今天早上apache無法訪問，查看日誌發現
[Thu Feb 21 09:47:48 2008] [error] (111)Connection refused: proxy: HTTP:
attempt to connect to 127.0.0.1:3000 (localhost) failed
[Thu Feb 21
09:47:48 2008] [error] ap_proxy_connect_backend disabling worker for
(localhost)
[Thu Feb 21 09:47:48 2008] [error] proxy: HTTP: disabled
connection for (localhost)
3000端口運行的是ruby的radiant cms系統，所以便懷疑radiant啓動失敗，便手工啓動該服務
[root@localhost ~]#
service mongrel_cluster start
Starting all mongrel_clusters…
** !!! PID
file tmp/pids/mongrel.3000.pid already exists. Mongrel could be running
already. Check your log/mongrel.3000.log for errors.
** !!! Exiting with
error. You must stop mongrel and clear the .pid before I’ll attempt a
start.
** !!! PID file tmp/pids/mongrel.4000.pid already exists. Mongrel
could be running already. Check your log/mongrel.4000.log for errors.
** !!!
Exiting with error. You must stop mongrel and clear the .pid before I’ll
attempt a start.
[root@localhost ~]# service mongrel_cluster
start
Starting all mongrel_clusters…
** !!! PID file
tmp/pids/mongrel.4000.pid already exists. Mongrel could be running already.
Check your log/mongrel.4000.log for errors.
** !!! Exiting with error. You
must stop mongrel and clear the .pid before I’ll attempt a start.
看意思應該是一些臨時文件存在，所以無法啓動，到該目錄下刪除，重新啓動，果然可以。
發現apache如果在httpd中轉向到其他web server，如果那個web server啓動失敗，則同時會導致apache無法啓動，
所以如果在linux下使用service自動啓動各種服務，需要注意服務的啓動順序。