logging: Fix a bug in ringbuffer

When ringbuffer is full, it does not return any entries.  Simplify
ringbuffer logic by keeping track of number of log entries rather than
last entry.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Pair-Programmed-With: Martin Schwenke <martin@meltin.net>

diff --git a/common/ctdb_logging.c b/common/ctdb_logging.c
index de5ca6e68f6641d62ded3b9749e9987e2a6a9e47..339198b013f1894d86f83399a2849b393bafb633 100644 (file)
--- a/common/ctdb_logging.c
+++ b/common/ctdb_logging.c
@@ -27,8 +27,8 @@ int log_ringbuf_size;
 
 #define MAX_LOG_SIZE 128
 
-static int first_entry;
-static int last_entry;
+static int first_entry = 0;
+static int ringbuf_count = 0;
 
 struct ctdb_log_entry {
        int32_t level;
@@ -45,6 +45,7 @@ static struct ctdb_log_entry *log_entries;
 static void log_ringbuffer_v(const char *format, va_list ap)
 {
        int ret;
+       int next_entry;
 
        if (log_entries == NULL && log_ringbuf_size != 0) {
                /* Hope this works. We cant log anything if it doesnt anyway */
@@ -54,25 +55,24 @@ static void log_ringbuffer_v(const char *format, va_list ap)
                return;
        }
 
-       log_entries[last_entry].message[0] = '\0';
+       next_entry = (first_entry + ringbuf_count) % log_ringbuf_size;
 
-       ret = vsnprintf(&log_entries[last_entry].message[0], MAX_LOG_SIZE, format, ap);
+       if (ringbuf_count > 0 && first_entry == next_entry) {
+               first_entry = (first_entry + 1) % log_ringbuf_size;
+       }
+
+       log_entries[next_entry].message[0] = '\0';
+
+       ret = vsnprintf(&log_entries[next_entry].message[0], MAX_LOG_SIZE, format, ap);
        if (ret == -1) {
                return;
        }
 
-       log_entries[last_entry].level = this_log_level;
-       log_entries[last_entry].t = timeval_current();
+       log_entries[next_entry].level = this_log_level;
+       log_entries[next_entry].t = timeval_current();
 
-       last_entry++;
-       if (last_entry >= log_ringbuf_size) {
-               last_entry = 0;
-       }
-       if (first_entry == last_entry) {
-               first_entry++;
-       }
-       if (first_entry >= log_ringbuf_size) {
-               first_entry = 0;
+       if (ringbuf_count < log_ringbuf_size) {
+               ringbuf_count++;
        }
 }
 
@@ -100,8 +100,11 @@ void ctdb_collect_log(struct ctdb_context *ctdb, struct ctdb_get_log_addr *log_a
        FILE *f;
        long fsize;
        int tmp_entry;
-       int count = 0;
-       DEBUG(DEBUG_ERR,("Marshalling log entries  first:%d last:%d\n", first_entry, last_entry));
+       struct tm *tm;
+       char tbuf[100];
+       int i;
+
+       DEBUG(DEBUG_ERR,("Marshalling %d log entries\n", ringbuf_count));
 
        /* dump to a file, then send the file as a blob */
        f = tmpfile();
@@ -110,20 +113,10 @@ void ctdb_collect_log(struct ctdb_context *ctdb, struct ctdb_get_log_addr *log_a
                return;
        }
 
-       tmp_entry = first_entry;
-       while (tmp_entry != last_entry) {
-               struct tm *tm;
-               char tbuf[100];
-
-               if (log_entries == NULL) {
-                       break;
-               }
+       for (i=0; i<ringbuf_count; i++) {
+               tmp_entry = (first_entry + i) % log_ringbuf_size;
 
                if (log_entries[tmp_entry].level > log_addr->level) {
-                       tmp_entry++;
-                       if (tmp_entry >= log_ringbuf_size) {
-                               tmp_entry = 0;
-                       }
                        continue;
                }
 
@@ -131,12 +124,9 @@ void ctdb_collect_log(struct ctdb_context *ctdb, struct ctdb_get_log_addr *log_a
                strftime(tbuf, sizeof(tbuf)-1,"%Y/%m/%d %H:%M:%S", tm);
 
                if (log_entries[tmp_entry].message) {
-                       count += fprintf(f, "%s:%s %s", tbuf, get_debug_by_level(log_entries[tmp_entry].level), log_entries[tmp_entry].message);
-               }
-
-               tmp_entry++;
-               if (tmp_entry >= log_ringbuf_size) {
-                       tmp_entry = 0;
+                       fprintf(f, "%s:%s %s", tbuf,
+                               get_debug_by_level(log_entries[tmp_entry].level),
+                               log_entries[tmp_entry].message);
                }
        }
 
@@ -184,7 +174,7 @@ int32_t ctdb_control_get_log(struct ctdb_context *ctdb, TDB_DATA addr)
 void ctdb_clear_log(struct ctdb_context *ctdb)
 {
        first_entry = 0;
-       last_entry  = 0;
+       ringbuf_count  = 0;
 }
 
 int32_t ctdb_control_clear_log(struct ctdb_context *ctdb)