16.6.4. Running the transaction

⁠16.6.4. Running the transaction

After setting up the transaction set, perform the transaction by calling run. You need to provide two parameters:

ts.run(callback, client_data)

The callback parameter must be a Python function. The client_data is any data you want to pass to the callback. There may be more than one package in the transaction set, so this data should not be specific to a particular package.

Warning

You must not pass None as the client_data or you will get a Python error.

⁠16.6.4.1. Transaction run Method Callbacks

The callback you pass to the run method on a transaction set is essential. Your callback must work properly, or the transaction will fail. You must provide a callback.

Your callback will get called a number of times, mostly as a means to report progress. If you are writing a graphical user interface, for example, you can use the progress callbacks to update a visual progress meter.

The basic syntax for the transaction set run callback is:

def runCallback(reason, amount, total, key, client_data):

# Do your stuff...

The key is the data you provided in the call to the addInstall method. The client_data is the data you passed to the run method.

Each time your callback is called, the transaction set will provide a reason flag. Table 17-5 lists the values for the reason parameter.

Table 17-5 Transaction set run callback reason values

Value	Reason
rpm.RPMCALLBACK_UNKNOWN	Unknown problem
rpm.RPMCALLBACK_INST_PROGRESS	Progress for installation
rpm.RPMCALLBACK_INST_START	Start of installation
rpm.RPMCALLBACK_INST_OPEN_FILE	Callback should open package file
rpm.RPMCALLBACK_INST_CLOSE_FILE	Callback should close package file
rpm.RPMCALLBACK_TRANS_PROGRESS	Transaction progress
rpm.RPMCALLBACK_TRANS_START	Transaction start
rpm.RPMCALLBACK_TRANS_STOP	Transaction stop
rpm.RPMCALLBACK_UNINST_PROGRESS	Uninstallation progress
rpm.RPMCALLBACK_UNINST_START	Uninstallation start
rpm.RPMCALLBACK_UNINST_STOP	Uninstallation stop
rpm.RPMCALLBACK_REPACKAGE_PROGRESS	Repackaging progress
rpm.RPMCALLBACK_REPACKAGE_START	Repackaging start
rpm.RPMCALLBACK_REPACKAGE_STOP	Repackaging stop
rpm.RPMCALLBACK_UNPACK_ERROR	Error unpacking package file
rpm.RPMCALLBACK_CPIO_ERROR	cpio error getting package payload

Your callback must handle at least two cases: a reason value of rpm.RPMCALLBACK_INST_OPEN_FILE and rpm.RPMCALLBACK_INST_CLOSE_FILE.

With the reason of rpm.RPMCALLBACK_INST_OPEN_FILE, you must open the RPM package file and return a file descriptor for the file. You need to keep this file descriptor in a global-scope or otherwise-accessible variable, because with the reason of rpm.RPMCALLBACK_INST_CLOSE_FILE, you must close this file.