From e619f51c8778847c3acb3ad01f5b8b60d44c2caa Mon Sep 17 00:00:00 2001
From: David McGrew <mcgrew@cisco.com>
Date: Wed, 12 May 2021 13:59:04 -0400
Subject: [PATCH] adding file name rotation to stats output

---
 src/Makefile.in |  1 +
 src/control.h   | 21 ++++++++++++++-----
 src/mercury.c   |  2 +-
 src/rotator.h   | 56 +++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 74 insertions(+), 6 deletions(-)
 create mode 100644 src/rotator.h

diff --git a/src/Makefile.in b/src/Makefile.in
index 8cec8475..ca31b97a 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -91,6 +91,7 @@ MERC_H += pkt_processing.h
 MERC_H += pcap_file_io.h
 MERC_H += pcap_reader.h
 MERC_H += rnd_pkt_drop.h
+MERC_H += rotator.h
 MERC_H += signal_handling.h
 
 MERC_OBJ = $(MERCC:%.cc=%.o) $(MERC:%.c=%.o)
diff --git a/src/control.h b/src/control.h
index d48b8ecf..eb872d25 100644
--- a/src/control.h
+++ b/src/control.h
@@ -9,6 +9,7 @@
 #include <unistd.h>
 #include <string>
 #include <atomic>
+#include "rotator.h"
 #include "libmerc/libmerc.h"
 
 class controller {
@@ -18,11 +19,12 @@ class controller {
                const char *stats_filename,
                size_t num_secs) :
         mc{merc_ctx},
-        stats_file{stats_filename},
+        stats_file{stats_filename, ".json.gz"},
         num_secs_between_writes{num_secs},
         count{num_secs},
         controller_thread{},
-        shutdown_requested{false}
+        shutdown_requested{false},
+        has_run_at_least_once{false}
     {
         if (mc == nullptr) {
             throw "error: null mercury context passed to control thread";
@@ -35,19 +37,22 @@ class controller {
     }
 
 private:
+
     mercury_context mc;
-    std::string stats_file;
+    rotator stats_file;
     size_t num_secs_between_writes;
     size_t count;
     std::thread controller_thread;
     std::atomic<bool> shutdown_requested;
+    bool has_run_at_least_once;
 
     void run_tasks() {
         while (shutdown_requested.load() == false) {
             if (count == 0) {
                 count = num_secs_between_writes;
-                if (mercury_write_stats_data(mc, stats_file.c_str()) == false) {
-                    fprintf(stderr, "error: could not write stats file %s\n", stats_file.c_str());
+                const char *fname = stats_file.get_next_name();
+                if (mercury_write_stats_data(mc, fname) == false) {
+                    fprintf(stderr, "error: could not write stats file %s\n", fname);
                 }
             }
             --count;
@@ -64,6 +69,12 @@ class controller {
         if(controller_thread.joinable()) {
             controller_thread.join();
         }
+        if (!has_run_at_least_once) {
+            const char *fname = stats_file.get_current_name();
+            if (mercury_write_stats_data(mc, fname) == false) {
+                fprintf(stderr, "error: could not write stats file %s\n", fname);
+            }
+        }
     }
 
 };
diff --git a/src/mercury.c b/src/mercury.c
index 8dc37519..f301aa2f 100644
--- a/src/mercury.c
+++ b/src/mercury.c
@@ -541,7 +541,7 @@ int main(int argc, char *argv[]) {
 
     controller *ctl = nullptr;
     if (cfg.stats_filename) {
-        ctl = new controller{mc, "mercury-stats.json.gz", 2};
+        ctl = new controller{mc, cfg.stats_filename, 30};
     }
 
     pthread_t output_thread;
diff --git a/src/rotator.h b/src/rotator.h
new file mode 100644
index 00000000..be55ea72
--- /dev/null
+++ b/src/rotator.h
@@ -0,0 +1,56 @@
+// rotator.h
+//
+// file name rotation
+
+#ifndef ROTATOR_H
+#define ROTATOR_H
+
+#include <string>
+
+class rotator {
+public:
+
+    rotator(const char *filename,
+            const char *filename_extension=nullptr) :
+        file_number{0},
+        base_name{filename},
+        extension{filename_extension},
+        file_name{filename}
+    {
+        file_name.append(extension);
+    }
+
+    const char *get_next_name() {
+        /*
+         * create filename that includes sequence number and date/timestamp
+         */
+        file_name = base_name;
+
+        char file_num[MAX_HEX];
+        snprintf(file_num, MAX_HEX, "%x", file_number++);
+        file_name.append("-").append(file_num);
+
+        char time_str[128];
+        struct timeval now;
+        gettimeofday(&now, NULL);
+        strftime(time_str, sizeof(time_str) - 1, "%Y-%m-%d-%H-%M-%S", localtime(&now.tv_sec));
+        file_name.append("-").append(time_str);
+
+        file_name.append(extension);
+
+        return file_name.c_str();
+    }
+
+    const char *get_current_name() const {
+        return file_name.c_str();
+    }
+
+private:
+    unsigned int file_number;
+    std::string base_name;   // prefix common to all files
+    std::string extension;   // extension, if any
+    std::string file_name;   // name of current file
+
+};
+
+#endif // ROTATOR_H