With "wait" consul-template spawns the child process before rendering the template

[aryklein]

Consul Template version

consul-template v0.20.0
(The same setup works fine in consul-template v0.19.5)

Configuration

/etc/consul-template.conf:

consul {
  address = "consul.query.consul:28500"
  retry {
    enabled = true
    attempts = 12
    backoff = "250ms"
    max_backoff = "1m"
  }
}
reload_signal = "SIGHUP"
kill_signal = "SIGINT"
log_level = "warn"
pid_file = "/var/run/consul-template/consul-template.pid"
exec {
  command = "/usr/local/bin/pgpool -n -D"
  kill_signal = "SIGINT"
  kill_timeout = "10s"
}
template {
  source = "/usr/local/etc/pgpool.conf.tpl"
  destination = "/usr/local/etc/pgpool.conf"
  wait {
    min = "5s"
    max = "10s"
  }
}

Command

consul-template -config /etc/consul-template.conf

Expected behavior

After the wait time, it should render the template and then spawn the child process.

Actual behavior

It spawns the child process before rendering the template (only when you use wait in the template block). It seems that it executes the command in the exec block and then waits for rendering the template.

[eikenb]

Hey @aryklein, thanks for reporting this issue.

I think this might be a duplicate of the issue fixed with #1227. So if you want to try out a build off the master branch I think it might already be fixed. If you get a chance to try, I'd appreciate hearing back if it is fixed or not.

Thanks.

[aryklein]

Hey @eikenb,

Sure thing. I was using the pre-compiled versions from here: https://releases.hashicorp.com/consul-template
Can you give me some instructions how to compile it from the master branch?

Thanks

[eikenb]

To build the master branch you'd need a Go dev setup and then you could run make dev to build it locally. But getting that all setup takes some work.

Thinking about it I'm not 100% this is a replication of that issue though. If you have a chance to spend some time on this I think, instead of doing the work to build it yourself, it'd be better if you could try to create a standalone, simple way to replicate the issue. Something I could run locally with minimal setup.

If you don't have time for that would you mind adding your template here so I have all the parts involved. It's hard to get a good idea of what's happening without all the setup.

Thanks.

[eikenb]

I don't think this is a duplicate of #1227 as I'm able to reproduce it with a simple test using current master (that has the fix).

This (and a better understanding of the code) also makes me think that #1209 is a case of this same issue and not related to #1227.

[eikenb]

Most obvious fix for this is to not have it setup the wait/quiescence timers until all templates have been rendered once. The most obvious way to do that is to move the quiescence initialization code down a few lines into the existing conditional block, conditional on allTemplateRendered().

I.E. Moving this chunk...

consul-template/manager/runner.go

Lines 226 to 247 in 4170dc9

	NEXT_Q:
	for _, t := range r.templates {
	if _, ok := r.quiescenceMap[t.ID()]; ok {
	continue NEXT_Q
	}
	for _, c := range r.templateConfigsFor(t) {
	if *c.Wait.Enabled {
	log.Printf("[DEBUG] (runner) enabling template-specific quiescence for %q", t.ID())
	r.quiescenceMap[t.ID()] = newQuiescence(
	r.quiescenceCh, *c.Wait.Min, *c.Wait.Max, t)
	continue NEXT_Q
	}
	}
	if *r.config.Wait.Enabled {
	log.Printf("[DEBUG] (runner) enabling global quiescence for %q", t.ID())
	r.quiescenceMap[t.ID()] = newQuiescence(
	r.quiescenceCh, *r.config.Wait.Min, *r.config.Wait.Max, t)
	continue NEXT_Q
	}
	}

To just after here...

consul-template/manager/runner.go

Lines 257 to 258 in 4170dc9

	if r.allTemplatesRendered() {
	log.Printf("[DEBUG] (runner) all templates rendered")

[aryklein]

@eikenb thanks for taking care of this issue 👍