systemd: build: Add sethostname workaround for AmazonLinux2

CMakeLists.txt

@@ -34,6 +34,24 @@ if(CMAKE_SYSTEM_NAME MATCHES "Linux")
     set(FLB_LINUX_ON_AARCH64 On)
     add_definitions(-DFLB_LINUX_ON_AARCH64)
   endif()
+
+  find_program(CAT_EXEC cat)
+  if (CAT_EXEC)
+    set(RELEASE_FILE "/etc/system-release")
+    if (EXISTS ${RELEASE_FILE})
+      execute_process(COMMAND ${CAT_EXEC} ${RELEASE_FILE}
+        OUTPUT_VARIABLE CAT_SYSTEM_RELEASE
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+      )
+
+      message(STATUS "##### cat /etc/system-release -- OK")
+
+      if (CAT_SYSTEM_RELEASE STREQUAL "Amazon Linux release 2 (Karoo)")
+        set(FLB_AMAZON_LINUX2 On)
+        add_definitions(-DFLB_AMAZON_LINUX2)
+      endif()
+    endif()
+  endif()
 endif()
 
 # Update CFLAGS

init/az2-sethostname.in

@@ -0,0 +1,12 @@
+[Unit]
+Description=Set Hostname Workaround coreos/bugs#1272
+Wants=network-online.target
+After=network-online.target
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/bin/sh -c "/usr/bin/hostnamectl set-hostname $(curl -s http://169.254.169.254/latest/meta-data/hostname)"
+
+[Install]
+WantedBy=multi-user.target

init/az2-systemd.in

@@ -0,0 +1,17 @@
+[Unit]
+Description=@FLB_PROG_NAME@
+Documentation=https://docs.fluentbit.io/manual/
+Requires=network.target
+After=network.target
+Requires=sethostname.service
+After=sethostname.service
+
+[Service]
+Type=simple
+EnvironmentFile=-/etc/sysconfig/@FLB_OUT_NAME@
+EnvironmentFile=-/etc/default/@FLB_OUT_NAME@
+ExecStart=@CMAKE_INSTALL_FULL_BINDIR@/@FLB_OUT_NAME@ -c /@CMAKE_INSTALL_SYSCONFDIR@/@FLB_OUT_NAME@/@[email protected]
+Restart=always
+
+[Install]
+WantedBy=multi-user.target

src/CMakeLists.txt

@@ -546,13 +546,30 @@ if(FLB_BINARY)
   endif()
 
   if(SYSTEMD_UNITDIR)
-    set(FLB_SYSTEMD_SCRIPT "${PROJECT_SOURCE_DIR}/init/${FLB_OUT_NAME}.service")
-    configure_file(
-      "${PROJECT_SOURCE_DIR}/init/systemd.in"
-      ${FLB_SYSTEMD_SCRIPT}
-      )
-    install(FILES ${FLB_SYSTEMD_SCRIPT} COMPONENT binary DESTINATION ${SYSTEMD_UNITDIR})
-    install(DIRECTORY DESTINATION ${FLB_INSTALL_CONFDIR} COMPONENT binary)
+    if (FLB_AMAZON_LINUX2)
+      set(FLB_SYSTEMD_SCRIPT "${PROJECT_SOURCE_DIR}/init/${FLB_OUT_NAME}.service")
+      configure_file(
+        "${PROJECT_SOURCE_DIR}/init/az2-systemd.in"
+        ${FLB_SYSTEMD_SCRIPT}
+        )
+      install(FILES ${FLB_SYSTEMD_SCRIPT} COMPONENT binary DESTINATION ${SYSTEMD_UNITDIR})
+      install(DIRECTORY DESTINATION ${FLB_INSTALL_CONFDIR} COMPONENT binary)
+      set(FLB_HOSTNAME_SYSTEMD_SCRIPT "${PROJECT_SOURCE_DIR}/init/sethostname.service")
+      configure_file(
+        "${PROJECT_SOURCE_DIR}/init/az2-sethostname.in"
+        ${FLB_HOSTNAME_SYSTEMD_SCRIPT}
+        )
+      install(FILES ${FLB_HOSTNAME_SYSTEMD_SCRIPT} COMPONENT binary DESTINATION ${SYSTEMD_UNITDIR})
+      install(DIRECTORY DESTINATION ${FLB_INSTALL_CONFDIR} COMPONENT binary)
+    else()
+      set(FLB_SYSTEMD_SCRIPT "${PROJECT_SOURCE_DIR}/init/${FLB_OUT_NAME}.service")
+      configure_file(
+        "${PROJECT_SOURCE_DIR}/init/systemd.in"
+        ${FLB_SYSTEMD_SCRIPT}
+        )
+      install(FILES ${FLB_SYSTEMD_SCRIPT} COMPONENT binary DESTINATION ${SYSTEMD_UNITDIR})
+      install(DIRECTORY DESTINATION ${FLB_INSTALL_CONFDIR} COMPONENT binary)
+    endif()
   elseif(IS_DIRECTORY /usr/share/upstart)
     set(FLB_UPSTART_SCRIPT "${PROJECT_SOURCE_DIR}/init/${FLB_OUT_NAME}.conf")
     configure_file(