Add configuration parameter for namespace mount path

Support changing the path used by the watchdog to read the funcion
namespace by setting the env variable 'namespace_mount_path'.

Required for running functions locally with jwt_auth.

Signed-off-by: Han Verstraete (OpenFaaS Ltd) <[email protected]>

README.md

@@ -197,6 +197,7 @@ Environmental variables:
 | `log_call_id`                    | In HTTP mode, when printing a response code, content-length and timing, include the X-Call-Id header at the end of the line in brackets i.e. `[079d9ff9-d7b7-4e37-b195-5ad520e6f797]` or `[none]` when it's empty. Default: `false` |
 | `max_inflight`                   |  Limit the maximum number of requests in flight, and return a HTTP status 429 when exceeded           |
 | `mode`                           |  The mode which of-watchdog operates in, Default `streaming` [see doc](#3-streaming-fork-modestreaming---default). Options are [http](#1-http-modehttp), [serialising fork](#2-serializing-fork-modeserializing), [streaming fork](#3-streaming-fork-modestreaming---default), [static](#4-static-modestatic) |
+| `namespace_mount_path | Path used by the watchdog to lookup the namespace the function is deployed in. | `/var/run/secrets/kubernetes.io/serviceaccount/namespace` |
 | `port`                           |  Specify an alternative TCP port for testing. Default: `8080`            |
 | `prefix_logs`                    |  When set to `true` the watchdog will add a prefix of "Date Time" + "stderr/stdout" to every line read from the function process. Default `true`             |
 | `read_timeout`                   |  HTTP timeout for reading the payload from the client caller (in seconds)          |

executor/jwt_authenticator.go

@@ -207,7 +207,12 @@ func getFnName() (string, error) {
 }
 
 func getFnNamespace() (string, error) {
-	nsVal, err := os.ReadFile("/var/run/secrets/kubernetes.io/serviceaccount/namespace")
+	namespacePath := "/var/run/secrets/kubernetes.io/serviceaccount/namespace"
+	if v, ok := os.LookupEnv("namespace_mount_path"); ok && len(v) > 0 {
+		namespacePath = v
+	}
+
+	nsVal, err := os.ReadFile(namespacePath)
 	if err != nil {
 		return "", err
 	}