Akihiro Motoki b6ceda28a4 doc: Clean up unnecessary left vertical lines

In HTML documents with openstackdocstheme, vertical lines are shown
at the left side for literal blocks. Indented blocks are considered
as literal blocks in ReST text.
Unnecessary indented blocks are found in the glance document and
it leads to blocks with unexpected vertical left lines and
sometimes with unexpected fonts like [1].
Unexpected literal blocks are cleanup.

This commit also converts Definition lists in user/formats.rst and
user/common-image-properties.rst into the proper way in ReST text.

[1] https://docs.openstack.org/glance/latest/user/formats.html#container-format

Change-Id: I1b026f919bb22a59d23e3bb93bb7919d202a62fc

2019-12-23 13:58:32 +00:00

5.2 KiB

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glance-scrubber

Glance scrub service

SYNOPSIS

glance-scrubber [options]

DESCRIPTION

glance-scrubber is a utility that allows an operator to configure Glance for the asynchronous deletion of images or to revert the image's status from pending_delete to active. Whether this makes sense for your deployment depends upon the storage backend you are using and the size of typical images handled by your Glance installation.

An image in glance is really a combination of an image record (stored in the database) and a file of image data (stored in a storage backend). Under normal operation, the image-delete call is synchronous, that is, Glance receives the DELETE request, deletes the image data from the storage backend, then deletes the image record from the database, and finally returns a 204 as the result of the call. If the backend is fast and deletion time is not a function of data size, these operations occur very quickly. For backends where deletion time is a function of data size, however, the image-delete operation can take a significant amount of time to complete, to the point where a client may timeout waiting for the response. This in turn leads to user dissatisfaction.

To avoid this problem, Glance has a delayed_delete configuration option (False by default) that may be set in the glance-api.conf file. With this option enabled, when Glance receives a DELETE request, it does only the database part of the request, marking the image's status as pending_delete, and returns immediately. (The pending_delete status is not visible to users; an image-show request for such an image will return 404.) However, it is important to note that when delayed_delete is enabled, Glance does not delete image data from the storage backend. That's where the glance-scrubber comes in.

The glance-scrubber cleans up images that have been deleted. If you run Glance with delayed_delete enabled, you must run the glance-scrubber occasionally or your storage backend will eventually fill up with "deleted" image data.

The glance-scrubber can also revert a image to active if operators delete the image by mistake and the pending-delete is enabled in Glance. Please make sure the glance-scrubber is not running before restoring the image to avoid image data inconsistency.

Configuration of glance-scrubber is done in the glance-scrubber.conf file. Options are explained in detail in comments in the sample configuration file, so we only point out a few of them here.

scrub_time: minimum time in seconds that an image will stay in pending_delete status (default is 0)
scrub_pool_size: configures a thread pool so that scrubbing can be performed in parallel (default is 1, that is, serial scrubbing)
daemon: a boolean indicating whether the scrubber should run as a daemon (default is False)
wakeup_time: time in seconds between runs when the scrubber is run in daemon mode (ignored if the scrubber is not being run in daemon mode)
metadata_encryption_key: If your glance-api.conf sets a value for this option (the default is to leave it unset), you must include the same setting in your glance-scrubber.conf or the scrubber won't be able to determine the locations of your image data.
restore: reset the specified image's status from'pending_delete' to 'active' when the image is deleted by mistake.
[database]: As of the Queens release of Glance (16.0.0), the glance-scrubber does not use the deprecated Glance registry, but instead contacts the Glance database directly. Thus your glance-scrubber.conf file must contain a [database] section specifying the relevant information.
[glance_store]: This section of the file contains the configuration information for the storage backends used by your Glance installation.

The usual situation is that whatever your glance-api.conf has for the [database] and [glance_store] configuration groups should go into your glance-scrubber.conf, too. Of course, if you have heavily customized your setup, you know better than we do what you are doing. The key thing is that the scrubber needs to be able to access the Glance database to determine what images need to be scrubbed (and to mark them as deleted once their associated data has been removed from the storage backend), and it needs the glance_store information so it can delete the image data.

OPTIONS

General options

-D, --daemon: Run as a long-running process. When not specified (the default) run the scrub operation once and then exits. When specified do not exit and run scrub on wakeup_time interval as specified in the config.
--nodaemon: The inverse of --daemon. Runs the scrub operation once and then exits. This is the default.
--restore <IMAGE_ID>: Restore the specified image status from 'pending_delete' to 'active'.

FILES

/etc/glance/glance-scrubber.conf: Default configuration file for the Glance Scrubber

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