Fix healthcheck issue with Docker containers (#5011)

Fixes #5010

Dockerfile

@@ -8,8 +8,10 @@ ENV CGO_ENABLED 0
 
 WORKDIR /go/src/github.com/minio/
 
+COPY dockerscripts/docker-entrypoint.sh dockerscripts/healthcheck.sh /usr/bin/
+
 RUN  \
-     apk add --no-cache ca-certificates && \
+     apk add --no-cache ca-certificates curl && \
      apk add --no-cache --virtual .build-deps git go musl-dev && \
      echo 'hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4' >> /etc/nsswitch.conf && \
      go get -v -d github.com/minio/minio && \
@@ -19,12 +21,11 @@ RUN  \
 
 EXPOSE 9000
 
-COPY buildscripts/docker-entrypoint.sh /usr/bin/
-
-RUN chmod +x /usr/bin/docker-entrypoint.sh
-
 ENTRYPOINT ["/usr/bin/docker-entrypoint.sh"]
 
 VOLUME ["/export"]
 
+HEALTHCHECK --interval=30s --timeout=5s \
+    CMD /usr/bin/healthcheck.sh
+
 CMD ["minio"]

Dockerfile.release

@@ -2,7 +2,7 @@ FROM alpine:3.6
 
 MAINTAINER Minio Inc <dev@minio.io>
  
-COPY buildscripts/docker-entrypoint.sh buildscripts/healthcheck.sh /usr/bin/ 
+COPY dockerscripts/docker-entrypoint.sh dockerscripts/healthcheck.sh /usr/bin/
 
 RUN \
      apk add --no-cache ca-certificates && \

dockerscripts/healthcheck.sh

@@ -15,6 +15,8 @@
 # limitations under the License.
 #
 
+set -x
+
 _init () {
     scheme="http://"
     address="127.0.0.1:9000"
@@ -23,32 +25,32 @@ _init () {
 }
 
 healthcheck_main () {
-    # In distributed environment like Swarm, traffic is routed 
-    # to a container only when it reports a `healthy` status. So, we exit 
-    # with 0 to ensure healthy status till distributed Minio starts (120s). 
+    # In distributed environment like Swarm, traffic is routed
+    # to a container only when it reports a `healthy` status. So, we exit
+    # with 0 to ensure healthy status till distributed Minio starts (120s).
     #
     # Refer: https://github.com/moby/moby/pull/28938#issuecomment-301753272
     if [ $(( $(date +%s) - start )) -lt 120 ]; then
         exit 0
     else
         # Get the http response code
-        http_response=$(curl -s -k -o /dev/null -I -w "%{http_code}" \
+        http_response=$(curl -H "User-Agent: Mozilla" -s -k -o /dev/null -I -w "%{http_code}" \
             ${scheme}${address}${resource})
 
         # Get the http response body
-        http_response_body=$(curl -k -s ${scheme}${address}${resource})
+        http_response_body=$(curl -H "User-Agent: Mozilla" -k -s ${scheme}${address}${resource})
 
-        # server returns response 403 and body "SSL required" if non-TLS 
+        # server returns response 403 and body "SSL required" if non-TLS
         # connection is attempted on a TLS-configured server. Change
         # the scheme and try again
         if [ "$http_response" = "403" ] && \
         [ "$http_response_body" = "SSL required" ]; then
             scheme="https://"
-            http_response=$(curl -s -k -o /dev/null -I -w "%{http_code}" \
+            http_response=$(curl -H "User-Agent: Mozilla" -s -k -o /dev/null -I -w "%{http_code}" \
                 ${scheme}${address}${resource})
         fi
 
-        # If http_repsonse is 200 - server is up. When MINIO_BROWSER is 
+        # If http_repsonse is 200 - server is up. When MINIO_BROWSER is
         # set to off, curl responds with 404. We assume that the server
         # is up
         [ "$http_response" = "200" ] || [ "$http_response" = "404" ]