vswitchd: Add entity-relationship diagram to ovs-vswitchd.conf.db.5.

[sliver-openvswitch.git] / lib / ovsdb-idl.c

diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c
index 94dd466..aa2f2ce 100644 (file)
--- a/lib/ovsdb-idl.c
+++ b/lib/ovsdb-idl.c
@@ -136,6 +136,11 @@ static void ovsdb_idl_txn_abort_all(struct ovsdb_idl *);
 static bool ovsdb_idl_txn_process_reply(struct ovsdb_idl *,
                                         const struct jsonrpc_msg *msg);
 
+/* Creates and returns a connection to database 'remote', which should be in a
+ * form acceptable to jsonrpc_session_open().  The connection will maintain an
+ * in-memory replica of the remote database whose schema is described by
+ * 'class'.  (Ordinarily 'class' is compiled from an OVSDB schema automatically
+ * by ovsdb-idlc.) */
 struct ovsdb_idl *
 ovsdb_idl_create(const char *remote, const struct ovsdb_idl_class *class)
 {
@@ -171,6 +176,7 @@ ovsdb_idl_create(const char *remote, const struct ovsdb_idl_class *class)
     return idl;
 }
 
+/* Destroys 'idl' and all of the data structures that it manages. */
 void
 ovsdb_idl_destroy(struct ovsdb_idl *idl)
 {
@@ -231,9 +237,30 @@ ovsdb_idl_clear(struct ovsdb_idl *idl)
     }
 }
 
-void
+/* Processes a batch of messages from the database server on 'idl'.  Returns
+ * true if the database as seen through 'idl' changed, false if it did not
+ * change.  The initial fetch of the entire contents of the remote database is
+ * considered to be one kind of change.
+ *
+ * When this function returns false, the client may continue to use any data
+ * structures it obtained from 'idl' in the past.  But when it returns true,
+ * the client must not access any of these data structures again, because they
+ * could have freed or reused for other purposes.
+ *
+ * This function can return occasional false positives, that is, report that
+ * the database changed even though it didn't.  This happens if the connection
+ * to the database drops and reconnects, which causes the database contents to
+ * be reloaded even if they didn't change.  (It could also happen if the
+ * database server sends out a "change" that reflects what we already thought
+ * was in the database, but the database server is not supposed to do that.)
+ *
+ * As an alternative to checking the return value, the client may check for
+ * changes in the value returned by ovsdb_idl_get_seqno().
+ */
+bool
 ovsdb_idl_run(struct ovsdb_idl *idl)
 {
+    unsigned int initial_change_seqno = idl->change_seqno;
     int i;
 
     assert(!idl->txn);
@@ -290,8 +317,12 @@ ovsdb_idl_run(struct ovsdb_idl *idl)
         }
         jsonrpc_msg_destroy(msg);
     }
+
+    return initial_change_seqno != idl->change_seqno;
 }
 
+/* Arranges for poll_block() to wake up when ovsdb_idl_run() has something to
+ * do or when activity occurs on a transaction on 'idl'. */
 void
 ovsdb_idl_wait(struct ovsdb_idl *idl)
 {
@@ -299,18 +330,30 @@ ovsdb_idl_wait(struct ovsdb_idl *idl)
     jsonrpc_session_recv_wait(idl->session);
 }
 
+/* Returns a number that represents the state of 'idl'.  When 'idl' is updated
+ * (by ovsdb_idl_run()), the return value changes. */
 unsigned int
 ovsdb_idl_get_seqno(const struct ovsdb_idl *idl)
 {
     return idl->change_seqno;
 }
 
+/* Returns true if 'idl' successfully connected to the remote database and
+ * retrieved its contents (even if the connection subsequently dropped and is
+ * in the process of reconnecting).  If so, then 'idl' contains an atomic
+ * snapshot of the database's contents (but it might be arbitrarily old if the
+ * connection dropped).
+ *
+ * Returns false if 'idl' has never connected or retrieved the database's
+ * contents.  If so, 'idl' is empty. */
 bool
 ovsdb_idl_has_ever_connected(const struct ovsdb_idl *idl)
 {
     return ovsdb_idl_get_seqno(idl) != 0;
 }
 
+/* Forces 'idl' to drop its connection to the database and reconnect.  In the
+ * meantime, the contents of 'idl' will not change. */
 void
 ovsdb_idl_force_reconnect(struct ovsdb_idl *idl)
 {
@@ -1460,13 +1503,20 @@ ovsdb_idl_txn_delete(const struct ovsdb_idl_row *row_)
 
 const struct ovsdb_idl_row *
 ovsdb_idl_txn_insert(struct ovsdb_idl_txn *txn,
-                     const struct ovsdb_idl_table_class *class)
+                     const struct ovsdb_idl_table_class *class,
+                     const struct uuid *uuid)
 {
     struct ovsdb_idl_row *row = ovsdb_idl_row_create__(class);
-    uuid_generate(&row->uuid);
+
+    if (uuid) {
+        assert(!ovsdb_idl_txn_get_row(txn, uuid));
+        row->uuid = *uuid;
+    } else {
+        uuid_generate(&row->uuid);
+    }
+
     row->table = ovsdb_idl_table_from_class(txn->idl, class);
     row->new = xmalloc(class->n_columns * sizeof *row->new);
-    row->written = bitmap_allocate(class->n_columns);
     hmap_insert(&row->table->rows, &row->hmap_node, uuid_hash(&row->uuid));
     hmap_insert(&txn->txn_rows, &row->txn_node, uuid_hash(&row->uuid));
     return row;