FEATURE: Add stats_tcp_retrans()

Makefile.am

@@ -81,6 +81,8 @@ memcached_SOURCES = \
                     sasl_defs.h \
                     stats_prefix.c \
                     stats_prefix.h \
+                    stats.c \
+                    stats.h \
                     thread.c \
                     thread.h \
                     mc_util.c \

include/memcached/types.h

@@ -40,6 +40,7 @@ struct iovec {
 #define SUPPORT_BOP_SMGET
 #define JHPARK_OLD_SMGET_INTERFACE
 #define MULTI_NOTIFY_IO_COMPLETE
+#define STATS_TCP_RETRANS
 
 #ifdef __cplusplus
 extern "C" {

memcached.c

@@ -8092,6 +8092,11 @@ static void server_stats(ADD_STAT add_stats, conn *c, bool aggregate)
     APPEND_STAT("limit_maxconns", "%d", settings.maxconns);
     APPEND_STAT("threads", "%d", settings.num_threads);
     APPEND_STAT("conn_yields", "%"PRIu64, thread_stats.conn_yields);
+#ifdef STATS_TCP_RETRANS
+    if (IS_TCP(c->transport)) {
+        APPEND_STAT("tcp_retrans", "%ld", stats_tcp_retrans());
+    }
+#endif
     UNLOCK_STATS();
 }
 

memcached.h

@@ -190,6 +190,8 @@ enum network_transport {
     udp_transport
 };
 
+#define IS_TCP(x) (x == tcp_transport)
+
 #define IS_UDP(x) (x == udp_transport)
 
 /**
@@ -575,6 +577,7 @@ extern int daemonize(int nochdir, int noclose);
 #endif
 
 #include "stats_prefix.h"
+#include "stats.h"
 #include "trace.h"
 #include "hash.h"
 #include <memcached/util.h>

stats.c

@@ -0,0 +1,140 @@
+/* -*- Mode: C; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
+/*
+ * arcus-memcached - Arcus memory cache server
+ * Copyright 2010-2014 NAVER Corp.
+ * Copyright 2015 JaM2in Co., Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/*
+ * Detailed statistics management. For simple stats like total number of
+ * "get" requests, we use inline code in memcached.c and friends, but when
+ * stats detail mode is activated, the code here records more information.
+ *
+ * Author:
+ *   Steven Grimm <[email protected]>
+ */
+#include "config.h"
+#include "memcached.h"
+
+#ifdef STATS_TCP_RETRANS
+#include <ctype.h>
+#include <stdlib.h>
+#include <string.h>
+
+static void rtrim(char **src) {
+    if (src == NULL || *src == NULL || strlen(*src) == 0) {
+        return;
+    }
+
+    char *str = *src;
+    for (int i = strlen(str) - 1; i >= 0; i--) {
+        if (!isspace(str[i])) {
+            break;
+        }
+
+        str[i] = '\0';
+    }
+
+    *src = str;
+}
+
+int64_t stats_tcp_retrans(void) {
+    char *key_line = NULL;
+    char *value_line = NULL;
+    uint64_t tcp_retrans = -1;
+
+    FILE *fp = fopen("/proc/net/snmp", "r");
+    if (fp == NULL) {
+        goto done;
+    }
+
+    size_t key_len = 0;
+    size_t value_len = 0;
+    ssize_t key_read = -1;
+    ssize_t value_read = -1;
+
+    char *prefix = "Tcp:";
+    size_t prefix_len = strlen(prefix);
+
+    while ((key_read = getline(&key_line, &key_len, fp)) != -1) {
+        if (strncmp(prefix, key_line, prefix_len) != 0) {
+            continue;
+        }
+
+        if ((value_read = getline(&value_line, &value_len, fp)) != -1) {
+            break;
+        }
+    }
+
+    if (key_read < 0 || value_read < 0) {
+        goto done;
+    }
+
+    /*
+     * below lines are examples of key_line and value_line.
+     * for examples below, tcp_retrans = 9814784
+     *
+     * Tcp: RtoAlgorithm RtoMin RtoMax MaxConn ActiveOpens PassiveOpens AttemptFails EstabResets CurrEstab InSegs OutSegs RetransSegs InErrs OutRsts InCsumErrors
+     * Tcp: 1 200 120000 -1 231273424 45758374 43975115 12045288 360 9853401239 10104984649 9814784 12765 17318799 883
+     */
+
+    char *delimiter = " ";
+    char *retrans_segs = "RetransSegs";
+
+    char *key_next = NULL;
+    char *value_next = NULL;
+
+    char *key_token = strtok_r(key_line, delimiter, &key_next);
+    char *value_token = strtok_r(value_line, delimiter, &value_next);
+
+    // first token is always "Tcp:"
+    key_token = strtok_r(NULL, delimiter, &key_next);
+    value_token = strtok_r(NULL, delimiter, &value_next);
+
+    while (key_token && value_token) {
+        // last token always ends with "\n"
+        rtrim(&key_token);
+        rtrim(&value_token);
+
+        if (strcmp(key_token, retrans_segs) == 0) {
+            char *end = NULL;
+            errno = 0;
+            tcp_retrans = strtoll(value_token, &end, 10);
+
+            if (errno > 0 || *end != '\0') {
+                tcp_retrans = -1;
+            }
+            goto done;
+        }
+
+        key_token = strtok_r(NULL, delimiter, &key_next);
+        value_token = strtok_r(NULL, delimiter, &value_next);
+    }
+
+done:
+    if (fp != NULL) {
+        fclose(fp);
+    }
+
+    if (key_line != NULL) {
+        free(key_line);
+    }
+
+    if (value_line != NULL) {
+        free(value_line);
+    }
+
+    return tcp_retrans;
+}
+#endif

stats.h

@@ -0,0 +1,22 @@
+/*
+ * arcus-memcached - Arcus memory cache server
+ * Copyright 2010-2014 NAVER Corp.
+ * Copyright 2015 JaM2in Co., Ltd.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/* stats */
+
+#ifdef STATS_TCP_RETRANS
+int64_t stats_tcp_retrans(void);
+#endif

stats_prefix.h

@@ -15,7 +15,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* stats */
+/* stats_prefix */
 void stats_prefix_init(char delimiter, void (*cb_when_prefix_overflow)(void));
 void stats_prefix_clear(void);
 int  stats_prefix_count(void);