DNF dependency resolution latency in multi-repository environments

Answer

The DNF parameters that control metadata refresh frequency are metadata_expire (seconds) and metadata_sync (boolean). Repository priority is set with priority= in each .repo file, and concurrent metadata downloads share the max_parallel_downloads limit.

Likely explanation

In multi‑repository setups, stale metadata or slow mirrors force DNF to re‑download repodata, increasing solver latency. Third‑party repos add more metadata files, and the solver must evaluate them together with BaseOS and AppStream, which can amplify any delay in metadata retrieval.

Confirmed facts (from DNF documentation)

• metadata_expire defines after how many seconds the local metadata is considered stale; a value of 0 forces a refresh on every command.
• metadata_sync (when true) tells DNF to synchronize metadata before solving, ensuring the solver sees the newest data.
• Each repository file can contain priority=N; lower numbers have higher precedence, so giving BaseOS a lower priority than AppStream makes DNF prefer BaseOS packages when versions are equal.
• DNF does not have a separate metadata‑only parallelism knob; it uses max_parallel_downloads (default 5) for both metadata and package downloads, limiting the number of simultaneous HTTP connections.

Steps to tune for Rocky Linux 9

1. Edit /etc/dnf/dnf.conf (or create a snippet in /etc/dnf/conf.d/) and set:

[main]
metadata_expire=3600
metadata_sync=True
max_parallel_downloads=3

2. For the BaseOS repo (usually /etc/yum.repos.d/rocky-baseos.repo) ensure:

[baseos]
name=Rocky Linux $releasever - BaseOS
baseurl=...
priority=1

3. For the AppStream repo (rocky-appstream.repo) set a higher priority number, e.g. priority=2.
4. Run dnf clean metadata then dnf update --assumeno to verify that metadata is refreshed according to the new metadata_expire value.
5. Check effective priorities with dnf repolist -v; the output includes a “Priority” column for each repo.
6. If you still see high latency, measure the time to download metadata with time dnf clean metadata && time dnf makecache and adjust max_parallel_downloads upward if your network allows more concurrent connections.

If you are unsure whether the current metadata_expire value is causing the delay, please share the output of grep metadata_expire /etc/dnf/dnf.conf /etc/dnf/conf.d/* so we can confirm whether a lower value is needed.