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Asset Caching
The latest version of this documentation is available on GitHub.
Experimental feature: this may change or be removed at any time
Vcpkg can utilize mirrors to cache downloaded assets, ensuring continued operation even if the original source changes or disappears.
In-tool help is available via vcpkg help assetcaching.
Configuration
Asset caching can be configured by setting the environment variable X_VCPKG_ASSET_SOURCES to a semicolon-delimited
list of source strings. Characters can be escaped using backtick (`).
Valid source strings
The <rw> optional parameter for certain strings controls how they will be accessed. It can be specified as read,
write, or readwrite and defaults to read.
clear
Syntax: clear
Removes all previous sources
x-azurl
Syntax: x-azurl,<url>[,<sas>[,<rw>]]
Adds an Azure Blob Storage source, optionally using Shared Access Signature validation. URL should include the container
path and be terminated with a trailing /. SAS, if defined, should be prefixed with a ?. Non-Azure servers will also
work if they respond to GET and PUT requests of the form: <url><sha512><sas>. As an example, if you set
X_VCPKG_ASSET_SOURCES to x-azurl,https://mydomain.com/vcpkg/,token=abc123,readwrite your server should respond to
GET and PUT requests of the form https://mydomain.com/vcpkg/<sha512>?token=abc123.
You can also use the filesystem (e.g. a network drive) via file:// as asset cache. For example you then set
X_VCPKG_ASSET_SOURCES to x-azurl,file:///Z:/vcpkg/assetcache/,,readwrite when you have a network folder mounted at
Z:/.
The workflow of this asset source is:
- Attemp to read from the mirror
- (If step 1 failed) Read from the original url
- (If step 2 succeeded) Write back to the mirror
You can enable/disable steps 1 and 3 via the <rw> specifier and you can disable step 2 via
x-block-origin below.
See also the binary caching documentation for Azure Blob Storage for
more information on how to set up an x-azurl source.
x-block-origin
Syntax: x-block-origin
Disables use of the original URLs in case the mirror does not have the file available.