From Newsgroup: comp.sys.raspberry-pi

Chris Elvidge <chris@internal.net> wrote:

On 03/06/2025 at 14:00, Oscar wrote:

In article <101itmk$2mr8t$1@dont-email.me>,
Lawrence D'Oliveiro <ldo@nz.invalid> wrote:

Instead of waiting for some fixed interval, you could add a prior command >> using wget or something to repeatedly try accessing that URL, say at 5
second intervals or whatever, until it becomes accessible, before allowing >> the startup to proceed.

For inspiration, I made a script to 'etherwake' a device and wait for it
to get ready using wget in combination with the 'timeout' command. I run 'timeout 1 wget <url>' which returns an error if wget does not respond
in 1 second, or wget returns an error itself. I use this in a while
loop that repeats this until the wget succeeds:

etherwake -D -i ${IFACE} ${MACADDR}

while ! timeout 1 curl --noproxy \* "${URL}" &> /dev/null
do
echo -n .
sleep 1
done

The OP could replace the 'sleep 120' in the other script with this loop.

I was going to suggest something similar like that too. It is worth
checking what the webserver is giving you - some services give a generic 'please wait while I start up' web page which may not be what you want.
Maybe you need to ask for a specific page and count a redirect (to the
'please wait') page as a failure.

Why waste a curl call when ping 8.8.8.8 would work with less overhead?

The purpose is to test a specific service *on this machine* has started up,
not generic internet connectivity.

Theo
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

On 03/06/2025 15:17, Chris Elvidge wrote:

On 03/06/2025 at 14:00, Oscar wrote:

In article <101itmk$2mr8t$1@dont-email.me>,
Lawrence D'Oliveiro  <ldo@nz.invalid> wrote:

Instead of waiting for some fixed interval, you could add a prior
command
using wget or something to repeatedly try accessing that URL, say at 5
second intervals or whatever, until it becomes accessible, before
allowing
the startup to proceed.

For inspiration, I made a script to 'etherwake' a device and wait for it
to get ready using wget in combination with the 'timeout' command. I run
'timeout 1 wget <url>' which returns an error if wget does not respond
in 1 second, or wget returns an error itself. I use this in a while
loop that repeats this until the wget succeeds:

     etherwake -D -i ${IFACE} ${MACADDR}

     while ! timeout 1 curl --noproxy \* "${URL}" &> /dev/null
     do
         echo -n .
         sleep 1
     done

The OP could replace the 'sleep 120' in the other script with this loop.

Why waste a curl call when ping 8.8.8.8 would work with less overhead?

+1. Assuming that pings to the Wide World are not blocked by the network
--
"Strange as it seems, no amount of learning can cure stupidity, and
higher education positively fortifies it."

- Stephen Vizinczey


--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

In article <101n06i$264r$1@dont-email.me>,
Chris Elvidge <chris@internal.net> wrote:

while ! timeout 1 curl --noproxy \* "${URL}" &> /dev/null
do
echo -n .
sleep 1
done

The OP could replace the 'sleep 120' in the other script with this loop.

Why waste a curl call when ping 8.8.8.8 would work with less overhead?

Will 'ping 8.8.8.8' return quickly (within 2 seconds) after my device
has woken up? No. My device does not respond to 8.8.8.8. You are just
testing internet connectivity, not the wakeup of my device.

And why waste a ping call (which is setuid) if a curl call will suffice
AND tells if the port is responding to http(s) requests?

In other words: why waste a post when you don't understand the problem?
--
[J|O|R] <- .signature.gz
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

In article <lKm*Ch8dA@news.chiark.greenend.org.uk>,
Theo <theom+news@chiark.greenend.org.uk> wrote:

I was going to suggest something similar like that too. It is worth
checking what the webserver is giving you - some services give a generic >'please wait while I start up' web page which may not be what you want. >Maybe you need to ask for a specific page and count a redirect (to the >'please wait') page as a failure.

In my use case this was enough. You can also direct curl output to grep
and use that as an indicator of your device's desired state.

Why waste a curl call when ping 8.8.8.8 would work with less overhead?

The purpose is to test a specific service *on this machine* has started up, >not generic internet connectivity.

Yeah. And curl is not *that* expensive to run. Maybe even less expensive
than ping, as it does not have the setuid overhead. But who's counting
clock cycles anyway?
--
[J|O|R] <- .signature.gz
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

In article <101n27u$20jc$5@dont-email.me>,
The Natural Philosopher <tnp@invalid.invalid> wrote:

+1. Assuming that pings to the Wide World are not blocked by the network

-1 for assuming that internet connectivity is the only requirement.
--
[J|O|R] <- .signature.gz
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

In article <101niml$7k6m$2@dont-email.me>,
Oscar <jornws200602@xs4all.nl> wrote:

Yeah. And curl is not *that* expensive to run. Maybe even less expensive
than ping, as it does not have the setuid overhead. But who's counting
clock cycles anyway?

Following up on myself: Okay, ping loads a bit quicker as it's
executable is smaller and it loads less libraries, but it still
is a setuid binary.

I must admit I still don't understand why you thing the overhead of
calling curl is a waste. Both are external programs and we're in a wait
loop anyway. Why hurry in between to sleep calls?

In this case curl beats ping, as OP's question was related to a slow
staring Grafana server. Ping can't tell if Grafana is running. With curl
you can see if a string is in the output.

Say for examplje you're waiting for a specific dasboard to load, with
the title "Hootenmany". You could run this slightly modified version:


while ! timeout 1 curl -s ${URL} | grep -qs Hootenanny
do
echo -n .
sleep 1
done

This will loop until curl returns something with the string 'Hootenanny'
within 1 second and fail if there's no network, no dns, no route to the
Grafana server or while Grafana server is still starting up.

And *that's* what the OP asked.
--
[J|O|R] <- .signature.gz
--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.sys.raspberry-pi

On 03/06/2025 20:34, Oscar wrote:

In article <101n27u$20jc$5@dont-email.me>,
The Natural Philosopher <tnp@invalid.invalid> wrote:

+1. Assuming that pings to the Wide World are not blocked by the network

-1 for assuming that internet connectivity is the only requirement.

Accepted.
--
It is the folly of too many to mistake the echo of a London coffee-house
for the voice of the kingdom.

Jonathan Swift


--- Synchronet 3.21a-Linux NewsLink 1.2