MINOR: stats: prepare stats-file support for values other than FN_COUNTER

Currently, only FN_COUNTER are dumped and preloaded via a stats-file.
Thus in several places we relied on the assumption that only FN_COUNTER
are valid in stats-file context.

New stats types will soon be implemented as they are also eligilible to
statistics reloading on process startup. Thus, prepare stats-file
functions to remove any FN_COUNTER restriction.

As one of this change, generate_stat_tree() now uses stcol_is_generic()
for stats name tree indexing before stats-file parsing.

Also related to stats-file parsing, individual counter preloading step
as been extracted from line parsing in a dedicated new function
load_ctr(). This will allow to extend it to support multiple mechanism
of counter preloading depending on the stats type.

include/haproxy/stats.h

@@ -74,6 +74,12 @@ int stats_emit_field_tags(struct buffer *out, const struct field *f,
 			  char delim);
 
 
+/* Returns true if <col> is fully defined, false if only used as name-desc. */
+static inline int stcol_is_generic(const struct stat_col *col)
+{
+	return !!(col->cap);
+}
+
 static inline enum field_format stcol_format(const struct stat_col *col)
 {
 	return col->type & FF_MASK;

src/stats-file.c

@@ -85,16 +85,20 @@ void stats_dump_file_header(int type, struct buffer *out)
 		chunk_strcat(out, "#fe guid,");
 		for (i = 0; i < ST_I_PX_MAX; ++i) {
 			col = &stat_cols_px[i];
-			if (stcol_nature(col) == FN_COUNTER && (col->cap & (STATS_PX_CAP_FE|STATS_PX_CAP_LI)))
+			if (stcol_is_generic(col) &&
+			    col->cap & (STATS_PX_CAP_FE|STATS_PX_CAP_LI)) {
 				chunk_appendf(out, "%s,", col->name);
+			}
 		}
 	}
 	else {
 		chunk_appendf(out, "#be guid,");
 		for (i = 0; i < ST_I_PX_MAX; ++i) {
 			col = &stat_cols_px[i];
-			if (stcol_nature(col) == FN_COUNTER && (col->cap & (STATS_PX_CAP_BE|STATS_PX_CAP_SRV)))
+			if (stcol_is_generic(col) &&
+			    col->cap & (STATS_PX_CAP_BE|STATS_PX_CAP_SRV)) {
 				chunk_appendf(out, "%s,", col->name);
+			}
 		}
 	}
 
@@ -189,6 +193,44 @@ static int parse_header_line(struct ist header, struct eb_root *st_tree,
 	return 1;
 }
 
+/* Preload an individual counter instance stored at <counter> with <token>
+ * value> for the <col> stat column.
+ *
+ * Returns 0 on success else non-zero if counter was not updated.
+ */
+static int load_ctr(const struct stat_col *col, const struct ist token,
+                    void* counter)
+{
+	const enum field_nature fn = stcol_nature(col);
+	const enum field_format ff = stcol_format(col);
+	const char *ptr = istptr(token);
+	struct field value;
+
+	switch (ff) {
+	case FF_U64:
+		value.u.u64 = read_uint64(&ptr, istend(token));
+		break;
+
+	default:
+		/* Unsupported field nature. */
+		return 1;
+	}
+
+	/* Do not load value if non numeric characters present. */
+	if (ptr != istend(token))
+		return 1;
+
+	if (fn == FN_COUNTER && ff == FF_U64) {
+		*(uint64_t *)counter = value.u.u64;
+	}
+	else {
+		/* Unsupported field format/nature combination. */
+		return 1;
+	}
+
+	return 0;
+}
+
 /* Parse a non header stats-file line <line>. Specify current parsing <domain>
  * and <cols> stats column matrix derived from the last header line.
  *
@@ -269,7 +311,6 @@ static int parse_stat_line(struct ist line,
 	i = 0;
 	while (istlen(line) && i < STAT_FILE_MAX_COL_COUNT) {
 		const struct stat_col *col = cols[i++];
-		enum field_format ff;
 
 		token = istsplit(&line, ',');
 		if (!istlen(token))
@@ -278,19 +319,7 @@ static int parse_stat_line(struct ist line,
 		if (!col)
 			continue;
 
-		ff = stcol_format(col);
+		load_ctr(col, token, base_off + col->metric.offset[off]);
-		if (ff == FF_U64) {
-			uint64_t *offset, value;
-			const char *ptr;
-
-			ptr = istptr(token);
-			value = read_uint64(&ptr, istend(token));
-			/* Do not load value if non numeric characters present. */
-			if (ptr == istend(token)) {
-				offset = (uint64_t *)(base_off + col->metric.offset[off]);
-				*offset = value;
-			}
-		}
 	}
 
 	return 0;

src/stats.c

@@ -92,12 +92,6 @@
     .cap = (cap_f),                                                           \
   }
 
-/* Returns true if <col> is fully defined, false if only used as name-desc. */
-static int stcol_is_generic(const struct stat_col *col)
-{
-	return !!(col->cap);
-}
-
 /* Convert stat_col <col> to old-style <name> as name_desc. */
 static void stcol2ndesc(struct name_desc *name, const struct stat_col *col)
 {
@@ -338,7 +332,7 @@ struct list stats_module_list[STATS_DOMAIN_COUNT] = {
 
 THREAD_LOCAL void *trash_counters;
 
-/* Insert into <st_tree> all stat columns from <cols> indexed by their name. */
+/* Insert <cols> generic stat columns into <st_tree> indexed by their name. */
 int generate_stat_tree(struct eb_root *st_tree, const struct stat_col cols[])
 {
 	const struct stat_col *col;
@@ -348,7 +342,8 @@ int generate_stat_tree(struct eb_root *st_tree, const struct stat_col cols[])
 
 	for (i = 0; i < ST_I_PX_MAX; ++i) {
 		col = &cols[i];
-		if (stcol_nature(col) == FN_COUNTER) {
+
+		if (stcol_is_generic(col)) {
 			len = strlen(col->name);
 			node = malloc(sizeof(struct stcol_node) + len + 1);
 			if (!node)
@@ -739,6 +734,7 @@ static struct field me_generate_field(const struct stat_col *col,
                                       const void *counters, uint8_t cap,
                                       int stat_file)
 {
+	enum field_nature fn;
 	struct field value;
 	void *counter = NULL;
 	int wrong_side = 0;
@@ -794,12 +790,19 @@ static struct field me_generate_field(const struct stat_col *col,
 			return (struct field){ .type = FF_EMPTY };
 	}
 
-	switch (stcol_format(col)) {
+	fn = stcol_nature(col);
-	case FF_U64:
+	if (fn == FN_COUNTER) {
-		value = mkf_u64(stcol_nature(col), *(uint64_t *)counter);
+		switch (stcol_format(col)) {
-		break;
+		case FF_U64:
-	default:
+			value = mkf_u64(FN_COUNTER, *(uint64_t *)counter);
-		/* only FF_U64 counters currently use generic metric calculation */
+			break;
+		default:
+			/* only FF_U64 counters currently use generic metric calculation */
+			ABORT_NOW();
+		}
+	}
+	else {
+		/* No generic column available for other field nature. */
 		ABORT_NOW();
 	}