knitr::opts_chunk$set( collapse = TRUE, comment = "#>", eval = FALSE )
Sometimes when using connectapi
, customizing HTTP requests is desirable. For
instance, some common use cases are:
This is possible with connectapi
thanks to the underlying library in use,
httr
.
When you initialize a connectapi
API client, you implicitly create a httr
HTTP client. The httr
package allows you to configure your HTTP requests
globally using httr::set_config()
or in a scoped variant httr::with_config
.
We will walk through a few examples below.
library(httr) library(connectapi) client <- connect() # notice that TLS verification fails get_users(client) # use a custom Certificate Authority to verify SSL/TLS requests httr::set_config(httr::config(cainfo = "/path/to/my.pem")) # now it should succeed! get_users(client)
Sometimes when first setting up a server, it is common to use self-signed certificates. This is generally bad for reliable communication and security (as there is no reason for any computer to trust this server as a "self-declared" trustworthy actor).
However, it can be useful while the organization's Certificate Authority (CA) is in the process of issuing a valid certificate, or while a certificate is procured from a public CA.
# disabling certificate trust (can allow man-in-the-middle attacks, etc.) httr::set_config(httr::config(ssl_verifypeer = 0, ssl_verifyhost = 0)) # should work client <- connect() get_users(client)
You can also do this in a more scoped fashion:
httr::with_config( httr::config(ssl_verifypeer = 0, ssl_verifyhost = 0), { client <- connect() get_users(client) } )
httr
has some helpers for common tasks like httr::add_headers()
,
httr::set_cookies()
, httr::use_proxy()
, etc. Using them is a bit tricky,
but can be done by way of the client$httr_config()
function.
Pass any usual httr
arguments to client$httr_config()
, and those arguments
will then be saved and passed to any subsequent GET
, PUT
, POST
, PATCH
,
HEAD
, DELETE
requests you send with that client.
# for instance, to set custom headers (i.e. to get through a proxy) client$httr_config(httr::add_headers(MY_MAGIC_HEADER="value")) # or to clear sticky cookies if you want to switch nodes in an HA cluster client <- connect() client$server_settings()$hostname client$httr_config(handle = httr::handle('')) # now you have a chance to get a new host client$server_settings()$hostname # use an outbound proxy client$httr_config(httr::use_proxy("http://myproxy.example.com"))
NOTE: these values are completely overwritten each time you call
client$httr_config()
, so ensure that you pass all desired values at the same time
Suffice it to say that effectively using Kerberos for HTTP is a bit of an
advanced topic. However, it is possible with httr
.
It is worth noting that today, this interferes with API key authentication, which we are hoping to improve in a future release of Posit Connect.
# disables authentication header that is included by default client$using_auth = FALSE # use Kerberos authentication mechanism (requires local credential cache) client$httr_config(httr::authenticate(":", "", type="gssnegotiate"))
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