编译加速

remote cache
大致原理就是根据编译输入的sha码与编译输出建立（key,value）对，存储在远端cache．编译过程如果能匹配到key，则获取GET到value.
如果hit不到key，则客户端在本地编译，并控制是否更新远端缓存库．

  build:remote --experimental_strict_action_env --remote_http_cache=http://192.168.1.102:8080
  build:remote --experimental_execution_log_file=/tmp/exec1.log
  build:remote --build_event_text_file=/tmp/bep.txt
  build:remote --remote_upload_local_results=false
  build:remote_cache --remote_upload_local_results=true

  [3,541 / 3,565] 12 actions, 7 running
  ...lation_world:simulation_world_service; 0s remote-cache
  .../backend/sim_control:sim_control; 0s remote-cache
  ...lation_world:simulation_world_service; 0s remote-cache
  Compiling .../dreamview/backend/main.cc; 0s remote-cache
  ...lation_world:simulation_world_updater; 0s remote-cache
  ...lation_world:simulation_world_updater; 0s remote-cache
  .../handlers:websocket_handler_test; 0s remote-cache
  [-----] .../backend/handlers:image_handler_cpplint ...

  ...  

  INFO: Elapsed time: 68.628s, Critical Path: 8.32s
  INFO: 1212 processes: 1212 remote cache hit.
  INFO: Build completed successfully, 3700 total actions
  modules/perception/proto/perception_lane.proto: warning: Import modules/common/proto/error_code.proto but not used.
  1============================
  [ OK ] Build passed!
  [INFO] Took 234 seconds
  ============================

===================================================================================================
distribute compilation 

  Some conclusions:
  Buildfarm: Now it maybe still exists much problems. The work plan of project Buildfarm https://github.com/bazelbuild/bazel/projects/1.
  Buildbarn: The implement of Buildfarm in go. So see Buildfarm.
  BuildGrid: This project is an open source proj by python. It seems may work for us, and not try yet.
  distcc: This proj may be mature, but cannot use in bazel directly．And the bazel team suggests that remote execution has made huge leaps in the past year and a half and should be ready for you to try as a replacement of distcc.

  In a word, try distcc or BuildGrid, and wait for Buildfarm.

在所有您想用来编译的机器上安装 distcc
启动每台机器上的 distcc 新进程
用变量名导出 DISTCC_HOSTS 环境变量
启动 distcc 监视器（这样就可以观察正在发生什么事！）
使用 CC=distcc ./configure ，而不是使用 ./configure 来进行配置
使用 make -j n ，而不是使用 make 或 make -j 2 来进行编译，其中，n 是 DISTCC_HOSTS中机器数目的两到三倍