Add Storage Policy Documentation

Add overview and example information for using Storage Policies.

DocImpact
Implements: blueprint storage-policies
Change-Id: I6f11f7a1bdaa6f3defb3baa56a820050e5f727f1
Add Storage Policy Support

The basic idea here is to replace the use of a single object ring in
the Application class with a collection of object rings. The
collection includes not only the Ring object itself but the policy
name associated with it, the filename for the .gz and any other
metadata associated with the policy that may be needed. When
containers are created, a policy (thus a specific obj ring) is
selected allowing apps to specify policy at container creation time
and leverage policies simply by using different containers for object
operations.

The policy collection is based off of info in the swift.conf file.
The format of the sections in the .conf file is as follows:

swift.conf format:

    [storage-policy:0]
    name = chicken

    [storage-policy:1]
    name = turkey
    default = yes

With the above format:

- Policy 0 will always be used for access to existing containers
  without the policy specified. The ring name for policy 0 is always
  'object', assuring backwards compatiblity. The parser will always
  create a policy 0 even if not specified

- The policy with 'default=yes' is the one used for new container
  creation. This allows the admin to specify which policy is used without
  forcing the application to add the metadata.

This commit simply introduces storage policies and the loading
thereof; nobody's using it yet. That will follow in subsequent
commits.

Expose storage policies in /info

Also updates SAIO makerings script and swift.conf to tie in with
the docs and create a 2nd policy as part of the SAIO install.

DocImpact
Implements: blueprint storage-policies
Change-Id: Ica05f41ecf3adb3648cc9182f11f1c8c5c678985
Update FakeRing and FakeLogger

FakeLogger gets better log level handling

Parameterize logger on some daemons which were previously
unparameterized and try and use the interface in tests.

FakeRing use more real code

The existing FakeRing mock's implementation bit me on some pretty subtle
character encoding issue by-passing the hash_path code that is normally
part of get_part_nodes.  This change tries to exercise more of the real
ring code paths when it makes sense and provide a better Fake for use in
testing.

Add write_fake_ring helper to test.unit for when you need a real ring.

DocImpact
Implements: blueprint storage-policies
Change-Id: Id2e3740b1dd569050f4e083617e7dd6a4249027e
Add Storage Policy support to Containers

Containers now have a storage policy index associated with them,
stored in the container_stat table. This index is only settable at
container creation time (PUT request), and cannot be changed without
deleting and recreating the container. This is because a container's
policy index will apply to all its objects, so changing a container's
policy index would require moving large amounts of object data
around. If a user wants to change the policy for data in a container,
they must create a new container with the desired policy and move the
data over.

Keep status_changed_at up-to-date with status changes.

In particular during container recreation and replication.

When a container-server receives a PUT for a deleted database an extra UPDATE
is issued against the container_stat table to notate the x-timestamp of the
request.

During replication if merge_timestamps causes a container's status to change
(from DELETED to ACTIVE or vice-versa) the status_changed_at field is set to
the current time.

Accurate reporting of status_changed_at is useful for container replication
forensics and allows resolution of "set on create" attributes like the
upcoming storage_policy_index.

Expose Backend container info on deleted containers.

Include basic container info in backend headers on 404 responses from the
container server.  Default empty values are used as placeholders if the
database does not exist.

Specifically the X-Backend-Status-Changed-At, X-Backend-DELETE-Timestamp and
the X-Backend-Storage-Policy-Index value will be needed by the reconciler to
deal with reconciling out of order object writes in the face of recently
deleted containers.

 * Add "status_changed_at" key to the response from ContainerBroker.get_info.
 * Add "Status Timestamp" field to swift.cli.info.print_db_info_metadata.
 * Add "status_changed_at" key to the response from AccountBroker.get_info.

DocImpact
Implements: blueprint storage-policies
Change-Id: Ie6d388f067f5b096b0f96faef151120ba23c8748
Add Storage Policy support to Object Server

Objects now have a storage policy index associated with them as well;
this is determined by their filesystem path. Like before, objects in
policy 0 are in /srv/node/$disk/objects; this provides compatibility
on upgrade. (Recall that policy 0 is given to all existing data when a
cluster is upgraded.) Objects in policy 1 are in
/srv/node/$disk/objects-1, objects in policy 2 are in
/srv/node/$disk/objects-2, and so on.

Containers now have a storage policy index associated with them,
stored in the container_stat table. This index is only at container
creation time, and cannot be changed without deleting and recreating
the container. This is because a container's policy index applies to
all its objects, so changing a container's policy index would require
moving large amounts of object data around.  Thus, if it is desired to
change the policy for data in a container, the supported method would
be to create a new container with the desired policy and move the data
over.

This commit does not address replicators, auditors, or updaters except
where method signatures changed. They'll still work if your cluster
has only one storage policy, though.

DocImpact
Implements: blueprint storage-policies
Change-Id: I459f3ed97df516cb0c9294477c28729c30f48e09
Add Storage Policy support to Object Updates

The object server will now send its storage policy index to the
container server synchronously and asynchronously (via async_pending).

Each storage policy gets its own async_pending directory under
/srv/node/$disk/objects-$N, so there's no need to change the on-disk
pickle format; the policy index comes from the async_pending's
filename. This avoids any hassle on upgrade. (Recall that policy 0's
objects live in /srv/node/$disk/objects, not objects-0.)

Also clean up a couple little things in the object updater. Now it
won't abort processing when it encounters a file (not directory) named
"async_pending-\d+", and it won't process updates in a directory that
does not correspond to a storage policy.

That is, if you have policies 1, 2, and 3, but there's a directory on
your disk named "async_pending-5", the updater will now skip over that
entirely. It won't even bother doing directory listings at all. This
is a good idea, believe it or not, because there's nothing good that
the container server can do with an update from some unknown storage
policy. It can't update the listing, it can't move the object if it's
misplaced... all it can do is ignore the request, so it's better to
just not send it in the first place. Plus, if this is due to a
misconfiguration on one storage node, then the updates will get
processed once the configuration is fixed.

There's also a drive by fix to update some backend http mocks for container
update tests that we're not fully exercising their their request fakes.
Because the object server container update code is resilient to to all manor
of failure from backend requests the general intent of the tests was
unaffected but this change cleans up some confusing logging in the debug
logger output.

The object-server will send X-Storage-Policy-Index headers with all
requests to container severs, including X-Delete containers and all
object PUT/DELETE requests.  This header value is persisted in the
pickle file for the update and sent along with async requests from the
object-updater as well.

The container server will extract the X-Storage-Policy-Index header from
incoming requests and apply it to container broker calls as appropriate
defaulting to the legacy storage policy 0 to support seemless migration.

DocImpact
Implements: blueprint storage-policies
Change-Id: I07c730bebaee068f75024fa9c2fa9e11e295d9bd
Add Storage Policy Support to the Auditor

This patch makes the object auditor policy-aware, so it'll audit
objects in any storage policy.

DocImpact
Implements: blueprint storage-policies
Change-Id: I94e3a7937d9814b9ecef6ca35371e245a43513d3
Add storage policy support for the Replicator

This makes it so that objects stored in all policies get replicated
properly. This is only for rsync replication, not ssync.

DocImpact
Implements: blueprint storage-policies
Change-Id: Ifdb4624841f35953ba80189e669d3ef15d5563fd
Add Storage Policy Support to ssync

This patch makes ssync policy aware so that clusters using storage
policies and ssync replication will replicate objects in all policies.

DocImpact
Implements: blueprint storage-policies
Change-Id: I64879077676d764c6330e03734fc6665bb26f552
Put X-Timestamp in object 404 responses

This way the container reconciler can tell (sometimes) that an object
was deleted at a certain time.

DocImpact
Implements: blueprint storage-policies
Change-Id: Idaba3255f4109e5150d6c457f913c600fd8923eb
Extend interface on InternalClient

 * add get_object
 * allow extra headers passthrough on HEAD/metadata reqeusts
 * expose (account|container|get_object)_ring properties

Pipeline propety access to the auto_create_account_prefix also allows us to
bypass the early exit on a container HEAD for auto_create_accounts if the
container-updater hasn't cycled yet.

Allow overriding of storage policy index.

This is something the reconciler will need so that it can GET from one
policy, PUT in another, and then DELETE from the first one again.

DocImpact
Implements: blueprint storage-policies
Change-Id: I9b287d15f2426022d669d1186c9e22dd8ca13fb9
Extend direct_client

Rework header handling and add some methods needed by the reconciler.

 * response headers are case insensitive HeaderKeyDicts
 * add direct client container obj put and delete
 * add headers param to direct head object
 * add headers to DirectClientException

DirectClientException is a subclass of ClientException with a convience
constructor.  ClientException now supports an http_headers kwarg.

Exceptions raised from direct_client will include headers.

DocImpact
Implements: blueprint storage-policies
Change-Id: Ia484d569619df0bf85f973e4e916de2ac6401d5e
Add container-reconciler daemon

This daemon will take objects that are in the wrong storage policy and
move them to the right ones, or delete requests that went to the wrong
storage policy and apply them to the right ones. It operates on a
queue similar to the object-expirer's queue.

Discovering that the object is in the wrong policy will be done in
subsequent commits by the container replicator; this is the daemon
that handles them once they happen.

Like the object expirer, you only need to run one of these per cluster
see etc/container-reconciler.conf.

DocImpact
Implements: blueprint storage-policies
Change-Id: I5ea62eb77ddcbc7cfebf903429f2ee4c098771c9
Add reconciler probetest outline

You can manually setup a split brain scenario for reconciler testing with the
enqueue script using the machinery from the included probetest.  Evoke the
test as a script with with 'split-brain' command for more help.

DocImpact
Implements: blueprint storage-policies
Change-Id: I3a7b3167d674eba5f6e4072b176f6c4d29cdcd72
Merge container storage_policy_index

Keep status_changed_at in container databases current with status changes that
occur as a result of container creation, deletion, or re-creation.

Merge container put/delete/created timestamps when handling replicate
responses from remote servers in addition to during the handling of the
REPLICATE request.

When storage policies are configured on a cluster send status_changed_at,
object_count and storage_policy_index as part of container replication sync
args.

Use status_changed_at during replication to determine the oldest active
container and merge storage_policy_index.

DocImpact
Implements: blueprint storage-policies
Change-Id: Ib9a0dd42c271145e641437dc04d0ebea1e11fc47
Add Storage Policy Support to Accounts

This change updates the account HEAD handler to report out per
policy object and byte usage for the account.  Cumulative values
are still reported and policy names are used in the report
out (unless request is sent to an account server directly in
which case policy indexes are used for easier accounting).

Below is an example of the relevant HEAD response for a cluster
with 3 policies and just a few small objects:

   X-Account-Container-Count: 3
   X-Account-Object-Count: 3
   X-Account-Bytes-Used: 21
   X-Storage-Policy-Bronze-Object-Count: 1
   X-Storage-Policy-Bronze-Bytes-Used: 7
   X-Storage-Policy-Silver-Object-Count: 1
   X-Storage-Policy-Silver-Bytes-Used: 7
   X-Storage-Policy-Gold-Object-Count: 1
   X-Storage-Policy-Gold-Bytes-Used: 7

Set a DEFAULT storage_policy_index for existing container rows during
migration.

Copy existing object_count and bytes_used in policy_stat table during
migration.

DocImpact
Implements: blueprint storage-policies
Change-Id: I5ec251f9a8014dd89764340de927d09466c72221
Add functional tests for Storage Policy

 * additional container tests
 * refactor test cross policy copy
 * make functional tests cleanup better

DocImpact
Implements: blueprint storage-policies
Change-Id: If17bc7b9737558d3b9a54eeb6ff3e6b51463f002
Update swift-container-info to be storage policy aware

Lookup policy name in swift.conf; 'Legacy' container will use
policy-0's name; 'Unknown' is shown if policy not found in swift.conf

DocImpact
Implements: blueprint storage-policies
Change-Id: I450d40dc6e2d8f759187dff36d658e52737ae2a5
Enqueue misplaced objects during container replication

After a container database is replicated, a _post_replicate_hook will enqueue
misplaced objects for the container-reconciler into the .misplaced_objects
containers.  Items to be reconciled are "batch loaded" into the reconciler
queue and the end of a container replication cycle by levering container
replication itself.

DocImpact
Implements: blueprint storage-policies
Change-Id: I3627efcdea75403586dffee46537a60add08bfda
Add LRUCache to common.utils

This decorator will memonize a function using a fixed size cache that evicts
the oldest entries.  It also supports a maxtime paramter to configure a
"time-to-live" for entries in the cache.

The reconciler code uses this to cache computations of the correct storage
policy index for a container for 30 seconds.

DocImpact
Implements: blueprint storage-policies
Change-Id: I0f220869e33c461a4100b21c6324ad725da864fa