On 3/23/21 11:59 PM, Kurtis Rader wrote:
> It sounds as if you might be running your "REST endpoint" program from
> an interactive shell (i.e., a terminal) and sending SIGTERM by
> pressing something like Ctrl-C. Interactive job control, which
> includes how signals generated by a "terminal" are handled, is a
> complex topic. So we need to know how you are sending SIGTERM to your
> process. Is it by something like the `kill` command or syscall to a
> specific PID or by pressing keys on your terminal to terminate the
> process?
The application is installed as a service and managed via systemctl
start/stop.
There are two types of children -- one type simply runs and then exits:
It's run like this...
funcextractFeatures(s session.Session) (string, error) {
output, err:= exec.Command(
"./signatureml",
//"-debug",
"-model",
"theModel",
"--no-csv-header",
"-csv",
s.ArtifactsPath(),
s.MessagePath()).CombinedOutput()
returnstring(output[:]), err
}
The other type is long-running and communicates via stdin/stdout: It's
run like this...
> typeLongRunningPredictorstruct{
> theCommand *exec.Cmd
> input io.WriteCloser
> output bytes.Buffer
> completionError error
> hasEnded bool
> }
> func(p *LongRunningPredictor) waitLoop() {
> p.hasEnded= false
> p.completionError= p.theCommand.Wait()
> p.hasEnded= true
> }
> func(p *LongRunningPredictor) start() string{
> p.theCommand= exec.Command("./long-running-predictor", "trained-model")
> p.theCommand.Stdout= &p.output
> p.theCommand.Stderr= &p.output
> p.input, _= p.theCommand.StdinPipe()
> p.theCommand.Start()
> startupText, _:= readLinesUpToPrefixBestEffort(&p.output, "Ready")
> gop.waitLoop()
> returnstartupText
> }
Long running predictors are cycled through a channel that acts like a
pool -- when one is needed it's pulled from the channel, and when it's
done it's put back to be re-used.
===
Once the rest endpoint app gets the signal to terminate these children
are killed even though, in theory, the signal was captured.
I know the signal was captured because the logic I have in place for a
clean shutdown begins to execute as expected.
Looking forward to a solution or at least an understanding.
Best,
_M
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