ovsdb: Introduce experimental support for clustered databases.

This commit adds support for OVSDB clustering via Raft.  Please read
ovsdb(7) for information on how to set up a clustered database.  It is
simple and boils down to running "ovsdb-tool create-cluster" on one server
and "ovsdb-tool join-cluster" on each of the others and then starting
ovsdb-server in the usual way on all of them.

One you have a clustered database, you configure ovn-controller and
ovn-northd to use it by pointing them to all of the servers, e.g. where
previously you might have said "tcp:1.2.3.4" was the database server,
now you say that it is "tcp:1.2.3.4,tcp:5.6.7.8,tcp:9.10.11.12".

This also adds support for database clustering to ovs-sandbox.

Acked-by: Justin Pettit <jpettit@ovn.org>
Tested-by: aginwala <aginwala@asu.edu>
Signed-off-by: Ben Pfaff <blp@ovn.org>

1 files changed, 25 insertions, 2 deletions

diff --git a/ovsdb/trigger.h b/ovsdb/trigger.h
index a6c10e012..79af7f6be 100644
--- a/ovsdb/trigger.h
+++ b/ovsdb/trigger.h
@@ -20,13 +20,35 @@
 
 struct ovsdb;
 
+/* Triggers have the following states:
+ *
+ *    - Initialized (reply == NULL, progress == NULL): Executing the trigger
+ *      can keep it in the initialized state, if it has a "wait" condition that
+ *      isn't met.  Executing the trigger can also yield an error, in which
+ *      case it transitions to "complete".  Otherwise, execution yields a
+ *      transaction, which the database attempts to commit.  If the transaction
+ *      completes immediately and synchronously, then the trigger transitions
+ *      to the "complete" state.  If the transaction requires some time to
+ *      complete, it transitions to the "committing" state.
+ *
+ *    - Committing (reply != NULL, progress != NULL): The transaction is
+ *      committing.  If it succeeds, or if it fails permanently, then the
+ *      trigger transitions to "complete".  If it fails temporarily
+ *      (e.g. because someone else committed to cluster-based storage before we
+ *      did), then we transition back to "initialized" to try again.
+ *
+ *    - Complete (reply != NULL, progress == NULL): The transaction is done
+ *      and either succeeded or failed.
+ */
 struct ovsdb_trigger {
+    /* In "initialized" or "committing" state, in db->triggers.
+     * In "complete", in session->completions. */
+    struct ovs_list node;
     struct ovsdb_session *session; /* Session that owns this trigger. */
     struct ovsdb *db;           /* Database on which trigger acts. */
-    struct ovs_list node;       /* !result: in db->triggers;
-                                 * result: in session->completions. */
     struct jsonrpc_msg *request; /* Database request. */
     struct jsonrpc_msg *reply;   /* Result (null if none yet). */
+    struct ovsdb_txn_progress *progress;
     long long int created;      /* Time created. */
     long long int timeout_msec; /* Max wait duration. */
     bool read_only;             /* Database is in read only mode. */
@@ -42,6 +64,7 @@ void ovsdb_trigger_destroy(struct ovsdb_trigger *);
 
 bool ovsdb_trigger_is_complete(const struct ovsdb_trigger *);
 struct jsonrpc_msg *ovsdb_trigger_steal_reply(struct ovsdb_trigger *);
+void ovsdb_trigger_cancel(struct ovsdb_trigger *, const char *reason);
 
 void ovsdb_trigger_prereplace_db(struct ovsdb_trigger *);