Re: HTTP Miss Reason: has_if_unmodified_since

peterjmonaghan · ‎12-08-2004

Hello,

The majority of my Content Engines HTTP requests misses miss-reason is has_if_unmodified_since. What does this mean and is it possible to fix?

YH0PCE01#show statistics http savings

Statistics - Savings

Requests Bytes

-----------------------------------------------------------

Total: 85948 335283777

Miss: 68646 261559801

Savings: 20.1 % 22.0 %

H0PCE01#show statistics http miss-reason

Statistics - No hit reasons

Reason: No. of Requests

---------------------------------------------------

not_in_cache: 10502

dmbuf_low: 0

none_get_method: 3519

ftp_not_anonymous: 0

http_not_anonymous: 0

suspicious_url: 0

ie_5_ims: 0

has_if_match: 0

has_invalid_if_range: 0

has_if_unmodified_since: 48200

has_invalid_range: 0

has_more_than_supported_range: 0

has_pragma_no_cache: 4624

has_authorization: 2488

has_cache_control_no_cache: 93

is_https: 2548

invalid_ims: 0

cert_check_fail: 196

second_validation: 101

invalid_ims_reply: 1785

ims_200_reply: 562

xfs_open_error: 21

has_unknown_length_transfer_pending: 10

object_in_cache_older_than_clients: 175

object_in_cache_expired_cannot_verified: 1590

different_protocol: 0

other_error: 655

seilsz · ‎12-08-2004

Hi -

From RFC2616:

"The If-Unmodified-Since request-header field is used with a method to make it conditional. If the requested resource has not been modified since the time specified in this field, the server SHOULD perform the requested operation as if the If-Unmodified-Since header were not present.

If the requested variant has been modified since the specified time, the server MUST NOT perform the requested operation, and MUST return a 412 (Precondition Failed)."

So basically, the CE receives a request from the client with IUS set, but the Last-Modified date of the requested content (in the cache) is greater than the date specified by the IUS. This causes the CE to log a "miss" and return a HTTP 412 to the client.

I don't know of a way to configure the CE to behave differently.

~Zach