GCT 6.2 Migrating Guide for XIO

The only significant change to Globus XIO in this release is the addition of "string attributes". The previous method of handling attributes still works in an entirely backward compatible way, but the string attributes adds a much needed convenience. Drivers can now provide a list of key=value pairs. A user can then specify these options at the command line and at run time. This make run time configuration much more flexible.

The only significant change to Globus XIO in this release is the addition of "string attributes". The previous method of handling attributes still works in an entirely backward compatible way, but the string attributes adds a much needed convenience. Drivers can now provide a list of key=value pairs. A user can then specify these options at the command line and at run time. This make run time configuration much more flexible.

A driver can choose to expose parameters in a string form. Providing this feature makes dynamically setting driver specific options much easier. A user can then load the driver by name and set specific options by name all at runtime with no object module references. For example, a TCP driver can be loaded with the string tcp and the options can be set with the string port=50668;keepalive=yes;nodelay=N.

This would set the port to 50668, keepalive to true and nodelay to false. The particular string definition is defined by the tcp driver. This is done by creating a globus_i_xio_attr_parse_table_t array within the drivers source code. See the TCP driver source code for an example. Each row of the array is 1 option. There are 3 sub-members of each row entry: key, cmd, and parse function. The key is a string that defines what option is to be set. In the above example string port would be a key. cmd tells the driver what cntl is associated with the key. In other words, once the string is parsed out it converts the key into a driver specific control enum. XIO then uses that enum as it would if a driver specific option was set in the source code. For more information on controls see globus_xio_attr_cntl.

The final value in the array entry is the parsing function. The passing function takes the value of the key=value string and turns it into the specific data type associated with that function. There are many available parsing functions but the developer is free to right their own. Here are some examples:

For GCT 6.2 no other differences will be noticed by those previously familiar with globus_xio.

Globus XIO has made very few changes in the API since its introduction. Users of GCT 6.2 who are previously familiar with globus_xio will notice no difference.

Globus XIO is a new component as of Globus 3.2. Previous versions of Globus provided an API called globus_io. XIO is a replacement for globus_io; however, a compatibility layer exists to allow full backward compatibility for applications written against globus_io. For users familiar with globus_io the learning curve for XIO will be very small. The APIs use the same event model and only significantly differ in connection establishment.