My web application needs updates from time to time. When this happens I often have to stop the server and shut down the JVM. Then the old (current) directories can be replaced by the new ones, and I restart the server.
It's okay when there are several copies of the server running behind a load balancer. This allows updates while the service is available. I would like to ask what other ways there are for updating services. One idea could be to reload a namespace? The application could offer a way for an admin to kick of a reload of a given namespace. Two problems I see: 1) On the dev machine I make the changes and (compile ...) the system. On the live machine there already exist .class files with the same name, or at least with a very similar name. I don't know if there could be naming conflicts, and in such a case the OS might now allow me to overwrite a .class file, as it is in use currently. Even if compile produces files with new names (other number suffixes or something like that) this could end up in a mess. 2) And even if we can manage point 1) there is still the problem with atomicity. Or not? I imagine a chain of n functions. Callers or callees may expect different args. I would like to update the whole namespace as one unit. Maybe this already works in Clojure? One more question: could it make sense to have a reload function which first saves the whole namespace (by referencing all toplevel vars and functions in that ns), then atomically reloads the namespace from a given path on disk (containing all .class files) and finally returns the old instances of the ns? My idea behind this was: when a web server starts a request then some threads could still want to continue to execute functions of the old ns because they did not finish their request. Or there could be still an open session for some users which requirs that as long this session exists these specific users are served with the previous functions, from before the update. This sounds a bit like making snapshots and transactions over a namespace. Please let me know what you think about it, if this makes sense or would only cause too many problems, or if it won't work, etc. -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en
