make chunkserver error message display all possibilities upon receivi…

[mckurt]

…ng EBADCLUSTERKEY [QFS-187]

[codecov-io]

Current coverage is 75.51% (diff: 100%)

Merging #169 into master will not change coverage

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[mikeov]

Presently the full condition is:
cluster key mismatch, or chunk server and meta server file system id mismatch, or chunk server executable's md5 is not in the meta server's list of md5. I think that it would make sense to update the error message in src/cc//common/kfsdecls.cc and then retrieve it and use for the trace message.

Please remove changes to ext directory from this pull request, as those are not relevant to the subject, and must be considered separately, if at all. The other thing, is that all changes under "ext" directory must be tracked separately, and should not be mixed with any other changes, in order to simplify any future updates / merges to this code from the external source repositories.

[mckurt]

I reverted the ext directory changes.

Can you elaborate on the error messaging? src/cc//common/kfsdecls.cc only has functions for ServerLocation only.

Also, EBADCLUSTERKEY error message seems to be assigned by the metaserver only in two cases: cluster key mismatch (https://github.com/quantcast/qfs/blob/master/src/cc/meta/LayoutManager.cc#L2367) and md5 mismatch (https://github.com/quantcast/qfs/blob/master/src/cc/meta/LayoutManager.cc#L2377).

What am I missing here?

[mikeov]

The relevant code apparently only is in multi master branch. I'll change it there.