[Pharo-dev] Spotter shortcut reset

Ben Coman btc at openinworld.com
Sun Feb 3 06:06:24 EST 2019

On Sat, 2 Feb 2019 at 18:54, ducasse <stepharo at netcourrier.com> wrote:
> On Sat, 2 Feb 2019 at 11:01, Ben Coman <btc at openinworld.com> wrote:
> > I am getting network errors trying to download latest Pharo Launcher,
> can you tell me how so that I try to reproduce it?

Since network performance depends a lot on location, and presuming you'd
need to be at my house to reproduce my experience,
I spent the afternoon learning about AWS so I could do some testing from a
Australian based cloud box
that you should be able to reproduce fairly easily, since this was my first
time using AWS.

With this 10 minute tutorial...
[Launch a Linux Virtual Machine](
1. Signed up and signed in
Tip: I struggled a long while looping on "Sign in with root account
credentials" until I discovered I needed to use the email address I signed
up with, not the account name.

[Edit:] In the top right between account name and support,
pulled down list and selected "Asia Pacfic (Sydney)"

2. Clicked "Launch a virtual machine"
(note, that only seems to show up for blank account, otherwise its "Launch

3. Ticked "Free tier only" filter.
+ Selected "Amazon Linux 2 AMI (HVM), SSD Volume Type"
+ Clicked <Review and Launch>  (used default t2.micro)
+ Clicked <Launch>
+ From the pull-down selected "Create a new key pair",
gave it a name and clicked <Download Keypair> saved as
+ Clicked <Launch Instance>
+ Clicked <View Instances>
noted instance...
* IP address:
* Zone: ap-southeast-2b
* Security Group: Launch Wizard 1

4. On my Windows 10 box, in WSL did...
$ cd ~/.ssh       # if it doesn't exist, first do...   mkdir -m 700 ~/.ssh
$ cp /mnt/c/Users/Ben/Downloads/SydneyPharoSpeedTest.pem   ~/.ssh
$ chmod 400 ~/.ssh/SydneyPharoSpeedTest.pem
$ ssh -i ~/.ssh/SydneyPharoSpeedTest.pem  ubuntu at$ cat
ID_LIKE="centos rhel fedora"

Ignoring any packet loss on poor networks, first testing low bandwidths on
a good network
$ vi test.sh
if [ -d out ]; then
    dirdate=`stat -c %z out | awk '{print $1"-"$2}' `
    mv out out.${dirdate}
mkdir out
for RATE in 1000k 500k 200k 100k 50k 20k 10k 5k 2k 1k
  echo $RATE
  /usr/bin/time -f "%e" -o out/time.$RATE \
       wget --quiet --limit-rate $RATE
https://files.pharo.org/pharo-launcher/1.6/pharo-launcher-1.6.msi -O
out/file.$RATE &

$ sh test.sh
monitoring with...
$ cat out/time* | sort -n
$ ls -lS out

results in following table and graphs...
(kb/s) TIME
(s) TIME
(min) TIME
1000 54 1 0.0
500 105 2 0.0
200 259 4 0.1
100 515 9 0.1
50 1029 17 0.3
20 2576 43 0.7
10 5149 86 1.4
5 10527 175 2.9

[image: download-speed.png]

Wow that surprised me.  I'm not sure what the behaviour of file servers at
low bandwidth should be,
but intuitively the above seems odd.  In the past troubleshooting seems to
have been
focused on the cause of slow speeds, but these can occur for many reasons
unrelated to the
the file server.  The above test ignores cause to isolate behaviour at slow

I forgot my own download speed yesterday (today is okay), but here is
another sample...
"(in Argentina) it is really slow ... 3.5KB/s ... average 10KB/s".

I would hope that download time was near linear with speed all the way down
to 1kb/s.
Anyone have some sysadmins they can lean on to understand if that is

The straightness of the line using a log-log axis makes it seem like policy
rather than physics.
[image: download-speed(log).png]

cheers -ben
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