Question

When starting an instance on Amazon EC2, how would I detect a failure, for instance, if there’s no machine available to fulfill my request? I’m using one of the less-common machine types and am concerned it won’t start up, but am having trouble finding out what message to look for to detect this.

I’m using the EC2 commandline tools to do this. I know I can look for ‘running’ when I do ec2-describe-instance to see if the machine is up, but don’t know what to look for to see if the startup failed.

Thanks!

Answer 1

The output from ec2-start-instances only returns you stopped pending, and as you say you need to use ec2-describe-instances to retrieve the state.

For that, you have a couple of choices; you can either use a loop to check for instance-state-name, looking for a result of running or stopped; alternatively you could look at either the reason or state-reason-code fields; unfortunately you’ll need to trigger the failure you’re worried about, to obtain the values that indicate failure.

The batch file I use to wait for a successful startup (fill in the underscores):

@echo off
set EC2_HOME=C:\tools\ec2-api-tools
set EC2_PRIVATE_KEY=C:\_\pk-_.pem
set EC2_CERT=C:\_\cert-_.pem
set JAVA_HOME=C:\Program Files (x86)\Java\jre6
%EC2_HOME%\bin\ec2-start-instances i-_
:docheck
%EC2_HOME%\bin\ec2-describe-instances | C:\tools\gnuwin32\bin\grep.exe -c stopped > %EC2_HOME%\temp.txt
findstr /m "1" %EC2_HOME%\temp.txt > nul
if %errorlevel%==0 (c:\tools\gnuwin32\bin\echo -n "."
goto docheck)
del temp.txt