The built file system image that results from your build process is mounted read-only. That means it cannot be edited in production, even by accident.
Many applications still require the ability to write and store files, however. For that, applications can specify one or more mount points, that is, directories that will be mounted from a writeable network file system cluster. They may be mounted anywhere within the file system of your application. If the specified directory already exists the contents of it will be masked by the writeable mount and inaccessible at runtime.
disk key is required, and defines the size of the persistent disk of the application (in MB). Its minimum value is 256 MB and a validation error will occur if you try to set it lower.
mounts key is an object whose keys are paths relative to the root of the application (that is, where the
.platform.app.yaml file lives), and values are a 2-line mount definition.
This section is optional; if your application does not need writeable local file storage simply omit the
mounts section and set
disk to a value to the minimum of 256.
Note that whether a mounted directory is web-accessible or not depends on the configuration of the
web.locations block in
.platform.app.yaml. It may be accessible, or not, and have different rules for different file types as desired.
The following block defines a single writeable directory,
mounts: 'web/uploads': source: local source_path: uploads
source specifies where the writeable mount is.
source_path specifies the subdirectory from within the source that the mount should point at. It is often easiest to have it match the name of the mount point itself but that is not required.
At this time
local is the only legal source but more will be added in the future. The
local source indicates that the mount point will point to a local directory on the application container. The
source_path is then a subpath of that. That means they may overlap.
Be aware that the entire
local space for a single app container is a common directory, and the directory is not wiped. That means if you create a mount point with a
source_path of "uploads", then write files there, then remove the mount point, the files will still exist on disk indefinitely until manually removed.
If you have multiple application instances defined (using both
workers), each instance will have its own disk mounts. That's the case even if they are named the same, and even if there is only a single top-level mounts directive. In that case, every instance will have an identical configuration, but separate, independent file spaces. Shared file storage between different application instances is not supported at this time.
The following example sets up two file mounts. One is mounted at
/private within the application container, the other at
/web/uploads. The two file mounts together have a limit of 1024 MB of storage.
disk: 1024 mounts: 'private': source: local source_path: private 'web/uploads': source: local source_path: uploads
Then in the
web.locations block, you'd specify that the
web/uploads path is accessible. For example, this fragment would specify the
/web path as the docroot but provide a more locked-down access to the
web: locations: '/': # The public directory of the application relative to its root. root: 'web' # The front-controller script which determines where to send # non-static requests. passthru: '/app.php' # Allow uploaded files to be served, but do not run scripts. '/web/uploads': root: 'web/uploads' expires: 300s scripts: false allow: true
See the web locations documentation for more details.
While not recommended it is possible to setup multiple mount points whose source paths overlap. Consider the following example:
mounts: 'private': source: local source_path: stuff 'secret': source: local source_path: stuff/secret
In this configuration, there will be two mount points as seen from the application:
~/secret. However, the
secret mount will point to a directory that is also under the mount point for
private. That is, the
secret path and the
private/secret path will be the exact same directory.
Although this configuration won't cause any technical issues, it may be quite confusing so is generally not recommended.