Problem passing in a variable from a shell script into a deployment yaml - kubernetes

Question

In a shell scrip I want to assigning a variable what to use in a value in a deployment. For the life of me I can not figure out how to get it to work.
My helm deploy script file has the following in order to set the value to use my variable :
--set AuthConfValue=$AUTH_CONF_VALUE
And I have this in the deployment.yaml file in order to use the variable :
- name: KONG_SETTING
value: "{ {{ .Values.AuthConfValue }} }"
If I assign the variable in my shell script like the following :
AUTH_CONF_VALUE="ernie"
It will work and the value in the deployment will show up like so:
value: '{ ernie }'
Now if I try to assign the variable like this:
AUTH_CONF_VALUE="\\\"ernie\\\":\\\"123\\\""
I will then get the error error converting YAML to JSON: yaml: line 118: did not find expected key when the helm deploy runs.
I was hoping that this would give me the following value in the deployment :
value: "{ "ernie":"123" }"
If I hardcode the value into the deployment.yaml with this:
- name: KONG_SETTING
value: "{ \"ernie\": \"123\" }"
and then run the helm deploy it will work and populate the value in the deployment with this -
value: "{ "ernie":"123" }"
Can someone show me if/how I might be able to do this?

Answer 1

The Helm --set option also uses backslash escaping. So in your example, the $AUTH_CONF_VALUE variable in the host shell contains a single backslash before each quote, which is consumed by --set, so .Values.AuthConfValue contains no backslashes at all, and you get invalid YAML.
If you want to keep this as close to the existing form as you can, let's construct a string with no backslashes at all (and hopefully no commas or brackets either, since those also have special meaning to --set)
AUTH_CONF_VALUE='"ernie":"123"'
helm install --set AuthConfValue="$AUTH_CONF_VALUE" .
When Helm expands a template it doesn't know anything about the context where it might be used. In your case, you know
.Values.AuthConfValue is the body of a JSON object
If you surround it in curly braces { ... } then it should be a valid JSON object
You need to turn that into a correctly-escaped YAML string
Helm contains a lightly-documented toJson function that takes an arbitrary object and converts it to JSON; any valid JSON is also valid YAML. So the closest-to-what-you-have approach might look like
- name: KONG_SETTING
value: {{ printf "{%s}" .Values.AuthConfValue | toJson }}
If you're willing to modify your deploy process a little more, you can have less escaping and more certainty. In the sequence above, we have a string that happens to be a JSON object; what if we had an actual object? Imagine settings like
# kong-auth.yaml
authConf:
ernie: "123"
You could provide this file at install time with a helm install -f option. Since valid JSON is valid YAML, again, you could also provide a JSON file here without changing anything.
helm install -f kong-auth.yaml .
Now with this setup .Values.authConf is an object; the only escaping you need to do is standard YAML/JSON escaping (for example quoting "123" so it's a string and not a number). Now we can use toJson twice, once to get the {"ernie":"123"} JSON object string, and a second time to escape that string as a value "{\"ernie\":\"123\"}".
- name: KONG_SETTING
value: {{ .Values.authConf | toJson | toJson }}
Setting this up would require modifying your deployment script, but it would be much safer against quoting and escaping concerns.