Job for openstack-nova-scheduler.service failed because the control process exited with error code.

在Linux系统中，当服务启动失败时，通常会提示“Job for xxx.service failed because the control process exited with error code. See 'systemctl status xxx.service' and 'journalctl -xe' for details.”这个错误信息。这个错误信息提示我们可以通过运行'systemctl status xxx.service'和'journalctl -xe'来查看详细的错误信息。

对于'Job for openstack-nova-scheduler.service failed because the control process exited with error code.'这个错误，我们可以按照以下步骤来解决：

1. 运行'systemctl status openstack-nova-scheduler.service'命令来查看服务的状态和错误信息。

2. 运行'journalctl -xe'命令来查看系统日志，找到与服务启动相关的错误信息。

3. 根据错误信息来修复问题。可能的解决方案包括重新安装服务、更新配置文件、检查依赖项等。

以下是一个例子，演示如何通过运行'systemctl status'和'journalctl -xe'来查看错误信息并解决问题：

$ systemctl status openstack-nova-scheduler.service
● openstack-nova-scheduler.service - OpenStack Nova Scheduler Server
   Loaded: loaded (/usr/lib/systemd/system/openstack-nova-scheduler.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Tue 2021-11-02 10:00:00 CST; 5s ago
  Process: 1234 ExecStart=/usr/bin/nova-scheduler (code=exited, status=1/FAILURE)
 Main PID: 1234 (code=exited, status=1/FAILURE)

Nov 02 10:00:00 server systemd[1]: Starting OpenStack Nova Scheduler Server...
Nov 02 10:00:00 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 1 seconds.
Nov 02 10:00:01 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 2 seconds.
Nov 02 10:00:03 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 4 seconds.
Nov 02 10:00:07 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 8 seconds.
Nov 02 10:00:15 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 16 seconds.
Nov 02 10:00:31 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 32 seconds.
Nov 02 10:01:03 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 64 seconds.
Nov 02 10:02:07 server systemd[1]: openstack-nova-scheduler.service: main process exited, code=exited, status=1/FAILURE
Nov 02 10:02:07 server systemd[1]: Failed to start OpenStack Nova Scheduler Server.

从上面的输出中，我们可以看到服务启动失败，错误信息是“Unable to connect to AMQP server: [Errno 111] ECONNREFUSED.”。这个错误提示我们无法连接到AMQP服务器，可能是由于AMQP服务器未启动或配置错误导致的。

接下来，我们可以运行'journalctl -xe'命令来查看系统日志，找到与服务启动相关的错误信息：

$ journalctl -xe
...
Nov 02 10:00:00 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 1 seconds.
Nov 02 10:00:01 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 2 seconds.
Nov 02 10:00:03 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 4 seconds.
Nov 02 10:00:07 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 8 seconds.
Nov 02 10:00:15 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 16 seconds.
Nov 02 10:00:31 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 32 seconds.
Nov 02 10:01:03 server nova-scheduler[1234]: ERROR: Unable to connect to AMQP server: [Errno 111] ECONNREFUSED. Trying again in 64 seconds.
...

从上面的输出中，我们可以看到与服务启动相关的错误信息是“Unable to connect to AMQP server: [Errno 111] ECONNREFUSED.”，这个错误信息与'systemctl status'命令输出的错误信息是一致的。

因此，我们可以得出结论，服务启动失败是由于无法连接到AMQP服务器导致的。我们需要检查AMQP服务器是否已启动，并确保配置文件中的AMQP服务器地址和端口号正确。