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OVSDB Monitor¶
This blueprint describe the addition of OVSDB monitor support for Dragonflow. It implements the lightweight OVSDB driver which based on the OVSDB monitornotification mechanism, it solves the performance problem for Dragonflow to fetch vm ports/interfaces info from OVSDB.
Problem Description¶
In current Dragonflow implementation of fetch OVSDB data, Dragonflow will start a loop to detect the addupdatedelete for logical ports, for example after Dragonflow finds a new logical port, it will establish a socket channel to OVSDB, fetch many data from some OVSDB tables(BridgePortInterface Table) and find several useful info(ofportchassis id) for the new logical port. There are some performance problems for above implementation:
The loop will consume many server resources because it will pull large amount data from DB cluster and do the comparison with the local cache frequently;
For each new logical port, Dragonflow will create a socket channel to fetch data from OVSDB, if we create many new logical ports in the future or even in a very short time, it will consume the server resources further;
For each session between Dragonflow and OVSDB for a new logical port, it will fetch many unnecessary data from many OVSDB tables;
Solution Description¶
We bring in OVSDB monitornotification mechanism which has detail description in OVSDB protocol rfc (https://tools.ietf.org/html/rfc7047#section-4.1.5)
We have Dragonflow and open vswitch on the same server, when OVS start up, OVSDB will listen on port 6640, while when Dragonflow start up, OVSDB driver will attempt to connect the OVSDB and subscribe the data to OVSDB server which it is interested in, the details show below:
1. OVSDB server start up and listen on port 6640 and Dragonflow start up while the OVSDB driver try to connect to OVSDB server as OVSDB client with tcp:127.0.0.1:6640;
2. When OVSDB driver establish the channel with OVSDB server, OVSDB driver send the OVSDB monitor command with below jsonrpc content:
method:monitor params:[<db-name>,<json-value>,<monitor-requests>] id:nonnull-json-value
In our solution, we only monitor the OVSDB “Interface Table”, so OVSDB driver will send the monitor Interface table jsonrpc message to OVSDB server;
3. When OVSDB server receive the monitor message sent by OVSDB driver, it will send a reply message which contains all the interfaces detail info (if it has) back to OVSDB driver;
4. OVSDB driver receives and decodes the monitor reply message, it will map each interface info to different type events(bridge online, vm online, tunnel port online, patch port online), OVSDB driver will notify these events to upper layer modules;
5. When tenant boot a vm on the host and add the vm port to the OVS bridge, OVSDB server will send a notification to OVSDB driver according to the update of OVS Interface Table, the notification will only contain the new vm interface detail info, and after OVSDB driver receive the notification it will do the same work as step 4;
6. When tenant shutdown a vm on the host and delete the vm port from the OVS bridge, OVSDB server will send a notification to OVSDB driver according to the update of OVS Interface Table, the notification will only contain the delete vm interface detail info, and after OVSDB driver receive the notification it will do the same work as step 4.
If we restart Dragonflow process or restart the OVSDB, Dragonflow OVSDB driver will reconnect to OVSDB server, so step1 to 6 will be executed again.
Event Classification¶
We could judge the event type according to the fields content in the monitor reply or table change notification, if you want to see the detail content in the message, you can execute the command on the OVS(OVSDB monitor Interface -v) , the detail judgement fields show below:
Bridge onlineoffline:
type internal name Br-intbr-tunbr-ex
Vm onlineoffline:
Iface-id 4aa64e21-d9d6-497e-bfa9-cf6dbb574054 name tapxxx
Tunnel port onlineoffline:
Remote_ip 10.10.10.10 name dfxxx type Vxlangregeneve
Patch port onlineoffline:
type patch options Peer=<peer port name>
Conclusion¶
Our solution provides a lightweight OVSDB driver functionality which implements the OVSDB data monitor and synchronize, remove the Dragonflow loop process, maintain only one socket channel and transfer less data.