Utilizing Question Logs in Rockset

At Rockset, we frequently search for methods to provide our clients higher visibility into the product. Towards this objective, we not too long ago determined to enhance our customer-facing question logging. Our earlier iteration of question logs was primarily based 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 might 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 site visitors from one org may have an effect on question logging in different orgs.
2. Incomplete logs: due to the problems brought about through the use of shared companies, we solely logged question errors – profitable queries wouldn’t be logged. Moreover, it was not attainable 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 approach for the consumer 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 considered one of Rockset’s shared companies. This provides question logs the benefit of isolation. Moreover, each question you submit will probably be routinely logged when you have already created a group 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 closing aggregator when a question has accomplished, a file containing metadata related along with your question is created. At this level, we may have to gather info from different aggregators that had been concerned within the question. After that is executed, the file 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 have been created.

INFO vs DEBUG Logs

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 clients to debug question bottlenecks with these logs. Nonetheless, the question profiler requires fairly a bit of knowledge, which means it might be not possible for each question log to comprise all the knowledge crucial for the profiler. To resolve this downside, 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 comprise some fundamental metadata related along with your question however can’t be used with the question profiler. When you understand that you could be wish 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 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 accessible for each question and question lambda execution requests.

Be aware that since DEBUG logs are a lot bigger than INFO logs, the speed restrict for DEBUG logs is way decrease. For that reason, it is suggested that you simply solely present a DEBUG log threshold when you understand that this info may very well be helpful. In any other case, you run the chance of hitting the speed restrict once 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 knowledge originating from Rockset. Nonetheless, 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 will probably be introducing extra system supply varieties as time goes on.

Getting Began with Question Logging

With the intention to begin logging your queries, all it is advisable to do is create a group with a question logs supply. This may be executed via the console.

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

With the intention to use the question profiler with these logs, open the Rockset Console’s question editor and difficulty a question that targets considered one of your question logs collections. The question editor will detect that you’re trying to question a group with a question logs supply and a column known as ‘Profiler’ will probably be added to the question outcomes desk. Any paperwork which have a populated stats discipline may have a hyperlink on this column. Clicking on this hyperlink will open the question profile in a brand new tab.

Be aware that customized ingest transformations or question aliases can intervene with this performance so it is suggested that you don’t rename any columns.

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

Conclusion

Hopefully, this has given you a fast look into the performance that question logs can provide. Whether or not it is advisable to debug question efficiency or examine why beforehand accomplished queries have failed, your expertise with Rockset will probably be improved by making use of question logs.