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/* $Id: pfs_datanode.x 235 2010-06-20 22:23:05Z gerd $ -*- c -*- */


Datanode access.

#include "pfs_types.x"


program Datanode {
    version V1 {


	void null(void) = 0;


	longstring identity(longstring) = 1;
Returns the identity of this node (an ID which is assigned anew when the datanode is initialized). The arg is the clustername. If the node belongs to the wrong cluster, this RPC must return SYSTEM_ERR.


	hyper size(void) = 2;
Returns the number of blocks. The blocks have numbers from 0 to size-1


	int blocksize(void) = 3;
Returns the blocksize


	longstring clustername(void) = 4;
Returns the clustername


	dn_channel_rd_data read
	    (dn_channel_rd_req, hyper, int, int, hyper, hyper) = 5;
read(req, block, pos, len, st_id, st_vfy): Reads a block, or a part of it. req defines how the data is passed back to the caller (see docs for dn_channel_rd_req in Pfs_types). The block is the block number of this datanode. pos and len select a substring of this block. st_id and st_vfy are the safetrans ticket returned by get_blocks.

Right now this ticket is not checked.


	void write(hyper, dn_channel_wr_data, hyper, hyper) = 6;
write(block, contents, st_id, st_vfy): Writes a block. It is only possible to write a block completely. The block is the block number of this datanode. In contents the data to write is passed. (See the docs for dn_channel_wr_data in Pfs_types for details.) The data in contents must have the length blocksize. st_id is the safetrans ID, and st_vfy is the verifier as returned by the namenode.

The safetrans ticket is checked!


	void copy(hyper, longstring, longstring, hyper,
		  hyper, hyper, hyper, hyper) = 7;
copy(block, dest_node, dest_identity, dest_block, st_id, st_vfy, dest_st_id, dest_st_vfy): Copies a block, possibly to a remote system. block identifies the block on this datanode. dest_node is the datanode server to where the block is written to. dest_identity is the identity of the destination server. dest_block is the block number of the destination server.

If dest_identity is equal to the own identity, this is a local copy. Otherwise, dest_node is interpreted as "host:port", and the block is written to the remote host.

st_id, st_vfy: as in read

dest_st_id, dest_st_vfy: as in write


	void zero(hyper, hyper, hyper) = 8;
zero(block, st_id, st_vfy): Fills a block with zeros


	void sync(void) = 9;
Waits until the next sync cycle is done


	longstring_opt alloc_shm_if_local(void) = 10;
If the client is on the same node, this RPC allocates a new POSIX shm object, and returns the path of this object. The object has zero size, and is created with mode 666. If the client is not on the same node, the RPC returns NULL.

The shm object exists only as long as the TCP connection persists (i.e. the client needs not to care about deleting it).

This method of shm-based communication is inherently insecure.


	longstring_opt udsocket_if_local(void) = 11;
If the client is on the same node, this RPC may return the name of a Unix Domain socket to contact instead.

    } = 1;
} = 0x8000d001;


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