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openvstorage / alba

Open vStorage ALBA (alternate backend) creates a replicated or flexible network raid’ed object storage backend out of Seagate Kinetic drives and local disk supporting compression, encryption.
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Local backend is disqualified because on namespace already exists #737

Closed jeroenmaelbrancke closed 7 years ago

jeroenmaelbrancke commented 7 years ago

On the global proxies we see following error:

Disqualifying osd 1: Albamgr_protocol.Protocol.Error.Albamgr_exn(4, "Albamgr_protocol.Protocol.Error.Namespace_already_exists"); backtrace:; Raised at file "map.ml", line 122, characters 16-25; Called from file "src0/sexp_conv.ml", line 149, characters 10-37

similar issue: #550

Why do we get these errors? Can you improve this error?

wimpers commented 7 years ago

@jeroenmaelbrancke any idea why the namespace was created multiple times?

domsj commented 7 years ago

My current best guess: possibly multiple different namespaces were created on the main backend around the same time. This could cause a race in the osd message delivery where 2 proxies try to create the same local backend namespace simultaneously. Alba will/should correctly recover from the race, but a local-backend-osd might be temporarily disqualified. If the hypothesis is correct this can be solved by suppressing the Namespace_already_exists error here: https://github.com/openvstorage/alba/blob/1.3.16/ocaml/src/alba_osd.ml#L193-L197.