On crash print information about the current client (if any), command vector, and object associated to first argument assuming it is a key.

src/debug.c

@@ -337,6 +337,27 @@ void debugCommand(redisClient *c) {
     }
 }
 
+void redisLogObjectDebugInfo(robj *o) {
+    redisLog(REDIS_WARNING,"Object type: %d", o->type);
+    redisLog(REDIS_WARNING,"Object encoding: %d", o->encoding);
+    redisLog(REDIS_WARNING,"Object refcount: %d", o->refcount);
+    if (o->type == REDIS_STRING && o->encoding == REDIS_ENCODING_RAW) {
+        redisLog(REDIS_WARNING,"Object raw string len: %d", sdslen(o->ptr));
+        if (sdslen(o->ptr) < 4096)
+            redisLog(REDIS_WARNING,"Object raw string content: \"%s\"", (char*)o->ptr);
+    } else if (o->type == REDIS_LIST) {
+        redisLog(REDIS_WARNING,"List length: %d", (int) listTypeLength(o));
+    } else if (o->type == REDIS_SET) {
+        redisLog(REDIS_WARNING,"Set size: %d", (int) setTypeSize(o));
+    } else if (o->type == REDIS_HASH) {
+        redisLog(REDIS_WARNING,"Hash size: %d", (int) hashTypeLength(o));
+    } else if (o->type == REDIS_ZSET) {
+        redisLog(REDIS_WARNING,"Sorted set size: %d", (int) zsetLength(o));
+        if (o->encoding == REDIS_ENCODING_SKIPLIST)
+            redisLog(REDIS_WARNING,"Skiplist level: %d", (int) ((zset*)o->ptr)->zsl->level);
+    }
+}
+
 void _redisAssert(char *estr, char *file, int line) {
     bugReportStart();
     redisLog(REDIS_WARNING,"=== ASSERTION FAILED ===");

src/networking.c

@@ -467,6 +467,9 @@ static void freeClientArgv(redisClient *c) {
 void freeClient(redisClient *c) {
     listNode *ln;
 
+    /* If this is marked as current client unset it */
+    if (server.current_client == c) server.current_client = NULL;
+
     /* Note that if the client we are freeing is blocked into a blocking
      * call, we have to set querybuf to NULL *before* to call
      * unblockClientWaitingData() to avoid processInputBuffer() will get
@@ -875,6 +878,7 @@ void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask) {
     REDIS_NOTUSED(el);
     REDIS_NOTUSED(mask);
 
+    server.current_client = c;
     nread = read(fd, buf, REDIS_IOBUF_LEN);
     if (nread == -1) {
         if (errno == EAGAIN) {
@@ -893,6 +897,7 @@ void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask) {
         c->querybuf = sdscatlen(c->querybuf,buf,nread);
         c->lastinteraction = time(NULL);
     } else {
+        server.current_client = NULL;
         return;
     }
     if (sdslen(c->querybuf) > server.client_max_querybuf_len) {
@@ -906,6 +911,7 @@ void readQueryFromClient(aeEventLoop *el, int fd, void *privdata, int mask) {
         return;
     }
     processInputBuffer(c);
+    server.current_client = NULL;
 }
 
 void getClientsMaxBuffers(unsigned long *longest_output_list,

src/redis.c

@@ -716,8 +716,11 @@ void beforeSleep(struct aeEventLoop *eventLoop) {
             call(c);
             resetClient(c);
             /* There may be more data to process in the input buffer. */
-            if (c->querybuf && sdslen(c->querybuf) > 0)
+            if (c->querybuf && sdslen(c->querybuf) > 0) {
+                server.current_client = c;
                 processInputBuffer(c);
+                server.current_client = NULL;
+            }
         }
     }
 
@@ -907,6 +910,7 @@ void initServer() {
     }
 
     server.mainthread = pthread_self();
+    server.current_client = NULL;
     server.clients = listCreate();
     server.slaves = listCreate();
     server.monitors = listCreate();
@@ -1797,6 +1801,40 @@ static void sigsegvHandler(int sig, siginfo_t *info, void *secret) {
     redisLog(REDIS_WARNING, clients);
     /* Don't sdsfree() strings to avoid a crash. Memory may be corrupted. */
 
+    /* Log CURRENT CLIENT info */
+    if (server.current_client) {
+        redisClient *cc = server.current_client;
+        sds client;
+        int j;
+
+        redisLog(REDIS_WARNING, "--- CURRENT CLIENT INFO");
+        client = getClientInfoString(cc);
+        redisLog(REDIS_WARNING,"client: %s", client);
+        /* Missing sdsfree(client) to avoid crash if memory is corrupted. */
+        for (j = 0; j < cc->argc; j++) {
+            robj *decoded;
+
+            decoded = getDecodedObject(cc->argv[j]);
+            redisLog(REDIS_WARNING,"argv[%d]: '%s'", j, (char*)decoded->ptr);
+            decrRefCount(decoded);
+        }
+        /* Check if the first argument, usually a key, is found inside the
+         * selected DB, and if so print info about the associated object. */
+        if (cc->argc >= 1) {
+            robj *val, *key;
+            dictEntry *de;
+
+            key = getDecodedObject(cc->argv[1]);
+            de = dictFind(cc->db->dict, key->ptr);
+            if (de) {
+                val = dictGetEntryVal(de);
+                redisLog(REDIS_WARNING,"key '%s' found in DB containing the following object:", key->ptr);
+                redisLogObjectDebugInfo(val);
+            }
+            decrRefCount(key);
+        }
+    }
+
     redisLog(REDIS_WARNING,
 "=== REDIS BUG REPORT END. Make sure to include from START to END. ===\n\n"
 "    Please report the crash opening an issue on github:\n\n"

src/redis.h

@@ -400,6 +400,7 @@ struct redisServer {
     /* Fast pointers to often looked up command */
     struct redisCommand *delCommand, *multiCommand;
     list *slaves, *monitors;
+    redisClient *current_client; /* Current client, only used on crash report */
     char neterr[ANET_ERR_LEN];
     aeEventLoop *el;
     int cronloops;              /* number of times the cron function run */
@@ -1072,4 +1073,6 @@ void *malloc(size_t size) __attribute__ ((deprecated));
 void *realloc(void *ptr, size_t size) __attribute__ ((deprecated));
 #endif
 
+void redisLogObjectDebugInfo(robj *o);
+
 #endif