skewer

A really hackish way of detecting significant clock skew between hosts.

If you find this useful, I feel bad for you.

Usage

Requires agent based ssh access to all hosts.

go get github.com/lytics/skewer
skewer -hosts=host1,host2,host3,hostn

Running remotely

If you're running this from a server you're ssh'd into, you need to enable agent forwarding with either:

ssh -A remotehost

...or in your ~/.ssh/config:

Host remotehost
    ForwardAgent yes

Alerting

Use the -alert option to set a command to run (should be a shell script or single binary) if clock skew is detected.

skewer -hosts=... -alert=/path/to/alert.sh

The $MAXSKEW environment variable will be set to the maximum skew detected.

How It Works

1. Stores start time
2. Runs date on each host via ssh concurrently
3. Calculates elapsed time to run
4. If max(date)-min(date) > elapsed output per host times and skews
5. Sleeps -sleep amount and runs again

Everything is in seconds resolution, so only skews of 2 seconds or greater will be reported.

If you want subsecond skew detection you need a more sophisticated tool.

How It Doesn't Work

Probably a lot of ways. Consider this a toy.

There's a lot of log.Fatalf instead of more sophisticated error handling.