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From Josh Elser <>
Subject Re: [DISCUSS] Design for a "query log"
Date Fri, 02 Mar 2018 22:51:34 GMT
Yup, totally agree. Will also try to make these more clear in the doc.

We want to queue up the work to "log" and do it in the background. If 
that queue gets too full, we drop it right off that cliff :)

Thanks, Samarth!

On 3/2/18 5:47 PM, Samarth Jain wrote:
> A couple more points which I think you alluded to, Josh, but I would still
> like to call out:
> 1) Writing of these query logs to a phoenix table should be best effort
> i.e. a query definitely shouldn't fail because we encountered an issue
> while writing its log
> 2) Writing of query logs should happen in a manner that is async to the
> flow of the query i.e. a query shouldn't incur the cost of the write
> happening to the query log table
> Doing 2) will help out with 1)
> On Fri, Mar 2, 2018 at 2:28 PM, Josh Elser <> wrote:
>> Thanks Nick and Andrew! These are great points.
>> * A TTL out of the box is a must. That's such a good suggestion
>> * Sensitivity of data being stored is also a tricky-serious issue to
>> consider. We'll want to lock the table down and be able to state very
>> clearly what data may show up in it.
>> * I like the "levels" of detail that will be persisted. It will help break
>> up the development work (e.g. first impl can just be the INFO details), and
>> prevents concern of runtime impact.
>> * Sampling is a no-brainer for "always-on" situations. I like that too.
>> I'll work on taking these (and others) and updating the gdoc tonight.
>> Thanks again for your feedback!
>> On 3/2/18 1:50 PM, Andrew Purtell wrote:
>>> Agree with Nick's points but let me augment with an additional suggestion:
>>> Tunable/configurable threshold for sampling. In many cases it's sufficient
>>> to sample e.g. 1% of queries to get sufficient coverage and this would
>>> prune 99% of actual load from the query log.
>>> Also let me underline that compliance requirements will require either
>>> super strong controls of the query log if everything is always logged, in
>>> which case it is important that it works well with access control features
>>> to lock it down; or better what Nick suggests where we can turn off things
>>> like logging the values supplied for bound parameters.
>>> On Fri, Mar 2, 2018 at 8:41 AM, Nick Dimiduk <> wrote:
>>> I'm a big fan of this idea. There was a brief discussion on the topic over
>>>> on PHOENIX-2715.
>>>> My first concern is that the collected information is huge -- easily far
>>>> larger than the user data for a busy cluster. For instance, a couple 10's
>>>> of GB stored user data, guideposts set to default 100mb, enable salting
>>>> on
>>>> a table with an "innocent" value of 10 or 20 and the collection of RPCs
>>>> can
>>>> easily grow into the hundreds for simple queries. Even if you catalog
>>>> just
>>>> the "logical" RPC's - HBase Client API calls that Phoenix plans rather
>>>> than
>>>> the underlying HBase Client RPCs - this will be quite large. The
>>>> guidepost
>>>> themselves for such a table would be on the order of 30mb.
>>>> My next concern is about the sensitive query parameters being stored.
>>>> It's
>>>> entirely reasonable to expect a table to store sensitive information that
>>>> should not be exposed to operations.
>>>> Thus, my suggestions:
>>>> * minimize the unbounded nature of this table by truncating all columns
>>>> to
>>>> some max length -- perhaps 5k or 10k.
>>>> * enable a default TTL on the schema. 7 days seems like a good starting
>>>> point.
>>>> * consider controlling which columns are populated via some operational
>>>> mechanism. Use Logger level as an example, with INFO the default setting.
>>>> Which data is stored at this level? Then at DEBUG, then TRACE. Maybe
>>>> timestamp, SQL, and explain are at INFO. DEBUG adds bound parameters and
>>>> scan metrics. TRACE adds RPCs and timing, snapshot metadata.
>>>> Thanks,
>>>> Nick
>>>> On Mon, Feb 26, 2018 at 1:57 PM, Josh Elser <> wrote:
>>>> Hiya,
>>>>> I wanted to share this little design doc with you about some feature
>>>>> work
>>>>> we've been thinking about. The following is a Google doc in which anyone
>>>>> should be allowed to comment. Feel free to comment there, or here on
>>>>> thread.
>>>>> The high-level goal is to create a construct in which Phoenix clients
>>>> will
>>>>> automatically serialize information about the queries they run to a
>>>>> table
>>>>> for retrospective analysis. Ideally, this information would be stored
>>>> a
>>>>> Phoenix table. We want this data to help answer questions like:
>>>>> * What queries are running against my system
>>>>> * What specific queries started between 535AM and 620AM two days ago
>>>>> * What queries are user "bob" running
>>>>> * Are my user's queries effectively using the indexes in the system
>>>>> Anti-goals for include:
>>>>> * Cluster impact (computation/memory) usage of a query
>>>>> * Query performance may be slowed to ensure all data is serialized
>>>>> * A third-party service dedicated to ensuring query info is serialized
>>>> (in
>>>>> the event of client failure)
>>>>> Take a look at the document and let us know what you think please. I'm
>>>>> happy to try to explain this in greater detail.
>>>>> - Josh (on behalf of myself, Ankit, Rajeshbabu, and Sergey)

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