flux ping [OPTIONS] target
flux-ping(1) measures round-trip latency to a Flux service implementing the "ping" method in a manner analogous to ping(8). The ping response is essentially an echo of the request, with the route taken to the service added by the service. This route is displayed in the output and can give insight into how various addresses are routed.
target may be the name of a Flux service, e.g. "kvs". flux-ping(1) will send a request to "kvs.ping". As a shorthand, target can include a rank or host prefix delimited by an exclamation point. "flux ping 4!kvs" is equivalent to "flux ping --rank 4 kvs" (see --rank option below). Don't forget to quote the exclamation point if it is interpreted by your shell.
As a shorthand, target may also simply be a rank or host by itself indicating that the broker on that rank/host, rather than a Flux service, is to be pinged. "flux ping 1" is equivalent to "flux ping --rank 1 broker".
- -r, --rank=N
Find target on a specific broker rank. Special case strings “any” and “upstream” available to ping FLUX_NODEID_ANY and FLUX_NODEID_UPSTREAM respectively. Default: send to “any”.
- -p, --pad=N
Include in the payload a string of length N bytes. The payload will be echoed back in the response. This option can be used to explore the effect of message size on latency. Default: no padding.
- -i, --interval=N
Specify the delay, in seconds, between successive requests. A value of zero is valid and indicates that there should be no delay. Requests are sent without waiting for responses. Default: 1.0 seconds.
- -c, --count=N
Specify the number of requests to send, and terminate the command once responses have been received for all the requests. Default: unlimited.
- -b, --batch
Begin processing responses after all requests are sent. Requires --count.
- -u, --userid
Include userid and rolemask of original request, which are echoed back in ping response, in ping output.
One can ping a service by name, e.g.
$ flux ping kvs kvs.ping pad=0 seq=0 time=0.774 ms (0EB02!A3368!0!382A6) kvs.ping pad=0 seq=1 time=0.686 ms (0EB02!A3368!0!382A6) ...
This tells you that the local "kvs" service is alive and the round-trip latency is a bit over half a millisecond. The route hops are:
0EB02: UUID of the ping command A3368: UUID of the API module 0: rank of the local broker 382A6: UUID of the KVS module.