systemd execstart python守护进程使用virtualenv from环境变量动态启动

我在CentOS 7中使用Python脚本作为systemd守护进程。守护进程由我在virtualenv中创建的python版本执行。我正在尝试调整脚本，以便能够在环境变量中设置virtualenv路径，以便通过一个变量更改路径并重新启动服务，轻松切换到不同的virtualenv。我已经创建了我的systemd脚本，以便能够初始化守护进程的多个实例，这非常有效。当我试图使用一个环境变量来指向我的python解析器时，情况就不一样了。这是我到目前为止所拥有的

/etc/系统D/系统/管道-remove@.service:

[Unit]
Description=pipeline remove tickets worker instances as a service, instance %i
Requires=pipeline-remove.service
Before=pipeline-remove.service
BindsTo=pipeline-remove.service

[Service]
PermissionsStartOnly=true
Type=idle
User=root
ExecStart=/path/to/venv/bin/python /pipeline/python/daemons/remove_tickets.py
Restart=always
TimeoutStartSec=10
RestartSec=10

[Install]
WantedBy=pipeline-remove.service

[Unit]
Description=pipeline remove tickets worker instances as a service, instance %i
Requires=pipeline-remove.service
Before=pipeline-remove.service
BindsTo=pipeline-remove.service

[Service]
PermissionsStartOnly=true
Type=idle
User=root
EnvironmentFile=/etc/profile.d/pipeline_envvars.sh
ExecStart=/${PIPELINE_VIRTUALENV}/bin/python /pipeline/python/daemons/remove_tickets.py
Restart=always
TimeoutStartSec=10
RestartSec=10

[Install]
WantedBy=pipeline-remove.service

/etc/systemd/system/pipeline-remove.service（启动所有实例）：

pipeline-remove-start.sh：

#!/bin/bash
systemctl start pipeline-remove@{1..2}

这对我来说非常有用，但当我尝试按以下方式设置python目录时，情况就不一样了：

/etc/profile.d/pipeline_envvars.sh：

PIPELINE_VIRTUALENV=/path/to/venv

/etc/系统D/系统/管道-remove@.service:

[Unit]
Description=pipeline remove tickets worker instances as a service, instance %i
Requires=pipeline-remove.service
Before=pipeline-remove.service
BindsTo=pipeline-remove.service

[Service]
PermissionsStartOnly=true
Type=idle
User=root
ExecStart=/path/to/venv/bin/python /pipeline/python/daemons/remove_tickets.py
Restart=always
TimeoutStartSec=10
RestartSec=10

[Install]
WantedBy=pipeline-remove.service

[Unit]
Description=pipeline remove tickets worker instances as a service, instance %i
Requires=pipeline-remove.service
Before=pipeline-remove.service
BindsTo=pipeline-remove.service

[Service]
PermissionsStartOnly=true
Type=idle
User=root
EnvironmentFile=/etc/profile.d/pipeline_envvars.sh
ExecStart=/${PIPELINE_VIRTUALENV}/bin/python /pipeline/python/daemons/remove_tickets.py
Restart=always
TimeoutStartSec=10
RestartSec=10

[Install]
WantedBy=pipeline-remove.service

然后我尝试启动它：

sudo systemctl daemon-reload
sudo systemctl restart pipeline-remove@{1..1}
sudo systemctl status pipeline-remove@{1..1}

状态显示以下退出代码203，表示未找到可执行文件：

● pipeline-remove@1.service - pipeline remove tickets worker instances as a service, instance 1
   Loaded: loaded (/etc/systemd/system/pipeline-remove@.service; disabled; vendor preset: disabled)
   Active: activating (auto-restart) (Result: exit-code) since Fri 2018-01-26 15:04:50 UTC; 6s ago
  Process: 11716 ExecStart=/${PIPELINE_VIRTUALENV}/bin/python /pipeline/python/daemons/remove_tickets.py (code=exited, status=203/EXEC)
 Main PID: 11716 (code=exited, status=203/EXEC)

Jan 26 15:04:50 dev systemd[1]: pipeline-remove@1.service: main process exited, code=exited, status=203/EXEC
Jan 26 15:04:50 dev systemd[1]: Unit pipeline-remove@1.service entered failed state.
Jan 26 15:04:50 dev systemd[1]: pipeline-remove@1.service failed.

找到了exec代码。在syslog，/var/log/messages中也可以找到：

Jan 26 15:07:13 dev systemd: Starting pipeline remove tickets worker instances as a service, instance 1...
Jan 26 15:07:13 dev systemd: Failed at step EXEC spawning /${PIPELINE_VIRTUALENV}/bin/python: No such file or directory
Jan 26 15:07:13 dev systemd: pipeline-remove@1.service: main process exited, code=exited, status=203/EXEC
Jan 26 15:07:13 dev systemd: Unit pipeline-remove@1.service entered failed state.
Jan 26 15:07:13 dev systemd: pipeline-remove@1.service failed.
Jan 26 15:07:23 dev systemd: pipeline-remove@1.service holdoff time over, scheduling restart.
Jan 26 15:07:23 dev systemd: Started pipeline remove tickets worker instances as a service, instance 1.

当我尝试在

ExecStart

中删除前导的

/

时，即使我的环境变量包含绝对路径，我也会得到一个相对路径错误：

Failed to start pipeline-remove@1.service: Unit is not loaded properly: 
Invalid argument.
See system logs and 'systemctl status pipeline-remove@1.service' for 
details.

状态显示如下：

vagrant@dev:~$ sudo systemctl status pipeline-remove@{1..1}
● pipeline-remove@1.service - pipeline remove tickets worker instances as a service, instance 1
   Loaded: error (Reason: Invalid argument)
   Active: inactive (dead)

Jan 26 15:11:39 dev systemd[1]: pipeline-remove@1.service failed.
Jan 26 15:11:42 dev systemd[1]: Stopped pipeline remove tickets worker instances as a service, instance 1.
Jan 26 15:11:42 dev systemd[1]: [/etc/systemd/system/pipeline-remove@.service:12] Executable path is not absolute, ignoring: ${PIPELINE_VIRTUALENV}/bin/python /pipel...e_tickets.py
Jan 26 15:11:42 dev systemd[1]: pipeline-remove@1.service lacks both ExecStart= and ExecStop= setting. Refusing.

---

我用指南来帮助我开始，但现在我被卡住了。如何在从环境变量设置python可执行路径时启动python守护进程？

在进一步阅读之后，我偶然发现了答案。问题是

ExecStart

的第一个参数必须是文本：

ExecStart=执行此操作时执行的命令及其参数 服务已启动。对于每个指定的命令，第一个 参数必须是可执行文件的绝对文本路径

进一步阅读ExecStart，它说：

在展开时其值未知的变量被视为 空字符串请注意，第一个参数（即 执行）可能不是变量

我最后也遇到了同样的问题。最后，这是有效的：用shell包装整个东西以运行：

[Unit]
Description=pipeline remove tickets worker instances as a service, instance %i
Requires=pipeline-remove.service
Before=pipeline-remove.service
BindsTo=pipeline-remove.service

[Service]
PermissionsStartOnly=true
Type=idle
User=root
EnvironmentFile=/etc/profile.d/pipeline_envvars.sh
ExecStart=/bin/sh -c '${PIPELINE_VIRTUALENV}/bin/python /pipeline/python/daemons/remove_tickets.py'
Restart=always
TimeoutStartSec=10
RestartSec=10

[Install]
WantedBy=pipeline-remove.service

---

因此

ExecStart=/bin/sh-c'

节省了时间，现在我可以为我的环境变量指定python解释器路径。我将保留答案，希望能为其他人节省一些时间。

再读几遍后，我无意中找到了答案。问题是

ExecStart

的第一个参数必须是文本：

ExecStart=执行此操作时执行的命令及其参数 服务已启动。对于每个指定的命令，第一个 参数必须是可执行文件的绝对文本路径

进一步阅读ExecStart，它说：

在展开时其值未知的变量被视为 空字符串请注意，第一个参数（即 执行）可能不是变量

我最后也遇到了同样的问题。最后，这是有效的：用shell包装整个东西以运行：

[Unit]
Description=pipeline remove tickets worker instances as a service, instance %i
Requires=pipeline-remove.service
Before=pipeline-remove.service
BindsTo=pipeline-remove.service

[Service]
PermissionsStartOnly=true
Type=idle
User=root
EnvironmentFile=/etc/profile.d/pipeline_envvars.sh
ExecStart=/bin/sh -c '${PIPELINE_VIRTUALENV}/bin/python /pipeline/python/daemons/remove_tickets.py'
Restart=always
TimeoutStartSec=10
RestartSec=10

[Install]
WantedBy=pipeline-remove.service

因此

ExecStart=/bin/sh-c'

节省了时间，现在我可以为我的环境变量指定python解释器路径。将保留答案，希望能为其他人节省一些时间