glance/doc/source/cli/glancescrubber.rst

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. 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.

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.

[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.

FILES

/etc/glance/glance-scrubber.conf

Default configuration file for the Glance Scrubber