Fix divide-by-zero in redis-benchmark and redis-cli (#14371)

Resolve https://github.com/redis/redis/issues/14358 and
https://github.com/redis/redis/issues/14359. Fix division by zero in
redis-benchmark and redis-cli when histograms are empty or elapsed time
is zero. Guard all affected divisions in showLatencyReport(),
showThroughput(), and displayKeyStatsSizeDist(). Added integration tests
for both cases.

---------

Co-authored-by: debing.sun <debing.sun@redis.com>

src/redis-benchmark.c

@@ -828,8 +828,21 @@ static void createMissingClients(client c) {
 }
 
 static void showLatencyReport(void) {
+    if (config.latency_histogram->total_count == 0) {
+        if (config.csv) {
+            printf("\"%s\",\"0.00\",\"0.000\",\"0.000\",\"0.000\",\"0.000\",\"0.000\",\"0.000\"\n", config.title);
+        } else if (config.quiet) {
+            printf("%*s\r", config.last_printed_bytes, " "); // ensure there is a clean line
+            printf("%s: 0.00 requests per second, p50=0.000 msec\n", config.title);
+        } else {
+            printf("%*s\r", config.last_printed_bytes, " "); // ensure there is a clean line
+            printf("====== %s ======\n", config.title);
+            printf("No latency samples collected\n");
+        }
+        return;
+    }
 
-    const float reqpersec = (float)config.requests_finished/((float)config.totlatency/1000.0f);
+    const float reqpersec = config.totlatency > 0 ? (float)config.requests_finished/((float)config.totlatency/1000.0f) : 0.0f;
     const float p0 = ((float) hdr_min(config.latency_histogram))/1000.0f;
     const float p50 = hdr_value_at_percentile(config.latency_histogram, 50.0 )/1000.0f;
     const float p95 = hdr_value_at_percentile(config.latency_histogram, 95.0 )/1000.0f;
@@ -1666,13 +1679,15 @@ int showThroughput(struct aeEventLoop *eventLoop, long long id, void *clientData
         return SHOW_THROUGHPUT_INTERVAL;
     }
     const float dt = (float)(current_tick-config.start)/1000.0;
-    const float rps = (float)requests_finished/dt;
+    const float rps = dt > 0 ? (float)requests_finished/dt : 0.0f;
     const float instantaneous_dt = (float)(current_tick-config.previous_tick)/1000.0;
-    const float instantaneous_rps = (float)(requests_finished-previous_requests_finished)/instantaneous_dt;
+    const float instantaneous_rps = instantaneous_dt > 0 ? (float)(requests_finished-previous_requests_finished)/instantaneous_dt : 0.0f;
     config.previous_tick = current_tick;
     atomicSet(config.previous_requests_finished,requests_finished);
     printf("%*s\r", config.last_printed_bytes, " "); /* ensure there is a clean line */
-    int printed_bytes = printf("%s: rps=%.1f (overall: %.1f) avg_msec=%.3f (overall: %.3f)\r", config.title, instantaneous_rps, rps, hdr_mean(config.current_sec_latency_histogram)/1000.0f, hdr_mean(config.latency_histogram)/1000.0f);
+    double avg_mean = config.current_sec_latency_histogram->total_count > 0 ? hdr_mean(config.current_sec_latency_histogram)/1000.0f : 0.0;
+    double overall_mean = config.latency_histogram->total_count > 0 ? hdr_mean(config.latency_histogram)/1000.0f : 0.0;
+    int printed_bytes = printf("%s: rps=%.1f (overall: %.1f) avg_msec=%.3f (overall: %.3f)\r", config.title, instantaneous_rps, rps, avg_mean, overall_mean);
     config.last_printed_bytes = printed_bytes;
     hdr_reset(config.current_sec_latency_histogram);
     fflush(stdout);

src/redis-cli.c

@@ -10492,6 +10492,11 @@ static int displayKeyStatsSizeDist(struct hdr_histogram *keysize_histogram) {
     struct hdr_iter iter;
     int64_t last_displayed_cumulative_count = 0;
 
+    if (keysize_histogram->total_count == 0) {
+        line_count += cleanPrintfln("No key size samples collected");
+        return line_count;
+    }
+
     hdr_iter_percentile_init(&iter, keysize_histogram, 1);
 
     line_count += cleanPrintfln("Key size Percentile Total keys");

tests/integration/redis-benchmark.tcl

@@ -134,6 +134,15 @@ tags {"benchmark network external:skip logreqres:skip"} {
             r get key
         } {arg}
 
+        test {benchmark: no NaN or Inf in latency report with fast requests} {
+            # With -n 1 on localhost, totlatency can round to 0 ms. Verify showLatencyReport() handles this gracefully.
+            set cmd [redisbenchmark $master_host $master_port "-c 1 -n 1 -t set"]
+            set output [exec {*}$cmd 2>@1]
+            if {[regexp -nocase {nan|(?:^|[^a-z])inf(?:[^o]|$)} $output]} {
+                fail "redis-benchmark output contains NaN or Inf: $output"
+            }
+        }
+
         # tls specific tests
         if {$::tls} {
             test {benchmark: specific tls-ciphers} {

tests/integration/redis-cli.tcl

@@ -849,4 +849,18 @@ start_server {tags {"cli external:skip"}} {
     }
 }
 
+start_server {tags {"cli external:skip"}} {
+    test "keystats on empty database should not produce garbage stats" {
+        # On an empty DB the keystats histogram has total_count = 0. Verify hdr_mean(), hdr_stddev(),
+        # and the percentile calculation handle this gracefully.
+        set cmd [rediscli [srv host] [srv port] [list --keystats]]
+        catch {exec {*}$cmd 2>@1} result
+        assert_match "*Scanning the entire keyspace*" $result
+
+        # The "Note:" line with Mean/StdDeviation is only printed when displayKeyStatsSizeDist()
+        # compute stats. When keysize_histogram->total_count == 0, it should be skipped entirely.
+        assert_match "*No key size samples collected*" $result
+    }
+}
+
 file delete ./.rediscli_history_test