On 12/09/2006 06:52 AM, Roy T. Fielding wrote:
>
> The best solution is to not mess with content-encoding at all, which
> gets us out of both this consistency problem and related problems
> with the entity-header fields (content-md5, signatures, etc.).
> That is why transfer encoding was invented in the first place.
>
> We should have an implementation of deflate as a transfer encoding,
> but it should be configurable independent of the existing filter.
> Some people will want TE specifically to avoid the addition of Vary
> and all the other problems that content-changing filters cause.
> For example, an additional directive option for CE, TE, or "either".
I think fixing the current CE filter is easier right now then to
add the option above. I think this can be done in a second step
and sounds like a good idea to me.
>
> The existing filter needs to modify the ETag field value (and
> any other entity-dependent values that we can think of) or be
> removed as a feature. Weak etags are not a solution -- being able
> to make range requests of large cached representations requires a
> strong etag, and it really isn't hard to provide one. It is better
> to not deflate the response at all than to interfere with caching.
Would the following patch address all your points for a CE mod_deflate filter?
Index: modules/filters/mod_deflate.c
===================================================================
--- modules/filters/mod_deflate.c (Revision 484803)
+++ modules/filters/mod_deflate.c (Arbeitskopie)
@@ -320,6 +320,7 @@
if (!ctx) {
char *token;
const char *encoding;
+ const char *etag;
/* only work on main request/no subrequests */
if (r->main != NULL) {
@@ -483,7 +484,26 @@
else {
apr_table_mergen(r->headers_out, "Content-Encoding", "gzip");
}
+ /*
+ * Unset headers which are no longer valid after we have compressed
+ * the content.
+ */
apr_table_unset(r->headers_out, "Content-Length");
+ apr_table_unset(r->headers_out, "Content-MD5");
+ /* Adjust ETag if present */
+ etag = apr_table_get(r->headers_out, "ETag");
+ if (etag) {
+ if (*etag) {
+ /* Remove the '"' at the end of the ETag */
+ etag[strlen(etag) - 1] = '\0';
+ apr_table_set(r->headers_out, "ETag",
+ apr_pstrcat(r->pool, etag, "-gzip\"", NULL));
+ }
+ else {
+ /* Does not seem to be a valid ETag. So remove it. */
+ apr_table_unset(r->headers_out, "ETag");
+ }
+ }
/* initialize deflate output buffer */
ctx->stream.next_out = ctx->buffer;
Regards
Rüdiger
