lib/connections, lib/model: Refactor connection close handling (fixes #3466) #3490
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…3466) So there were some issues here. The main problem was that model.Close(deviceID) was overloaded to mean "the connection was closed by the protocol layer" and "i want to close this connection". That meant it could get called twice - once *to* close the connection and then once more when the connection *was* closed. After this refactor there is instead a Closed(conn) method that is the callback. I didn't need to change the parameter in the end, but I think it's clearer what it means when it takes the connection that was closed instead of a device ID. To close a connection, the new close(deviceID) method is used instead, which only closes the underlying connection and leaves the cleanup to the Closed() callback. I also changed how we do connection switching. Instead of the connection service calling close and then adding the connection, it just adds the new connection. The model knows that it already has a connection and makes sure to close and clean out that one before adding the new connection. To make sure to sequence this properly I added a new map of channels that get created on connection add and closed by Closed(), so that AddConnection() can do the close and wait for the cleanup to happen before proceeding.
| @@ -729,7 +729,7 @@ func (c *rawConnection) close(err error) { | |||
| } | |||
| c.awaitingMut.Unlock() | |||
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| go c.receiver.Close(c.id, err) | |||
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I'm beginning to realize that "go" for these kinds of things as a workaround against locking issues is a quite bad code smell.
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@st-review merge |
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…3466) So there were some issues here. The main problem was that model.Close(deviceID) was overloaded to mean "the connection was closed by the protocol layer" and "i want to close this connection". That meant it could get called twice - once *to* close the connection and then once more when the connection *was* closed. After this refactor there is instead a Closed(conn) method that is the callback. I didn't need to change the parameter in the end, but I think it's clearer what it means when it takes the connection that was closed instead of a device ID. To close a connection, the new close(deviceID) method is used instead, which only closes the underlying connection and leaves the cleanup to the Closed() callback. I also changed how we do connection switching. Instead of the connection service calling close and then adding the connection, it just adds the new connection. The model knows that it already has a connection and makes sure to close and clean out that one before adding the new connection. To make sure to sequence this properly I added a new map of channels that get created on connection add and closed by Closed(), so that AddConnection() can do the close and wait for the cleanup to happen before proceeding. GitHub-Pull-Request: #3490
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Purpose
So there were some issues here. The main problem was that model.Close(deviceID) was overloaded to mean "the connection was closed by the protocol layer" and "i want to close this connection". That meant it could get called twice - once to close the connection and then once more when the connection was closed.
After this refactor there is instead a Closed(conn) method that is the callback. I didn't need to change the parameter in the end, but I think it's clearer what it means when it takes the connection that was closed instead of a device ID. To close a connection, the new close(deviceID) method is used instead, which only closes the underlying connection and leaves the cleanup to the Closed() callback.
I also changed how we do connection switching. Instead of the connection service calling close and then adding the connection, it just adds the new connection. The model knows that it already has a connection and makes sure to close and clean out that one before adding the new connection.
To make sure to sequence this properly I added a new map of channels that get created on connection add and closed by Closed(), so that AddConnection() can do the close and wait for the cleanup to happen before proceeding.
Testing
Our testing capabilities here really suck and we should work on that.
What I did was remove all of the already-connected and priority checks in the connection service, so that the connection loop ran continuously and every new connection became a connection switch. This crashed instantly on the old code, but runs for at least a few minutes with a connection switch every five seconds on the new code. I also run the TestRestart* integration things and they still work.
I might have missed a possible deadlock somewhere, but hey... :/