[ovs-dev] [PATCH RFC 31/52] ovsdb-idl: Document state machine.
Ben Pfaff
blp at ovn.org
Tue Sep 19 22:01:04 UTC 2017
Signed-off-by: Ben Pfaff <blp at ovn.org>
---
lib/ovsdb-idl.c | 33 +++++++++++++++++++++++++++++++--
1 file changed, 31 insertions(+), 2 deletions(-)
diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c
index 62a6c3898227..d71188ab3c7c 100644
--- a/lib/ovsdb-idl.c
+++ b/lib/ovsdb-idl.c
@@ -79,12 +79,41 @@ struct ovsdb_idl_arc {
struct ovsdb_idl_row *dst; /* Destination row. */
};
+/* Connection state machine.
+ *
+ * When a JSON-RPC session connects, the IDL sends a "get_schema" request and
+ * transitions to IDL_S_SCHEMA_REQUESTED. If the session drops and reconnects,
+ * the IDL starts over again in the same way. */
enum ovsdb_idl_state {
+ /* Waits for "get_schema" reply, then sends a "monitor_cond" request whose
+ * details are informed by the schema and transitions to
+ * IDL_S_MONITOR_COND_REQUESTED. */
IDL_S_SCHEMA_REQUESTED,
- IDL_S_MONITOR_REQUESTED,
- IDL_S_MONITORING,
+
+ /* Waits for "monitor_cond" reply:
+ *
+ * - If the reply indicates success, replaces the IDL contents by the
+ * data carried in the reply and transitions to IDL_S_MONITORING_COND.
+ *
+ * - If the reply indicates failure because the database is too old to
+ * support monitor_cond, sends a "monitor" request and transitions to
+ * IDl_S_MONITOR_REQUESTED. */
IDL_S_MONITOR_COND_REQUESTED,
+
+ /* Waits for "monitor" reply, then replaces the IDL contents by the data
+ * carried in the reply and transitions to IDL_S_MONITORING. */
+ IDL_S_MONITOR_REQUESTED,
+
+ /* Terminal states that process "update2" (IDL_S_MONITORING_COND) or
+ * "update" (IDL_S_MONITORING) notifications. */
IDL_S_MONITORING_COND,
+ IDL_S_MONITORING,
+
+ /* Terminal error state that indicates that nothing useful can be done.
+ * The most likely reason is that the database server doesn't actually have
+ * the desired database. We maintain the session with the database server
+ * anyway. If it starts serving the database that we want, then it will
+ * kill the session and we will automatically reconnect and try again. */
IDL_S_NO_SCHEMA
};
--
2.10.2
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