Edge headers

1

We have an API that uses CORS to be accessible from a web app. In some cases Fly Edge makes a response, such as when the worker takes more than 60s to respond. When this happens, the CORS headers are gone. This leads to a 502 (in this example) being sent back that the web app / browser presents as a CORS error. Its misleading and confusing. Is there a way for the headers Fly Edge will respond with to be customized?

2

There’s an undocumented option in fly.toml to modify outgoing headers that might be useful for you:

[services.ports.http_options.response.headers]
"set_header" = "value"
"set_header_multiple_values" = ["value1", "value2"]
"remove_header" = false

Keep in mind this will add the headers even when your app responds successfully, so you won’t be able to have CORS logic in your app.

1 Like
3

I have this TOML now, is it correct? Its different than yours in the double bracket nested part.

app = "..."

[env]
  PORT = "8082"

[[services]]
  internal_port = 8082
  protocol = "tcp"

  [[services.ports]]
    force_https = true
    handlers = ["http"]
    port = 80

  [[services.ports]]
    handlers = ["tls", "http"]
    port = 443

  [[services.ports.http_options.response.headers]]
    Access-Control-Allow-Origin = "*"
    Access-Control-Allow-Methods = "*"
    Access-Control-Allow-Headers = "*"
4

ah, no, I made the same mistake when figuring this out :sweat_smile: [[two brackets]] is TOML for an array with an inner object; [one bracket] puts an object directly on that key.

5

Ok, so this IIUC:

app = "..."

[env]
  PORT = "8082"

[[services]]
  internal_port = 8082
  protocol = "tcp"

  [[services.ports]]
    force_https = true
    handlers = ["http"]
    port = 80

  [[services.ports]]
    handlers = ["tls", "http"]
    port = 443

  # https://community.fly.io/t/edge-headers/9278
  [services.ports.http_options.response.headers]
    Access-Control-Allow-Origin = "*"
    Access-Control-Allow-Methods = "*"
    Access-Control-Allow-Headers = "*"
6

That should work, yes.

1 Like