New StateWait changes - the main point of all this is to move to our new
model of waiting for state changes. Before we were watching the database (which means we can only watch for terminal/stable/long-lived states, and have to poll the db). Now things that are waiting for states to change become event listeners, and watch the stream of events flow by, and don't have to do any polling. They can now watch for any state, and even sequences of states (ie a Shutdown followed by an Isup). To do this, there is now a cool StateWait.pm library that encapsulates the functionality needed. To use it, you call initStateWait before you start the chain of events (ie before you call node reboot). Then do your stuff, and call waitForState() when you're ready to wait. It can be told to return periodically with the results so far, and you can cancel waiting for things. An example program called waitForState is in testbed/event/stated/ , and can also be used nicely as a command line tool that wraps up the library functionality. This also required the introduction of a TBFAILED event that can be sent when a node isn't going to make it to the state that someone may be waiting for. Ie if it gets wedged coming up, and stated retries, but eventually gives up on it, it sends this to let things know that the node is hozed and won't ever come up. Another thing that is part of this is that node_reboot moves (back) to the fully-event-driven model, where users call node reboot, and it does some checks and sends some events. Then stated calls node_reboot in "real mode" to actually do the work, and handles doing the appropriate retries until the node either comes up or is deemed "failed" and stated gives up on it. This means stated is also the gatekeeper of when you can and cannot reboot a node. (See mail archives for extensive discussions of the details.) A big part of the motivation for this was to get uninformed timeouts and retries out of os_load/os_setup and put them in stated where we can make a wiser choice. So os_load and os_setup now use this new stuff and don't have to worry about timing out on nodes and rebooting. Stated makes sure that they either come up, get retried, or fail to boot. tbrestart also underwent a similar change.
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