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77 lines
2.7 KiB
Bash
77 lines
2.7 KiB
Bash
#!/usr/bin/env bash
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# shellcheck disable=SC2015
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# vim:ts=4:sts=4:sw=4:et
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#
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# Author: Hari Sekhon
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# Date: 2019-11-07 14:25:06 +0000 (Thu, 07 Nov 2019)
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#
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# https://github.com/harisekhon/bash-tools
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#
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# License: see accompanying Hari Sekhon LICENSE file
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#
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# If you're using my code you're welcome to connect with me on LinkedIn and optionally send me feedback
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#
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# https://www.linkedin.com/in/harisekhon
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#
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# https://aws.amazon.com/blogs/aws/new-ec2-spot-instance-termination-notices/
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set -euo pipefail
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[ -n "${DEBUG:-}" ] && set -x
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usage(){
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cat <<EOF
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Executes the arguments as shell commands when the EC2 instance running this script is notified of Spot Termination
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Can be used as a latch mechanism to wait before allowing a shell or script to proceed past calling this script
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Usage:
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${0##*/} "command1; command2; command 3" All commands execute in a subshell
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${0##*/}; command 1; command2; command 3 All commands execute in current shell
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(notice the semi-colon immediately after the script giving it no argument, merely using it as a latch mechanism)
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${0##*/} command1; command2; command 3 First command executes in the subshell (it's an argument). Commands 2 & 3 execute in the current shell after this script
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${0##*/} 'x=test; echo \$x' Variable is interpolated inside the single quotes at runtime after receiving Spot Termination notice
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Inspired by whenup() / whendown() for hosts and whendone() for processes from interactive bash library .bash.d/* sourced as part of the .bashrc in this repo
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You can trigger this as part of rc.local or similar on an EC2 Spot instance and when it gets the termination notice it'll execute all of its arguments as commands
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For GCP there is a similar adjacent script gce_when_preempted.sh
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EOF
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exit 3
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}
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if [[ "${1:-}" =~ ^- ]]; then
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usage
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fi
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if ! curl -sS --connect-timeout 2 http://169.254.169.254/ &>/dev/null; then
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echo "This script must be run from within an EC2 instance as that is the only place the AWS EC2 Metadata API is available"
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exit 2
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fi
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termination_time=""
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while true; do
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# regex borrowed from AWS Systems Administration book by O'Reilly and also here:
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# https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/spot-interruptions.html
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termination_time="$(curl -s --max-time 1 http://169.254.169.254/latest/meta-data/spot/termination-time | grep '.*T.*Z' || :)"
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if [ -n "$termination_time" ]; then
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break
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fi
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echo -n '.'
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# AWS recommended check interval
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sleep 5
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done
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echo "Termination Time: $termination_time"
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echo "Executing: $*"
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# eval'ing so that "command1; command2" works as well as 'x=test; echo $x'
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eval "$@"
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