diff --git a/docs/history.rst b/docs/history.rst
index 51124bb..5590628 100644
--- a/docs/history.rst
+++ b/docs/history.rst
@@ -3,6 +3,10 @@
 Version History
 ===============
 
+1.1.0 (2018-03-19)
+------------------
+ - Add ``close`` method to ``AWSClient`` (#9 from `31z4 <https://github.com/31z4>_`)
+
 1.0.0 (2018-01-19)
 ------------------
  - Add new exception type ``tornado_aws.exceptions.RequestException`` (#5 from `nvllsvm <https://github.com/nvllsvm>_`)
diff --git a/requires/installation.txt b/requires/installation.txt
index c98ba2b..78ed743 100644
--- a/requires/installation.txt
+++ b/requires/installation.txt
@@ -1,1 +1,1 @@
-tornado>=4.0
+tornado>=4.0,<5.0
diff --git a/setup.py b/setup.py
index d2addcf..daebb99 100644
--- a/setup.py
+++ b/setup.py
@@ -39,7 +39,7 @@ def read_requirements(name):
 
 setuptools.setup(
     name='tornado-aws',
-    version='1.0.0',
+    version='1.1.0',
     description=DESC,
     long_description=open('README.rst').read(),
     author='Gavin M. Roy',
diff --git a/tornado_aws/__init__.py b/tornado_aws/__init__.py
index 81ee2f7..4fb5d99 100644
--- a/tornado_aws/__init__.py
+++ b/tornado_aws/__init__.py
@@ -6,6 +6,6 @@ from tornado_aws.client import AWSClient
 from tornado_aws.client import AsyncAWSClient
 from tornado_aws.client import exceptions
 
-__version__ = '1.0.0'
+__version__ = '1.1.0'
 
 __all__ = ['AWSClient', 'AsyncAWSClient', 'exceptions']
diff --git a/tornado_aws/client.py b/tornado_aws/client.py
index 95c8e90..775c40a 100644
--- a/tornado_aws/client.py
+++ b/tornado_aws/client.py
@@ -181,6 +181,10 @@ class AWSClient(object):
                                       headers, body, True)
             raise aws_error if aws_error else error
 
+    def close(self):
+        """Closes the underlying HTTP client, freeing any resources used."""
+        self._client.close()
+
     def _process_error(self, error):
         """Attempt to process the error coming from AWS. Returns ``True``
         if the client should attempt to fetch credentials and the AWSError

AsyncHTTPClient(force_instance=True) could cause memory leaks
What's the reason of forcing a new instance of the `AsyncHTTPClient`? The Tornado documentation states
> close() is generally only necessary when either the IOLoop is also being closed, or the force_instance=True argument was used when creating the AsyncHTTPClient

Not closing an `AsyncHTTPClient ` instance is potentially causing memory leaks.
And I see an evidence of this within my running Tornado application that uses `AsyncAWSClient` with `AsyncHTTPClient.configure('tornado.curl_httpclient.CurlAsyncHTTPClient')`

```
>>> import objgraph
>>> objgraph.show_most_common_types()
Curl                       393010
list                       33683
function                   23579
```
With 393010 `Curl` instances the proccess eats about 14GB of memory which is insane!

At the very least the `close` method of the `AsyncHTTPClient` must be exposed so that one could close it explicitly. Additionally `force_instance=True` could be removed if there was no particular reason for it.
diff --git a/tests/client_tests.py b/tests/client_tests.py
index 0d02db9..42eed16 100644
--- a/tests/client_tests.py
+++ b/tests/client_tests.py
@@ -125,6 +125,20 @@ class AsyncClientConfigTestCase(ClientConfigTestCase):
     CLIENT = client.AsyncAWSClient
 
 
+class ClientCloseTestCase(TestCase):
+
+    def test_close_is_called(self):
+        with self.client_with_default_creds('s3') as obj:
+            with mock.patch.object(obj._client, 'close') as close:
+                obj.close()
+                close.assert_called_once()
+
+
+class AsyncClientCloseTestCase(ClientCloseTestCase):
+
+    CLIENT = client.AsyncAWSClient
+
+
 class AMZErrorTestCase(TestCase):
 
     def test_awz_error(self):

pip install -e .[curl]
parse_log_pytest
requirements.txt
nose coverage codecov flake8 futures mock pycurl pylint wheel pytest
3.6
requires/installation.txt requires/testing.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
astroid==2.11.7
attrs==22.2.0
certifi==2021.5.30
charset-normalizer==2.0.12
codecov==2.1.13
coverage==6.2
dill==0.3.4
flake8==5.0.4
futures==2.2.0
idna==3.10
importlib-metadata==4.2.0
iniconfig==1.1.1
isort==5.10.1
lazy-object-proxy==1.7.1
mccabe==0.7.0
mock==5.2.0
nose==1.3.7
packaging==21.3
platformdirs==2.4.0
pluggy==1.0.0
py==1.11.0
pycodestyle==2.9.1
pycurl==7.45.6
pyflakes==2.5.0
pylint==2.13.9
pyparsing==3.1.4
pytest==7.0.1
requests==2.27.1
tomli==1.2.3
tornado==6.1
-e git+https://github.com/gmr/tornado-aws.git@549b844677b8112f7da3a57dd86e4a2e7178235f#egg=tornado_aws
typed-ast==1.5.5
typing_extensions==4.1.1
urllib3==1.26.20
wrapt==1.16.0
zipp==3.6.0

name: tornado-aws
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - pip=21.2.2=py36h06a4308_0
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - astroid==2.11.7
      - attrs==22.2.0
      - charset-normalizer==2.0.12
      - codecov==2.1.13
      - coverage==6.2
      - dill==0.3.4
      - flake8==5.0.4
      - futures==2.2.0
      - idna==3.10
      - importlib-metadata==4.2.0
      - iniconfig==1.1.1
      - isort==5.10.1
      - lazy-object-proxy==1.7.1
      - mccabe==0.7.0
      - mock==5.2.0
      - nose==1.3.7
      - packaging==21.3
      - platformdirs==2.4.0
      - pluggy==1.0.0
      - py==1.11.0
      - pycodestyle==2.9.1
      - pycurl==7.45.6
      - pyflakes==2.5.0
      - pylint==2.13.9
      - pyparsing==3.1.4
      - pytest==7.0.1
      - requests==2.27.1
      - tomli==1.2.3
      - tornado==6.1
      - typed-ast==1.5.5
      - typing-extensions==4.1.1
      - urllib3==1.26.20
      - wrapt==1.16.0
      - zipp==3.6.0
prefix: /opt/conda/envs/tornado-aws

tests/client_tests.py::ClientCloseTestCase::test_close_is_called tests/client_tests.py::AsyncClientCloseTestCase::test_close_is_called
tests/client_tests.py::AsyncClientFetchTestCase::test_fetch_credentials_and_request_fail tests/client_tests.py::AsyncClientFetchTestCase::test_fetch_credentials_fail tests/client_tests.py::AsyncClientFetchTestCase::test_fetch_expired_credentials tests/client_tests.py::AsyncClientFetchTestCase::test_fetch_needs_credentials tests/client_tests.py::AsyncClientFetchTestCase::test_fetch_os_error tests/client_tests.py::AsyncClientFetchTestCase::test_fetch_refresh_failure tests/client_tests.py::AsyncClientFetchTestCase::test_fetch_success
tests/client_tests.py::ClientConfigTestCase::test_passed_in_values tests/client_tests.py::ClientConfigTestCase::test_with_valid_config_default_profile tests/client_tests.py::ClientConfigTestCase::test_with_valid_config_specified_profile tests/client_tests.py::AsyncClientConfigTestCase::test_passed_in_values tests/client_tests.py::AsyncClientConfigTestCase::test_with_valid_config_default_profile tests/client_tests.py::AsyncClientConfigTestCase::test_with_valid_config_specified_profile tests/client_tests.py::AMZErrorTestCase::test_awz_error tests/client_tests.py::AMZErrorTestCase::test_unsupported_payload tests/client_tests.py::XMLErrorTestCase::test_advertising_error tests/client_tests.py::XMLErrorTestCase::test_ec2_error tests/client_tests.py::XMLErrorTestCase::test_s3_error tests/client_tests.py::XMLErrorTestCase::test_simpledb_error tests/client_tests.py::XMLErrorTestCase::test_unparsable_error tests/client_tests.py::XMLErrorTestCase::test_unsupported_error tests/client_tests.py::ProcessErrorTestCase::test_599_bypasses_processing tests/client_tests.py::ProcessErrorTestCase::test_process_bogus_response tests/client_tests.py::ProcessErrorTestCase::test_process_dynamodb_error_creds tests/client_tests.py::ProcessErrorTestCase::test_process_error_awz_creds tests/client_tests.py::ProcessErrorTestCase::test_process_error_ec2_non_auth tests/client_tests.py::ProcessErrorTestCase::test_process_error_s3 tests/client_tests.py::ProcessErrorTestCase::test_process_simpledb_non_auth tests/client_tests.py::ClientFetchTestCase::test_fetch_needs_credentials tests/client_tests.py::ClientFetchTestCase::test_fetch_no_headers tests/client_tests.py::ClientFetchTestCase::test_fetch_os_error tests/client_tests.py::ClientFetchTestCase::test_fetch_success tests/client_tests.py::ClientFetchTestCase::test_fetch_when_client_fails_credentials tests/client_tests.py::ClientFetchTestCase::test_fetch_when_client_needs_credentials tests/client_tests.py::ClientFetchTestCase::test_fetch_when_client_raises_error tests/client_tests.py::NoCurlAsyncTestCase::test_no_curl_raises_exception
tornado_aws/client.py setup.py requires/installation.txt docs/history.rst tornado_aws/__init__.py
tornado_aws/client.py setup.py requires/installation.txt docs/history.rst tornado_aws/__init__.py