Product - Refresh: Reload a filesystem-based Python product.

Description

This view allows you to reload filesystem-based product code without restarting Zope. This function is useful during development of products.

To enable your product to be refreshed, it is required that you put a file called refresh.txt in your product directory. It can optionally contain a warning for others who might use the refresh function.

(Producting refreshing is not perfect. Some products, especially "hotfix" style products which patch Zope, should not be refreshed. That's why refresh.txt is required. Most products are safe to refresh, however.)

There are two modes of operation. You can visit your product's Refresh tab and manually push the refresh button. Or you can turn on "auto-refresh" mode, which causes Zope to periodically scan the modification time of the Python files that make up your product and execute a refresh operation in the background.

NOTE: Don't enable auto-refresh for too many products at once. Scanning file modification times can take a lot of time per request.

You can also select dependent refreshable products. If you have a product that subclasses from a product you're working on, you'll want to enable refresh for both products and add the product that subclasses as a dependent of the product you're modifying. This enables subclasses to be updated.

Controls

Refresh this product

The manual refresh button.

Auto refresh mode

Check the checkbox to enable auto-refresh.

Dependent auto-refreshable products

A list of other products which are auto-refreshable.

How it works

To execute a refresh, Zope looks in the sys.modules dictionary for modules with names that start with the prefix for your product. It tries to scan for dependencies between the modules that make up your product then uses Python's reload() function for each module in order. Then it sets a flag that will cause ZODB to dump its cache on the next connection so that changes to persistent classes will take effect.

To implement auto-refresh, Zope stores a PersistentMapping called RefreshData on the database root object (below the Application object). The contents of the PersistentMapping are examined at the moment a database connection is opened by ZApplication. The PersistentMapping contains a list of which products have auto-refresh enabled. For each product with auto-refresh enabled, Zope compares the file mod times with the last recorded times and executes a refresh if there are any changes.