From 00c4bbcbfb1ee3f5393a82dd26bd1ae164d232b0 Mon Sep 17 00:00:00 2001
From: Neville Kadwa <neville@kadwa.com>
Date: Fri, 3 Nov 2017 13:10:09 -0400
Subject: [PATCH] shell only reimplementation of retry! #6 * currently needs
 gnu awk and getopt

---
 retry | 153 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)
 create mode 100755 retry

diff --git a/retry b/retry
new file mode 100755
index 0000000..48d964b
--- /dev/null
+++ b/retry
@@ -0,0 +1,153 @@
+#!/usr/bin/env bash
+
+__sleep_amount() {
+  if [ -n "$constant_sleep" ]; then 
+    sleep_time=$constant_sleep
+  else
+    sleep_time=`awk "BEGIN {t = $min_sleep * $(( (1<<($attempts -1)) )); print (t > $max_sleep ? $max_sleep : t)}"`
+  fi
+}
+
+__log_out() {
+  echo "$1" 1>&2
+}
+
+# Paramters: max_tries min_sleep max_sleep constant_sleep fail_script EXECUTION_COMMAND
+retry()
+{
+  local max_tries="$1"; shift
+  local min_sleep="$1"; shift
+  local max_sleep="$1"; shift
+  local constant_sleep="$1"; shift
+  local fail_script="$1"; shift
+  if [ -n "$VERBOSE" ]; then
+    __log_out "Retry Parameters: max_tries=$max_tries min_sleep=$min_sleep max_sleep=$max_sleep constant_sleep=$constant_sleep"
+    if [ -n "$fail_script" ]; then __log_out "Fail script: $fail_script"; fi
+    __log_out ""
+    __log_out "Execution Command: $*"
+    __log_out ""
+  fi
+
+  local attempts=0
+  local return_code=1
+
+
+  while [[ $return_code -ne 0 && $attempts -le $max_tries ]]; do
+    if [ $attempts -gt 0 ]; then
+      __sleep_amount
+      __log_out "Before retry #$attempts: sleeping $sleep_time seconds"
+      sleep $sleep_time
+    fi
+    eval $*
+    return_code=$?
+    #__log_out "Process returned $return_code on attempt $attempts"
+    if [ $return_code -eq 127 ]; then
+      # command not found
+      exit $return_code
+    else
+      attempts=$[$attempts +1]
+    fi
+  done
+
+  if [ $attempts -gt $max_tries ]; then
+    if [ -n "$fail_script" ]; then
+      __log_out "Retries exhausted, running fail script"
+      eval $fail_script
+    else
+      __log_out "Retries exhausted"
+    fi
+  fi
+
+  exit $return_code
+}
+
+# If we're being sourced, don't worry about such things
+if [ "$BASH_SOURCE" == "$0" ]; then
+  # Prints the help text
+  help()
+  {
+    local retry=$(basename $0)
+    cat <<EOF
+Usage: $retry [options] -- execute command
+    -h, -?, --help
+    -v, --verbose                    Verbose output
+    -t, --tries=#                    Set max retries: Default 10
+    -s, --sleep=secs                 Constant sleep amount (seconds)
+    -m, --min=secs                   Exponenetial Backoff: minimum sleep amount (seconds): Default 0.3
+    -x, --max=secs                   Exponenetial Backoff: maximum sleep amount (seconds): Default 60
+    -f, --fail="script +cmds"        Fail Script: run in case of final failure
+EOF
+  }
+
+  # show help for no arguments if stdin is a terminal
+  if { [ -z "$1" ] && [ -t 0 ] ; } || [ "$1" == '-h' ] || [ "$1" == '-?' ] || [ "$1" == '--help' ]
+  then
+    help
+    exit 0
+  fi
+
+  getopt --test > /dev/null
+  if [[ $? -ne 4 ]]; then
+      echo "I’m sorry, 'getopt --test' failed in this environment. Please load GNU getopt."
+      exit 1
+  fi
+
+  OPTIONS=vt:s:m:x:f:
+  LONGOPTIONS=verbose,tries:,sleep:,min:,max:,fail:
+
+  PARSED=$(getopt --options="$OPTIONS" --longoptions="$LONGOPTIONS" --name "$0" -- "$@")
+  if [[ $? -ne 0 ]]; then
+    # e.g. $? == 1
+    #  then getopt has complained about wrong arguments to stdout
+    exit 2
+  fi
+  # read getopt’s output this way to handle the quoting right:
+  eval set -- "$PARSED"
+
+  max_tries=10
+  min_sleep=0.3
+  max_sleep=60.0
+  constant_sleep=
+  fail_script=
+
+  # now enjoy the options in order and nicely split until we see --
+  while true; do
+      case "$1" in
+          -v|--verbose)
+              VERBOSE=true
+              shift
+              ;;
+          -t|--tries)
+              max_tries="$2"
+              shift 2
+              ;;
+          -s|--sleep)
+              constant_sleep="$2"
+              shift 2
+              ;;
+          -m|--min)
+              min_sleep="$2"
+              shift 2
+              ;;
+          -x|--max)
+              max_sleep="$2"
+              shift 2
+              ;;
+          -f|--fail)
+              fail_script="$2"
+              shift 2
+              ;;
+          --)
+              shift
+              break
+              ;;
+          *)
+              echo "Programming error"
+              exit 3
+              ;;
+      esac
+  done
+
+  retry "$max_tries" "$min_sleep" "$max_sleep" "$constant_sleep" "$fail_script" $*
+  
+fi