Query a metron process for the read/write head delta.

diode_heads.dlv

b github.com/cloudfoundry/diodes.(*OneToOne).TryNext
c
p d.readIndex
p d.writeIndex
q
n

search.sh

#!/bin/bash

if [ "$1" = "" ]; then
    echo i need how many iterations
    exit 1
fi

pid=$(ps aux | grep metron | grep -E '.json$' | awk '{print $2}')

if [ "$(echo "$pid" | wc -l)" != "1" ]; then
    echo bad pid
    exit 1
fi

for i in $(seq "$1"); do
    echo attempting dump "$i"
    cat ./diode_heads.dlv |
        ./dlv attach "$pid" /var/vcap/packages/metron_agent/metron |
        tail -n 3 |
        head -n 2 |
        awk '{print $2}' |
        python -c 'import sys; r = int(sys.stdin.readline().strip()); w = int(sys.stdin.readline().strip()); print w-r'
    sleep 1
done