[mod_accesslog] %{ratio}n logs compression ratio (fixes #2133)

mod_deflate and mod_compress now provide data for mod_accesslog
"%{ratio}n%%" log format to log compression ratio

Implementation detail: compression ratio is stored in con->environment
since lighttpd does not currently have concept of module notes, which is
from where %{VARNAME}n originates.  In the future, this might change in
lighttpd, so be sure to use %{ratio}n%% and not %{...}e for this info.

x-ref:
  "accesslog support "%n" (compress ratio)"
  https://redmine.lighttpd.net/issues/2133

src/mod_accesslog.c

@@ -57,7 +57,8 @@ typedef struct {
 			FORMAT_BYTES_OUT,
 
 			FORMAT_KEEPALIVE_COUNT,
-			FORMAT_RESPONSE_HEADER
+			FORMAT_RESPONSE_HEADER,
+			FORMAT_NOTE
 	} type;
 } format_mapping;
 
@@ -90,7 +91,7 @@ static const format_mapping fmap[] =
 	{ 'H', FORMAT_REQUEST_PROTOCOL },
 	{ 'k', FORMAT_KEEPALIVE_COUNT },
 	{ 'm', FORMAT_REQUEST_METHOD },
-	{ 'n', FORMAT_UNSUPPORTED }, /* we have no notes */
+	{ 'n', FORMAT_NOTE },
 	{ 'p', FORMAT_SERVER_PORT },
 	{ 'P', FORMAT_UNSUPPORTED }, /* we are only one process */
 	{ 'q', FORMAT_QUERY_STRING },
@@ -942,6 +943,7 @@ REQUESTDONE_FUNC(log_access_write) {
 				}
 				break;
 			case FORMAT_ENV:
+			case FORMAT_NOTE:
 				if (NULL != (ds = (data_string *)array_get_element(con->environment, f->string->ptr))) {
 					accesslog_append_escaped(b, ds->value);
 				} else {

src/mod_compress.c

@@ -434,6 +434,20 @@ static int deflate_file_to_buffer_bzip2(server *srv, connection *con, plugin_dat
 }
 #endif
 
+static void mod_compress_note_ratio(server *srv, connection *con, off_t in, off_t out) {
+    /* store compression ratio in con->environment
+     * for possible logging by mod_accesslog
+     * (late in response handling, so not seen by most other modules) */
+    /*(should be called only at end of successful response compression)*/
+    char ratio[LI_ITOSTRING_LENGTH];
+    if (0 == in) return;
+    li_itostrn(ratio, sizeof(ratio), out * 100 / in);
+    array_set_key_value(con->environment,
+                        CONST_STR_LEN("ratio"),
+                        ratio, strlen(ratio));
+    UNUSED(srv);
+}
+
 static int deflate_file_to_file(server *srv, connection *con, plugin_data *p, buffer *fn, stat_cache_entry *sce, int type) {
 	int ifd, ofd;
 	int ret;
@@ -442,6 +456,7 @@ static int deflate_file_to_file(server *srv, connection *con, plugin_data *p, bu
 #endif
 	void *start;
 	const char *filename = fn->ptr;
+	stat_cache_entry *sce_ofn;
 	ssize_t r;
 
 	/* overflow */
@@ -483,6 +498,17 @@ static int deflate_file_to_file(server *srv, connection *con, plugin_data *p, bu
 
 	buffer_append_string_buffer(p->ofn, sce->etag);
 
+	if (HANDLER_ERROR != stat_cache_get_entry(srv, con, p->ofn, &sce_ofn)) {
+		if (0 == sce->st.st_size) return -1; /* cache file being created */
+		/* cache-entry exists */
+#if 0
+		log_error_write(srv, __FILE__, __LINE__, "bs", p->ofn, "compress-cache hit");
+#endif
+		mod_compress_note_ratio(srv, con, sce->st.st_size, sce_ofn->st.st_size);
+		buffer_copy_buffer(con->physical.path, p->ofn);
+		return 0;
+	}
+
 	if (-1 == mkdir_for_file(p->ofn->ptr)) {
 		log_error_write(srv, __FILE__, __LINE__, "sb", "couldn't create directory for file", p->ofn);
 		return -1;
@@ -490,13 +516,7 @@ static int deflate_file_to_file(server *srv, connection *con, plugin_data *p, bu
 
 	if (-1 == (ofd = open(p->ofn->ptr, O_WRONLY | O_CREAT | O_EXCL | O_BINARY, 0600))) {
 		if (errno == EEXIST) {
-			/* cache-entry exists */
-#if 0
-			log_error_write(srv, __FILE__, __LINE__, "bs", p->ofn, "compress-cache hit");
-#endif
-			buffer_copy_buffer(con->physical.path, p->ofn);
-
-			return 0;
+			return -1; /* cache file being created */
 		}
 
 		log_error_write(srv, __FILE__, __LINE__, "sbss", "creating cachefile", p->ofn, "failed", strerror(errno));
@@ -612,6 +632,8 @@ static int deflate_file_to_file(server *srv, connection *con, plugin_data *p, bu
 	}
 
 	buffer_copy_buffer(con->physical.path, p->ofn);
+	mod_compress_note_ratio(srv, con, sce->st.st_size,
+				(off_t)buffer_string_length(p->b));
 
 	return 0;
 }
@@ -699,6 +721,8 @@ static int deflate_file_to_buffer(server *srv, connection *con, plugin_data *p,
 
 	if (ret != 0) return -1;
 
+	mod_compress_note_ratio(srv, con, sce->st.st_size,
+				(off_t)buffer_string_length(p->b));
 	chunkqueue_reset(con->write_queue);
 	chunkqueue_append_buffer(con->write_queue, p->b);
 

src/mod_deflate.c

@@ -647,6 +647,20 @@ static int mod_deflate_stream_flush(server *srv, connection *con, handler_ctx *h
 	}
 }
 
+static void mod_deflate_note_ratio(server *srv, connection *con, handler_ctx *hctx) {
+    /* store compression ratio in con->environment
+     * for possible logging by mod_accesslog
+     * (late in response handling, so not seen by most other modules) */
+    /*(should be called only at end of successful response compression)*/
+    char ratio[LI_ITOSTRING_LENGTH];
+    if (0 == hctx->bytes_in) return;
+    li_itostrn(ratio, sizeof(ratio), hctx->bytes_out * 100 / hctx->bytes_in);
+    array_set_key_value(con->environment,
+                        CONST_STR_LEN("ratio"),
+                        ratio, strlen(ratio));
+    UNUSED(srv);
+}
+
 static int mod_deflate_stream_end(server *srv, handler_ctx *hctx) {
 	switch(hctx->compression_type) {
 #ifdef USE_ZLIB
@@ -679,9 +693,6 @@ static void deflate_compress_cleanup(server *srv, connection *con, handler_ctx *
 	}
       #endif
 
-	/* future: might store ((double)hctx->bytes_out / hctx->bytes_in)
-	 * in con->environment, for possible logging by mod_accesslog */
-
 	handler_ctx_free(hctx);
 }
 
@@ -1190,6 +1201,9 @@ CONNECTION_FUNC(mod_deflate_handle_response_start) {
 
 	rc = deflate_compress_response(srv, con, hctx);
 	if (HANDLER_GO_ON != rc) {
+		if (HANDLER_FINISHED == rc) {
+			mod_deflate_note_ratio(srv, con, hctx);
+		}
 		deflate_compress_cleanup(srv, con, hctx);
 		if (HANDLER_ERROR == rc) return HANDLER_ERROR;
 	}