bes  Updated for version 3.19.1
BESStoredDapResultCache Class Reference

#include <BESStoredDapResultCache.h>

Inheritance diagram for BESStoredDapResultCache:
Inheritance graph

Public Member Functions

bool cache_enabled ()
 
virtual bool cache_too_big (unsigned long long current_size) const
 look at the cache size; is it too large? Look at the cache size and see if it is too big. More...
 
virtual bool create_and_lock (const string &target, int &fd)
 Create a file in the cache and lock it for write access. More...
 
void disable ()
 Disable the cache. More...
 
virtual void dump (ostream &strm) const
 dumps information about this object More...
 
void enable ()
 Enabel the cache. More...
 
virtual void exclusive_to_shared_lock (int fd)
 Transfer from an exclusive lock to a shared lock. More...
 
const string get_cache_directory ()
 
virtual string get_cache_file_name (const string &src, bool mangle=true)
 
const string get_cache_file_prefix ()
 
virtual unsigned long long get_cache_size ()
 Get the cache size. Read the size information from the cache info file and return it. This methods locks the cache. More...
 
libdap::DMR * get_cached_dap4_data (const string &cache_file_name, libdap::D4BaseTypeFactory *factory, const string &filename)
 
virtual bool get_read_lock (const string &target, int &fd)
 Get a read-only lock on the file if it exists. More...
 
void initialize (const string &cache_dir, const string &prefix, unsigned long long size)
 
virtual void lock_cache_read ()
 
virtual void lock_cache_write ()
 
virtual void purge_file (const string &file)
 Purge a single file from the cache. More...
 
virtual string store_dap4_result (libdap::DMR &dmr, const string &constraint, BESDapResponseBuilder *rb)
 
virtual void unlock_and_close (const string &target)
 
virtual void unlock_cache ()
 
virtual void update_and_purge (const string &new_file)
 Purge files from the cache. More...
 
virtual unsigned long long update_cache_info (const string &target)
 Update the cache info file to include 'target'. More...
 

Static Public Member Functions

static bool dir_exists (const string &dir)
 
static BESStoredDapResultCacheget_instance (const string &bes_catalog_root_dir, const string &stored_results_subdir, const string &prefix, unsigned long long size)
 
static BESStoredDapResultCacheget_instance ()
 

Static Public Attributes

static const string PREFIX_KEY = "DAP.StoredResultsCache.prefix"
 
static const string SIZE_KEY = "DAP.StoredResultsCache.size"
 
static const string SUBDIR_KEY = "DAP.StoredResultsCache.subdir"
 

Protected Member Functions

 BESStoredDapResultCache (const string &data_root_dir, const string &stored_results_subdir, const string &prefix, unsigned long long size)
 

Friends

class ResponseBuilderTest
 
class StoredDap2ResultTest
 
class StoredDap4ResultTest
 

Detailed Description

This class is used to cache DAP2 response objects.

Author
jhrg 5/3/13

Definition at line 52 of file BESStoredDapResultCache.h.

Constructor & Destructor Documentation

◆ BESStoredDapResultCache()

BESStoredDapResultCache::BESStoredDapResultCache ( const string &  data_root_dir,
const string &  stored_results_subdir,
const string &  result_file_prefix,
unsigned long long  max_cache_size 
)
protected

Definition at line 198 of file BESStoredDapResultCache.cc.

Member Function Documentation

◆ cache_enabled()

bool BESFileLockingCache::cache_enabled ( )
inlineinherited
Returns
Is this cache enabled?

Definition at line 182 of file BESFileLockingCache.h.

◆ cache_too_big()

bool BESFileLockingCache::cache_too_big ( unsigned long long  current_size) const
virtualinherited

look at the cache size; is it too large? Look at the cache size and see if it is too big.

Returns
True if the size is too big, false otherwise.

Definition at line 715 of file BESFileLockingCache.cc.

◆ create_and_lock()

bool BESFileLockingCache::create_and_lock ( const string &  target,
int &  fd 
)
virtualinherited

Create a file in the cache and lock it for write access.

If the file does not exist, make it, open it for read-write access and get an exclusive lock on it. The locking operation blocks, although that should never happen.

Parameters
targetThe name of the file to make/open/lock
fdValue-result param that holds the file descriptor of the opened file
Returns
True if the operation was successful, false otherwise. This method will return false if the file already existed (the file won't be locked and the descriptor reference is undefined - but likely -1).
Exceptions
BESBESInternalErrororif any error except EEXIST is returned by open(2) or if fcntl(2) returns an error.

Definition at line 534 of file BESFileLockingCache.cc.

◆ dir_exists()

bool BESFileLockingCache::dir_exists ( const string &  dir)
staticinherited

Does the directory exist?

Note
This is a static method, so it can be called from other static methods like those that build instances of singletons.
Parameters
dirThe pathname to test.
Returns
True if the directory exists, false otherwise

Definition at line 1051 of file BESFileLockingCache.cc.

◆ disable()

void BESFileLockingCache::disable ( )
inlineinherited

Disable the cache.

Definition at line 188 of file BESFileLockingCache.h.

◆ dump()

void BESFileLockingCache::dump ( ostream &  strm) const
virtualinherited

dumps information about this object

Displays the pointer value of this instance along with information about this cache.

Parameters
strmC++ i/o stream to dump the information to

Implements BESObj.

Definition at line 1066 of file BESFileLockingCache.cc.

◆ enable()

void BESFileLockingCache::enable ( )
inlineinherited

Enabel the cache.

Definition at line 194 of file BESFileLockingCache.h.

◆ exclusive_to_shared_lock()

void BESFileLockingCache::exclusive_to_shared_lock ( int  fd)
virtualinherited

Transfer from an exclusive lock to a shared lock.

If the file has an exclusive write lock on it, change that to a shared read lock. This is an atomic operation. If the call to fcntl(2) is protected by locking the cache, a dead lock will result given typical use of this class. This method exists to help with the situation where one process has the cache locked and is blocking on a shared read lock for a file that a second process has locked exclusively (for writing). By changing the exclusive lock to a shared lock, the first process can get its shared lock and then release the cache.

Parameters
fdThe file descriptor that is exclusively locked and which, on exit, will have a shared lock.

Definition at line 565 of file BESFileLockingCache.cc.

◆ get_cache_directory()

const string BESFileLockingCache::get_cache_directory ( )
inlineinherited
Returns
The directory used for the an instance of BESFileLockingCache

Definition at line 172 of file BESFileLockingCache.h.

◆ get_cache_file_name()

string BESFileLockingCache::get_cache_file_name ( const string &  src,
bool  mangle = true 
)
virtualinherited

Returns the fully qualified file system path name for the cache file associated with this particular cache resource.

Note
How names are mangled: ALl occurrences of the characters '<', '>', '=', ',', '/', '(', ')', '"', ''', ':', '?', and ' ' with the '#' character.
Parameters
srcThe source name to cache
mangleIf True, assume the name is a file pathname and mangle it. If false, do not mangle the name (assume the caller has sent a suitable string) but do turn the string into a pathname located in the cache directory with the cache prefix. The 'mangle' param is true by default.

Reimplemented in BESUncompressCache.

Definition at line 387 of file BESFileLockingCache.cc.

◆ get_cache_file_prefix()

const string BESFileLockingCache::get_cache_file_prefix ( )
inlineinherited
Returns
The prefix used for items in an instance of BESFileLockingCache

Definition at line 166 of file BESFileLockingCache.h.

◆ get_cache_size()

unsigned long long BESFileLockingCache::get_cache_size ( )
virtualinherited

Get the cache size. Read the size information from the cache info file and return it. This methods locks the cache.

Returns
The size of the cache.

Definition at line 727 of file BESFileLockingCache.cc.

◆ get_cached_dap4_data()

DMR * BESStoredDapResultCache::get_cached_dap4_data ( const string &  cache_file_name,
libdap::D4BaseTypeFactory *  factory,
const string &  filename 
)

Read data from cache. Allocates a new DDS using the given factory. If the file does not exists this will return null (0).

Definition at line 538 of file BESStoredDapResultCache.cc.

◆ get_instance()

BESStoredDapResultCache * BESStoredDapResultCache::get_instance ( )
static

Get the default instance of the BESStoredDapResultCache object. This will read "TheBESKeys" looking for the values of SUBDIR_KEY, PREFIX_KEY, an SIZE_KEY to initialize the cache.

Definition at line 240 of file BESStoredDapResultCache.cc.

◆ get_read_lock()

bool BESFileLockingCache::get_read_lock ( const string &  target,
int &  fd 
)
virtualinherited

Get a read-only lock on the file if it exists.

Try to get a read-only lock on the file, blocking until we can get it. If the file does not exist, return false.

Note
If this code returns false, that means the file did not exist in the cache at the time of the test. by the time the caller gets the result, the file may have been added to the cache by another process.
Parameters
targetThe path of the cached file
fdA value-result parameter set to the locked cached file. Undefined if the file could not be locked for read access.
Returns
true if the file is in the cache and has been locked, false if the file is/was not in the cache.
Exceptions
Errorif the attempt to get the (shared) lock failed for any reason other than that the file does/did not exist.

Definition at line 479 of file BESFileLockingCache.cc.

◆ lock_cache_read()

void BESFileLockingCache::lock_cache_read ( )
virtualinherited

Get a shared lock on the 'cache info' file.

Definition at line 604 of file BESFileLockingCache.cc.

◆ lock_cache_write()

void BESFileLockingCache::lock_cache_write ( )
virtualinherited

Get an exclusive lock on the 'cache info' file. The 'cache info' file is used to control certain cache actions, ensuring that they are atomic. These include making sure that the create_and_lock() and read_and_lock() operations are atomic as well as the purge and related operations.

Note
This is intended to be used internally only but might be useful in some settings.

Definition at line 589 of file BESFileLockingCache.cc.

◆ purge_file()

void BESFileLockingCache::purge_file ( const string &  file)
virtualinherited

Purge a single file from the cache.

Purge a single file from the cache. The file might be old, etc., and need to be removed. Don't use this to shrink the cache when it gets too big, use update_and_purge() instead since that file optimizes accesses to the cache control file for several changes in a row.

Parameters
fileThe name of the file to purge.

Definition at line 1000 of file BESFileLockingCache.cc.

◆ store_dap4_result()

string BESStoredDapResultCache::store_dap4_result ( libdap::DMR &  dmr,
const string &  constraint,
BESDapResponseBuilder rb 
)
virtual
Returns
The local ID (relative to the BES data root directory) of the stored dataset.

Definition at line 739 of file BESStoredDapResultCache.cc.

◆ unlock_and_close()

void BESFileLockingCache::unlock_and_close ( const string &  file_name)
virtualinherited

Unlock the named file.

This does not do any name mangling; it just closes and unlocks whatever is named (or throws BESBESInternalErroror if the file cannot be closed). If the file was opened more than once, all descriptors are closed. If you need to close a specific descriptor, use the other version of unlock_and_close().

Note
This method assumes that the file was opened/locked using one of read_and_lock() or create_and_lock(). Those methods record the name/file- descriptor pairs so that the files can be properly closed and locks released.
Parameters
file_nameThe name of the file to unlock.
Exceptions
BESBESInternalErroror

Definition at line 648 of file BESFileLockingCache.cc.

◆ unlock_cache()

void BESFileLockingCache::unlock_cache ( )
virtualinherited

Unlock the cache info file.

Note
This is intended to be used internally only bt might be useful in some settings.

Definition at line 621 of file BESFileLockingCache.cc.

◆ update_and_purge()

void BESFileLockingCache::update_and_purge ( const string &  new_file)
virtualinherited

Purge files from the cache.

Purge files, oldest to newest, if the current size of the cache exceeds the size of the cache specified in the constructor. This method uses an exclusive lock on the cache for the duration of the purge process.

Parameters
new_fileThe name of a file this process just added to the cache. Using fcntl(2) locking there is no way this process can detect its own lock, so the shared read lock on the new file won't keep this process from deleting it (but will keep other processes from deleting it).

Definition at line 865 of file BESFileLockingCache.cc.

◆ update_cache_info()

unsigned long long BESFileLockingCache::update_cache_info ( const string &  target)
virtualinherited

Update the cache info file to include 'target'.

Add the size of the named file to the total cache size recorded in the cache info file. The cache info file is exclusively locked by this method for its duration. This updates the cache info file and returns the new size.

Parameters
targetThe name of the file
Returns
The new size of the cache

Definition at line 672 of file BESFileLockingCache.cc.


The documentation for this class was generated from the following files: