139 lines
6.0 KiB
Markdown
139 lines
6.0 KiB
Markdown
This tool is a component of a cross-platform auto-update system.
|
|
It is responsible for performing the installation of an update after
|
|
the necessary files have been downloaded to a temporary directory.
|
|
|
|
It was originally written for use with Mendeley Desktop (see www.mendeley.com)
|
|
|
|
The tool consists of a single small binary which performs update installation,
|
|
an XML file format describing the contents of an update (an 'update script')
|
|
and a tool to create update scripts from a directory containing an installed application.
|
|
|
|
To perform an update, the application (or another separate tool) needs to download
|
|
the updater binary, an update script and one or more compressed packages
|
|
containing the files for the update to a temporary directory. It then needs
|
|
to invoke the updater, specifying the location where the application is installed,
|
|
the location of the compressed packages and the path to the update script.
|
|
|
|
Once the updater has been started, it:
|
|
|
|
1. Waits for the application to exit
|
|
2. Acquires the necessary priviledges to install the updates, prompting
|
|
the user if necessary.
|
|
3. Installs the updates, displaying progress to the user in a small dialog
|
|
4. Performs cleanup and any additional actions required as part of the update
|
|
5. Starts the new version of the main application.
|
|
|
|
In the event of a failure during the update, the installation is rolled back
|
|
to its previous state and a message is presented to the user.
|
|
|
|
## Building the Updater
|
|
|
|
Create a new directory for the build and from that directory run:
|
|
|
|
cmake <path to source directory>
|
|
make
|
|
|
|
The updater binary will be built in the src/ directory.
|
|
|
|
You should also run the tests in src/tests to verify that the updater is
|
|
functioning correctly.
|
|
|
|
## Preparing an Update
|
|
|
|
1. Create a directory containing your application's files,
|
|
laid out in the same way and with the same permissions as they would be when installed.
|
|
2. Create a config file specifying how the application's files should be
|
|
partitioned into packages - see tools/config-template.json
|
|
3. Use the tools/create-packages.rb script to create a file_list.xml file
|
|
and a set of package files required for updates.
|
|
4. Upload the file_list.xml file and packages to a server
|
|
|
|
After step 4 is done, you need to notify existing installs that an update
|
|
is available. The installed application then needs to download the
|
|
relevant packages, file_list.xml file and updater binary to a temporary
|
|
directory and invoke the updater.
|
|
|
|
See doc/update-hosting for more details on hosting and delivering the updates.
|
|
|
|
## Invoking the Updater
|
|
|
|
Once the application has downloaded an update, it needs to invoke it. The syntax is:
|
|
|
|
updater --install-dir <install-dir> --package-dir <package-dir> --script <script file>
|
|
|
|
Where `<install-dir>` is the directory which the application is installed into,
|
|
`<package-dir>` is the directory containing the packages required for the update
|
|
and `<script>` is the `file_list.xml` file describing the update.
|
|
|
|
Once the updater has run, it will launch the file specified in the `file_list.xml` file
|
|
as being the main application binary.
|
|
|
|
See the updater test in `src/tests/test-update.rb` for an example
|
|
of how to invoke the updater.
|
|
|
|
You should design the process used to download and launch the updater so that new
|
|
versions of the updater itself can be delivered as part of the update if necessary.
|
|
|
|
## Customizing the Updater
|
|
|
|
To customize the application name, organization and messages displayed by the updater:
|
|
|
|
1. Edit the AppInfo class (in AppInfo.h, AppInfo.cpp) to set the name
|
|
of the application and associated organization.
|
|
2. Replace the icons in src/resources
|
|
3. Change the product name and organization in src/resources/updater.rc
|
|
4. If you are building the updater on Windows and have a suitable Authenticode
|
|
certificate, use it to sign the Windows binary. This will make the application
|
|
show a less scary UAC prompt if administrator permissions are required
|
|
to complete the installation.
|
|
|
|
## Updater Dependencies
|
|
|
|
The external dependencies of the updater binary are:
|
|
|
|
* The C/C++ runtime libraries (Linux, Mac),
|
|
* pthreads (Linux, Mac),
|
|
* zlib (Linux, Mac)
|
|
* native UI library (Win32 API on Windows, Cocoa on Mac, GTK on Linux if available)
|
|
|
|
## Full and Delta Updates
|
|
|
|
The simplest auto-update implementation is for existing installs
|
|
to download a complete copy of the new version and install it. This is
|
|
appropriate if a full download and install will not take a long time for most users
|
|
(eg. if the application is small or they have a fast internet connection).
|
|
|
|
With this tool, a full-update involves putting all files in a build of
|
|
the application into a single package.
|
|
|
|
To reduce the download size, delta updates can be created which only include
|
|
the necessary files or components to update from the old to the new version.
|
|
|
|
The file_list.xml file format can be used to represent either a complete
|
|
install - in which every file that makes up the application is included,
|
|
or a delta update - in which case only new or updated files and packages
|
|
are included.
|
|
|
|
There are several ways in which this can be done:
|
|
|
|
* Pre-computed Delta Updates
|
|
For each release, create a full update plus delta updates from the
|
|
previous N releases. Users of recent releases will receive a small
|
|
delta update. Users of older releases will receive the full update.
|
|
|
|
* Server-computed Delta Updates
|
|
The server receives a request for an update from client version X and in response,
|
|
computes an update from version X to the current version Y, possibly
|
|
caching that information for future use. The client then receives the
|
|
delta file_list.xml file and downloads only the listed packages.
|
|
|
|
Applications such as Chrome and Firefox use a mixture of the above methods.
|
|
|
|
* Client-computed Delta Updates
|
|
The client downloads the file_list.xml file for the latest version and
|
|
computes a delta update file locally. It then downloads only the required
|
|
packages and invokes the updater, which installs only the changed or updated
|
|
files from those packages.
|
|
|
|
This is similar to Linux package management systems.
|