missing settings document causes permanent problems

[Roger Peppe]

In a production controller, we encountered a model which was missing a settings document. This meant that:

a) the all-watcher couldn't start, because backingModel.updated fails if ModelConfig for the model fails, which is the case when there's no settings document
b) juju list-models fails because the settings can't be found for the model (it actually succeeds in getting details of all the other models, but doesn't print any of their details because of the one failure)

There are two issues here:
1) how we could have ended up in a state with a model with no associated settings document
2) make backingModel.updated more resilient in this case so we can start the all-watcher anyway.

For the record, the model had been marked as dead for a couple months before this issue arose.
This was its entry in the database:

{ "_id" : "c8b676d5-0090-46c6-8823-e372154de20e", "name" : "mymodel7", "life" : 2, "owner" : "frankban@external", "controller-uuid" : "5392879a-6c3b-47f8-8bd4-cec06c2a1c4d", "migration-mode" : "", "cloud" : "aws", "cloud-region" : "eu-central-1", "cloud-credential" : "aws/frankban@external/aws", "txn-revno" : NumberLong(4), "txn-queue" : [ "589e89e07a067a4c5589cda9_4f5b51a2", "589e89e47a067a4c5589d113_99c4b867", "589e89e57a067a4c5589d19e_187438bc", "589e89e67a067a4c5589d269_b0a3e379", "589e89e87a067a4c5589d325_cb0211f9", "589e89e97a067a4c5589d447_a8a70a5b", "589e89ea7a067a4c5589d50a_977cace9", "589e89ec7a067a4c5589d616_82fe5357", "589e89ed7a067a4c5589d78a_5c702c3d", "589e89f17a067a4c5589d9d5_2e2b954d", "589e89f27a067a4c5589da4a_4531e457", "589e89f27a067a4c5589dad8_637b5333", "589e89f37a067a4c5589dc1c_6e4c10f7", "589e89f57a067a4c5589dcb7_16d208cc", "589e89f57a067a4c5589de16_3c41e460", "589e89f87a067a4c5589dfd2_f4d783c3", "589e89f97a067a4c5589e02d_9769db75", "589e89f97a067a4c5589e087_ba83a836", "589e89fa7a067a4c5589e0d5_f56d6103", "589e89fa7a067a4c5589e127_6649a613", "589e89fb7a067a4c5589e1bc_0bde48ce", "589e89fd7a067a4c5589e238_656401ef", "589e89fe7a067a4c5589e30c_fcdabc96", "589e8a007a067a4c5589e340_a0f7a541", "589e8a017a067a4c5589e3cd_fbf18663", "589e8a047a067a4c5589e45a_e710414f", "589e8a067a067a4c5589e4ed_d130c7e5", "589e8a087a067a4c5589e5a0_1fdeb99c", "589e8a0c7a067a4c5589e639_9958b84a", "589e8a0e7a067a4c5589e6c3_e683b013", "589e8a127a067a4c5589e74d_999dba38", "589e8a157a067a4c5589e80c_5dd4e082", "589e8a177a067a4c5589e8a3_95320179" ], "time-of-dying" : ISODate("2017-02-09T08:12:35Z"), "time-of-death" : ISODate("2017-02-11T03:49:53Z") }

[Ian Booth (wallyworld)]

PR for the all model watcher bit https://github.com/juju/juju/pull/7272

[Ian Booth (wallyworld)]

model watcher fixed, list-models issue in new bug 1685718

[Roger Peppe (rogpeppe)]

I'm not sure it's quite right to mark this bug as "Fix committed" as there's still a bug in this situation - ListModels fails.

[Ian Booth (wallyworld)]

I've raised a new bug for list models issue. They are totally separate fixes to different parts of the code base therefore 2 bugs are required. We try to avoid putting up PRs with more than one fix in the PR.

[Ian Booth (wallyworld)]

Actually, there's a good reason for doing this as separate PRs (one issue per bug). There's already a PR for the list-models issue https://github.com/juju/juju/pull/7265 which was done for bug 1674805 or bug 1674805 (which takes your fancy)