[sheepdog] [disscuss] Design of Libsheepdog

[Kai Zhang]

Hi all

As we discussed in the last IRC meeting, I would like to propose an initial design
of libsheepdog. 

It is just quite initial, to avoid of waisting much time on wrong things.

Please feel free to raise your suggestions.

(PS: the doc is in html format. if you stuck on it, I will send a plain text version)

Thanks,
Kyle


Design of Libsheepdog

Table of Contents

1. Original Intention
2. APIs
1 Original Intention

Libsheepdog has been discussed for a long time. And it's time to introduce it to sheepdog project.

Libsheepdog provides the ability of operating vdi and vdi snapshot. It will be used by other systems which are built on top of sheepdog or use sheepdog as a sub-module.

2 APIs

typedef void *sd_t;
typedef struct sd_inode *sd_vdi_t;
struct string_iterator {
	void *opaqe;
	bool (*has_next)(void);
	char *(*next)(void);
	void (*destory)(void);
};

/* connection */
int sd_init(char *addr, const sd_t *sd);
int sd_close(sd_t *sd);

/* vdi */
int sd_vdi_create(sd_t sd, const char *name, size_t size, int copies,
		  bool prealloc, const sd_vdi_t *vdi);
int sd_vdi_clone(sd_t sd, const sd_vdi_t src_vdi, const char *dst_name,
		 int copies, const sd_vdi_t *dst_vdi);
int sd_vdi_open(sd_t sd, const char *name, const sd_vdi_t *vdi);
int sd_vdi_close(const sd_vdi_t *vdi);

int sd_vdi_read(sd_t sd, const sd_vdi_t vdi, void *data, size_t size,
		size_t offset);
int sd_vdi_write(sd_t sd, const sd_vdi_t vdi, void *data, size_t size,
		 size_t offset, bool writeback);
int sd_vdi_resize(sd_t sd, const sd_vdi_t vdi, size_t size);
int sd_vdi_delete(sd_t sd, const char *name);
int sd_vdi_setattr(sd_t sd, const char *name, const char *key, void *value,
		   size_t value_len);
int sd_vdi_getattr(sd_t sd, const char *name, const char *key, void *value,
		   size_t value_len);
int sd_vdi_list(sd_t sd, string_iterator *si);

/* snapshot */
int sd_vdi_snap_create(sd_t sd, const sd_vdi_t vdi, const char *tag,
		       const sd_vdi_t snap_vdi);
int sd_vdi_snap_open(sd_t sd, const char *name, const char *tag, int idx,
		     const sd_vdi_t *snap_vdi);
int sd_vdi_snap_rollback(sd_t sd, const sd_vdi_t vdi);
int sd_vdi_snap_read(sd_t sd, const sd_vdi_t vdi, void *data, size_t size,
		     size_t offset);
Here are some semantics behind them:

sd_t and sd_vdi_t are created and destroyed explicitly by calling the APIs, but user don't need to care about the memory
current APIs are all blocking, and no additional thread in backgroud
TODO:

asychronous APIs if needed
cluster operations if needed
Author: Kai Zhang
Created: 2013-06-25 Tue 19:34
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