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Diffstat (limited to 'backends/nc-backend.sh')
| -rwxr-xr-x | backends/nc-backend.sh | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/backends/nc-backend.sh b/backends/nc-backend.sh new file mode 100755 index 0000000..7280f86 --- /dev/null +++ b/backends/nc-backend.sh @@ -0,0 +1,158 @@ +#!/usr/bin/env bash + +# SPDX-License-Identifier: GPL-3.0-or-later + +# This is a simple backend database proxy, written in BASH, using the nc command. +# Run the script without any parameters for help. + +MODE="${1}" +MY_PORT="${2}" +BACKEND_HOST="${3}" +BACKEND_PORT="${4}" +FILE="${NETDATA_NC_BACKEND_DIR-/tmp}/netdata-nc-backend-${MY_PORT}" + +log() { + logger --stderr --id=$$ --tag "netdata-nc-backend" "${*}" +} + +mync() { + local ret + + log "Running: nc ${*}" + nc "${@}" + ret=$? + + log "nc stopped with return code ${ret}." + + return ${ret} +} + +listen_save_replay_forever() { + local file="${1}" port="${2}" real_backend_host="${3}" real_backend_port="${4}" ret delay=1 started ended + + while true + do + log "Starting nc to listen on port ${port} and save metrics to ${file}" + + started=$(date +%s) + mync -l -p "${port}" | tee -a -p --output-error=exit "${file}" + ended=$(date +%s) + + if [ -s "${file}" ] + then + if [ ! -z "${real_backend_host}" ] && [ ! -z "${real_backend_port}" ] + then + log "Attempting to send the metrics to the real backend at ${real_backend_host}:${real_backend_port}" + + mync "${real_backend_host}" "${real_backend_port}" <"${file}" + ret=$? + + if [ ${ret} -eq 0 ] + then + log "Successfuly sent the metrics to ${real_backend_host}:${real_backend_port}" + mv "${file}" "${file}.old" + touch "${file}" + else + log "Failed to send the metrics to ${real_backend_host}:${real_backend_port} (nc returned ${ret}) - appending more data to ${file}" + fi + else + log "No backend configured - appending more data to ${file}" + fi + fi + + # prevent a CPU hungry infinite loop + # if nc cannot listen to port + if [ $((ended - started)) -lt 5 ] + then + log "nc has been stopped too fast." + delay=30 + else + delay=1 + fi + + log "Waiting ${delay} seconds before listening again for data." + sleep ${delay} + done +} + +if [ "${MODE}" = "start" ] + then + + # start the listener, in exclusive mode + # only one can use the same file/port at a time + { + flock -n 9 + # shellcheck disable=SC2181 + if [ $? -ne 0 ] + then + log "Cannot get exclusive lock on file ${FILE}.lock - Am I running multiple times?" + exit 2 + fi + + # save our PID to the lock file + echo "$$" >"${FILE}.lock" + + listen_save_replay_forever "${FILE}" "${MY_PORT}" "${BACKEND_HOST}" "${BACKEND_PORT}" + ret=$? + + log "listener exited." + exit ${ret} + + } 9>>"${FILE}.lock" + + # we can only get here if ${FILE}.lock cannot be created + log "Cannot create file ${FILE}." + exit 3 + +elif [ "${MODE}" = "stop" ] + then + + { + flock -n 9 + # shellcheck disable=SC2181 + if [ $? -ne 0 ] + then + pid=$(<"${FILE}".lock) + log "Killing process ${pid}..." + kill -TERM "-${pid}" + exit 0 + fi + + log "File ${FILE}.lock has been locked by me but it shouldn't. Is a collector running?" + exit 4 + + } 9<"${FILE}.lock" + + log "File ${FILE}.lock does not exist. Is a collector running?" + exit 5 + +else + + cat <<EOF +Usage: + + "${0}" start|stop PORT [BACKEND_HOST BACKEND_PORT] + + PORT The port this script will listen + (configure netdata to use this as a second backend) + + BACKEND_HOST The real backend host + BACKEND_PORT The real backend port + + This script can act as fallback backend for netdata. + It will receive metrics from netdata, save them to + ${FILE} + and once netdata reconnects to the real-backend, this script + will push all metrics collected to the real-backend too and + wait for a failure to happen again. + + Only one netdata can connect to this script at a time. + If you need fallback for multiple netdata, run this script + multiple times with different ports. + + You can run me in the background with this: + + screen -d -m "${0}" start PORT [BACKEND_HOST BACKEND_PORT] +EOF + exit 1 +fi |