I had a strange problem preventing Syncthing from starting on my Mac after months of flawless operation. This is the log file
4/24/15 12:27:32.751 com.apple.launchd.peruser.501[135]: (net.syncthing.syncthing[439]) Exited with code: 1
4/24/15 12:27:32.751 com.apple.launchd.peruser.501[135]: (net.syncthing.syncthing) Throttling respawn: Will start in 9 seconds
and here is the output of running Syncthing on the command line:
[monitor] 12:25:44 INFO: Starting syncthing
[GNYXX] 12:25:44 INFO: syncthing v0.10.30 (go1.4.2 darwin-amd64 default) unknown-user@syncthing-builder 2015-03-29 07:46:44 UTC
[GNYXX] 12:25:44 INFO: My ID: GNYXXP5-SDHQCMR-WC5DSTD-KQPCHLK-FAPFOGR-BJ2ZJZT-5I2DTSJ-QMC3TQP
[GNYXX] 12:25:44 FATAL: Cannot open database: read /Users/andrew/Library/Application Support/Syncthing/index/010489.log: result too large - Is another copy of Syncthing already running?
[monitor] 12:25:44 INFO: Syncthing exited: exit status 1
[monitor] 12:25:45 INFO: Starting syncthing ...
I had to delete the offending 01489.log file that was too big. Then it started successfully.