Riak: reliable object deletion

al so volkswak at gmail.com
Fri Feb 24 00:53:29 EST 2017


>
> Present both in Solr and Riak. It's a 1-way replication in MDC. MDC is not
> the cause unless there is a bug there as well.
>
>
> On Thu, Feb 23, 2017 at 6:02 AM, Fred Dushin <fdushin at basho.com> wrote:
>
>> Running a Solr query has no impact on writes -- Riak search queries are
>> direct pass throughs to Solr query and don't touch any of the salient Riak
>> systems (batching writes to Solr, YZ AAE, etc).  I believe the timing of
>> the reappearance is a coincidence.
>>
>> Is it possible the object reappeared via MDC?  Do you have record of the
>> reappeared object in your other cluster?
>>
>> Also, just to confirm, when you say the object reappeared -- it
>> re-appeared in Riak (and subsequently in Solr), correct?  Or are you saying
>> you just find the object in Solr (via a search)?
>>
>> -Fred
>>
>> On Feb 23, 2017, at 1:43 AM, al so <volkswak at gmail.com> wrote:
>>
>>  Here is brief env:
>>>  Riak v 2.0.8 + Solr/ 5 node cluster/ MDC
>>>
>>>  Problem:
>>>   Deleted object suddenly resurrected after few days. Solr search query(
>>> "*:*") was executed around the time of reappearance.
>>>
>>>  Bucket property for this reappeared object
>>>  {
>>>   "props": {
>>>     "name": "UsaHype",
>>>     "allow_mult": false,
>>>     "basic_quorum": false,
>>>     "big_vclock": 50,
>>>     "chash_keyfun": {
>>>       "mod": "riak_core_util",
>>>       "fun": "chash_std_keyfun"
>>>     },
>>>     "dvv_enabled": true,
>>>     "dw": "quorum",
>>>     "last_write_wins": false,
>>>     "linkfun": {
>>>       "mod": "riak_kv_wm_link_walker",
>>>       "fun": "mapreduce_linkfun"
>>>     },
>>>     "n_val": 3,
>>>     "notfound_ok": true,
>>>     "old_vclock": 86400,
>>>     "postcommit": [
>>>       {
>>>         "mod": "riak_repl_leader",
>>>         "fun": "postcommit"
>>>       },
>>>       {
>>>         "mod": "riak_repl2_rt",
>>>         "fun": "postcommit"
>>>       }
>>>     ],
>>>     "pr": 0,
>>>     "precommit": [
>>>
>>>     ],
>>>     "pw": 0,
>>>     "r": "quorum",
>>>     "repl": true,
>>>     "rw": "quorum",
>>>     "small_vclock": 50,
>>>     "w": "quorum",
>>>     "young_vclock": 20
>>>   }
>>> }
>>>
>>>
>>> * delete_mode is not configured at all. Defaults to 3 sec? Do Tombstone still get created when no delete_mode at all in the config? Can we query metadata(*X-Riak-Deleted)* for this reappeared object.*
>>>
>>>  How would one go about finding root cause. I do know the date when the
>>> object was deleted from our app logs. I also seem to know when it
>>> reappeared. Seems like a solr search ("*:*") in code was executed just
>>> before this object reappeared? Look at AAE? Is there a way to find if Solr
>>> and Riak backends are out-of-sync (AAE?).
>>>
>>>  I understand tuning other params (allow_mult = true, ...) will have its
>>> own implications.
>>>
>>>  In summary:
>>>   How do I find root cause of this issue.
>>>   How to reliable delete an object.
>>>
>>> -Volk
>>>
>>
>>
>
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