Mention workaround for too many file handles
Add information on how to handle too many open file handles in troubleshooting guide
@@ -17,6 +17,22 @@ use a GitHub personal access token to circumvent this.
For more details, see ["GitHub token" section in README.md](https://github.com/lycheeverse/lychee#github-token).
+## Too Many Open Files
+
+The number of concurrent network requests (`MAX_CONCURRENCY`) is set to 128 by default.
+Every network request maps to an open socket, which is represented as a file on UNIX systems.
+If you see error messages like "error trying to connect: tcp open error: Too
+many open files (os error 24)" then you ran out of file handles.
+
+You have two options:
+
+1. Lower the concurrency by setting `--max-concurrency` to something more
+ conservative like 32. This works, but it also comes with a performance
+ penalty.
+2. Increase the number of maximum file handles. See instructions
+ [here](https://wilsonmar.github.io/maximum-limits/) or
+ [here](https://synthomat.de/blog/2020/01/increasing-the-file-descriptor-limit-on-macos/).
+
## Unexpected Status Codes
Some websites don't respond with a `200` (OK) status code. \
