Don't eagerly restart the service when the binary hasn't changed

This will help with metrics collection as the counters won't be zeroed
out as frequently.

Author: shepmaster

deployment/update.sh

@@ -3,13 +3,20 @@
 set -euv -o pipefail
 
 root=/home/ubuntu
+binary_path=$root/playground-artifacts/ui
 
 # Get new docker images
 $root/rust-playground/compiler/fetch.sh
 
 # Clean old docker images
 docker system prune -f || true
 
+# Get the binary's hash so we know if it has changed
+previous_binary_hash=""
+if [[ -f "${binary_path}" ]]; then
+    previous_binary_hash=$(md5sum "${binary_path}")
+fi
+
 # Get new artifacts
 aws s3 sync --region=us-east-2 s3://playground-artifacts-i32 $root/playground-artifacts
 # These artifacts don't change names and might stay the same size
@@ -23,8 +30,10 @@ aws s3 sync \
     --include=build/robots.txt \
     --exact-timestamps \
     s3://playground-artifacts-i32 $root/playground-artifacts
-chmod +x $root/playground-artifacts/ui
+chmod +x "${binary_path}"
 
 # Restart to get new server binary
-sudo service playground stop || true
-sudo service playground start
+if [[ -z "${previous_binary_hash}" ]] || ! md5sum -c <(echo "${previous_binary_hash}") --status; then
+    sudo service playground stop || true
+    sudo service playground start
+fi