dse_process_slow

#!/usr/bin/env sudo bash

# dse_process_slow 

#
# Pause a list of processes and restart when user presses return
# 
# Slowing DSE process is slowed by hitting the DSE process with timed alternating signals SiGSTOP and SIGCONT.
# The process is aligned to modulo 60 minutes. 
# Determine the DSE pid periodically in case it is restarted.

# For general slow node testing a good starting point is 
# seconds_to_sigstop=0.90
# seconds_to_sigcont=0.10
#
# If testing Speculative Retry and Speculative Execution operations,
# use a 1 second slow and 1 second fast pattern to better see the results in monitoring graphs.
# seconds_to_sigstop=1
# seconds_to_sigcont=1
#
# Rich Rein 2019.03.20
#


trace_slow_fullspeed=true	
trace_stop_start=false	
minutes_to_slow=5
seconds_to_sigstop=0.90
seconds_to_sigcont=0.10
was_stopped=88

while [ 1 ]; do
	# The pids for a command may change. Reaquire the list of pids every 5 seconds.

	slowPids=$(ps aux | grep com.datastax.bdp | grep -v grep  | awk '{print $2}')

	# Make sure DSE continues at full speed if the scipt is cancelled.
	trap 'kill -SIGCONT $slowPids 2>/dev/null' EXIT

	if [ x"$slowPids" = x ]; then echo DSE not running; exit 0; fi

	minute=$(date '+%M' | sed -e 's/.*\(.\)/\1/')
	minutes=$((minute/$minutes_to_slow))    
	dostop=$(( $minutes % 2 ))

	if [ $was_stopped != $dostop ]; then
		was_stopped=$dostop
		if [ $dostop == 0 ]; then
			if [ $trace_slow_fullspeed == true ]; then echo "$(date)" - Start slowing DSE ; fi
		else
			if [ $trace_slow_fullspeed == true ]; then echo "$(date)" - Start full speed DSE ; fi
		fi
	fi

	for i in {1..10}; do
		# SIGSTOP and SIGCONT the processes to reduce CPU used 2>/dev/null
	   	if [ $dostop == 0 ]; then
			kill -SIGSTOP $slowPids 2>/dev/null;
			if [ $trace_stop_start == true ]; then echo Stopping DSE at $(date) ; fi
		fi
		sleep $seconds_to_sigstop;

		kill -SIGCONT $slowPids 2>/dev/null;
	   	if [ $dostop == 0 ]; then
			if [ $trace_stop_start == true ]; then echo Continuing DSE at $(date) ; fi
		fi
		sleep $seconds_to_sigcont;
	done
done