Add pretend_min_part_hours_passed to ring build

Expose the "pretend_min_part_hours_passed" option when accessing
swift-ring-builder.

This PR adds a variable "swift_pretend_min_part_hours_passed" which
defaults to False.

Change-Id: Ief94f011049b57f1ab0c2c48dfa81659d7ba13f7

defaults/main.yml

@@ -296,6 +296,14 @@ swift_object_program_names:
 swift_proxy_program_names:
   - swift-proxy-server
 
+# Set to True to reset the clock on the last time a rebalance happened,
+# circumventing the min_part_hours check.
+# USE WITH EXTREME CAUTION
+# If you run the swift playbook with this option enabled, before a swift
+# replication pass completes, you may introduce unavailability in your
+# cluster. This has an end-user impact.
+swift_pretend_min_part_hours_passed: False
+
 # Set this option to enable or disable the pypy interpreter for swift
 swift_pypy_enabled: false
 swift_pypy_archive:

releasenotes/notes/swift-pretend-mph-passed-7e5c15eeb35861c3.yaml

@@ -0,0 +1,17 @@
+---
+features:
+  - The ``pretend_min_part_hours_passed`` option can now be
+    passed to swift-ring-builder prior to performing a
+    rebalance. This is set by the
+    ``swift_pretend_min_part_hours_passed`` boolean variable.
+    The default for this variable is False. We recommend setting
+    this by running the os-swift.yml playbook with
+    ``-e swift_pretend_min_part_hours_passed=True``, to avoid
+    resetting ``min_part_hours`` unintentionally on every run.
+    Setting ``swift_pretend_min_part_hours_passed`` to True will
+    reset the clock on the last time a rebalance happened, thus
+    circumventing the min_part_hours check. This should only be
+    used with extreme caution. If you run this command and deploy
+    rebalanced rings before a replication pass completes, you may
+    introduce unavailability in your cluster. This has an end-user
+    imapct.

tasks/swift_rings_build.yml

@@ -51,7 +51,7 @@
     - swift-rings-contents
 
 - name: "build rings for account/container from contents files"
-  command: "/etc/swift/scripts/swift_rings.py -f /etc/swift/scripts/{{ item[0] }}.contents{% if item[1] %} -r {{ item[1] }} {% endif %}"
+  command: "/etc/swift/scripts/swift_rings.py -f /etc/swift/scripts/{{ item[0] }}.contents{% if item[1] %} -r {{ item[1] }}{% endif %}{{ (swift_pretend_min_part_hours_passed | bool) | ternary(' -p', '')}}"
   with_nested:
     - [ 'account', 'container' ]
     - swift_managed_regions | default([None])
@@ -64,7 +64,7 @@
     - swift-rings-build
 
 - name: "build rings for storage policies from contents files"
-  command: "/etc/swift/scripts/swift_rings.py -f /etc/swift/scripts/object-{{ item[0].policy.index }}.contents{% if item[1] %} -r {{ item[1] }} {% endif %}"
+  command: "/etc/swift/scripts/swift_rings.py -f /etc/swift/scripts/object-{{ item[0].policy.index }}.contents{% if item[1] %} -r {{ item[1] }}{% endif %}{{ (swift_pretend_min_part_hours_passed | bool) | ternary(' -p', '')}}"
   with_nested:
     - "{{ swift.storage_policies }}"
     - swift_managed_regions | default([None])

templates/swift_rings.py.j2

@@ -150,7 +150,7 @@ def get_build_file_data(build_file):
 
 
 def build_ring(build_name, repl, min_part_hours, part_power, hosts,
-               region=None, validate=False):
+               region=None, validate=False, reset_mph_clock=False):
     # Create the build file
     build_file = "%s.builder" % build_name
     build_file_data = get_build_file_data(build_file)
@@ -195,12 +195,17 @@ def build_ring(build_name, repl, min_part_hours, part_power, hosts,
                 rb_main, ["swift-ring-builder", build_file, "write_ring"]
             )
         else:
+            if reset_mph_clock:
+                run_and_wait(
+                    rb_main, ["swift-ring-builder", build_file,
+                              "pretend_min_part_hours_passed"]
+                )
             run_and_wait(
                 rb_main, ["swift-ring-builder", build_file, "rebalance"]
             )
 
 
-def main(setup, region):
+def main(setup, region, reset_mph_clock):
     # load the json file
     try:
         with open(setup) as json_stream:
@@ -210,7 +215,8 @@ def main(setup, region):
         return 1
 
     hosts = _contents_file['drives']
-    kargs = {'validate': True, 'hosts': hosts, 'region': region}
+    kargs = {'validate': True, 'hosts': hosts, 'region': region,
+             'reset_mph_clock': reset_mph_clock}
     ring_call = [
         _contents_file['builder_file'],
         _contents_file['repl_number'],
@@ -246,6 +252,14 @@ if __name__ == "__main__":
         type='int',
         metavar="REGION"
     )
+    parser.add_option(
+        "-p",
+        "--pretend_min_part_hours_passed",
+        help="Reset the clock on the last time a rebalance happened.",
+        dest="reset_mph_clock",
+        action="store_true",
+        default='False'
+    )
 
     options, _args = parser.parse_args(sys.argv[1:])
     if options.setup and not exists(options.setup):
@@ -253,4 +267,4 @@ if __name__ == "__main__":
         parser.print_help()
         sys.exit(1)
 
-    sys.exit(main(options.setup, options.region))
+    sys.exit(main(options.setup, options.region, options.reset_mph_clock))