cache_info() gives details of cacheability of a response,
rerequest() re-performs the original request doing as little work
as possible (if not expired, returns response as is, or performs
revalidation if Etag or Last-Modified headers are present).
Examples
# Never cached, always causes redownload
r1 <- GET("https://www.google.com")
cache_info(r1)
#> <cache_info> https://www.google.com/
#> Cacheable: TRUE
#> Expires: Tue, 15 Aug 2023 18:20:32 GMT <expired>
#> Last-Modified:
#> Etag:
r1$date
#> [1] "2023-08-15 18:20:32 GMT"
rerequest(r1)$date
#> [1] "2023-08-15 18:20:32 GMT"
# Expires in a year
r2 <- GET("https://www.google.com/images/srpr/logo11w.png")
cache_info(r2)
#> <cache_info> https://www.google.com/images/srpr/logo11w.png
#> Cacheable: TRUE
#> Expires: Wed, 14 Aug 2024 18:20:33 GMT
#> Last-Modified: Tue, 22 Oct 2019 18:30:00 GMT
#> Etag:
r2$date
#> [1] "2023-08-15 18:20:33 GMT"
rerequest(r2)$date
#> [1] "2023-08-15 18:20:33 GMT"
if (FALSE) {
# Has last-modified and etag, so does revalidation
r3 <- GET("http://httpbin.org/cache")
cache_info(r3)
r3$date
rerequest(r3)$date
# Expires after 5 seconds
r4 <- GET("http://httpbin.org/cache/5")
cache_info(r4)
r4$date
rerequest(r4)$date
Sys.sleep(5)
cache_info(r4)
rerequest(r4)$date
}