WIP: Experimental support to detect unconsumed data

michael-grunder · michael-grunder · commit d68579562b29 · 2021-10-05T14:35:56.000-07:00
This commit is an attempt at detecting unconsumed data on a socket when we pull it from the connection pool. Two new INI settings are introduced related to the changes: redis.pconnect.pool_detect_dirty: Value Explanation ----- ---------------------------------------------------------------- 0 Don't execute new logic at all. 1 Abort and close the socket if we find unconsumed bytes in the read buffer. 2 Seek to the end of our read buffer if we find unconsumed bytes and then poll the socket FD to detect if we're still readable in which case we fail and close the socket. redis.pconnect.pool_poll_timeout: The poll timeout to employ when checking if the socket is readable. This value is in milliseconds and can be zero. Review changes See #2013 Perform cheaper PHP liveness check first.
diff --git a/common.h b/common.h
@@ -133,6 +133,17 @@ typedef enum {
 #define MULTI    1
 #define PIPELINE 2
 
+#define PHPREDIS_DEBUG_LOGGING 0
+
+#if PHPREDIS_DEBUG_LOGGING == 1
+#define redisDbgFmt(fmt, ...) \
+    php_printf("%s:%d:%s(): " fmt "\n", __FILE__, __LINE__, __func__, __VA_ARGS__)
+#define redisDbgStr(str) phpredisDebugFmt("%s", str)
+#else
+#define redisDbgFmt(fmt, ...) ((void)0)
+#define redisDbgStr(str) ((void)0)
+#endif
+
 #define IS_ATOMIC(redis_sock) (redis_sock->mode == ATOMIC)
 #define IS_MULTI(redis_sock) (redis_sock->mode & MULTI)
 #define IS_PIPELINE(redis_sock) (redis_sock->mode & PIPELINE)
diff --git a/library.c b/library.c
@@ -2159,6 +2159,82 @@ static int redis_stream_liveness_check(php_stream *stream) {
                                  SUCCESS : FAILURE;
 }
 
+/* Try to get the underlying socket FD for use with poll/select.
+ * Returns -1 on failure. */
+static php_socket_t redis_stream_fd_for_select(php_stream *stream) {
+    php_socket_t fd;
+    int flags;
+
+    flags = PHP_STREAM_AS_FD_FOR_SELECT | PHP_STREAM_CAST_INTERNAL;
+    if (php_stream_cast(stream, flags, (void*)&fd, 1) == FAILURE)
+        return -1;
+
+    return fd;
+}
+
+static int redis_detect_dirty_config(void) {
+    int val = INI_INT("redis.pconnect.pool_detect_dirty");
+
+    if (val >= 0 && val <= 2)
+        return val;
+    else if (val > 2)
+        return 2;
+    else
+        return 0;
+}
+
+static int redis_pool_poll_timeout(void) {
+    int val = INI_INT("redis.pconnect.pool_poll_timeout");
+    if (val >= 0)
+        return val;
+
+    return 0;
+}
+
+#define REDIS_POLL_FD_SET(_pfd, _fd, _events) \
+    (_pfd).fd = _fd; (_pfd).events = _events; (_pfd).revents = 0
+
+/* Try to determine if the socket is out of sync (has unconsumed replies) */
+static int redis_stream_detect_dirty(php_stream *stream) {
+    php_socket_t fd;
+    php_pollfd pfd;
+    int rv, action;
+
+    /* Short circuit if this is disabled */
+    if ((action = redis_detect_dirty_config()) == 0)
+        return SUCCESS;
+
+    /* Seek past unconsumed bytes if we detect them */
+    if (stream->readpos < stream->writepos) {
+        redisDbgFmt("%s on unconsumed buffer (%ld < %ld)",
+                    action > 1 ? "Aborting" : "Seeking",
+                    (long)stream->readpos, (long)stream->writepos);
+
+        /* Abort if we are configured to immediately fail */
+        if (action == 1)
+            return FAILURE;
+
+        /* Seek to the end of buffered data */
+        zend_off_t offset = stream->writepos - stream->readpos;
+        if (php_stream_seek(stream, offset, SEEK_CUR) == FAILURE)
+            return FAILURE;
+    }
+
+    /* Get the underlying FD */
+    if ((fd = redis_stream_fd_for_select(stream)) == -1)
+        return FAILURE;
+
+    /* We want to detect a readable socket (it shouln't be) */
+    REDIS_POLL_FD_SET(pfd, fd, PHP_POLLREADABLE);
+    rv = php_poll2(&pfd, 1, redis_pool_poll_timeout());
+
+    /* If we detect the socket is readable, it's dirty which is
+     * a failure.  Otherwise as best we can tell it's good.
+     * TODO:  We could attempt to consume up to N bytes */
+    redisDbgFmt("Detected %s socket", rv > 0 ? "readable" : "unreadable");
+    return rv == 0 ? SUCCESS : FAILURE;
+}
+
 static int
 redis_sock_check_liveness(RedisSock *redis_sock)
 {
@@ -2167,11 +2243,14 @@ redis_sock_check_liveness(RedisSock *redis_sock)
     smart_string cmd = {0};
     size_t len;
 
-    /* Short circuit if we detect the stream has gone bad or if the user has
-     * configured persistent connection "YOLO mode". */
-    if (redis_stream_liveness_check(redis_sock->stream) != SUCCESS) {
+    /* Short circuit if PHP detects the stream isn't live */
+    if (redis_stream_liveness_check(redis_sock->stream) != SUCCESS)
+        goto failure;
+
+    /* Short circuit if we detect the stream is "dirty", can't or are
+       configured not to try and fix it */
+    if (redis_stream_detect_dirty(redis_sock->stream) != SUCCESS)
         goto failure;
-    }
 
     redis_sock->status = REDIS_SOCK_STATUS_CONNECTED;
     if (!INI_INT("redis.pconnect.echo_check_liveness")) {
@@ -2290,6 +2369,7 @@ PHP_REDIS_API int redis_sock_connect(RedisSock *redis_sock)
                 if (redis_sock_check_liveness(redis_sock) == SUCCESS) {
                     return SUCCESS;
                 }
+
                 p->nb_active--;
             }
 
diff --git a/redis.c b/redis.c
@@ -98,6 +98,8 @@ PHP_INI_BEGIN()
     PHP_INI_ENTRY("redis.pconnect.pooling_enabled", "1", PHP_INI_ALL, NULL)
     PHP_INI_ENTRY("redis.pconnect.connection_limit", "0", PHP_INI_ALL, NULL)
     PHP_INI_ENTRY("redis.pconnect.echo_check_liveness", "1", PHP_INI_ALL, NULL)
+    PHP_INI_ENTRY("redis.pconnect.pool_detect_dirty", "0", PHP_INI_ALL, NULL)
+    PHP_INI_ENTRY("redis.pconnect.pool_poll_timeout", "0", PHP_INI_ALL, NULL)
     PHP_INI_ENTRY("redis.pconnect.pool_pattern", "", PHP_INI_ALL, NULL)
 
     /* redis session */
