From e559a8e0fb157ceddcec7fd848e3d2d0ac339379 Mon Sep 17 00:00:00 2001 From: Giles Hall Date: Tue, 2 Feb 2016 14:23:09 -0500 Subject: [PATCH] initial commit --- README.md | 45 ++++++++++++++ wait-for-it.sh | 156 +++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 201 insertions(+) create mode 100644 README.md create mode 100755 wait-for-it.sh diff --git a/README.md b/README.md new file mode 100644 index 0000000..80b3eb7 --- /dev/null +++ b/README.md @@ -0,0 +1,45 @@ += Wait for it + +wait-for-it.sh is a pure bash script that wait on the availability of a host and TCP port. It is useful for synchronizing the spin-up of interdependent services, such as linked docker containers. Since it is a pure bash script, it does not have any external dependencies. + +For example, let's test to see if we can access port 80 on www.google.com, and if it is available, echo the message "Let's start googling!" + +``` +$ ./wait-for-it.sh www.google.com:80 -- echo "google is up" +wait-for-it.sh: waiting 15 seconds for www.google.com:80 +wait-for-it.sh: www.google.com:80 is available after 0 seconds +google is up +``` + +You can set your own timeout with the `-t` or `--timeout=` option. Setting the timeout value to 0 will disable the timeout: + +``` +$ ./wait-for-it.sh -t 0 www.google.com:80 -- echo "google is up" +wait-for-it.sh: waiting for www.google.com:80 without a timeout +wait-for-it.sh: www.google.com:80 is available after 0 seconds +google is up +``` + +The subcommand will be executed regardless if the service is up or not. If you wish to only execute the subcommand only if the service is up, add the `--strict` argument. In this example, we will test port 81 on www.google.com which will fail: + +``` +$ ./wait-for-it.sh www.google.com:81 --timeout=1 --strict -- echo "google is up" +wait-for-it.sh: waiting 1 seconds for www.google.com:81 +wait-for-it.sh: timeout occurred after waiting 1 seconds for www.google.com:81 +wait-for-it.sh: strict mode, refusing to execute subprocess +``` + +If you don't want to execute a subcommand, leave off the `--` argument. This way, you can test the exit condition of `wait-for-it.sh` in your own scripts, and determine how to proceed: + +``` +$ ./wait-for-it.sh www.google.com:80 +wait-for-it.sh: waiting 15 seconds for www.google.com:80 +wait-for-it.sh: www.google.com:80 is available after 0 seconds +$ echo $? +0 +$ ./wait-for-it.sh www.google.com:81 +wait-for-it.sh: waiting 15 seconds for www.google.com:81 +wait-for-it.sh: timeout occurred after waiting 15 seconds for www.google.com:81 +$ echo $? +124 +``` diff --git a/wait-for-it.sh b/wait-for-it.sh new file mode 100755 index 0000000..7df6b16 --- /dev/null +++ b/wait-for-it.sh @@ -0,0 +1,156 @@ +#!/usr/bin/env bash +# Use this script to test if a given TCP host/port are available + +cmdname=$(basename $0) + +echoerr() { if [[ $QUIET -ne 1 ]]; then echo "$@" 1>&2; fi } + +usage() +{ + cat << USAGE >&2 +Usage: + $cmdname host:port [-s] [-t timeout] [-- command args] + -h HOST | --host=HOST Host or IP under test + -p PORT | --port=PORT TCP port under test + Alternatively, you specify the host and port as host:port + -s | --strict Only execute subcommand if the test succeeds + -q | --quiet Don't output any status messages + -t TIMEOUT | --timeout=TIMEOUT + Timeout in seconds, zero for no timeout + -- COMMAND ARGS Execute command with args after the test finishes +USAGE + exit 1 +} + +wait_for() +{ + if [[ $TIMEOUT -gt 0 ]]; then + echoerr "$cmdname: waiting $TIMEOUT seconds for $HOST:$PORT" + else + echoerr "$cmdname: waiting for $HOST:$PORT without a timeout" + fi + start_ts=$(date +%s) + while : + do + (echo > /dev/tcp/$HOST/$PORT) >/dev/null 2>&1 + result=$? + if [[ $result -eq 0 ]]; then + end_ts=$(date +%s) + echoerr "$cmdname: $HOST:$PORT is available after $((end_ts - start_ts)) seconds" + break + fi + sleep 1 + done + return $result +} + +wait_for_wrapper() +{ + # In order to support SIGINT during timeout: http://unix.stackexchange.com/a/57692 + if [[ $QUIET -eq 1 ]]; then + timeout $TIMEOUT $0 --quiet --child --host=$HOST --port=$PORT --timeout=$TIMEOUT & + else + timeout $TIMEOUT $0 --child --host=$HOST --port=$PORT --timeout=$TIMEOUT & + fi + PID=$! + trap "kill -INT -$PID" INT + wait $PID + RESULT=$? + if [[ $RESULT -ne 0 ]]; then + echoerr "$cmdname: timeout occurred after waiting $TIMEOUT seconds for $HOST:$PORT" + fi + return $RESULT +} + +# process arguments +while [[ $# -ne 0 ]] +do + case "$1" in + *:* ) + hostport=(${1//:/ }) + HOST=${hostport[0]} + PORT=${hostport[1]} + shift 1 + ;; + --child) + CHILD=1 + shift 1 + ;; + -q | --quiet) + QUIET=1 + shift 1 + ;; + -s | --strict) + STRICT=1 + shift 1 + ;; + -h) + HOST="$2" + shift 2 + ;; + --host=*) + HOST="${1#*=}" + shift 1 + ;; + -p) + PORT="$2" + shift 2 + ;; + --port=*) + PORT="${1#*=}" + shift 1 + ;; + -t) + TIMEOUT="$2" + shift 2 + ;; + --timeout=*) + TIMEOUT="${1#*=}" + shift 1 + ;; + --) + shift + CLI="$@" + break + ;; + --help) + usage + ;; + *) + echoerr "Unknown argument: $1" + usage + ;; + esac +done + +if [[ "$HOST" == "" || "$PORT" == "" ]]; then + echoerr "Error: you need to provide a host and port to test." + usage +fi + +TIMEOUT=${TIMEOUT:-15} +STRICT=${STRICT:-0} +CHILD=${CHILD:-0} +QUIET=${QUIET:-0} + +if [[ $CHILD -gt 0 ]]; then + RESULT=$(wait_for) + exit $RESULT +else + if [[ $TIMEOUT -gt 0 ]]; then + wait_for_wrapper + RESULT=$? + else + RESULT=$(wait_for) + fi +fi + +if [[ $CLI != "" ]]; then + if [[ $RESULT -ne 0 && $STRICT -eq 1 ]]; then + echoerr "$cmdname: strict mode, refusing to execute subprocess" + exit $RESULT + fi + exec $CLI +else + exit $RESULT +fi