I have one system I keep pointed directly at my mirror (not relying on mirrorlist) so I can find problems with my local mirror. Today it says:
Cannot download 'http://download.wpi.edu/pub/fedora/linux/updates/25/x86_64/': Yum repo downloading error: Downloading error(s): repodata/0cbc1e966823acb0f4addccb4db219617335c54e85554fed2f3bca01c6383ea4-filelists.xml.gz - Cannot download, all mirrors were already tried without success; repodata/3e93bf5f3f9f9e242a136cd8487f9b917880373791533ec41c429f3942d1b61f-prestodelta.xml.xz - Cannot download, all mirrors were already tried without success; repodata/32d7de1743b6533476c1dfbcc9a7ded8fb71cf389b21e61602ede8313559d5dc-primary.xml.gz - Cannot download, all mirrors were already tried without success; repodata/fc618e356dcf2d17199eb8118651274f146c4bb4720b1b9ab8a731036daed7da-updateinfo.xml.xz - Cannot download, all mirrors were already tried without success. Error: Failed to synchronize cache for repo 'updates'
I traced this problem to a stale repomd.xml from Apr 3:
-rw-r--r--. 1 mirror mirror 4848 Apr 3 18:12 repomd.xml
Compare this to the one on the master:
-rw-r--r-- 4848 2017/04/05 14:27:41 repomd.xml
Same size. Uh oh. q-f-m doesn't think this file needs to be synced--it isn't showing up in the mastertransferlist:
grep updates/25/x86_64/repodata/repomd.xml quick-mirror.YksUUJhBIF/*
quick-mirror.YksUUJhBIF/fullfiletimelist-fedora:1491369612 f 4848 linux/updates/25/x86_64/repodata/repomd.xml quick-mirror.YksUUJhBIF/fullfiletimelist-fedora:e2fcb793861a193d2c3d8ed255723bfa241c2a34 linux/updates/25/x86_64/repodata/repomd.xml
sha1sum /srv/ftp/pub/fedoraproject.org/fedora/linux/updates/25/x86_64/repodata/repomd.xml ~/repomd.xml
5145e1fcb2207cce33a0d202e6834b5fe792a3e1 /srv/ftp/pub/fedoraproject.org/fedora/linux/updates/25/x86_64/repodata/repomd.xml d76ad1ef03095a97e2d5e4c9a36cf4598c4b4477 /home/cra/repomd.xml
(the last file being one I directly downloaded from the master just now)