# Internal Server Errors

When `hi` encounters a problem that prevents a request from completing, it may report a `500 Internal Server Error` to clients, along with an error code. The actual error will be printed to standard error, with the error code. The following sections describe errors we've encountered, the likely operational consequences, and recommend approaches for addressing them.

## database is locked

The server attempted two write transactions at the same time, and encountered [sqlite's write locks](https://www.sqlite.org/rescode.html#busy). This is unfortunately unavoidable, but generally only occurs as a result of extremely bad luck, or very high load.

This error will almost always resolve itself if clients re-try their requests; no further action is needed.

This is a known issue. If you are encountering this consistently (or if you can trigger it on demand), let us know. We are aware of sqlite's features for mitigating this issue but have been unsuccessful in applying them; we're working on it, but patches _are_ welcome, if you have the opportunity.