globus_gass_cache(3)

Library Functions Manual

globus_gass_cache(3)

NAME¶

globus_gass_cache - Globus GASS Cache

- Globus GASS Cache.

SYNOPSIS¶

Macros¶

#define GLOBUS_GASS_CACHE_MODULE (&globus_i_gass_cache_module)
module_descriptor

Typedefs¶

typedef struct globus_i_gass_cache_t * globus_gass_cache_t
GASS Cache Handle.

Functions¶

int globus_gass_cache_open (const char *cache_directory_path, globus_gass_cache_t *cache_handlep)
Open a GASS Cache. int globus_gass_cache_close (globus_gass_cache_t *cache_handlep)
Close a cache handle. int globus_gass_cache_add (globus_gass_cache_t cache_handle, const char *url, const char *tag, globus_bool_t create, unsigned long *timestamp, char **local_filename)
Add a tag to an URL in the cache. int globus_gass_cache_add_done (globus_gass_cache_t cache_handle, const char *url, const char *tag, unsigned long timestamp)
Complete adding a cache entry and unlock it. int globus_gass_cache_query (globus_gass_cache_t cache_handle, const char *url, const char *tag, globus_bool_t wait_for_lock, unsigned long *timestamp, char **local_filename, globus_bool_t *is_locked)
Query the GASS Cache. int globus_gass_cache_delete_start (globus_gass_cache_t cache_handle, const char *url, const char *tag, unsigned long *timestamp)
Remove a cache tag. int globus_gass_cache_delete (globus_gass_cache_t cache_handle, const char *url, const char *tag, unsigned long timestamp, globus_bool_t is_locked)
Remove one instance of the tag from the cache entry's tag list. int globus_gass_cache_cleanup_tag (globus_gass_cache_t cache_handle, const char *url, const char *tag)
Remove a tag from a cache entry. int globus_gass_cache_cleanup_tag_all (globus_gass_cache_t cache_handle, char *tag)
Remove a tag from all cache entries

Remove all instances of the tag from the cache entry's tag list. If there are no more tags in the tag list, then remove this cache entry and delete the associated local cache file. If the cache entry is locked with the same tag as is passed to this function, then the entry is unlocked after removing the tags. Otherwise, the cache entry's lock is left untouched. " int globus_gass_cache_mangle_url (const globus_gass_cache_t cache_handle, const char *url, char **mangled_url, int *length)
Convert a URL to a string suitable as a file path. int globus_gass_cache_mangle_tag (const globus_gass_cache_t cache_handle, const char *tag, char **mangled_tag, int *length)
Convert a tag to a string suitable as a file path. int globus_gass_cache_get_cache_dir (const globus_gass_cache_t cache_handle, char **cache_dir)
Get the GASS Cache's root directory. int globus_gass_cache_get_dirs (const globus_gass_cache_t cache_handle, const char *url, const char *tag, char **global_root, char **local_root, char **tmp_root, char **log_root, char **global_dir, char **local_dir)
Get the set of directories used by a GASS Cache. int globus_gass_cache_get_cache_type_string (const globus_gass_cache_t cache_handle, char **cache_type)
Get the type of GASS Cache directory layout. const char * globus_gass_cache_error_string (int error_code)
Look up the error string corresponding to a GASS Cache error.

Detailed Description¶

Globus GASS Cache.

The GASS cache management API is part of the Globus module called 'GASS', (Global Access to Secondary Storage) The GASS cache management API defines calls for manipulating a local file cache.

Each cache entry can be locked during addition and deletion to allow for atomic handling of the cache file contents.

Each cache entry also has an associated timestamp. This timestamp is independent of the local cache file's modification time. Rather, the cache entry timestamp is maintained by the user. It can, for example, be used to keep track of the timestamp of a remote file that is associated with the cache entry.

Note: all timestamps are as seconds since the epoch. (01 Jan 1970, 00:00 GMT)

The following functions are part of the API:

globus_gass_cache_open()
globus_gass_cache_close()
globus_gass_cache_add()
globus_gass_cache_add_done()
globus_gass_cache_delete_start()
globus_gass_cache_delete()
globus_gass_cache_cleanup_tag()
globus_gass_cache_cleanup_tag_all()
globus_gass_cache_mangle_url()
globus_gass_cache_mangle_tag()
globus_gass_cache_get_dirs()
globus_gass_cache_get_cache_dir()

Typedef Documentation¶

typedef struct globus_i_gass_cache_t* globus_gass_cache_t¶

GASS Cache Handle. Data structure used to store information concerning an open cache directory. This structure MUST NOT be modified directly, but passed to the globus_gass_cache functions

Function Documentation¶

int globus_gass_cache_add (globus_gass_cache_t cache_handle, const char * url, const char * tag, globus_bool_t create, unsigned long * timestamp, char ** local_filename) [extern]¶

Add a tag to an URL in the cache. Create a new cache file or add a tag on it.

If the URL is already in the cache but is locked, then this call will block until the cache entry is unlocked, then will proceed with the subsequent operations.

If the URL is already in the cache and unlocked, then add the tag to the cache entry's tag list, return the local cache filename in *local_filename, return the entry's current timestamp in *timestamp, lock the cache entry, and return GLOBUS_GASS_CACHE_ADD_EXISTS.

If the URL is not in the cache, and create==GLOBUS_TRUE, then create a new unique empty local cache file, add it to the cache with the specified tag, return the filename in *local_filename, return *timestamp set to GLOBUS_GASS_CACHE_TIMESTAMP_UNKNOWN, lock the cache entry, and return GLOBUS_GASS_CACHE_ADD_NEW.

If the URL is not in the cache, and create==GLOBUS_FALSE, then do not add it to the cache, and return GLOBUS_GASS_CACHE_URL_NOT_FOUND.

If this function returns GLOBUS_GASS_CACHE_ADD_EXISTS or GLOBUS_GASS_CACHE_ADD_NEW, then globus_gass_cache_add_done() or globus_gass_cache_delete() must be subsequently called to unlock the cache entry.

Subsequent calls to globus_gass_cache_add() and globus_gass_cache_delete_start() on the same cache and url, made either from this process or another, will block until the cache entry is unlocked.

If tag==NULL, then a tag with the value 'null' will be added to the cache entry's tag list.

The same tag can be used multiple times, in which case this tag will be added to the entry's tag list multiple times.

Note: It is recommended that proglobus_grams started via GLOBUS_GRAM pass a tag value of getenv('GLOBUS_GRAM_JOB_CONTACT'), since upon completion of a job GLOBUS_GRAM will automatically cleanup entries with this tag.

Note

the local_filename MUST be free by the user in a subsequent operation, using free()

Parameters

cache_handle Handle to the opened cache directory to use.
url URL of the file to be cached. It is used as the main key to the cache entries.
tag Tag specifying which job is/are using the cache. This is usually the GLOBUS_GRAM_JOB_CONTACT. Can be NULL or empty; the tag 'null' is then used. create - Tells if the cache entry should be created if it is not already existing.
create Flag to create if it does not already exist.
timestamp Timestamp of the cached file, set by globus_gass_cache_done(), (or globus_gass_cache_delete() ).
local_filename Path the the local file caching the file specified by 'url'. NULL if 'url' not yet cached and creation not requested (create false).

Returns

GLOBUS_GASS_CACHE_URL_NOT_FOUND
GLOBUS_GASS_CACHE_ADD_NEW
GLOBUS_GASS_CACHE_ADD_EXISTS
or any of the defined gass error code.

int globus_gass_cache_add_done (globus_gass_cache_t cache_handle, const char * url, const char * tag, unsigned long timestamp) [extern]¶

Complete adding a cache entry and unlock it. globus_gass_cache_add_done() MUST be called after globus_gass_cache_add(), to set the timestamp in the cache entry for the URL, and then unlock the cache entry. (The only case it does not need to be called is if globus_gass_cache_add() has returned GLOBUS_GASS_CACHE_URL_NOT_FOUND, of course.

Parameters

cache_handle Handle to the opened cache directory to use.
url URL of the cached file to set as 'done' (unlock)
tag Tag specifying which job has locked the cache and must therefore be unlocked. It is an error to call this function with a tag which does not currently own the cache lock.
timestamp Timestamp of the cached file.

Returns

globus_gass_cache_add_done() returns GLOBUS_SUCCESS or any of the defined GASS Cache error codes.

int globus_gass_cache_cleanup_tag (globus_gass_cache_t cache_handle, const char * url, const char * tag) [extern]¶

Remove a tag from a cache entry. Remove all instances of the tag from the cache entry's tag list. If there are no more tags in the tag list, then remove this cache entry and delete the associated local cache file. If the cache entry is locked with the same tag as is passed to this function, then the entry is unlocked after removing the tags. Otherwise, the cache entry's lock is left untouched.

This function does not block on a locked reference.

Note

The GLOBUS_GRAM job manager will automatically call this function with a tag of getenv('GLOBUS_GRAM_JOB_CONTACT') upon completion of a job.

Parameters

Returns

The globus_gass_cache_cleanup_tag() function returns GLOBUS_SUCCESS or any of the defined GASS Cache error codes.

int globus_gass_cache_cleanup_tag_all (globus_gass_cache_t cache_handle, char * tag) [extern]¶

Remove a tag from all cache entries

Note

The GLOBUS_GRAM job manager will automatically call this function with a tag of getenv('GLOBUS_GRAM_JOB_CONTACT') upon completion of a job.

Parameters

cache_handle Handle to the opened cache directory to use.
tag Tag specifying which job is/are using the cache. This is usually the GLOBUS_GRAM_JOB_CONTACT. Can be NULL or empty; the tag 'null' is then used.

Returns

The globus_gass_cache_cleanup_tag_all() function returns GLOBUS_SUCCESS or any of the defined GASS Cache error codes.

int globus_gass_cache_close (globus_gass_cache_t * cache_handlep)¶

Close a cache handle. Close (NOT delete) a previously opened cache:

close the opened files and
free the memory allocated for the cache_handle.
mark the handle as 'not initialized'.

Parameters: cache_handle: Handle to the opened cache directory to use.

cache_handle->is_init set to 'not initialized' and all the files opened bu globus_gass_cache_open are closed .

Returns: GLOBUS_SUCCESS or error code: GLOBUS_GASS_CACHE_ERROR_CACHE_NOT_OPENED

int globus_gass_cache_delete (globus_gass_cache_t cache_handle, const char * url, const char * tag, unsigned long timestamp, globus_bool_t is_locked) [extern]¶

Remove one instance of the tag from the cache entry's tag list. If there are no more tags in the tag list, then remove this cache entry and delete the associated local cache file.

Otherwise, update the timestamp to the passed value.

This call will leave the cache entry unlocked.

If is_locked==GLOBUS_TRUE, then this cache entry was locked during a previous call to globus_gass_cache_add() or globus_gass_cache_delete_start(). The cache file should be locked by the corresponding url/tag, or an error is returned. If it is locked by the corresponding url/tag, then the normal operation occur, without blocking (remove one instance from the tag update the timestamp and unlock the cache).

If is_locked==GLOBUS_FALSE, eventually wait the cache is not locked any more, and then proceed with the normal operations.(remove one instance from the tag list and update the timestamp).

Parameters

Returns

The globus_gass_cache_delete() function returns GLOBUS_SUCCESS or any of the defined GASS Cache error codes.

int globus_gass_cache_delete_start (globus_gass_cache_t cache_handle, const char * url, const char * tag, unsigned long * timestamp) [extern]¶

Remove a cache tag. Lock the cache entry for the URL, and return the cache entry's current timestamp in *timestamp. This function will block if the data file is already locked, until it is unlocked.

Parameters

Returns

The globus_gass_cache_delete_start() function returns GLOBUS_SUCCESS or any of the defined GASS Cache error code.

const char * globus_gass_cache_error_string (int error_code) [extern]¶

Look up the error string corresponding to a GASS Cache error. Return a pointer on an error description string.

Parameters

error_code error code returned by a previously called globus_gass_cache function.

Returns

The globus_gass_cache_error_string() function returns a pointer to an error message, or NULL if error_code is invalid.

int globus_gass_cache_get_cache_dir (const globus_gass_cache_t cache_handle, char ** cache_dir) [extern]¶

Get the GASS Cache's root directory. Get a the root cache of directory. This is exported for use in the globus_gass_cache program.

Parameters

cache_handle Handle to the opened cache directory to use.
cache_dir Pointer to the cache directory

Return values