/null
+++ b/packetary/tests/test_streams.py
@@ -0,0 +1,93 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright 2015 Mirantis, Inc.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import gzip
+import six
+
+from packetary.library import streams
+from packetary.tests import base
+
+
+class TestBufferedStream(base.TestCase):
+    def setUp(self):
+        super(TestBufferedStream, self).setUp()
+        self.stream = streams.StreamWrapper(
+            six.BytesIO(b"line1\nline2\nline3\n")
+        )
+
+    def test_read(self):
+        self.stream.CHUNK_SIZE = 10
+        chunk = self.stream.read(5)
+        self.assertEqual(b"line1", chunk)
+        self.assertEqual(b"\nline", self.stream.unread_tail)
+        chunk = self.stream.read(1024)
+        self.assertEqual(b"\nline2\nline3\n", chunk)
+        self.assertEqual(b"", self.stream.unread_tail)
+
+    def test_readline(self):
+        self.stream.CHUNK_SIZE = 12
+        chunk = self.stream.readline()
+        self.assertEqual(b"line1\n", chunk)
+        self.assertEqual(b"line2\n", self.stream.unread_tail)
+        lines = list(self.stream.readlines())
+        self.assertEqual([b"line2\n", b"line3\n"], lines)
+        self.assertEqual(b"", self.stream.unread_tail)
+
+    def test_readlines(self):
+        self.stream.CHUNK_SIZE = 12
+        lines = list(self.stream.readlines())
+        self.assertEqual(
+            [b"line1\n", b"line2\n", b"line3\n"],
+            lines)
+
+
+class TestGzipDecompress(base.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        cls.gzipped = six.BytesIO()
+        gz = gzip.GzipFile(fileobj=cls.gzipped, mode="w")
+        gz.write(b"line1\nline2\nline3\n")
+        gz.flush()
+        gz.close()
+
+    def setUp(self):
+        super(TestGzipDecompress, self).setUp()
+        self.gzipped.seek(0)
+        self.stream = streams.GzipDecompress(self.gzipped)
+
+    def test_read(self):
+        chunk = self.stream.read(5)
+        self.assertEqual(b"line1", chunk)
+        self.assertEqual(b"\nline2\nline3\n", self.stream.unread_tail)
+        chunk = self.stream.read(1024)
+        self.assertEqual(b"\nline2\nline3\n", chunk)
+        self.assertEqual(b"", self.stream.unread_tail)
+
+    def test_readline(self):
+        self.stream.CHUNK_SIZE = 12
+        chunk = self.stream.readline()
+        self.assertEqual(b"line1\n", chunk)
+        self.assertEqual(b"line2\nl", self.stream.unread_tail)
+        lines = list(self.stream.readlines())
+        self.assertEqual([b"line2\n", b"line3\n"], lines)
+        self.assertEqual(b"", self.stream.unread_tail)
+
+    def test_readlines(self):
+        self.stream.CHUNK_SIZE = 12
+        lines = list(self.stream.readlines())
+        self.assertEqual(
+            [b"line1\n", b"line2\n", b"line3\n"],
+            lines)
diff --git a/requirements.txt b/requirements.txt
index 08b0f01..2aee4db 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -2,5 +2,6 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-pbr>=1.6
 Babel>=1.3
+eventlet>=0.17
+pbr>=1.6
diff --git a/tox.ini b/tox.ini
index ab6ca39..ebc1142 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,6 +1,6 @@
 [tox]
 minversion = 1.6
-envlist = py34,py26,py27,pep8
+envlist = py34,py27,py26,pep8
 skipsdist = True
 
 [testenv]
@@ -9,22 +9,22 @@ install_command = pip install -U {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/test-requirements.txt
-commands = python setup.py test --slowest --testr-args='{posargs}'
+commands = python setup.py test --slowest --testr-args='{posargs:packetary}'
 
 [testenv:pep8]
-commands = flake8
+commands = flake8 {posargs:packetary}
 
 [testenv:venv]
-commands = {posargs}
+commands = {posargs:packetary}
 
 [testenv:cover]
-commands = python setup.py test --coverage --testr-args='{posargs}'
+commands = python setup.py test --coverage --testr-args='{posargs:packetary}'
 
 [testenv:docs]
 commands = python setup.py build_sphinx
 
 [testenv:debug]
-commands = oslo_debug_helper {posargs}
+commands = oslo_debug_helper {posargs:packetary}
 
 [flake8]
 # E123, E125 skipped as they are invalid PEP-8.
@@ -32,4 +32,4 @@ commands = oslo_debug_helper {posargs}
 show-source = True
 ignore = E123,E125
 builtins = _
-exclude=.venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build,util,.idea
+exclude=*egg,*lib/python*,*openstack/common*,.git,.idea,.tox,.venv,build,dist,doc