check_http_cache

gistfile1.sh

#!/bin/sh

# Check HTTP cache
# Nagios test to check if a website has the correct cache control headers

ADDRESS="$1"

# Make two requests, capture the response headers on the second so we can see if it was delivered from the cache
curl -s "http://$ADDRESS/" -o /dev/null
HEADERS="$(curl -s -D - "http://$ADDRESS/" -o /dev/null)"

# If the page was actually delivered by a cache, that's proof it worked
if X_CACHE="$(echo "$HEADERS" | grep '^X-Cache:')"; then
        if X_CACHE_HIT="$(echo "$X_CACHE" | grep 'HIT')"; then
                echo "$X_CACHE_HIT"
                return 0
        fi
fi

# Look for bypass directives
if CACHE_CONTROL="$(echo "$HEADERS" | grep -e '^Cache-Control:')"; then
        if CACHE_CONTROL_NO_CACHE="$(echo "$CACHE_CONTROL" | grep 'no-cache')"; then
                echo "$CACHE_CONTROL_NO_CACHE"
                return 2
        fi
fi

if PRAGMA="$(echo "$HEADERS" | grep -e '^Pragma:')"; then
        if PRAGMA_NO_CACHE="$(echo "$PRAGMA" | grep 'no-cache')"; then
                echo "$PRAGMA_NO_CACHE"
                return 2
        fi
fi

# If the expires header is in the future, it should be cachable
if EXPIRES="$(echo "$HEADERS" | grep -e '^Expires:')"; then
        EXPIRES_DATE="$(echo "$EXPIRES" | head -n 1 | sed 's/^Expires://' | sed 's/\r$//')"
        TIME_NOW="$(date +'%s')"
        TIME_EXPIRES="$(date -d "$EXPIRES_DATE" +'%s')"
        if [ "$TIME_NOW" -lt "$TIME_EXPIRES" ]; then
                echo "$EXPIRES"
                return 0
        fi
fi

# An ETag header isn't really right, but it downgrades from critical to warning
if ETAG="$(echo "$HEADERS" | grep -e '^ETag:')"; then
        echo "$ETAG"
        return 1
fi

echo "No cache control headers found"
echo ""
echo "$HEADERS"
return 2