Arvados

Noted #5414 as a "check for conflicts if 5414 isn't merged yet" reminder.

At e41260f

In the Go SDK, WritableRoots and writableRoots seem to mean writableLocalRoots, so should probably be renamed accordingly.

For style and readability, suggest collapsing the types, putting the locals together, and keeping the newX parameter name trend:

-func (kc *KeepClient) SetServiceRoots(newLocals, newGateways map[string]string, writableRoots map[string]string)
+func (kc *KeepClient) SetServiceRoots(newLocals, newWritableLocals, newGateways map[string]string)

pull worker doesn't write to its keepClient, so suggest this in pull_worker.go:

-       keepClient.SetServiceRoots(service_roots, nil, keepClient.WritableRoots())
+       keepClient.SetServiceRoots(service_roots, nil, nil)

Please use go test -check.vv instead of cluttering tests with debug printfs:

log.Printf("TestPutWant2ReplicasWithOnlyOneWritableRoots")

In keep.py, suggest:

-        if (need_writable == True):
+        if need_writable:

And:

-                self._writable_services = [{
-                    'uuid': 'proxy',
-                    '_service_root': proxy,
-                    }]
+                self._writable_services = self._keep_services

Migration: I think you could change "def up" to "def change" and remove the explicit down-migration, and Rails would DTRT. (But then, I also thought "rails g migration" would have done this for you, but maybe not...?)

Addressed all comments and merged into master. (Yes, the change method worked for both up and down for this case). Thanks.