Initial changes for persistent connections - add some basic functionality.

server/core/dcb.c

@@ -632,7 +632,18 @@ DCB		*dcb;
 GWPROTOCOL	*funcs;
 int             fd;
 int             rc;
+char            *user;
 
+        user = session_getUser(session);
+        if (NULL != user && strlen(user))
+        {
+            dcb = server_get_persistent(server, user);
+            if (NULL != dcb)
+            {
+                return dcb;
+            }
+        }
+        
 	if ((dcb = dcb_alloc(DCB_ROLE_REQUEST_HANDLER)) == NULL)
 	{
 		return NULL;
@@ -1271,6 +1282,13 @@ dcb_close(DCB *dcb)
 	
 		if (rc == 0)
 		{
+                        spinlock_acquire(&dcb->server->persistlock);
+                        dcb->nextpersistent = dcb->server->persistent;
+                        dcb->server->persistent = dcb;
+                        spinlock_release(&dcb->server->persistlock);
+                        atomic_add(&dcb->server->stats.n_persistent, 1);
+                        return;
+                        
 			/**
 			 * close protocol and router session
 			 */

server/core/server.c

@@ -78,6 +78,8 @@ SERVER 	*server;
 	server->rlag = -2;
 	server->master_id = -1;
 	server->depth = -1;
+        server->persistent = NULL;
+        spinlock_init(server->persistlock);
 
 	spinlock_acquire(&server_spin);
 	server->next = allServers;
@@ -128,6 +130,56 @@ SERVER *ptr;
 	return 1;
 }
 
+/**
+ * Get a DCB from the persistent connection pool, if possible
+ *
+ * @param	server	The server to set the name on
+ * @param	user	The name of the user needing the connection
+ */
+DCB *
+server_get_persistent(SERVER *server, char *user)
+{
+    DCB *dcb, *previous;
+    int rc;
+    
+    spinlock_acquire(server->persistlock);
+    dcb = server->persistent;
+    previous = NULL;
+    while (dcb) {
+        /* Test for expired, free and remove from list if it is */
+        if (0 == strcmp(dcb->user, user))
+        {
+            if (NULL == previous)
+            {
+                server->persistent = dcb->nextpersistent;
+            }
+            else
+            {
+                previous->nextpersistent = dcb->nextpersistent;
+            }
+            rc = poll_add_dcb(dcb);
+            if (rc == DCBFD_CLOSED) {
+                dcb_set_state(dcb, DCB_STATE_DISCONNECTED, NULL);
+                dcb_free(dcb);
+            }
+            else
+            {
+                spinlock_release(server->persistlock);
+                atomic_add(&server->stats.n_persistent, -1);
+                return dcb;
+            }
+        }
+        previous = dcb;
+        dcb = dcb->nextpersistent;
+    }
+    if (NULL != server->persistent)
+    {
+        /* Change user, remove DCB from list, release spinlock, return dcb */
+    }
+    spinlock_release(server->persistlock);
+    return NULL;
+}
+
 /**
  * Set a unique name for the server
  *

server/include/dcb.h

@@ -249,6 +249,7 @@ typedef struct dcb {
 	DCBSTATS	stats;		/**< DCB related statistics */
         unsigned int    dcb_server_status; /*< the server role indicator from SERVER */
 	struct dcb	*next;		/**< Next DCB in the chain of allocated DCB's */
+        struct dcb      *nextpersistent;   /**< Next DCB in the persistent pool for SERVER */
 	struct service	*service;	/**< The related service */
 	void		*data;		/**< Specific client data */
 	DCBMM		memdata;	/**< The data related to DCB memory management */
@@ -261,7 +262,7 @@ typedef struct dcb {
 	SPINLOCK	polloutlock;
 	int		polloutbusy;
 	int		writecheck;
-        unsigned long          last_read;      /*< Last time the DCB received data */
+        unsigned long   last_read;      /*< Last time the DCB received data */
 	unsigned int	high_water;	/**< High water mark */
 	unsigned int	low_water;	/**< Low water mark */
 	struct server	*server;	/**< The associated backend server */

server/include/server.h

@@ -66,6 +66,7 @@ typedef struct {
 	int		n_connections;	/**< Number of connections */
 	int		n_current;	/**< Current connections */
 	int             n_current_ops;  /**< Current active operations */
+	int             n_persistent;  /**< Current persistent pool */
 } SERVER_STATS;
 
 /**
@@ -94,6 +95,8 @@ typedef struct server {
 	int		depth;		/**< Replication level in the tree */
 	long		*slaves;	/**< Slaves of this node */
 	bool            master_err_is_logged; /*< If node failed, this indicates whether it is logged */
+        DCB             *persistent;    /**< List of unused persistent connections to the server */
+        SPINLOCK        *persistlock;   /**< Lock for adjusting the persistent connections list */
 } SERVER;
 
 /**
@@ -189,5 +192,6 @@ extern void	serverAddParameter(SERVER *, char *, char *);
 extern char	*serverGetParameter(SERVER *, char *);
 extern void	server_update(SERVER *, char *, char *, char *);
 extern void     server_set_unique_name(SERVER *, char *);
+extern DCB      *server_get_persistent(SERVER *, char *);
 extern RESULTSET	*serverGetList();
 #endif