How to read the server logs

Here's an example log from running a query:

2021-07-07 15:53:18,560 DEBUG middleware.log :: POST /api/dataset 202 [ASYNC: completed] 46.9 ms (17 DB calls) App DB connections: 1/10 Jetty threads: 3/50 (4 idle, 0 queued) (72 total active threads) Queries in flight: 0 (0 queued); h2 DB 4 connections: 0/1 (0 threads blocked)

Let's unpack the log:

• Time of log: 2021-07-07 15:53:18,560.
• Log level: DEBUG. There are different types of log levels. To learn more, check out Metabase logs.
• Namespace:. middleware.log. You can tweak your logging level to get more or less information from this namespace.
• Method: POST. The HTTP method verb, like POST, PUT, GET, DELETE.
• Path: /api/dataset. The handling URL. Note that URL parameters aren't included, which can make debugging certain issues a little tricky.
• Code: 202. The HTTP status code.
• ASYNC: [ASYNC: completed]. Whether Metabase could deliver the results to the browser. If Metabase couldn't deliver the results, for example if someone starts a query and closes their browser before the query finishes, the ASYNC status will say "cancelled".
• Response time: 46.9 ms. The time Metabase takes to handle the request (from when Metabase receives the request until it's returned results back to the browser).
• Database calls: (17 DB calls). The number of query statements used, which in addition to calls to the queried data source(s), includes calls to the Metabase application database.
• Application database connections: App DB connections: 1/10. The number of active connections, and the available pool of connections.
• Jetty threads: Jetty threads: 3/50 (4 idle, 0 queued). List the number of active threads, and the total pool of threads available. The (4 idle, 0 queued) are the spare hot threads, and the number of threads queued. If you find you're maxing out the number threads in your pool, check out Metabase at scale.
• Java threads: (72 total active threads). The total number of threads Metabase is using.
• Queries in flight: Queries in flight: 0 (0 queued). The number of active and queued queries across all database sources connected to Metabase. We recommend checking the Database info below for troubleshooting issues with the database related to the request.
• Database info:h2 DB 4 connections: 0/1 (0 threads blocked). Shows database type, database ID, connections active/pool (and queue). This info is specific to the database related to the request (in this case a POST request), and not to the overall queries in flight.