Pfs_nn_internal

/* $Id: pfs_nn_internal.x 450 2011-10-11 12:30:40Z gerd $ -*- c -*- */

Internal interfaces used by the namenodes

#include "pfs_types.x"

#ifndef PFS_NN_INTERNAL_X
#define PFS_NN_INTERNAL_X

Elect

The election happens at cluster startup. The goal is to determine the coordinator. Participants are all namenodes.

program Elect {
    version V1 {

null

	void null(void) = 0;

announce

	ann_result announce(announcement) = 1;

At cluster start the namenodes start calling the announce RPC of all other namenodes - until they get a reply from each, or until the end of the startup period is reached.

If received within the startup period, the response is ANN_ACCEPT if the announcement is better than the server to which it is sent. Otherwise it is ANN_REJECT. If received after startup, the response is always ANN_REJECT, and the sender must not start up. The response is ANN_SELF if the namenode instance sends the announcement to itself.

As all namenodes call announce of all other namenodes, the question is whether there is a winner. If we assume there is a total ordering between the announcements, there is a best announcement if no two namenodes emit equal announcements. So given the announcements are all distinct, there is a winner.

set_coordinator

	void set_coordinator(mediumstring, mediumstring, mediumstring) = 2;

When the end of the startup period is reached, one of the name nodes sends set_coordinator to all other nodes, and becomes the coordinator. The coordinator must be eligible by all other nodes that actually respond. Also, the coordinator must have a highest revision number, and among all nodes with the highest revision number, the coordinator has the lowest rank.

The first arg is the "host:port" name of the coordinator. (Instead of the host name this string can also name the coordinator by IP address if this is the preferred method of referencing it.)

The second arg is the clustername.

The third arg is the revision identifier.

There is right now no provision for the case that the coordinator crashes - no other node is then automatically elected. Best is to restart everything then.

	
    } = 1;
} = 0x8000f001;

Nameslave

This RPC program is activated on the non-coordinator namenodes. It is called by the coordinator to push updates of the database.

program Nameslave {
    version V1 {
	/* This is what the non-coordinators implement */

null

	void null(void) = 0;

begin_transaction

	void begin_transaction(mediumstring, mediumstring) = 1;

Begin a transaction: clustername, expected_rev. The 2nd arg is the expected revision string

prepare_commit

	bool prepare_commit(void) = 2;

Result is true if the name database could be updated.

commit

	void commit(void) = 3;

The response of commit is the ACK in the extended 2-phase commit protocol

	/* void abort(void) = 4; */

Note that the names of the following RPCs correspond to function names in Nn_db:

set_ds_cache

	void set_ds_cache(ds_info_list) = 5;

set_ds_cache(l): calls Nn_db.ds_cache_init(`Datastores l)

push_inode_ins

	void push_inode_ins(hyper, inodeinfo) = 7;

push_inode_ins(inode, ii)

push_inode_upd

	void push_inode_upd(hyper, inodeinfo) = 8;

push_inode_upd(inode, ii)

push_inode_upd_time

	void push_inode_upd_time(hyper, time_opt, time_opt) = 18;

push_inode_upd_time(inode, mtime, ctime)

push_inode_del

	void push_inode_del(hyper) = 9;

push_inode_del(inode)

push_blockalloc_upd

	void push_blockalloc_upd(int, hyper, longstring) = 10;

push_blockalloc_upd(datastore,blkidx,blkmap)

push_datastore_upd

	void push_datastore_upd(int, mediumstring, hyper, bool) = 11;

push_upd_datastore(id,identity,size,enabled): Updates the datastore table. If the record is new, it is added.

The blockalloc table is updated, too: For new stores, the rows are added. If the size of the existing store is increased, further rows are added.

It is an error to decrease the size.

push_datastore_del

	void push_datastore_del(int) = 12;

Deletes the datastore with this ID and all rows referencing it

push_revision_upd

	void push_revision_upd(mediumstring) = 13;

Sets the revision id in the db

push_inodeblocks_ins

	void push_inodeblocks_ins(hyper, blocklist) = 14;

push_inodeblocks_ins(inode, bl)

push_inodeblocks_del

	void push_inodeblocks_del(hyper, hyper, hyper) = 15;

push_inodeblocks_del(inode, blkidx, len)

push_names_ins

	void push_names_ins(hyper, mediumstring, hyper) = 16;

push_names_ins(dir_inode, path, inode)

push_names_del

	void push_names_del(hyper, mediumstring) = 17;

push_names_del(dir_inode,path)

push_admin_table

	void push_admin_table(mediumstring, longstring) = 19;

push_admin_table(key,contents)

    } = 1;
} = 0x8000f002;

Monitor

program Monitor {
    version V1 {

null

	void null(void) = 0;

start

	void start(void) = 1;

Starts the monitor: First, the state is loaded from the db. Second, all known datanodes are discovered and enabled. Third, the newsfeed for monitoring results is started. Fourth, the Dn_admin interface is enabled.

    } = 1;
} = 0x8000f003;


#endif

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