Plug-ins

LS4 uses of plug-in archtecture. It describes how to switch and use the plug-ins in this document.

MDS plug-in

You can choose the implementation of metadata server (MDS) by specifing scheme to the –mds option on config server (CS). The default is Tokyo Tyrant (tt:).

Tokyo Tyrant (tt:)

This uses Tokyo Tyrant‘s table database for the MDS. It supports versioning.

You cna use single-server mode, master-slave mode and dual-master mode.

In single-server mode, use –mds tt:<server[:port]> format.

In master-slave mode, specify addresses of the servers in comma-separated form like host1[:port],host2[:port],.... In addition, you can specify the weight of the reference as in comma-separated form followed by ; like –mds tt:host:port,host:port,...;weight1,weight2,.... For example, if you use host1 as a master server, and host2 and host2 as slave servers, and divide reference loads in 2:1 raito on slave servers, specify: –mds tt:host1,host2,host3;0,2,1

In dual-master mode, speficy the two addresses of the servers with separator like host1[:port]–host2[:port]. For example, if you use host1 and host2 in dual-master mode, specify: –mds tt:host1–host2.

Memcache (mc:)

This uses memcached protocol for the MDS. It does NOT support versioning.

This plug-in is intended to use persistent storage system that supports memcached protocol like Kumofs, Flare, Membase, etc. Don’t use memcached.

Scheme is mc:host[:port]. The default port number is 11211.

MDS cache plug-in

You can enable metadata cache by adding –mds-cache option on config server.

Memcached (mc:)

This uses memcached for the the MDS cache. You can use Kyoto Tycoon instead of memcached.

Scheme is mc:<servers>[;<expire>]

Local memory (local:)

This uses local memory for the MDS cache. Because cached data are not shared, updating APIs operations may occur consistency problem.

Schem is local:<size>. You can use size suffixes like “k”, “m” or “g”.

For example, if you use 32MB of the local memory for the MDS cache, specify: –mds-cache local:32m.

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