busybox容器内while循环中echo的输出不会更改

Question

我正试图让一个busyboxPod每秒以JSON格式输出一些日志，同时更新time时间戳和msg值以进行调试。

为此，我创建了以下hello-pod

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: Pod
metadata:
name: hello-pod
spec:
containers:
- name: count
image: busybox
args: [
/bin/sh,
-c,
'i=0; while true; do echo "{"time":$(date +%s),"msg":"This is my dummy log number $i"}"; i=$((i+1)); sleep 1; done'
]
EOF

我希望Pod将以下内容写入标准输出

{"time":1662474158,"msg":"This is my dummy log number 0"}
{"time":1662474159,"msg":"This is my dummy log number 1"}
{"time":1662474160,"msg":"This is my dummy log number 2"}

然而，我得到了相同的日志输出，time保持不变，i没有值。

{"time":1662473834,"msg":"This is my dummy log number "}
{"time":1662473834,"msg":"This is my dummy log number "}
{"time":1662473834,"msg":"This is my dummy log number "}

在查看了这个线程之后，我尝试用echo "{"time":my-time}" | sed "s/my-time/$(date +%s)/"更新第三个参数中的echo语句，我希望用新的当前时间替换my-time字符串，但我仍然得到了相同的结果。(每秒输出的第一个回波(

Answer 1

如果删除kubectl apply -f -，您将看到cat'd到kubectl是什么，我想您会发现在生成文件时变量已经被替换过一次。

这应该有效：

echo 'apiVersion: v1
kind: Pod
metadata:
name: hello-pod
spec:           
containers:
- name: count
image: busybox
args: [
/bin/sh,
-c,
"i=0; while true; do echo {"time":$(date +%s),"msg":"This is my dummy log number ${i}"}; i=$((i+1)); sleep 1; done"
]' | kubectl apply --filename=-

我个人的偏好是避免将JSON[...]与YAML组合，并使用YAML的管道(|(来更干净地布置脚本：

echo 'apiVersion: v1
kind: Pod
metadata:
name: hello-pod
spec:           
containers:
- name: count
image: busybox
command:
- /bin/sh
- -c
args:
- |
i=0
while true
do
echo "{"time":$(date +%s),"msg":"This is my dummy log number ${i}"}"
i=$((i+1))
sleep 1
done
' | kubectl apply --filename=-