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Utilizing Question Logs in Rockset

At Rockset, we frequently search for methods to offer our prospects higher visibility into the product. Towards this aim, we just lately determined to enhance our customer-facing question logging. Our earlier iteration of question logs was based mostly in one in every of our shared companies known as apiserver. As a part of the work that apiserver would do when finishing a question execution request, it might create a log that might ultimately be ingested into the _events assortment. Nevertheless, there have been points that made us rethink this implementation of question logs:

  1. No isolation: as a result of the question logs in _events relied on shared companies, heavy site visitors from one org might have an effect on question logging in different orgs.
  2. Incomplete logs: due to the problems induced by utilizing shared companies, we solely logged question errors – profitable queries wouldn’t be logged. Moreover, it was not doable for us to log information about async queries.
  3. No potential to debug question efficiency – the question logs in _events solely contained fundamental details about every question. There was no approach for the person to get details about why a given question might have run slowly or exhausted compaute sources for the reason that logs contained no details about the question plan.

Improved Question Logging

The brand new question logs characteristic addresses all of those points. The mechanisms that deal with question logs are contained completely inside your Digital Occasion versus being inside one in every of Rockset’s shared companies. This provides question logs the benefit of isolation. Moreover, each question you submit shall be routinely logged when you’ve got already created a set with a question logs supply (offered you don’t hit a charge restrict).

How Question Logs Work

Question logging begins on the finish of question execution. As a part of the steps which can be run within the remaining aggregator when a question has accomplished, a report containing metadata related along with your question is created. At this level, we may have to gather data from different aggregators that had been concerned within the question. After that is completed, the report is briefly saved in an in-memory buffer. The contents of this buffer are flushed to S3 each few seconds. As soon as question logs have been dumped to S3, they are going to be ingested into any of your question log collections which were created.



After we first designed this venture, we had all the time meant for it to work with the question profiler within the console. This is able to enable our prospects to debug question bottlenecks with these logs. Nevertheless, the question profiler requires fairly a bit of information, which means it might be not possible for each question log to include all the knowledge needed for the profiler. To unravel this drawback, we opted to create two tiers of question logs – INFO and DEBUG logs.

INFO logs are routinely created for each question issued by your org. They include some fundamental metadata related along with your question however can’t be used with the question profiler. When you understand that you could be need to have the flexibility to debug a sure question with the profiler, you possibly can specify a DEBUG log threshold along with your question request. If the question execution time is bigger than the desired threshold, Rockset will create each an INFO and a DEBUG log. There are two methods of specifying a threshold:

  1. Use the debug_log_threshold_ms question trace

    SELECT * FROM _events HINT(debug_log_threshold_ms=1000)

  2. Use the debug_threshold_ms parameter in API requests. That is accessible for each question and question lambda execution requests.

Observe that since DEBUG logs are a lot bigger than INFO logs, the speed restrict for DEBUG logs is far decrease. Because of this, it’s endorsed that you just solely present a DEBUG log threshold when you understand that this data may very well be helpful. In any other case, you run the danger of hitting the speed restrict while you most want a DEBUG log.

System Sources

As a part of this venture, we determined to introduce a brand new idea known as system sources. These are sources which ingest information originating from Rockset. Nevertheless, not like the _events assortment, collections with system sources are managed completely by your group. This lets you configure all the settings of those collections. We shall be introducing extra system supply varieties as time goes on.

Getting Began with Question Logging

So as to begin logging your queries, all it’s good to do is create a set with a question logs supply. This may be completed by way of the console.


Rockset will start ingesting question logs into this assortment as you submit queries. Logs for the final 24 hours of queries may even be ingested into this assortment. Please be aware that it may take a couple of minutes after a question has accomplished earlier than the related log will present up in your assortment.

So as to use the question profiler with these logs, open the Rockset Console’s question editor and situation a question that targets one in every of your question logs collections. The question editor will detect that you’re making an attempt to question a set with a question logs supply and a column known as ‘Profiler’ shall be added to the question outcomes desk. Any paperwork which have a populated stats discipline can have a hyperlink on this column. Clicking on this hyperlink will open the question profile in a brand new tab.



Observe that customized ingest transformations or question aliases can intrude with this performance so it’s endorsed that you don’t rename any columns.

For an in depth dive into utilizing Rockset’s Question Profiler, please discuss with the video accessible right here.


Hopefully, this has given you a fast look into the performance that question logs can supply. Whether or not it’s good to debug question efficiency or verify why beforehand accomplished queries have failed, your expertise with Rockset shall be improved by making use of question logs.



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