Apparatus and method for live loading of version upgrades in a process control environment

An apparatus, comprising:

• at least one memory configured to store at least one or more old object instances of a running program created from an old version of a class, the old version of the class associated with an old version of assembly code;
• and
• at least one processor configured to:
• load a new version of the class, the new version of the class being an updated version of the old version of the class, the old version of the class have a first layout of data elements and the new version of the class having a second layout of data elements;
• set a flag in response to the loading of the new version of the class;
• initiate a garbage collection process that includes:
• determining if the flag is set;
• when the flag is not set, performing a normal garbage collection;
• and
• when the flag is set, scanning the at least one memory, identifying the one or more old object instances contained in the at least one memory, and recording one or more addresses of the one or more old object instances stored in the at least one memory and one or more references to the one or more old object instances;
• and
• initiate a live load after the garbage collection process has recorded the one or more addresses of the one or more old object instances that includes:
• for each of the one or more recorded addresses:
• selecting the old object instance stored at the address;
• updating method information in the selected old object instance to identify one or more methods defined by the new version of the class only when the old and new versions of the class define the same data elements as determined by comparing the first and second layouts of data elements;
• and
• creating a new object instance from the new version of the class and transferring one or more values of one or more of the data elements from the selected old object instance to the new object instance only when the old and new versions of the class do not define the same data elements as determined by comparing the first and second layouts of data elements.

A non-transitory computer readable medium embodying a computer program, the computer program comprising computer readable program code, the computer readable program code when executed by a processor configured to perform a method of:

• loading a new version of a class, the new version of the class being an updated version of an old version of the class, the old version of the class have a first layout of data elements and the new version of the class having a second layout of data elements;
• setting a flag in response to the loading of the new version of the class;
• initiating a garbage collection process that includes:
• determining if the flag is set;
• when the flag is not set, performing a normal garbage collection;
• and
• when the flag is set, scanning a memory where at least one or more old object instances of the running program are stored, identifying the one or more old object instances contained in the memory, and recording one or more addresses of the one or more old object instances stored in the memory and one or more references to the one or more old object instances, the one or more old object instances having been created from the old version of the class;
• and
• initiating a live load after the garbage collection process has recorded the one or more addresses of the one or more old object instances that includes:
• for each of the one or more recorded addresses:
• selecting the old object instance stored at the address;
• updating method information in the selected old object instance to identify one or more methods defined by the new version of the class only when the old and new versions of the class define the same data elements as determined by comparing the first and second layouts of data elements;
• and
• creating a new object instance from the new version of the class and transferring one or more values of one or more of the data elements from the selected old object instance to the new object instance only when the old and new versions of the class do not define the same data elements as determined by comparing the first and second layouts of data elements.