Stats to file (twitter#186)

* add support for logging stats (in CSV format with each entry as name:value) to a file

include/cc_stats_log.h

@@ -0,0 +1,38 @@
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <cc_metric.h>
+#include <cc_option.h>
+
+
+#define STATS_LOG_FILE  NULL    /* default log file */
+#define STATS_LOG_NBUF  0       /* default log buf size */
+
+/*          name            type              default           description */
+#define STATSLOG_OPTION(ACTION)                                                         \
+    ACTION( stats_log_file, OPTION_TYPE_STR,  NULL,             "file storing stats"   )\
+    ACTION( stats_log_nbuf, OPTION_TYPE_UINT, STATS_LOG_NBUF,   "stats log buf size"   )
+
+typedef struct {
+    STATSLOG_OPTION(OPTION_DECLARE)
+} stats_log_options_st;
+
+
+/* dump stats as CSV records into a log file, this allows metrics to be captured
+ * locally without setting up an observability infrastructure
+ */
+void stats_log_setup(stats_log_options_st *options);
+void stats_log_teardown(void);
+
+void stats_log(struct metric metrics[], unsigned int nmetric);
+
+void stats_log_flush(void);
+
+
+#ifdef __cplusplus
+}
+#endif
+

src/cc_debug.c

@@ -20,7 +20,6 @@
 #include <cc_log.h>
 #include <cc_mm.h>
 #include <cc_print.h>
-#include <time/cc_wheel.h>
 
 #include <ctype.h>
 #include <errno.h>

src/stats/CMakeLists.txt

@@ -1,4 +1,5 @@
 set(SOURCE
     ${SOURCE}
     stats/cc_metric.c
+    stats/cc_stats_log.c
     PARENT_SCOPE)

src/stats/cc_stats_log.c

@@ -0,0 +1,88 @@
+#include <cc_stats_log.h>
+
+#include <cc_debug.h>
+#include <cc_log.h>
+#include <cc_metric.h>
+
+#define STATS_LOG_MODULE_NAME "util::stats_log"
+#define STATS_LOG_FMT "%s: %s, "
+#define PRINT_BUF_LEN 64
+
+static struct logger *slog = NULL;
+static bool stats_log_init = false;
+
+static char buf[PRINT_BUF_LEN];
+
+
+void
+stats_log_setup(stats_log_options_st *options)
+{
+    size_t log_nbuf = STATS_LOG_NBUF;
+    char *filename = STATS_LOG_FILE;
+
+    log_info("set up the %s module", STATS_LOG_MODULE_NAME);
+
+    if (stats_log_init) {
+        log_warn("%s has already been setup, overwrite", STATS_LOG_MODULE_NAME);
+        if (slog != NULL) {
+            log_destroy(&slog);
+        }
+    }
+
+    if (options != NULL) {
+        filename = option_str(&options->stats_log_file);
+        log_nbuf = option_uint(&options->stats_log_nbuf);
+    }
+
+    if (filename != NULL) {
+        slog = log_create(filename, log_nbuf);
+        if (slog == NULL) {
+            log_warn("Could not create logger");
+        }
+    }
+
+    stats_log_init = true;
+}
+
+void
+stats_log_teardown(void)
+{
+    log_info("tear down the %s module", STATS_LOG_MODULE_NAME);
+
+    if (!stats_log_init) {
+        log_warn("%s has never been setup", STATS_LOG_MODULE_NAME);
+    }
+
+    if (slog != NULL) {
+        log_destroy(&slog);
+    }
+
+    stats_log_init = false;
+}
+
+void
+stats_log(struct metric metrics[], unsigned int nmetric)
+{
+    unsigned int i;
+
+    if (slog == NULL) {
+        return;
+    }
+
+    for (i = 0; i < nmetric; i++, metrics++) {
+        int len = 0;
+
+        len = metric_print(buf, PRINT_BUF_LEN, STATS_LOG_FMT, metrics);
+        log_write(slog, buf, len);
+    }
+}
+
+void
+stats_log_flush(void)
+{
+    if (slog == NULL) {
+        return;
+    }
+    log_flush(slog);
+}
+