scheduler_ha.h File Reference

Scheduling functions for chunk and peer selection. More...

#include "scheduler_common.h"

Go to the source code of this file.

Functions
int	schedInit (char *cfg)
void	schedSelectPushList (schedPeerID *peers, int peers_len, schedChunkID *chunks, int chunks_len, struct PeerChunk *selected, int *selected_len)
void	schedSelectRequestList (schedPeerID *peers, int peers_len, schedChunkID *chunks, int chunks_len, struct PeerChunk *selected, int *selected_len)
void	schedSelectOfferList (schedPeerID *peers, int peers_len, schedChunkID *chunks, int chunks_len, struct PeerChunk *selected, int *selected_len)
void	schedSelectProposeList (schedPeerID *peers, int peers_len, schedChunkID *chunks, int chunks_len, struct PeerChunk *selected, int *selected_len)
void	schedSelectAcceptList (schedPeerID *peers, int peers_len, schedChunkID *chunks, int chunks_len, struct PeerChunk *selected, int *selected_len)

---

Detailed Description

Scheduling functions for chunk and peer selection.

The chunk & peer scheduler (or simply ``scheduler'') is responsible for selecting a list of peer-chunk pairs whenever chunks or trade messages are to be sent. It can e.g. select destination peers and chunks to be sent when push streaming is used, or the peer to request from and the list of chunks to ask for when pull mode operation is required. Note that in this design the scheduler has nothing to do with the timing (it does not decide when to send chunks, but only decides which chunks to send/reqest/offer/propose/accept and the destination/source peer). Hence, the scheduler is non-blocking and has to be invoked at the correct time.

The scheduler uses:

• information about the neighbourhood and its state: hence, it directly communicates with the NeighborhoodList;
• information about the chunks currently contained in the chunk buffer: hence, it directly interacts with the chunk buffer.

---

Function Documentation

int schedInit

(

char *

cfg

)

Initialize the scheduler

Parameters:

[in]

cfg

configuration string

void schedSelectAcceptList	(	schedPeerID *	peers,
		int	peers_len,
		schedChunkID *	chunks,
		int	chunks_len,
		struct PeerChunk *	selected,
		int *	selected_len
	)

Select chunks to accept based on proposals.

This selection function which proposed chunks to ask for.

Parameters:

[in]	peers	list of peers to choose from.
[in]	peers_len	length of the peers list
[in]	chunks	list of chunks to choose from.
[in]	chunks_len	length of the chunks list
[out]	selected	ordered list of peer-chunk pairs selected
[in,out]	selected_len	in: maximum number of selectable pairs, also defines the allocated space for selected. out: length of the selected list

void schedSelectOfferList	(	schedPeerID *	peers,
		int	peers_len,
		schedChunkID *	chunks,
		int	chunks_len,
		struct PeerChunk *	selected,
		int *	selected_len
	)

Select what to offer based on the requests that arrived.

In a simple pull model, all requests are served, therefore no selection is needed on the sender side. In a more sophisicated model, the sender side should evaluate requests that have arrived and select the ones that are satisfied. This selection funciton is to

Parameters:

[in]	peers	list of peers to choose from.
[in]	peers_len	length of the peers list
[in]	chunks	list of chunks to choose from.
[in]	chunks_len	length of the chunks list
[out]	selected	ordered list of peer-chunk pairs selected
[in,out]	selected_len	in: maximum number of OCselectable pairs, also defines the allocated space for selected. out: length of the selected list

void schedSelectProposeList	(	schedPeerID *	peers,
		int	peers_len,
		schedChunkID *	chunks,
		int	chunks_len,
		struct PeerChunk *	selected,
		int *	selected_len
	)

Select chunks to propose to other peers.

This selection function decides which chunks to propose to which peers. In this case first a decision is made at the peer initiating the transaction about the set of peers it is willing to send to the other peer.

Parameters:

[in]	peers	list of peers to choose from.
[in]	peers_len	length of the peers list
[in]	chunks	list of chunks to choose from.
[in]	chunks_len	length of the chunks list
[out]	selected	ordered list of peer-chunk pairs selected
[in,out]	selected_len	in: maximum number of selectable pairs, also defines the allocated space for selected. out: length of the selected list

void schedSelectPushList	(	schedPeerID *	peers,
		int	peers_len,
		schedChunkID *	chunks,
		int	chunks_len,
		struct PeerChunk *	selected,
		int *	selected_len
	)

Select a list of peer-chunk pairs for sending.

In a simple push model, chunks are sent to peers without further messaging. This selection function selects the chunk-peer pairs for this simple pull operation.

Parameters:

[in]	peers	list of peers to choose from.
[in]	peers_len	length of the peers list
[in]	chunks	list of chunks to choose from.
[in]	chunks_len	length of the chunks list
[out]	selected	ordered list of peer-chunk pairs selected
[in,out]	selected_len	in: maximum number of selectable pairs, also defines the allocated space for selected. out: length of the selected list

void schedSelectRequestList	(	schedPeerID *	peers,
		int	peers_len,
		schedChunkID *	chunks,
		int	chunks_len,
		struct PeerChunk *	selected,
		int *	selected_len
	)

Select what chunks to request from which peers.

In a pull model, chunk requests shuold be explicitly signaled. This selection function serves to select the peer-chunk combinations for such requests. E.g. one well known implementation of this selection creates a partitioning of the missing chunk set and assigns a peer to each of these subsets.

Parameters:

[in]	peers	list of peers to choose from.
[in]	peers_len	length of the peers list
[in]	chunks	list of chunks to choose from.
[in]	chunks_len	length of the chunks list
[out]	selected	ordered list of peer-chunk pairs selected
[in,out]	selected_len	in: maximum number of selectable pairs, also defines the allocated space for selected. out: length of the selected list