View the original community article here
Last tested: Jun 4, 2019
Since we can only run two simultaneous rendering processes by default (see the --concurrent-render-jobs=<i> startup flag), two slow queries can back everything else up. So, image download jobs really can be queued for rendering.
Looker will try to run the queries and cache the results before entering the renderer queue, but sometimes the cache will be invalidated by the time Looker starts rendering. Below is an explanation and image of the behaviour seen.
- ~30mins to fully render on the EIn that example, the instance had an Explore where a newly run query could take explore page.
- When this instance had multiple queries run based on that underlying Explore, it caused a render backlog.
- Even the simplest PNG download request had to wait for that ~30min explore to finish rendering (or have it be manually stopped via Admin > Queries Panel)
if you see a long-running Queued for Rendering page, review the Queries Admin Panel for long-running queries. This can help identify why PNG downloads, which may be long-running, are simply waiting for something else to finish.