find alive and close peers for cardano-node (based on traceroute hops)

find-optimal-peers

#!/bin/bash
# apt install -y netcat-traditional mtr jq curl

MAX_PEERS=20
PROBE_CONN_TIMEOUT=1
SOURCE_ROUTE_POINTER=4
TOPOLOGY_JSON_URL=https://explorer.shelley-testnet.dev.cardano.org/relays/topology.json
TOPOLOGY_JSON_FILE=/tmp/topology.json
PROXIMITY_TOPOLOGY_JSON=/tmp/proximity-topology.json

curl -SLo ${TOPOLOGY_JSON_FILE} ${TOPOLOGY_JSON_URL}

echo '{"Producers":[]}' > ${TOPOLOGY_JSON_FILE}.tmp

jq -r '.Producers[] | "\(.addr):\(.port)"' ${TOPOLOGY_JSON_FILE} | while read line
do
  ADDR=$(echo ${line} | awk -F: '{print $1}')
  PORT=$(echo ${line} | awk -F: '{print $2}')
  nc -G ${SOURCE_ROUTE_POINTER} -w ${PROBE_CONN_TIMEOUT} -zv ${ADDR} ${PORT} &> /dev/null
  # if connected, extract valency from the peers file
  if [ $? -eq 0 ]
  then
    VALENCY=$(jq -r \
                 --arg addr ${ADDR} \
                 --arg port ${PORT} \
                 '.Producers[] | select((.addr==($addr | tostring)) and (.port==($port | tonumber))) | .valency' 2> /dev/null \
                 ${TOPOLOGY_JSON_FILE})
    if [[ "${VALENCY}" == "null" ]] || [[ "${VALENCY}" == "" ]]
    then
      VALENCY=1
    fi
    jq -r \
       --arg addr ${ADDR} \
       --arg port ${PORT} \
       --arg valency ${VALENCY} \
       '.Producers += [{"addr":$addr,"port":($port|tonumber),"valency":($valency|tonumber)}]' \
       ${TOPOLOGY_JSON_FILE}.tmp > ${TOPOLOGY_JSON_FILE}
    mv ${TOPOLOGY_JSON_FILE} ${TOPOLOGY_JSON_FILE}.tmp
  fi
done

jq -r .Producers[].addr ${TOPOLOGY_JSON_FILE}.tmp | sort | uniq | while read relay; do HOPS=$(mtr --json -c 1 -n -Z 1 -G 1 -U 5 ${relay} | jq -r .report.hubs[].count | sort -n | tail -n1 | awk '{print $1}'); echo "$HOPS - ${relay}"; done | sort -n -k1 > /tmp/peers-hops.log

echo '{"Producers":[]}' > ${PROXIMITY_TOPOLOGY_JSON}.tmp
head -n ${MAX_PEERS} /tmp/peers-hops.log | awk '{print $3}' | while read peer
do
  PEER_OBJECTS=$(jq -r \
                   --arg addr ${peer} \
                   '.Producers[] | select(.addr==($addr | tostring))' \
                   ${TOPOLOGY_JSON_FILE}.tmp | \
                   jq -r --slurp . | \
                   awk '{printf "%s",$0} END {print ""}')
  jq -r \
     --argjson peer "${PEER_OBJECTS}" \
     '.Producers += $peer' \
     ${PROXIMITY_TOPOLOGY_JSON}.tmp > ${PROXIMITY_TOPOLOGY_JSON}
  mv ${PROXIMITY_TOPOLOGY_JSON} ${PROXIMITY_TOPOLOGY_JSON}.tmp
done
jq -r . ${PROXIMITY_TOPOLOGY_JSON}.tmp > ${PROXIMITY_TOPOLOGY_JSON}