Utilizing Question Logs in Rockset

At Rockset, we frequently search for methods to offer our clients higher visibility into the product. Towards this aim, we not too long ago determined to enhance our customer-facing question logging. Our earlier iteration of question logs was based mostly in one in every of our shared providers referred to as apiserver. As a part of the work that apiserver would do when finishing a question execution request, it will create a log that might 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 providers, heavy site visitors from one org might have an effect on question logging in different orgs.
2. Incomplete logs: due to the problems brought on through the use of shared providers, 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 manner 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 completely inside your Digital Occasion versus being inside one in every of Rockset’s shared providers. This offers question logs the benefit of isolation. Moreover, each question you submit might be mechanically logged in case 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 ultimate aggregator when a question has accomplished, a file containing metadata related together with your question is created. At this level, we can also have to gather data from different aggregators that have been concerned within the question. After that is accomplished, 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

Once we first designed this mission, we had all the time supposed for it to work with the question profiler within the console. This might permit our clients to debug question bottlenecks with these logs. Nonetheless, the question profiler requires fairly a bit of knowledge, which means it will be not possible for each question log to include all the data mandatory for the profiler. To resolve this drawback, we opted to create two tiers of question logs – INFO and DEBUG logs.

INFO logs are mechanically created for each question issued by your org. They include some fundamental metadata related together with your question however can’t be used with the question profiler. When you realize 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 together 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 out there 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 is strongly recommended that you just solely present a DEBUG log threshold when you realize that this data might be helpful. In any other case, you run the danger of hitting the speed restrict if you most want a DEBUG log.

System Sources

As a part of this mission, we determined to introduce a brand new idea referred to as system sources. These are sources which ingest information originating from Rockset. Nonetheless, in contrast to the _events assortment, collections with system sources are managed completely by your group. This lets you configure all the settings of those collections. We might be introducing extra system supply varieties as time goes on.

Getting Began with Question Logging

So as to begin logging your queries, all it is advisable to do is create a group with a question logs supply. This may be accomplished 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 also be ingested into this assortment. Please word 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.

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 trying to question a group with a question logs supply and a column referred to as ‘Profiler’ might be added to the question outcomes desk. Any paperwork which have a populated stats discipline could 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 intervene with this performance so it is strongly recommended that you don’t rename any columns.

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

Conclusion

Hopefully, this has given you a fast look into the performance that question logs can supply. Whether or not it is advisable 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.