Riak: reliable object deletion

Fred Dushin fdushin at basho.com
Thu Feb 23 09:02:12 EST 2017


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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