Utilizing Question Logs in Rockset

At Rockset, we regularly search for methods to provide our clients higher visibility into the product. Towards this purpose, we just lately determined to enhance our customer-facing question logging. Our earlier iteration of question logs was based mostly in considered one of our shared companies known as apiserver. As a part of the work that apiserver would do when finishing a question execution request, it will create a log that will finally be ingested into the _events assortment. Nonetheless, 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 visitors from one org may have an effect on question logging in different orgs.
2. Incomplete logs: due to the problems precipitated through the use of shared companies, we solely logged question errors – profitable queries wouldn’t be logged. Moreover, it was not doable for us to log knowledge about async queries.
3. No capacity to debug question efficiency – the question logs in _events solely contained fundamental details about every question. There was no means for the consumer to get details about why a given question might have run slowly or exhausted compaute assets because the 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 solely inside your Digital Occasion versus being inside considered one of Rockset’s shared companies. This offers question logs the benefit of isolation. Moreover, each question you submit might be robotically logged in case you have already created a set with a question logs supply (supplied you don’t hit a fee restrict).

How Question Logs Work

Question logging begins on the finish of question execution. As a part of the steps which might be run within the ultimate aggregator when a question has accomplished, a document containing metadata related together with your question is created. At this level, we can also have to gather info from different aggregators that have been concerned within the question. After that is completed, the document is quickly 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.

INFO vs DEBUG Logs

Once we first designed this undertaking, we had at all times supposed for it to work with the question profiler within the console. This may enable our clients to debug question bottlenecks with these logs. Nonetheless, the question profiler requires fairly a bit of knowledge, which means it will be unimaginable for each question log to comprise all the knowledge needed for the profiler. To resolve this downside, we opted to create two tiers of question logs – INFO and DEBUG logs.

INFO logs are robotically created for each question issued by your org. They comprise some fundamental metadata related together with your question however can’t be used with the question profiler. When you recognize that you could be wish to have the flexibility to debug a sure question with the profiler, you’ll be able to specify a DEBUG log threshold together with your question request. If the question execution time is bigger than the required 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 obtainable 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 way decrease. Because of this, it is suggested that you simply solely present a DEBUG log threshold when you recognize that this info may very well be helpful. In any other case, you run the danger of hitting the speed restrict once you most want a DEBUG log.

System Sources

As a part of this undertaking, we determined to introduce a brand new idea known as system sources. These are sources which ingest knowledge originating from Rockset. Nonetheless, not like the _events assortment, collections with system sources are managed solely by your group. This lets you configure the entire settings of those collections. We might be introducing extra system supply sorts as time goes on.

Getting Began with Question Logging

With a purpose to begin logging your queries, all it’s essential to do is create a set with a question logs supply. This may be completed via 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 observe that it might probably take a couple of minutes after a question has accomplished earlier than the related log will present up in your assortment.

With a purpose to use the question profiler with these logs, open the Rockset Console’s question editor and situation a question that targets considered one of your question logs collections. The question editor will detect that you’re trying to question a set with a question logs supply and a column known as ‘Profiler’ might be added to the question outcomes desk. Any paperwork which have a populated stats area 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 is suggested that you don’t rename any columns.

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

Conclusion

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