Add warning logs for manifests, siblings, bytes and history

[shino]

Add three kinks of warning logs for potentially bloated manifests.
Original issue is #882.

• many siblings
• large size
• long history ({UUID, M} pairs)

Each has default value and enabled, but has kill switch disabled.

[kuenishi]

Nitpick, the name of this function seems too general. I prefer this be maybe_warn_manifest_size/4 and in riak_cs_manifest.erl .

[kuenishi]

I tested overwriting hundreds times, then I got logs like this per single put:

2014-07-15 16:41:59.286 [warning] <0.4983.0>@riak_cs_utils:maybe_log_warning:465 Long manifest history for key test/md.xml: 451 manifests
2014-07-15 16:41:59.299 [warning] <0.4985.0>@riak_cs_utils:maybe_log_warning:465 Long manifest history for key test/md.xml: 451 manifests

This is maybe because get_manifets is called twice somewhere in put_fsm ... I would like to get just once.

[shino]

This is maybe because get_manifets is called twice somewhere in put_fsm ... I would like to get just once.

Both riak_cs_get_fsm and riak_cs_put_fsm have riak_cs_manifest_fsm each.
It may be a sign for refactoring 😄 .
I want to defer it after 1.5 release. Thoughts?

[shino]

@kota Addressed your comments except the last one and pushed commit.

Now logs look like these:

11:46:55.124 [warning] Long manifest history (32 manifests) for bucket=<<"test2">> key=<<"\t">>
11:48:55.776 [warning] Many manifest siblings (210 siblings) for bucket=<<"test">> key=<<"mp5">>
11:48:55.776 [warning] Large manifest size (7882640 bytes) for bucket=<<"test">> key=<<"mp5">>

[shino]

Ouch, I mentioned wrong Kota-san. Sorry again and again.

I wanted to mention @kuenishi 😓

[shino]

@borshop merge