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#! /bin/bash
# Copyright 2013 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Get a metadata value from the metadata server.
declare -r VARNAME=$1
declare -r MDS_PREFIX=http://metadata.google.internal/computeMetadata/v1
declare -r MDS_TRIES=${MDS_TRIES:-100}
function print_metadata_value() {
local readonly tmpfile=$(mktemp)
http_code=$(curl -f "${1}" -H "Metadata-Flavor: Google" -w "%{http_code}" \
-s -o ${tmpfile} 2>/dev/null)
local readonly return_code=$?
# If the command completed successfully, print the metadata value to stdout.
if [[ ${return_code} == 0 && ${http_code} == 200 ]]; then
cat ${tmpfile}
fi
rm -f ${tmpfile}
return ${return_code}
}
function print_metadata_value_if_exists() {
local return_code=1
local readonly url=$1
print_metadata_value ${url}
return_code=$?
return ${return_code}
}
function get_metadata_value() {
local readonly varname=$1
# Print the instance metadata value.
print_metadata_value_if_exists ${MDS_PREFIX}/instance/${varname}
return_code=$?
# If the instance doesn't have the value, try the project.
if [[ ${return_code} != 0 ]]; then
print_metadata_value_if_exists ${MDS_PREFIX}/project/${varname}
return_code=$?
fi
return ${return_code}
}
function get_metadata_value_with_retries() {
local return_code=1 # General error code.
for ((count=0; count <= ${MDS_TRIES}; count++)); do
get_metadata_value $VARNAME
return_code=$?
case $return_code in
# No error. We're done.
0) exit ${return_code};;
# Failed to resolve host or connect to host. Retry.
6|7) sleep 0.3; continue;;
# A genuine error. Exit.
*) exit ${return_code};
esac
done
# Exit with the last return code we got.
exit ${return_code}
}
get_metadata_value_with_retries
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