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88 lines
2.8 KiB
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88 lines
2.8 KiB
ReStructuredText
===================================
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RGW Dynamic Bucket Index Resharding
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===================================
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.. versionadded:: Luminous
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A large bucket index can lead to performance problems. In order
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to address this problem we introduced bucket index sharding.
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Until Luminous, changing the number of bucket shards (resharding)
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needed to be done offline, from Luminous we support
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online bucket resharding.
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Each bucket index shard can handle its entries efficiently up until
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reaching a certain threshold of entries. If this threshold is exceeded the system
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could encounter performance issues.
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The dynamic resharding feature detects this situation and increases
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automatically the number of shards used by the bucket index,
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resulting in the reduction of the number of entries in each bucket index shard.
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This process is transparent to the user.
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The detection process runs:
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1. When new objects are added to the bucket
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2. In a background process that periodically scans all the buckets
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This is needed in order to deal with existng buckets in the system that are not being updated.
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A bucket that requires resharding is added to the ``reshard_log`` queue and will be
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scheduled to be resharded later.
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The reshard threads run in the background and execute the scheduled resharding, one at a time.
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Multisite
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=========
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Dynamic resharding is not supported in multisite environment.
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Configuration
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=============
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Enable/Disable Dynamic bucket index resharding:
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-``rgw_dynamic_resharding``: true/false, default: true.
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Parameters to control the resahrding process in Ceph configuration fie:
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-``rgw_reshard_num_logs``: number of shards for the resharding log, default: 16
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-``rgw_reshard_bucket_lock_duration``: duration of lock on bucket obj during resharding, default: 120 seconds.
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-``rgw_max_objs_per_shard``: maximum number of objects per bucket index shard, default: 100000 objects.
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-``rgw_reshard_thread_interval``: maximum time between rounds of reshard thread processing, default: 600 seconds
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Admin commands
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==============
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Add a bucket to the resharding queue
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------------------------------------
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::
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# radosgw-admin reshard add --bucket <bucket_name> --num-shards <new number of shards>
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List resharding queue
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---------------------
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::
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# radosgw-admin reshard list
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Process/Schedule a bucket resharding
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------------------------------------
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::
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# radosgw-admin reshard process
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bucket resharding status
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------------------------
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::
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# radosgw-admin reshard status --bucket <bucket_name>
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Cancel pending bucket resharding
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--------------------------------
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Ongoing bucket resharding operations cannot be cancelled.
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::
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# radosgw-admin reshard cancel --bucket <bucket_name>
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Manual bucket resharding
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------------------------
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::
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# radosgw-admin bucket reshard --bucket <bucket_name> --num-shards <new number of shards>
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