mirror of
https://github.com/ceph/ceph
synced 2024-12-13 23:17:07 +00:00
6415044df3
It's nice to describe that write I/Os are blocked during resharding. Signed-off-by: Satoru Takeuchi <satoru.takeuchi@gmail.com>
237 lines
7.0 KiB
ReStructuredText
237 lines
7.0 KiB
ReStructuredText
.. _rgw_dynamic_bucket_index_resharding:
|
|
|
|
===================================
|
|
RGW Dynamic Bucket Index Resharding
|
|
===================================
|
|
|
|
.. versionadded:: Luminous
|
|
|
|
A large bucket index can lead to performance problems. In order
|
|
to address this problem we introduced bucket index sharding.
|
|
Until Luminous, changing the number of bucket shards (resharding)
|
|
needed to be done offline. Starting with Luminous we support
|
|
online bucket resharding.
|
|
|
|
Each bucket index shard can handle its entries efficiently up until
|
|
reaching a certain threshold number of entries. If this threshold is
|
|
exceeded the system can suffer from performance issues. The dynamic
|
|
resharding feature detects this situation and automatically increases
|
|
the number of shards used by the bucket index, resulting in a
|
|
reduction of the number of entries in each bucket index shard. This
|
|
process is transparent to the user. Write I/Os to the target bucket
|
|
are blocked and read I/Os are not during resharding process.
|
|
|
|
By default dynamic bucket index resharding can only increase the
|
|
number of bucket index shards to 1999, although this upper-bound is a
|
|
configuration parameter (see Configuration below). When
|
|
possible, the process chooses a prime number of bucket index shards to
|
|
spread the number of bucket index entries across the bucket index
|
|
shards more evenly.
|
|
|
|
The detection process runs in a background process that periodically
|
|
scans all the buckets. A bucket that requires resharding is added to
|
|
the resharding queue and will be scheduled to be resharded later. The
|
|
reshard thread runs in the background and execute the scheduled
|
|
resharding tasks, one at a time.
|
|
|
|
Multisite
|
|
=========
|
|
|
|
Dynamic resharding is not supported in a multisite environment.
|
|
|
|
|
|
Configuration
|
|
=============
|
|
|
|
Enable/Disable dynamic bucket index resharding:
|
|
|
|
- ``rgw_dynamic_resharding``: true/false, default: true
|
|
|
|
Configuration options that control the resharding process:
|
|
|
|
- ``rgw_max_objs_per_shard``: maximum number of objects per bucket index shard before resharding is triggered, default: 100000 objects
|
|
|
|
- ``rgw_max_dynamic_shards``: maximum number of shards that dynamic bucket index resharding can increase to, default: 1999
|
|
|
|
- ``rgw_reshard_bucket_lock_duration``: duration, in seconds, of lock on bucket obj during resharding, default: 360 seconds (i.e., 6 minutes)
|
|
|
|
- ``rgw_reshard_thread_interval``: maximum time, in seconds, between rounds of resharding queue processing, default: 600 seconds (i.e., 10 minutes)
|
|
|
|
- ``rgw_reshard_num_logs``: number of shards for the resharding queue, default: 16
|
|
|
|
Admin commands
|
|
==============
|
|
|
|
Add a bucket to the resharding queue
|
|
------------------------------------
|
|
|
|
::
|
|
|
|
# radosgw-admin reshard add --bucket <bucket_name> --num-shards <new number of shards>
|
|
|
|
List resharding queue
|
|
---------------------
|
|
|
|
::
|
|
|
|
# radosgw-admin reshard list
|
|
|
|
Process tasks on the resharding queue
|
|
-------------------------------------
|
|
|
|
::
|
|
|
|
# radosgw-admin reshard process
|
|
|
|
Bucket resharding status
|
|
------------------------
|
|
|
|
::
|
|
|
|
# radosgw-admin reshard status --bucket <bucket_name>
|
|
|
|
The output is a json array of 3 objects (reshard_status, new_bucket_instance_id, num_shards) per shard.
|
|
|
|
For example, the output at different Dynamic Resharding stages is shown below:
|
|
|
|
``1. Before resharding occurred:``
|
|
::
|
|
|
|
[
|
|
{
|
|
"reshard_status": "not-resharding",
|
|
"new_bucket_instance_id": "",
|
|
"num_shards": -1
|
|
}
|
|
]
|
|
|
|
``2. During resharding:``
|
|
::
|
|
|
|
[
|
|
{
|
|
"reshard_status": "in-progress",
|
|
"new_bucket_instance_id": "1179f470-2ebf-4630-8ec3-c9922da887fd.8652.1",
|
|
"num_shards": 2
|
|
},
|
|
{
|
|
"reshard_status": "in-progress",
|
|
"new_bucket_instance_id": "1179f470-2ebf-4630-8ec3-c9922da887fd.8652.1",
|
|
"num_shards": 2
|
|
}
|
|
]
|
|
|
|
``3, After resharding completed:``
|
|
::
|
|
|
|
[
|
|
{
|
|
"reshard_status": "not-resharding",
|
|
"new_bucket_instance_id": "",
|
|
"num_shards": -1
|
|
},
|
|
{
|
|
"reshard_status": "not-resharding",
|
|
"new_bucket_instance_id": "",
|
|
"num_shards": -1
|
|
}
|
|
]
|
|
|
|
|
|
Cancel pending bucket resharding
|
|
--------------------------------
|
|
|
|
Note: Ongoing bucket resharding operations cannot be cancelled. ::
|
|
|
|
# radosgw-admin reshard cancel --bucket <bucket_name>
|
|
|
|
Manual immediate bucket resharding
|
|
----------------------------------
|
|
|
|
::
|
|
|
|
# radosgw-admin bucket reshard --bucket <bucket_name> --num-shards <new number of shards>
|
|
|
|
When choosing a number of shards, the administrator should keep a
|
|
number of items in mind. Ideally the administrator is aiming for no
|
|
more than 100000 entries per shard, now and through some future point
|
|
in time.
|
|
|
|
Additionally, bucket index shards that are prime numbers tend to work
|
|
better in evenly distributing bucket index entries across the
|
|
shards. For example, 7001 bucket index shards is better than 7000
|
|
since the former is prime. A variety of web sites have lists of prime
|
|
numbers; search for "list of prime numbers" withy your favorite web
|
|
search engine to locate some web sites.
|
|
|
|
Troubleshooting
|
|
===============
|
|
|
|
Clusters prior to Luminous 12.2.11 and Mimic 13.2.5 left behind stale bucket
|
|
instance entries, which were not automatically cleaned up. The issue also affected
|
|
LifeCycle policies, which were not applied to resharded buckets anymore. Both of
|
|
these issues can be worked around using a couple of radosgw-admin commands.
|
|
|
|
Stale instance management
|
|
-------------------------
|
|
|
|
List the stale instances in a cluster that are ready to be cleaned up.
|
|
|
|
::
|
|
|
|
# radosgw-admin reshard stale-instances list
|
|
|
|
Clean up the stale instances in a cluster. Note: cleanup of these
|
|
instances should only be done on a single site cluster.
|
|
|
|
::
|
|
|
|
# radosgw-admin reshard stale-instances rm
|
|
|
|
|
|
Lifecycle fixes
|
|
---------------
|
|
|
|
For clusters that had resharded instances, it is highly likely that the old
|
|
lifecycle processes would have flagged and deleted lifecycle processing as the
|
|
bucket instance changed during a reshard. While this is fixed for newer clusters
|
|
(from Mimic 13.2.6 and Luminous 12.2.12), older buckets that had lifecycle policies and
|
|
that have undergone resharding will have to be manually fixed.
|
|
|
|
The command to do so is:
|
|
|
|
::
|
|
|
|
# radosgw-admin lc reshard fix --bucket {bucketname}
|
|
|
|
|
|
As a convenience wrapper, if the ``--bucket`` argument is dropped then this
|
|
command will try and fix lifecycle policies for all the buckets in the cluster.
|
|
|
|
Object Expirer fixes
|
|
--------------------
|
|
|
|
Objects subject to Swift object expiration on older clusters may have
|
|
been dropped from the log pool and never deleted after the bucket was
|
|
resharded. This would happen if their expiration time was before the
|
|
cluster was upgraded, but if their expiration was after the upgrade
|
|
the objects would be correctly handled. To manage these expire-stale
|
|
objects, radosgw-admin provides two subcommands.
|
|
|
|
Listing:
|
|
|
|
::
|
|
|
|
# radosgw-admin objects expire-stale list --bucket {bucketname}
|
|
|
|
Displays a list of object names and expiration times in JSON format.
|
|
|
|
Deleting:
|
|
|
|
::
|
|
|
|
# radosgw-admin objects expire-stale rm --bucket {bucketname}
|
|
|
|
|
|
Initiates deletion of such objects, displaying a list of object names, expiration times, and deletion status in JSON format.
|