MINOR: stats: parse header lines from stats-file

This patch implements parsing of headers line from stats-file.

A header line is defined as starting with '#' character. It is directly
followed by a domain name. For the moment, either 'fe' or 'be' is
allowed. The following lines will contain counters values relatives to
the domain context until the next header line.

This is implemented via static function parse_header_line(). It first
sets the domain context used during apply_stats_file(). A stats column
array is generated to contains the order on which column are stored.
This will be reused to parse following lines values.

If an invalid line is found and no header was parsed, considered the
stats-file as ill formatted and stop parsing. This allows to immediately
interrupt parsing if a garbage file was used without emitting a ton of
warnings to the user.

include/haproxy/stats-file-t.h

@@ -0,0 +1,12 @@
+#ifndef _HAPROXY_STATS_FILE_T_H
+#define _HAPROXY_STATS_FILE_T_H
+
+/* Sections present in stats-file separated by header lines. */
+enum stfile_domain {
+	STFILE_DOMAIN_UNSET = 0,
+
+	STFILE_DOMAIN_PX_FE,  /* #fe headers */
+	STFILE_DOMAIN_PX_BE,  /* #be headers */
+};
+
+#endif /* _HAPROXY_STATS_FILE_T_H */

include/haproxy/stats-file.h

@@ -1,6 +1,8 @@
 #ifndef _HAPROXY_STATS_FILE_H
 #define _HAPROXY_STATS_FILE_H
 
+#include <haproxy/stats-file-t.h>
+
 #include <sys/types.h>
 
 #include <haproxy/buf-t.h>

src/stats-file.c

@@ -5,6 +5,8 @@
 #include <string.h>
 
 #include <import/ebmbtree.h>
+#include <import/ebsttree.h>
+#include <import/ist.h>
 #include <haproxy/api.h>
 #include <haproxy/buf.h>
 #include <haproxy/chunk.h>
@@ -98,11 +100,103 @@ void stats_dump_file_header(int type, struct buffer *out)
 	chunk_strcat(out, "\n");
 }
 
+/* Parse an identified header line <header> starting with '#' character.
+ *
+ * If the section is recognized, <domain> will point to the current stats-file
+ * scope. <cols> will be filled as a matrix to identify each stat_col position
+ * using <st_tree> as prefilled proxy stats columns. If stats-file section is
+ * unknown, only <domain> will be set to STFILE_DOMAIN_UNSET.
+ *
+ * Returns 0 on sucess. On fatal error, non-zero is returned and parsing shoud
+ * be interrupted.
+ */
+static int parse_header_line(struct ist header, struct eb_root *st_tree,
+                             enum stfile_domain *domain,
+                             const struct stat_col *cols[])
+{
+	enum stfile_domain dom = STFILE_DOMAIN_UNSET;
+	struct ist token;
+	char last;
+	int i;
+
+	header = iststrip(header);
+	last = istptr(header)[istlen(header) - 1];
+	token = istsplit(&header, ' ');
+
+	/* A header line is considered valid if:
+	 * - a space delimiter is found and first token is several chars
+	 * - last line character must be a comma separator
+	 */
+	if (!istlen(header) || istlen(token) == 1 || last != ',')
+		goto err;
+
+	if (isteq(token, ist("#fe")))
+		dom = STFILE_DOMAIN_PX_FE;
+	else if (isteq(token, ist("#be")))
+		dom = STFILE_DOMAIN_PX_BE;
+
+	/* Remove 'guid' field. */
+	token = istsplit(&header, ',');
+	if (!isteq(token, ist("guid"))) {
+		/* Fatal error if FE/BE domain without guid token. */
+		if (dom == STFILE_DOMAIN_PX_FE || dom == STFILE_DOMAIN_PX_BE)
+			goto err;
+	}
+
+	/* Unknown domain. Following lines should be ignored until next header. */
+	if (dom == STFILE_DOMAIN_UNSET)
+		return 0;
+
+	/* Generate matrix of stats column into cols[]. */
+	memset(cols, 0, sizeof(void *) * STAT_FILE_MAX_COL_COUNT);
+
+	i = 0;
+	while (istlen(header) && i < STAT_FILE_MAX_COL_COUNT) {
+		struct stcol_node *col_node;
+		const struct stat_col *col;
+		struct ebmb_node *node;
+
+		/* Lookup column by its name into <st_tree>. */
+		token = istsplit(&header, ',');
+		node = ebst_lookup(st_tree, ist0(token));
+		if (!node) {
+			++i;
+			continue;
+		}
+
+		col_node = ebmb_entry(node, struct stcol_node, name);
+		col = col_node->col;
+
+		/* Ignore column if its cap is not valid with current stats-file section. */
+		if ((dom == STFILE_DOMAIN_PX_FE &&
+		    !(col->cap & (STATS_PX_CAP_FE|STATS_PX_CAP_LI))) ||
+		    (dom == STFILE_DOMAIN_PX_BE &&
+		     !(col->cap & (STATS_PX_CAP_BE|STATS_PX_CAP_SRV)))) {
+			++i;
+			continue;
+		}
+
+		cols[i] = col;
+		++i;
+	}
+
+	*domain = dom;
+	return 0;
+
+ err:
+	*domain = STFILE_DOMAIN_UNSET;
+	return 1;
+}
+
 /* Parse a stats-file and preload haproxy internal counters. */
 void apply_stats_file(void)
 {
+	const struct stat_col *cols[STAT_FILE_MAX_COL_COUNT];
 	struct eb_root st_tree = EB_ROOT;
+	enum stfile_domain domain;
+	int valid_format = 0;
 	FILE *file;
+	struct ist istline;
 	char *line = NULL;
 	ssize_t len;
 	size_t alloc_len;
@@ -124,14 +218,38 @@ void apply_stats_file(void)
 	}
 
 	linenum = 0;
+	domain = STFILE_DOMAIN_UNSET;
 	while (1) {
 		len = getline(&line, &alloc_len, file);
 		if (len < 0)
 			break;
 
 		++linenum;
-		if (!len || (len == 1 && line[0] == '\n'))
+		istline = iststrip(ist2(line, len));
+		if (!istlen(istline))
 			continue;
+
+		if (*istptr(istline) == '#') {
+			if (parse_header_line(istline, &st_tree, &domain, cols)) {
+				if (!valid_format) {
+					ha_warning("config: Invalid stats-file format.\n");
+					break;
+				}
+
+				ha_warning("config: Ignored stats-file header line '%d'.\n", linenum);
+			}
+
+			valid_format = 1;
+		}
+		else if (domain == STFILE_DOMAIN_UNSET) {
+			/* Stop parsing if first line is not a valid header.
+			 * Allows to immediately stop reading garbage file.
+			 */
+			if (!valid_format) {
+				ha_warning("config: Invalid stats-file format.\n");
+				break;
+			}
+		}
 	}
 
  out: