BuildKite pre-command: Use alternate way to reload Docker when available.

PiperOrigin-RevId: 456884864

.buildkite/hooks/pre-command

@@ -36,7 +36,15 @@ export TOTAL_PARTITIONS=${BUILDKITE_PARALLEL_JOB_COUNT:-1}
 export RUNTIME="buildkite_runtime_${BUILDKITE_BRANCH}-${BUILDKITE_BUILD_ID}"
 export RUNTIME="$(echo "$RUNTIME" | sed -r 's~[^-_a-z0-9]+~_~g')"
 
-# Ensure Docker has experimental enabled.
+# If running in a container, set the reload command appropriately.
+if [[ -x /tmp/buildkite-reload-host-docker/reload ]]; then
+  export DOCKER_RELOAD_COMMAND='/tmp/buildkite-reload-host-docker/reload'
+else
+  export DOCKER_RELOAD_COMMAND='sudo systemctl reload docker'
+fi
+
+# Ensure Docker has experimental enabled, install runtimes.
+HAD_EXPERIMENTAL="$(docker version --format='{{.Server.Experimental}}')"
 if [[ -n "${STAGED_BINARIES:-}" ]]; then
   # Used `runsc` from STAGED_BINARIES instead of building it from scratch.
   tmpdir="$(mktemp -d)"
@@ -49,9 +57,16 @@ else
   make sudo TARGETS=//runsc:runsc \
     ARGS="install --experimental=true --runtime=${RUNTIME} -- ${RUNTIME_ARGS:-}"
 fi
-# WARNING: We may be running in a container when this command executes.
-# This only makes sense if Docker's `live-restore` feature is enabled.
-sudo systemctl restart docker
+if [[ "$HAD_EXPERIMENTAL" == false ]]; then
+  # WARNING: We may be running in a container when this command executes.
+  # This only makes sense if Docker's `live-restore` feature is enabled.
+  sudo systemctl restart docker
+else
+  # If experimental-ness was already enabled, we don't need to restart, as the
+  # only thing we modified is the list of runtimes, which can be reloaded with
+  # just a SIGHUP.
+  bash -c "$DOCKER_RELOAD_COMMAND"
+fi
 
 # Helper for benchmarks, based on the branch.
 if test "${BUILDKITE_BRANCH}" = "master"; then

Makefile

@@ -102,7 +102,8 @@ endif
 ##     RUNTIME_ARGS    - Arguments passed to the runtime when installed.
 ##     STAGED_BINARIES - A tarball of staged binaries. If this is set, then binaries
 ##                       will be installed from this staged bundle instead of built.
-##
+##     DOCKER_RELOAD_COMMAND - The command to run to reload Docker. (default: sudo systemctl reload docker).
+
 ifeq (,$(BRANCH_NAME))
 RUNTIME     := runsc
 RUNTIME_DIR := $(shell dirname $(shell mktemp -u))/$(RUNTIME)
@@ -114,6 +115,7 @@ RUNTIME_BIN     := $(RUNTIME_DIR)/runsc
 RUNTIME_LOG_DIR := $(RUNTIME_DIR)/logs
 RUNTIME_LOGS    := $(RUNTIME_LOG_DIR)/runsc.log.%TEST%.%TIMESTAMP%.%COMMAND%
 RUNTIME_ARGS    ?=
+DOCKER_RELOAD_COMMAND ?= sudo systemctl reload docker
 
 ifeq ($(shell stat -f -c "%T" /sys/fs/cgroup 2>/dev/null),cgroup2fs)
 CGROUPV2 := true
@@ -138,7 +140,8 @@ configure_noreload = \
   sudo $(RUNTIME_BIN) install --experimental=true --runtime="$(1)" -- $(RUNTIME_ARGS) --debug-log "$(RUNTIME_LOGS)" $(2) && \
   sudo rm -rf "$(RUNTIME_LOG_DIR)" && mkdir -p "$(RUNTIME_LOG_DIR)"
 reload_docker = \
-  sudo systemctl reload docker && \
+  $(call header,DOCKER RELOAD); \
+  bash -xc "$(DOCKER_RELOAD_COMMAND)" && \
   if test -f /etc/docker/daemon.json; then \
     sudo chmod 0755 /etc/docker && \
     sudo chmod 0644 /etc/docker/daemon.json; \