X-Git-Url: https://git.arvados.org/arvados.git/blobdiff_plain/d2f68bd1e108c3f2dda2322c427050d019b17e04..ebb2559b3a09636ff687316bbe512e0e8a86b168:/sdk/python/tests/test_keep_client.py

diff --git a/sdk/python/tests/test_keep_client.py b/sdk/python/tests/test_keep_client.py
index be13c55048..85b5bc81f0 100644
--- a/sdk/python/tests/test_keep_client.py
+++ b/sdk/python/tests/test_keep_client.py
@@ -1,15 +1,19 @@
 import hashlib
 import mock
 import os
+import pycurl
 import random
 import re
 import socket
+import threading
+import time
 import unittest
 import urlparse
 
 import arvados
 import arvados.retry
 import arvados_testutil as tutil
+import keepstub
 import run_test_server
 
 class KeepTestCase(run_test_server.TestCaseWithServers):
@@ -25,14 +29,21 @@ class KeepTestCase(run_test_server.TestCaseWithServers):
                                              proxy='', local_store='')
 
     def test_KeepBasicRWTest(self):
+        self.assertEqual(0, self.keep_client.upload_counter.get())
         foo_locator = self.keep_client.put('foo')
         self.assertRegexpMatches(
             foo_locator,
             '^acbd18db4cc2f85cedef654fccc4a4d8\+3',
             'wrong md5 hash from Keep.put("foo"): ' + foo_locator)
+
+        # 6 bytes because uploaded 2 copies
+        self.assertEqual(6, self.keep_client.upload_counter.get())
+
+        self.assertEqual(0, self.keep_client.download_counter.get())
         self.assertEqual(self.keep_client.get(foo_locator),
                          'foo',
                          'wrong content from Keep.get(md5("foo"))')
+        self.assertEqual(3, self.keep_client.download_counter.get())
 
     def test_KeepBinaryRWTest(self):
         blob_str = '\xff\xfe\xf7\x00\x01\x02'
@@ -58,6 +69,7 @@ class KeepTestCase(run_test_server.TestCaseWithServers):
                          blob_str,
                          'wrong content from Keep.get(md5(<binarydata>))')
 
+    @unittest.skip("unreliable test - please fix and close #8752")
     def test_KeepSingleCopyRWTest(self):
         blob_str = '\xff\xfe\xfd\xfc\x00\x01\x02\x03'
         blob_locator = self.keep_client.put(blob_str, copies=1)
@@ -92,6 +104,17 @@ class KeepTestCase(run_test_server.TestCaseWithServers):
             # Must be a string type
             self.keep_client.put({})
 
+    def test_KeepHeadTest(self):
+        locator = self.keep_client.put('test_head')
+        self.assertRegexpMatches(
+            locator,
+            '^b9a772c7049325feb7130fff1f8333e9\+9',
+            'wrong md5 hash from Keep.put for "test_head": ' + locator)
+        self.assertEqual(True, self.keep_client.head(locator))
+        self.assertEqual(self.keep_client.get(locator),
+                         'test_head',
+                         'wrong content from Keep.get for "test_head"')
+
 class KeepPermissionTestCase(run_test_server.TestCaseWithServers):
     MAIN_SERVER = {}
     KEEP_SERVER = {'blob_signing_key': 'abcdefghijk0123456789',
@@ -217,8 +240,8 @@ class KeepProxyTestCase(run_test_server.TestCaseWithServers):
         super(KeepProxyTestCase, self).tearDown()
 
     def test_KeepProxyTest1(self):
-        # Will use ARVADOS_KEEP_PROXY environment variable that is set by
-        # setUpClass().
+        # Will use ARVADOS_KEEP_SERVICES environment variable that
+        # is set by setUpClass().
         keep_client = arvados.KeepClient(api_client=self.api_client,
                                          local_store='')
         baz_locator = keep_client.put('baz')
@@ -247,6 +270,22 @@ class KeepProxyTestCase(run_test_server.TestCaseWithServers):
                          'wrong content from Keep.get(md5("baz2"))')
         self.assertTrue(keep_client.using_proxy)
 
+    def test_KeepProxyTestMultipleURIs(self):
+        # Test using ARVADOS_KEEP_SERVICES env var overriding any
+        # existing proxy setting and setting multiple proxies
+        arvados.config.settings()['ARVADOS_KEEP_SERVICES'] = 'http://10.0.0.1 https://foo.example.org:1234/'
+        keep_client = arvados.KeepClient(api_client=self.api_client,
+                                         local_store='')
+        uris = [x['_service_root'] for x in keep_client._keep_services]
+        self.assertEqual(uris, ['http://10.0.0.1/',
+                                'https://foo.example.org:1234/'])
+
+    def test_KeepProxyTestInvalidURI(self):
+        arvados.config.settings()['ARVADOS_KEEP_SERVICES'] = 'bad.uri.org'
+        with self.assertRaises(arvados.errors.ArgumentError):
+            keep_client = arvados.KeepClient(api_client=self.api_client,
+                                             local_store='')
+
 
 class KeepClientServiceTestCase(unittest.TestCase, tutil.ApiClientMock):
     def get_service_roots(self, api_client):
@@ -267,97 +306,305 @@ class KeepClientServiceTestCase(unittest.TestCase, tutil.ApiClientMock):
         self.assertEqual('100::1', service.hostname)
         self.assertEqual(10, service.port)
 
-    # test_get_timeout and test_put_timeout test that
-    # KeepClient.get and KeepClient.put use the appropriate timeouts
-    # when connected directly to a Keep server (i.e. non-proxy timeout)
+    # test_*_timeout verify that KeepClient instructs pycurl to use
+    # the appropriate connection and read timeouts. They don't care
+    # whether pycurl actually exhibits the expected timeout behavior
+    # -- those tests are in the KeepClientTimeout test class.
 
     def test_get_timeout(self):
         api_client = self.mock_keep_services(count=1)
-        force_timeout = [socket.timeout("timed out")]
-        with tutil.mock_get(force_timeout) as mock_session:
+        force_timeout = socket.timeout("timed out")
+        with tutil.mock_keep_responses(force_timeout, 0) as mock:
             keep_client = arvados.KeepClient(api_client=api_client)
             with self.assertRaises(arvados.errors.KeepReadError):
                 keep_client.get('ffffffffffffffffffffffffffffffff')
-            self.assertTrue(mock_session.return_value.get.called)
             self.assertEqual(
-                arvados.KeepClient.DEFAULT_TIMEOUT,
-                mock_session.return_value.get.call_args[1]['timeout'])
+                mock.responses[0].getopt(pycurl.CONNECTTIMEOUT_MS),
+                int(arvados.KeepClient.DEFAULT_TIMEOUT[0]*1000))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_TIME),
+                int(arvados.KeepClient.DEFAULT_TIMEOUT[1]))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_LIMIT),
+                int(arvados.KeepClient.DEFAULT_TIMEOUT[2]))
 
     def test_put_timeout(self):
         api_client = self.mock_keep_services(count=1)
-        force_timeout = [socket.timeout("timed out")]
-        with tutil.mock_put(force_timeout) as mock_session:
+        force_timeout = socket.timeout("timed out")
+        with tutil.mock_keep_responses(force_timeout, 0) as mock:
             keep_client = arvados.KeepClient(api_client=api_client)
             with self.assertRaises(arvados.errors.KeepWriteError):
                 keep_client.put('foo')
-            self.assertTrue(mock_session.return_value.put.called)
             self.assertEqual(
-                arvados.KeepClient.DEFAULT_TIMEOUT,
-                mock_session.return_value.put.call_args[1]['timeout'])
+                mock.responses[0].getopt(pycurl.CONNECTTIMEOUT_MS),
+                int(arvados.KeepClient.DEFAULT_TIMEOUT[0]*1000))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_TIME),
+                int(arvados.KeepClient.DEFAULT_TIMEOUT[1]))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_LIMIT),
+                int(arvados.KeepClient.DEFAULT_TIMEOUT[2]))
+
+    def test_head_timeout(self):
+        api_client = self.mock_keep_services(count=1)
+        force_timeout = socket.timeout("timed out")
+        with tutil.mock_keep_responses(force_timeout, 0) as mock:
+            keep_client = arvados.KeepClient(api_client=api_client)
+            with self.assertRaises(arvados.errors.KeepReadError):
+                keep_client.head('ffffffffffffffffffffffffffffffff')
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.CONNECTTIMEOUT_MS),
+                int(arvados.KeepClient.DEFAULT_TIMEOUT[0]*1000))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_TIME),
+                int(arvados.KeepClient.DEFAULT_TIMEOUT[1]))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_LIMIT),
+                int(arvados.KeepClient.DEFAULT_TIMEOUT[2]))
 
     def test_proxy_get_timeout(self):
-        # Force a timeout, verifying that the requests.get or
-        # requests.put method was called with the proxy_timeout
-        # setting rather than the default timeout.
         api_client = self.mock_keep_services(service_type='proxy', count=1)
-        force_timeout = [socket.timeout("timed out")]
-        with tutil.mock_get(force_timeout) as mock_session:
+        force_timeout = socket.timeout("timed out")
+        with tutil.mock_keep_responses(force_timeout, 0) as mock:
             keep_client = arvados.KeepClient(api_client=api_client)
             with self.assertRaises(arvados.errors.KeepReadError):
                 keep_client.get('ffffffffffffffffffffffffffffffff')
-            self.assertTrue(mock_session.return_value.get.called)
             self.assertEqual(
-                arvados.KeepClient.DEFAULT_PROXY_TIMEOUT,
-                mock_session.return_value.get.call_args[1]['timeout'])
+                mock.responses[0].getopt(pycurl.CONNECTTIMEOUT_MS),
+                int(arvados.KeepClient.DEFAULT_PROXY_TIMEOUT[0]*1000))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_TIME),
+                int(arvados.KeepClient.DEFAULT_PROXY_TIMEOUT[1]))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_LIMIT),
+                int(arvados.KeepClient.DEFAULT_PROXY_TIMEOUT[2]))
+
+    def test_proxy_head_timeout(self):
+        api_client = self.mock_keep_services(service_type='proxy', count=1)
+        force_timeout = socket.timeout("timed out")
+        with tutil.mock_keep_responses(force_timeout, 0) as mock:
+            keep_client = arvados.KeepClient(api_client=api_client)
+            with self.assertRaises(arvados.errors.KeepReadError):
+                keep_client.head('ffffffffffffffffffffffffffffffff')
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.CONNECTTIMEOUT_MS),
+                int(arvados.KeepClient.DEFAULT_PROXY_TIMEOUT[0]*1000))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_TIME),
+                int(arvados.KeepClient.DEFAULT_PROXY_TIMEOUT[1]))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_LIMIT),
+                int(arvados.KeepClient.DEFAULT_PROXY_TIMEOUT[2]))
 
     def test_proxy_put_timeout(self):
-        # Force a timeout, verifying that the requests.get or
-        # requests.put method was called with the proxy_timeout
-        # setting rather than the default timeout.
         api_client = self.mock_keep_services(service_type='proxy', count=1)
-        force_timeout = [socket.timeout("timed out")]
-        with tutil.mock_put(force_timeout) as mock_session:
+        force_timeout = socket.timeout("timed out")
+        with tutil.mock_keep_responses(force_timeout, 0) as mock:
             keep_client = arvados.KeepClient(api_client=api_client)
             with self.assertRaises(arvados.errors.KeepWriteError):
                 keep_client.put('foo')
-            self.assertTrue(mock_session.return_value.put.called)
             self.assertEqual(
-                arvados.KeepClient.DEFAULT_PROXY_TIMEOUT,
-                mock_session.return_value.put.call_args[1]['timeout'])
+                mock.responses[0].getopt(pycurl.CONNECTTIMEOUT_MS),
+                int(arvados.KeepClient.DEFAULT_PROXY_TIMEOUT[0]*1000))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_TIME),
+                int(arvados.KeepClient.DEFAULT_PROXY_TIMEOUT[1]))
+            self.assertEqual(
+                mock.responses[0].getopt(pycurl.LOW_SPEED_LIMIT),
+                int(arvados.KeepClient.DEFAULT_PROXY_TIMEOUT[2]))
+
+    def check_no_services_error(self, verb, exc_class):
+        api_client = mock.MagicMock(name='api_client')
+        api_client.keep_services().accessible().execute.side_effect = (
+            arvados.errors.ApiError)
+        keep_client = arvados.KeepClient(api_client=api_client)
+        with self.assertRaises(exc_class) as err_check:
+            getattr(keep_client, verb)('d41d8cd98f00b204e9800998ecf8427e+0')
+        self.assertEqual(0, len(err_check.exception.request_errors()))
+
+    def test_get_error_with_no_services(self):
+        self.check_no_services_error('get', arvados.errors.KeepReadError)
 
-    def test_probe_order_reference_set(self):
+    def test_head_error_with_no_services(self):
+        self.check_no_services_error('head', arvados.errors.KeepReadError)
+
+    def test_put_error_with_no_services(self):
+        self.check_no_services_error('put', arvados.errors.KeepWriteError)
+
+    def check_errors_from_last_retry(self, verb, exc_class):
+        api_client = self.mock_keep_services(count=2)
+        req_mock = tutil.mock_keep_responses(
+            "retry error reporting test", 500, 500, 403, 403)
+        with req_mock, tutil.skip_sleep, \
+                self.assertRaises(exc_class) as err_check:
+            keep_client = arvados.KeepClient(api_client=api_client)
+            getattr(keep_client, verb)('d41d8cd98f00b204e9800998ecf8427e+0',
+                                       num_retries=3)
+        self.assertEqual([403, 403], [
+                getattr(error, 'status_code', None)
+                for error in err_check.exception.request_errors().itervalues()])
+
+    def test_get_error_reflects_last_retry(self):
+        self.check_errors_from_last_retry('get', arvados.errors.KeepReadError)
+
+    def test_head_error_reflects_last_retry(self):
+        self.check_errors_from_last_retry('head', arvados.errors.KeepReadError)
+
+    def test_put_error_reflects_last_retry(self):
+        self.check_errors_from_last_retry('put', arvados.errors.KeepWriteError)
+
+    def test_put_error_does_not_include_successful_puts(self):
+        data = 'partial failure test'
+        data_loc = tutil.str_keep_locator(data)
+        api_client = self.mock_keep_services(count=3)
+        with tutil.mock_keep_responses(data_loc, 200, 500, 500) as req_mock, \
+                self.assertRaises(arvados.errors.KeepWriteError) as exc_check:
+            keep_client = arvados.KeepClient(api_client=api_client)
+            keep_client.put(data)
+        self.assertEqual(2, len(exc_check.exception.request_errors()))
+
+    def test_proxy_put_with_no_writable_services(self):
+        data = 'test with no writable services'
+        data_loc = tutil.str_keep_locator(data)
+        api_client = self.mock_keep_services(service_type='proxy', read_only=True, count=1)
+        with tutil.mock_keep_responses(data_loc, 200, 500, 500) as req_mock, \
+                self.assertRaises(arvados.errors.KeepWriteError) as exc_check:
+          keep_client = arvados.KeepClient(api_client=api_client)
+          keep_client.put(data)
+        self.assertEqual(True, ("no Keep services available" in str(exc_check.exception)))
+        self.assertEqual(0, len(exc_check.exception.request_errors()))
+
+    def test_oddball_service_get(self):
+        body = 'oddball service get'
+        api_client = self.mock_keep_services(service_type='fancynewblobstore')
+        with tutil.mock_keep_responses(body, 200):
+            keep_client = arvados.KeepClient(api_client=api_client)
+            actual = keep_client.get(tutil.str_keep_locator(body))
+        self.assertEqual(body, actual)
+
+    def test_oddball_service_put(self):
+        body = 'oddball service put'
+        pdh = tutil.str_keep_locator(body)
+        api_client = self.mock_keep_services(service_type='fancynewblobstore')
+        with tutil.mock_keep_responses(pdh, 200):
+            keep_client = arvados.KeepClient(api_client=api_client)
+            actual = keep_client.put(body, copies=1)
+        self.assertEqual(pdh, actual)
+
+    def test_oddball_service_writer_count(self):
+        body = 'oddball service writer count'
+        pdh = tutil.str_keep_locator(body)
+        api_client = self.mock_keep_services(service_type='fancynewblobstore',
+                                             count=4)
+        headers = {'x-keep-replicas-stored': 3}
+        with tutil.mock_keep_responses(pdh, 200, 418, 418, 418,
+                                       **headers) as req_mock:
+            keep_client = arvados.KeepClient(api_client=api_client)
+            actual = keep_client.put(body, copies=2)
+        self.assertEqual(pdh, actual)
+        self.assertEqual(1, req_mock.call_count)
+
+
+@tutil.skip_sleep
+class KeepClientRendezvousTestCase(unittest.TestCase, tutil.ApiClientMock):
+
+    def setUp(self):
         # expected_order[i] is the probe order for
         # hash=md5(sprintf("%064x",i)) where there are 16 services
         # with uuid sprintf("anything-%015x",j) with j in 0..15. E.g.,
         # the first probe for the block consisting of 64 "0"
         # characters is the service whose uuid is
         # "zzzzz-bi6l4-000000000000003", so expected_order[0][0]=='3'.
-        expected_order = [
+        self.services = 16
+        self.expected_order = [
             list('3eab2d5fc9681074'),
             list('097dba52e648f1c3'),
             list('c5b4e023f8a7d691'),
             list('9d81c02e76a3bf54'),
             ]
-        hashes = [
-            hashlib.md5("{:064x}".format(x)).hexdigest()
-            for x in range(len(expected_order))]
-        api_client = self.mock_keep_services(count=16)
-        keep_client = arvados.KeepClient(api_client=api_client)
-        for i, hash in enumerate(hashes):
-            roots = keep_client.weighted_service_roots(arvados.KeepLocator(hash))
+        self.blocks = [
+            "{:064x}".format(x)
+            for x in range(len(self.expected_order))]
+        self.hashes = [
+            hashlib.md5(self.blocks[x]).hexdigest()
+            for x in range(len(self.expected_order))]
+        self.api_client = self.mock_keep_services(count=self.services)
+        self.keep_client = arvados.KeepClient(api_client=self.api_client)
+
+    def test_weighted_service_roots_against_reference_set(self):
+        # Confirm weighted_service_roots() returns the correct order
+        for i, hash in enumerate(self.hashes):
+            roots = self.keep_client.weighted_service_roots(arvados.KeepLocator(hash))
             got_order = [
                 re.search(r'//\[?keep0x([0-9a-f]+)', root).group(1)
                 for root in roots]
-            self.assertEqual(expected_order[i], got_order)
+            self.assertEqual(self.expected_order[i], got_order)
+
+    def test_get_probe_order_against_reference_set(self):
+        self._test_probe_order_against_reference_set(
+            lambda i: self.keep_client.get(self.hashes[i], num_retries=1))
+
+    def test_head_probe_order_against_reference_set(self):
+        self._test_probe_order_against_reference_set(
+            lambda i: self.keep_client.head(self.hashes[i], num_retries=1))
+
+    def test_put_probe_order_against_reference_set(self):
+        # copies=1 prevents the test from being sensitive to races
+        # between writer threads.
+        self._test_probe_order_against_reference_set(
+            lambda i: self.keep_client.put(self.blocks[i], num_retries=1, copies=1))
+
+    def _test_probe_order_against_reference_set(self, op):
+        for i in range(len(self.blocks)):
+            with tutil.mock_keep_responses('', *[500 for _ in range(self.services*2)]) as mock, \
+                 self.assertRaises(arvados.errors.KeepRequestError):
+                op(i)
+            got_order = [
+                re.search(r'//\[?keep0x([0-9a-f]+)', resp.getopt(pycurl.URL)).group(1)
+                for resp in mock.responses]
+            self.assertEqual(self.expected_order[i]*2, got_order)
+
+    def test_put_probe_order_multiple_copies(self):
+        for copies in range(2, 4):
+            for i in range(len(self.blocks)):
+                with tutil.mock_keep_responses('', *[500 for _ in range(self.services*3)]) as mock, \
+                     self.assertRaises(arvados.errors.KeepWriteError):
+                    self.keep_client.put(self.blocks[i], num_retries=2, copies=copies)
+                got_order = [
+                    re.search(r'//\[?keep0x([0-9a-f]+)', resp.getopt(pycurl.URL)).group(1)
+                    for resp in mock.responses]
+                # With T threads racing to make requests, the position
+                # of a given server in the sequence of HTTP requests
+                # (got_order) cannot be more than T-1 positions
+                # earlier than that server's position in the reference
+                # probe sequence (expected_order).
+                #
+                # Loop invariant: we have accounted for +pos+ expected
+                # probes, either by seeing them in +got_order+ or by
+                # putting them in +pending+ in the hope of seeing them
+                # later. As long as +len(pending)<T+, we haven't
+                # started a request too early.
+                pending = []
+                for pos, expected in enumerate(self.expected_order[i]*3):
+                    got = got_order[pos-len(pending)]
+                    while got in pending:
+                        del pending[pending.index(got)]
+                        got = got_order[pos-len(pending)]
+                    if got != expected:
+                        pending.append(expected)
+                        self.assertLess(
+                            len(pending), copies,
+                            "pending={}, with copies={}, got {}, expected {}".format(
+                                pending, copies, repr(got_order), repr(self.expected_order[i]*3)))
 
     def test_probe_waste_adding_one_server(self):
         hashes = [
             hashlib.md5("{:064x}".format(x)).hexdigest() for x in range(100)]
         initial_services = 12
-        api_client = self.mock_keep_services(count=initial_services)
-        keep_client = arvados.KeepClient(api_client=api_client)
+        self.api_client = self.mock_keep_services(count=initial_services)
+        self.keep_client = arvados.KeepClient(api_client=self.api_client)
         probes_before = [
-            keep_client.weighted_service_roots(arvados.KeepLocator(hash)) for hash in hashes]
+            self.keep_client.weighted_service_roots(arvados.KeepLocator(hash)) for hash in hashes]
         for added_services in range(1, 12):
             api_client = self.mock_keep_services(count=initial_services+added_services)
             keep_client = arvados.KeepClient(api_client=api_client)
@@ -392,14 +639,14 @@ class KeepClientServiceTestCase(unittest.TestCase, tutil.ApiClientMock):
     def check_64_zeros_error_order(self, verb, exc_class):
         data = '0' * 64
         if verb == 'get':
-            data = hashlib.md5(data).hexdigest() + '+1234'
+            data = tutil.str_keep_locator(data)
         # Arbitrary port number:
         aport = random.randint(1024,65535)
-        api_client = self.mock_keep_services(service_port=aport, count=16)
+        api_client = self.mock_keep_services(service_port=aport, count=self.services)
         keep_client = arvados.KeepClient(api_client=api_client)
-        with mock.patch('requests.' + verb,
-                        side_effect=socket.timeout) as req_mock, \
-                self.assertRaises(exc_class) as err_check:
+        with mock.patch('pycurl.Curl') as curl_mock, \
+             self.assertRaises(exc_class) as err_check:
+            curl_mock.return_value.side_effect = socket.timeout
             getattr(keep_client, verb)(data)
         urls = [urlparse.urlparse(url)
                 for url in err_check.exception.request_errors()]
@@ -412,49 +659,162 @@ class KeepClientServiceTestCase(unittest.TestCase, tutil.ApiClientMock):
     def test_put_error_shows_probe_order(self):
         self.check_64_zeros_error_order('put', arvados.errors.KeepWriteError)
 
-    def check_no_services_error(self, verb, exc_class):
-        api_client = mock.MagicMock(name='api_client')
-        api_client.keep_services().accessible().execute.side_effect = (
-            arvados.errors.ApiError)
-        keep_client = arvados.KeepClient(api_client=api_client)
-        with self.assertRaises(exc_class) as err_check:
-            getattr(keep_client, verb)('d41d8cd98f00b204e9800998ecf8427e+0')
-        self.assertEqual(0, len(err_check.exception.request_errors()))
 
-    def test_get_error_with_no_services(self):
-        self.check_no_services_error('get', arvados.errors.KeepReadError)
+class KeepClientTimeout(unittest.TestCase, tutil.ApiClientMock):
+    # BANDWIDTH_LOW_LIM must be less than len(DATA) so we can transfer
+    # 1s worth of data and then trigger bandwidth errors before running
+    # out of data.
+    DATA = 'x'*2**11
+    BANDWIDTH_LOW_LIM = 1024
+    TIMEOUT_TIME = 1.0
 
-    def test_put_error_with_no_services(self):
-        self.check_no_services_error('put', arvados.errors.KeepWriteError)
+    class assertTakesBetween(unittest.TestCase):
+        def __init__(self, tmin, tmax):
+            self.tmin = tmin
+            self.tmax = tmax
 
-    def check_errors_from_last_retry(self, verb, exc_class):
-        api_client = self.mock_keep_services(count=2)
-        req_mock = getattr(tutil, 'mock_{}_responses'.format(verb))(
-            "retry error reporting test", 500, 500, 403, 403)
-        with req_mock, tutil.skip_sleep, \
-                self.assertRaises(exc_class) as err_check:
-            keep_client = arvados.KeepClient(api_client=api_client)
-            getattr(keep_client, verb)('d41d8cd98f00b204e9800998ecf8427e+0',
-                                       num_retries=3)
-        self.assertEqual([403, 403], [
-                getattr(error, 'status_code', None)
-                for error in err_check.exception.request_errors().itervalues()])
+        def __enter__(self):
+            self.t0 = time.time()
 
-    def test_get_error_reflects_last_retry(self):
-        self.check_errors_from_last_retry('get', arvados.errors.KeepReadError)
+        def __exit__(self, *args, **kwargs):
+            # Round times to milliseconds, like CURL. Otherwise, we
+            # fail when CURL reaches a 1s timeout at 0.9998s.
+            delta = round(time.time() - self.t0, 3)
+            self.assertGreaterEqual(delta, self.tmin)
+            self.assertLessEqual(delta, self.tmax)
 
-    def test_put_error_reflects_last_retry(self):
-        self.check_errors_from_last_retry('put', arvados.errors.KeepWriteError)
+    class assertTakesGreater(unittest.TestCase):
+        def __init__(self, tmin):
+            self.tmin = tmin
 
-    def test_put_error_does_not_include_successful_puts(self):
-        data = 'partial failure test'
-        data_loc = '{}+{}'.format(hashlib.md5(data).hexdigest(), len(data))
-        api_client = self.mock_keep_services(count=3)
-        with tutil.mock_put_responses(data_loc, 200, 500, 500) as req_mock, \
-                self.assertRaises(arvados.errors.KeepWriteError) as exc_check:
-            keep_client = arvados.KeepClient(api_client=api_client)
-            keep_client.put(data)
-        self.assertEqual(2, len(exc_check.exception.request_errors()))
+        def __enter__(self):
+            self.t0 = time.time()
+
+        def __exit__(self, *args, **kwargs):
+            delta = round(time.time() - self.t0, 3)
+            self.assertGreaterEqual(delta, self.tmin)
+
+    def setUp(self):
+        sock = socket.socket()
+        sock.bind(('0.0.0.0', 0))
+        self.port = sock.getsockname()[1]
+        sock.close()
+        self.server = keepstub.Server(('0.0.0.0', self.port), keepstub.Handler)
+        self.thread = threading.Thread(target=self.server.serve_forever)
+        self.thread.daemon = True # Exit thread if main proc exits
+        self.thread.start()
+        self.api_client = self.mock_keep_services(
+            count=1,
+            service_host='localhost',
+            service_port=self.port,
+        )
+
+    def tearDown(self):
+        self.server.shutdown()
+
+    def keepClient(self, timeouts=(0.1, TIMEOUT_TIME, BANDWIDTH_LOW_LIM)):
+        return arvados.KeepClient(
+            api_client=self.api_client,
+            timeout=timeouts)
+
+    def test_timeout_slow_connect(self):
+        # Can't simulate TCP delays with our own socket. Leave our
+        # stub server running uselessly, and try to connect to an
+        # unroutable IP address instead.
+        self.api_client = self.mock_keep_services(
+            count=1,
+            service_host='240.0.0.0',
+        )
+        with self.assertTakesBetween(0.1, 0.5):
+            with self.assertRaises(arvados.errors.KeepWriteError):
+                self.keepClient().put(self.DATA, copies=1, num_retries=0)
+
+    def test_low_bandwidth_no_delays_success(self):
+        self.server.setbandwidth(2*self.BANDWIDTH_LOW_LIM)
+        kc = self.keepClient()
+        loc = kc.put(self.DATA, copies=1, num_retries=0)
+        self.assertEqual(self.DATA, kc.get(loc, num_retries=0))
+
+    def test_too_low_bandwidth_no_delays_failure(self):
+        # Check that lessening bandwidth corresponds to failing
+        kc = self.keepClient()
+        loc = kc.put(self.DATA, copies=1, num_retries=0)
+        self.server.setbandwidth(0.5*self.BANDWIDTH_LOW_LIM)
+        with self.assertTakesGreater(self.TIMEOUT_TIME):
+            with self.assertRaises(arvados.errors.KeepReadError) as e:
+                kc.get(loc, num_retries=0)
+        with self.assertTakesGreater(self.TIMEOUT_TIME):
+            with self.assertRaises(arvados.errors.KeepWriteError):
+                kc.put(self.DATA, copies=1, num_retries=0)
+
+    def test_low_bandwidth_with_server_response_delay_failure(self):
+        kc = self.keepClient()
+        loc = kc.put(self.DATA, copies=1, num_retries=0)
+        self.server.setbandwidth(self.BANDWIDTH_LOW_LIM)
+        self.server.setdelays(response=self.TIMEOUT_TIME)
+        with self.assertTakesGreater(self.TIMEOUT_TIME):
+            with self.assertRaises(arvados.errors.KeepReadError) as e:
+                kc.get(loc, num_retries=0)
+        with self.assertTakesGreater(self.TIMEOUT_TIME):
+            with self.assertRaises(arvados.errors.KeepWriteError):
+                kc.put(self.DATA, copies=1, num_retries=0)
+        with self.assertTakesGreater(self.TIMEOUT_TIME):
+            with self.assertRaises(arvados.errors.KeepReadError) as e:
+                kc.head(loc, num_retries=0)
+
+    def test_low_bandwidth_with_server_mid_delay_failure(self):
+        kc = self.keepClient()
+        loc = kc.put(self.DATA, copies=1, num_retries=0)
+        self.server.setbandwidth(self.BANDWIDTH_LOW_LIM)
+        self.server.setdelays(mid_write=self.TIMEOUT_TIME, mid_read=self.TIMEOUT_TIME)
+        with self.assertTakesGreater(self.TIMEOUT_TIME):
+            with self.assertRaises(arvados.errors.KeepReadError) as e:
+                kc.get(loc, num_retries=0)
+        with self.assertTakesGreater(self.TIMEOUT_TIME):
+            with self.assertRaises(arvados.errors.KeepWriteError):
+                kc.put(self.DATA, copies=1, num_retries=0)
+
+    def test_timeout_slow_request(self):
+        loc = self.keepClient().put(self.DATA, copies=1, num_retries=0)
+        self.server.setdelays(request=.2)
+        self._test_connect_timeout_under_200ms(loc)
+        self.server.setdelays(request=2)
+        self._test_response_timeout_under_2s(loc)
+
+    def test_timeout_slow_response(self):
+        loc = self.keepClient().put(self.DATA, copies=1, num_retries=0)
+        self.server.setdelays(response=.2)
+        self._test_connect_timeout_under_200ms(loc)
+        self.server.setdelays(response=2)
+        self._test_response_timeout_under_2s(loc)
+
+    def test_timeout_slow_response_body(self):
+        loc = self.keepClient().put(self.DATA, copies=1, num_retries=0)
+        self.server.setdelays(response_body=.2)
+        self._test_connect_timeout_under_200ms(loc)
+        self.server.setdelays(response_body=2)
+        self._test_response_timeout_under_2s(loc)
+
+    def _test_connect_timeout_under_200ms(self, loc):
+        # Allow 100ms to connect, then 1s for response. Everything
+        # should work, and everything should take at least 200ms to
+        # return.
+        kc = self.keepClient(timeouts=(.1, 1))
+        with self.assertTakesBetween(.2, .3):
+            kc.put(self.DATA, copies=1, num_retries=0)
+        with self.assertTakesBetween(.2, .3):
+            self.assertEqual(self.DATA, kc.get(loc, num_retries=0))
+
+    def _test_response_timeout_under_2s(self, loc):
+        # Allow 10s to connect, then 1s for response. Nothing should
+        # work, and everything should take at least 1s to return.
+        kc = self.keepClient(timeouts=(10, 1))
+        with self.assertTakesBetween(1, 9):
+            with self.assertRaises(arvados.errors.KeepReadError):
+                kc.get(loc, num_retries=0)
+        with self.assertTakesBetween(1, 9):
+            with self.assertRaises(arvados.errors.KeepWriteError):
+                kc.put(self.DATA, copies=1, num_retries=0)
 
 
 class KeepClientGatewayTestCase(unittest.TestCase, tutil.ApiClientMock):
@@ -468,28 +828,32 @@ class KeepClientGatewayTestCase(unittest.TestCase, tutil.ApiClientMock):
                 'service_type': 'gateway:test',
         } for i in range(gateways)]
         self.gateway_roots = [
-            "https://[{service_host}]:{service_port}/".format(**gw)
+            "https://{service_host}:{service_port}/".format(**gw)
             for gw in self.gateways]
         self.api_client = self.mock_keep_services(
             count=disks, additional_services=self.gateways)
         self.keepClient = arvados.KeepClient(api_client=self.api_client)
 
-    @mock.patch('requests.Session')
-    def test_get_with_gateway_hint_first(self, MockSession):
-        MockSession.return_value.get.return_value = tutil.fake_requests_response(
+    @mock.patch('pycurl.Curl')
+    def test_get_with_gateway_hint_first(self, MockCurl):
+        MockCurl.return_value = tutil.FakeCurl.make(
             code=200, body='foo', headers={'Content-Length': 3})
         self.mock_disks_and_gateways()
         locator = 'acbd18db4cc2f85cedef654fccc4a4d8+3+K@' + self.gateways[0]['uuid']
         self.assertEqual('foo', self.keepClient.get(locator))
-        self.assertEqual((self.gateway_roots[0]+locator,),
-                         MockSession.return_value.get.call_args_list[0][0])
+        self.assertEqual(self.gateway_roots[0]+locator,
+                         MockCurl.return_value.getopt(pycurl.URL))
+        self.assertEqual(True, self.keepClient.head(locator))
 
-    @mock.patch('requests.Session')
-    def test_get_with_gateway_hints_in_order(self, MockSession):
+    @mock.patch('pycurl.Curl')
+    def test_get_with_gateway_hints_in_order(self, MockCurl):
         gateways = 4
         disks = 3
-        MockSession.return_value.get.return_value = tutil.fake_requests_response(
-            code=404, body='')
+        mocks = [
+            tutil.FakeCurl.make(code=404, body='')
+            for _ in range(gateways+disks)
+        ]
+        MockCurl.side_effect = tutil.queue_with(mocks)
         self.mock_disks_and_gateways(gateways=gateways, disks=disks)
         locator = '+'.join(['acbd18db4cc2f85cedef654fccc4a4d8+3'] +
                            ['K@'+gw['uuid'] for gw in self.gateways])
@@ -497,23 +861,57 @@ class KeepClientGatewayTestCase(unittest.TestCase, tutil.ApiClientMock):
             self.keepClient.get(locator)
         # Gateways are tried first, in the order given.
         for i, root in enumerate(self.gateway_roots):
-            self.assertEqual((root+locator,),
-                             MockSession.return_value.get.call_args_list[i][0])
+            self.assertEqual(root+locator,
+                             mocks[i].getopt(pycurl.URL))
+        # Disk services are tried next.
+        for i in range(gateways, gateways+disks):
+            self.assertRegexpMatches(
+                mocks[i].getopt(pycurl.URL),
+                r'keep0x')
+
+    @mock.patch('pycurl.Curl')
+    def test_head_with_gateway_hints_in_order(self, MockCurl):
+        gateways = 4
+        disks = 3
+        mocks = [
+            tutil.FakeCurl.make(code=404, body='')
+            for _ in range(gateways+disks)
+        ]
+        MockCurl.side_effect = tutil.queue_with(mocks)
+        self.mock_disks_and_gateways(gateways=gateways, disks=disks)
+        locator = '+'.join(['acbd18db4cc2f85cedef654fccc4a4d8+3'] +
+                           ['K@'+gw['uuid'] for gw in self.gateways])
+        with self.assertRaises(arvados.errors.NotFoundError):
+            self.keepClient.head(locator)
+        # Gateways are tried first, in the order given.
+        for i, root in enumerate(self.gateway_roots):
+            self.assertEqual(root+locator,
+                             mocks[i].getopt(pycurl.URL))
         # Disk services are tried next.
         for i in range(gateways, gateways+disks):
             self.assertRegexpMatches(
-                MockSession.return_value.get.call_args_list[i][0][0],
+                mocks[i].getopt(pycurl.URL),
                 r'keep0x')
 
-    @mock.patch('requests.Session')
-    def test_get_with_remote_proxy_hint(self, MockSession):
-        MockSession.return_value.get.return_value = tutil.fake_requests_response(
+    @mock.patch('pycurl.Curl')
+    def test_get_with_remote_proxy_hint(self, MockCurl):
+        MockCurl.return_value = tutil.FakeCurl.make(
             code=200, body='foo', headers={'Content-Length': 3})
         self.mock_disks_and_gateways()
         locator = 'acbd18db4cc2f85cedef654fccc4a4d8+3+K@xyzzy'
         self.assertEqual('foo', self.keepClient.get(locator))
-        self.assertEqual(('https://keep.xyzzy.arvadosapi.com/'+locator,),
-                         MockSession.return_value.get.call_args_list[0][0])
+        self.assertEqual('https://keep.xyzzy.arvadosapi.com/'+locator,
+                         MockCurl.return_value.getopt(pycurl.URL))
+
+    @mock.patch('pycurl.Curl')
+    def test_head_with_remote_proxy_hint(self, MockCurl):
+        MockCurl.return_value = tutil.FakeCurl.make(
+            code=200, body='foo', headers={'Content-Length': 3})
+        self.mock_disks_and_gateways()
+        locator = 'acbd18db4cc2f85cedef654fccc4a4d8+3+K@xyzzy'
+        self.assertEqual(True, self.keepClient.head(locator))
+        self.assertEqual('https://keep.xyzzy.arvadosapi.com/'+locator,
+                         MockCurl.return_value.getopt(pycurl.URL))
 
 
 class KeepClientRetryTestMixin(object):
@@ -564,6 +962,10 @@ class KeepClientRetryTestMixin(object):
         with self.TEST_PATCHER(self.DEFAULT_EXPECT, 500, 200):
             self.check_success(num_retries=3)
 
+    def test_exception_then_success(self):
+        with self.TEST_PATCHER(self.DEFAULT_EXPECT, Exception('mock err'), 200):
+            self.check_success(num_retries=3)
+
     def test_no_default_retry(self):
         with self.TEST_PATCHER(self.DEFAULT_EXPECT, 500, 200):
             self.check_exception()
@@ -587,14 +989,14 @@ class KeepClientRetryGetTestCase(KeepClientRetryTestMixin, unittest.TestCase):
     DEFAULT_EXPECT = KeepClientRetryTestMixin.TEST_DATA
     DEFAULT_EXCEPTION = arvados.errors.KeepReadError
     HINTED_LOCATOR = KeepClientRetryTestMixin.TEST_LOCATOR + '+K@xyzzy'
-    TEST_PATCHER = staticmethod(tutil.mock_get_responses)
+    TEST_PATCHER = staticmethod(tutil.mock_keep_responses)
 
     def run_method(self, locator=KeepClientRetryTestMixin.TEST_LOCATOR,
                    *args, **kwargs):
         return self.new_client().get(locator, *args, **kwargs)
 
     def test_specific_exception_when_not_found(self):
-        with tutil.mock_get_responses(self.DEFAULT_EXPECT, 404, 200):
+        with tutil.mock_keep_responses(self.DEFAULT_EXPECT, 404, 200):
             self.check_exception(arvados.errors.NotFoundError, num_retries=3)
 
     def test_general_exception_with_mixed_errors(self):
@@ -603,7 +1005,7 @@ class KeepClientRetryGetTestCase(KeepClientRetryTestMixin, unittest.TestCase):
         # This test rigs up 50/50 disagreement between two servers, and
         # checks that it does not become a NotFoundError.
         client = self.new_client()
-        with tutil.mock_get_responses(self.DEFAULT_EXPECT, 404, 500):
+        with tutil.mock_keep_responses(self.DEFAULT_EXPECT, 404, 500):
             with self.assertRaises(arvados.errors.KeepReadError) as exc_check:
                 client.get(self.HINTED_LOCATOR)
             self.assertNotIsInstance(
@@ -611,30 +1013,174 @@ class KeepClientRetryGetTestCase(KeepClientRetryTestMixin, unittest.TestCase):
                 "mixed errors raised NotFoundError")
 
     def test_hint_server_can_succeed_without_retries(self):
-        with tutil.mock_get_responses(self.DEFAULT_EXPECT, 404, 200, 500):
+        with tutil.mock_keep_responses(self.DEFAULT_EXPECT, 404, 200, 500):
             self.check_success(locator=self.HINTED_LOCATOR)
 
     def test_try_next_server_after_timeout(self):
-        with tutil.mock_get([
-                socket.timeout("timed out"),
-                tutil.fake_requests_response(200, self.DEFAULT_EXPECT)]):
+        with tutil.mock_keep_responses(
+                (socket.timeout("timed out"), 200),
+                (self.DEFAULT_EXPECT, 200)):
             self.check_success(locator=self.HINTED_LOCATOR)
 
     def test_retry_data_with_wrong_checksum(self):
-        with tutil.mock_get((tutil.fake_requests_response(200, s) for s in ['baddata', self.TEST_DATA])):
+        with tutil.mock_keep_responses(
+                ('baddata', 200),
+                (self.DEFAULT_EXPECT, 200)):
+            self.check_success(locator=self.HINTED_LOCATOR)
+
+@tutil.skip_sleep
+class KeepClientRetryHeadTestCase(KeepClientRetryTestMixin, unittest.TestCase):
+    DEFAULT_EXPECT = True
+    DEFAULT_EXCEPTION = arvados.errors.KeepReadError
+    HINTED_LOCATOR = KeepClientRetryTestMixin.TEST_LOCATOR + '+K@xyzzy'
+    TEST_PATCHER = staticmethod(tutil.mock_keep_responses)
+
+    def run_method(self, locator=KeepClientRetryTestMixin.TEST_LOCATOR,
+                   *args, **kwargs):
+        return self.new_client().head(locator, *args, **kwargs)
+
+    def test_specific_exception_when_not_found(self):
+        with tutil.mock_keep_responses(self.DEFAULT_EXPECT, 404, 200):
+            self.check_exception(arvados.errors.NotFoundError, num_retries=3)
+
+    def test_general_exception_with_mixed_errors(self):
+        # head should raise a NotFoundError if no server returns the block,
+        # and a high threshold of servers report that it's not found.
+        # This test rigs up 50/50 disagreement between two servers, and
+        # checks that it does not become a NotFoundError.
+        client = self.new_client()
+        with tutil.mock_keep_responses(self.DEFAULT_EXPECT, 404, 500):
+            with self.assertRaises(arvados.errors.KeepReadError) as exc_check:
+                client.head(self.HINTED_LOCATOR)
+            self.assertNotIsInstance(
+                exc_check.exception, arvados.errors.NotFoundError,
+                "mixed errors raised NotFoundError")
+
+    def test_hint_server_can_succeed_without_retries(self):
+        with tutil.mock_keep_responses(self.DEFAULT_EXPECT, 404, 200, 500):
             self.check_success(locator=self.HINTED_LOCATOR)
 
+    def test_try_next_server_after_timeout(self):
+        with tutil.mock_keep_responses(
+                (socket.timeout("timed out"), 200),
+                (self.DEFAULT_EXPECT, 200)):
+            self.check_success(locator=self.HINTED_LOCATOR)
 
 @tutil.skip_sleep
 class KeepClientRetryPutTestCase(KeepClientRetryTestMixin, unittest.TestCase):
     DEFAULT_EXPECT = KeepClientRetryTestMixin.TEST_LOCATOR
     DEFAULT_EXCEPTION = arvados.errors.KeepWriteError
-    TEST_PATCHER = staticmethod(tutil.mock_put_responses)
+    TEST_PATCHER = staticmethod(tutil.mock_keep_responses)
 
     def run_method(self, data=KeepClientRetryTestMixin.TEST_DATA,
                    copies=1, *args, **kwargs):
         return self.new_client().put(data, copies, *args, **kwargs)
 
     def test_do_not_send_multiple_copies_to_same_server(self):
-        with tutil.mock_put_responses(self.DEFAULT_EXPECT, 200):
+        with tutil.mock_keep_responses(self.DEFAULT_EXPECT, 200):
             self.check_exception(copies=2, num_retries=3)
+
+
+class AvoidOverreplication(unittest.TestCase, tutil.ApiClientMock):
+
+    class FakeKeepService(object):
+        def __init__(self, delay, will_succeed=False, will_raise=None, replicas=1):
+            self.delay = delay
+            self.will_succeed = will_succeed
+            self.will_raise = will_raise
+            self._result = {}
+            self._result['headers'] = {}
+            self._result['headers']['x-keep-replicas-stored'] = str(replicas)
+            self._result['body'] = 'foobar'
+
+        def put(self, data_hash, data, timeout):
+            time.sleep(self.delay)
+            if self.will_raise is not None:
+                raise self.will_raise
+            return self.will_succeed
+
+        def last_result(self):
+            if self.will_succeed:
+                return self._result
+
+        def finished(self):
+            return False
+    
+    def setUp(self):
+        self.copies = 3
+        self.pool = arvados.KeepClient.KeepWriterThreadPool(
+            data = 'foo',
+            data_hash = 'acbd18db4cc2f85cedef654fccc4a4d8+3',
+            max_service_replicas = self.copies,
+            copies = self.copies
+        )
+
+    def test_only_write_enough_on_success(self):
+        for i in range(10):
+            ks = self.FakeKeepService(delay=i/10.0, will_succeed=True)
+            self.pool.add_task(ks, None)
+        self.pool.join()
+        self.assertEqual(self.pool.done(), self.copies)
+
+    def test_only_write_enough_on_partial_success(self):
+        for i in range(5):
+            ks = self.FakeKeepService(delay=i/10.0, will_succeed=False)
+            self.pool.add_task(ks, None)
+            ks = self.FakeKeepService(delay=i/10.0, will_succeed=True)
+            self.pool.add_task(ks, None)
+        self.pool.join()
+        self.assertEqual(self.pool.done(), self.copies)
+
+    def test_only_write_enough_when_some_crash(self):
+        for i in range(5):
+            ks = self.FakeKeepService(delay=i/10.0, will_raise=Exception())
+            self.pool.add_task(ks, None)
+            ks = self.FakeKeepService(delay=i/10.0, will_succeed=True)
+            self.pool.add_task(ks, None)
+        self.pool.join()
+        self.assertEqual(self.pool.done(), self.copies)
+
+    def test_fail_when_too_many_crash(self):
+        for i in range(self.copies+1):
+            ks = self.FakeKeepService(delay=i/10.0, will_raise=Exception())
+            self.pool.add_task(ks, None)
+        for i in range(self.copies-1):
+            ks = self.FakeKeepService(delay=i/10.0, will_succeed=True)
+            self.pool.add_task(ks, None)
+        self.pool.join()
+        self.assertEqual(self.pool.done(), self.copies-1)
+    
+
+@tutil.skip_sleep
+class RetryNeedsMultipleServices(unittest.TestCase, tutil.ApiClientMock):
+    # Test put()s that need two distinct servers to succeed, possibly
+    # requiring multiple passes through the retry loop.
+
+    def setUp(self):
+        self.api_client = self.mock_keep_services(count=2)
+        self.keep_client = arvados.KeepClient(api_client=self.api_client)
+
+    def test_success_after_exception(self):
+        with tutil.mock_keep_responses(
+                'acbd18db4cc2f85cedef654fccc4a4d8+3',
+                Exception('mock err'), 200, 200) as req_mock:
+            self.keep_client.put('foo', num_retries=1, copies=2)
+        self.assertEqual(3, req_mock.call_count)
+
+    def test_success_after_retryable_error(self):
+        with tutil.mock_keep_responses(
+                'acbd18db4cc2f85cedef654fccc4a4d8+3',
+                500, 200, 200) as req_mock:
+            self.keep_client.put('foo', num_retries=1, copies=2)
+        self.assertEqual(3, req_mock.call_count)
+
+    def test_fail_after_final_error(self):
+        # First retry loop gets a 200 (can't achieve replication by
+        # storing again on that server) and a 400 (can't retry that
+        # server at all), so we shouldn't try a third request.
+        with tutil.mock_keep_responses(
+                'acbd18db4cc2f85cedef654fccc4a4d8+3',
+                200, 400, 200) as req_mock:
+            with self.assertRaises(arvados.errors.KeepWriteError):
+                self.keep_client.put('foo', num_retries=1, copies=2)
+        self.assertEqual(2, req_mock.call_count)