Command-line interface

swh objstorage replay

Fill a destination Object Storage using a journal stream.

This is typically used for a mirror configuration, by reading a Journal and retrieving objects from an existing source ObjStorage.

There can be several ‘replayers’ filling a given ObjStorage as long as they use the same group-id. You can use the KAFKA_GROUP_INSTANCE_ID environment variable to use KIP-345 static group membership.

This service retrieves object ids to copy from the ‘content’ topic. It will only copy object’s content if the object’s description in the kafka nmessage has the status:visible set.

--exclude-sha1-file may be used to exclude some hashes to speed-up the replay in case many of the contents are already in the destination objstorage. It must contain a concatenation of all (sha1) hashes, and it must be sorted. This file will not be fully loaded into memory at any given time, so it can be arbitrarily large.

--check-dst sets whether the replayer should check in the destination ObjStorage before copying an object. You can turn that off if you know you’re copying to an empty ObjStorage.

--concurrency N sets the number of threads in charge of copy blob objects from the source objstorage to the destination one. Using a large concurrency value make sense if both the source and destination objstorages support highly parallel workloads. Make not to set the batch_size configuration option too low for the concurrency to be actually useful (each batch of kafka messages is dispatched among the threads).

The expected configuration file should have 3 sections:

In addition to these 3 mandatory sections, an optional ‘replayer’ section can be provided with an ‘error_reporter’ config entry allowing to specify a Redis connection parameter set that will be used to report objects that could not be copied, eg.:

objstorage:
  [...]
objstorage_dst:
  [...]
journal_client:
  [...]
replayer:
  error_reporter:
    host: redis.local
    port: 6379
    db: 1
swh objstorage replay [OPTIONS]

Options

-n, --stop-after-objects <stop_after_objects>

Stop after processing this many objects. Default is to run forever.

--exclude-sha1-file <exclude_sha1_file>

File containing a sorted array of hashes to be excluded.

--check-dst, --no-check-dst

Check whether the destination contains the object before copying.

--concurrency <concurrency>

Number of concurrent threads doing the actual copy of blobs between the source and destination objstorages.