Provided by: rrdtool_1.7.1-2_amd64 bug

NAME

       librrd - RRD library functions

DESCRIPTION

       librrd contains most of the functionality in RRDtool.  The command line utilities and
       language bindings are often just wrappers around the code contained in librrd.

       This manual page documents the librrd API.

       NOTE: This document is a work in progress, and should be considered incomplete as long as
       this warning persists.  For more information about the librrd functions, always consult
       the source code.

CORE FUNCTIONS

       rrd_dump_cb_r(char *filename, int opt_header, rrd_output_callback_t cb, void *user)
           In some situations it is necessary to get the output of "rrd_dump" without writing it
           to a file or the standard output. In such cases an application can ask rrd_dump_cb_r
           to call a user-defined function each time there is output to be stored somewhere. This
           can be used, to e.g. directly feed an XML parser with the dumped output or transfer
           the resulting string in memory.

           The arguments for rrd_dump_cb_r are the same as for rrd_dump_opt_r except that the
           output filename parameter is replaced by the user-defined callback function and an
           additional parameter for the callback function that is passed untouched, i.e. to store
           information about the callback state needed for the user-defined callback to function
           properly.

           Recent versions of rrd_dump_opt_r internally use this callback mechanism to write
           their output to the file provided by the user.

               size_t rrd_dump_opt_cb_fileout(
                   const void *data,
                   size_t len,
                   void *user)
               {
                   return fwrite(data, 1, len, (FILE *)user);
               }

           The associated call for rrd_dump_cb_r looks like

               res = rrd_dump_cb_r(filename, opt_header,
                   rrd_dump_opt_cb_fileout, (void *)out_file);

           where the last parameter specifies the file handle rrd_dump_opt_cb_fileout should
           write to. There's no specific condition for the callback to detect when it is called
           for the first time, nor for the last time. If you require this for initialization and
           cleanup you should do those tasks before and after calling rrd_dump_cb_r respectively.

       rrd_fetch_cb_register(rrd_fetch_cb_t c)
           If your data does not reside in rrd files, but you would like to draw charts using the
           rrd_graph functionality, you can supply your own rrd_fetch function and register it
           using the rrd_fetch_cb_register function.

           The argument signature and api must be the same of the callback function and must be
           equivalent to the one of rrd_fetch_fn in rrd_fetch.c.

           To activate the callback function you can use the pseudo filename cb//free_form_text.

           Note that rrdtool graph will not ask the same rrd for data twice. It determines this
           by building a key out of the values supplied to the fetch function. If the values are
           the same, the previous answer will be used.

UTILITY FUNCTIONS

       rrd_random()
           Generates random numbers just like random().  This further ensures that the random
           number generator is seeded exactly once per process.

       rrd_strtodbl
           an rrd aware string to double converter which sets rrd_error in if there is a problem
           and uses the return code exclusively for conversion status reporting.

       rrd_strtod
           works like normal strtod, but it is locale independent (and thread safe)

       rrd_snprintf
           works  like normal snprintf but it is locale independent (and thread safe)

       rrd_add_ptr(void ***dest, size_t *dest_size, void *src)
           Dynamically resize the array pointed to by "dest".  "dest_size" is a pointer to the
           current size of "dest".  Upon successful realloc(), the "dest_size" is incremented by
           1 and the "src" pointer is stored at the end of the new "dest".  Returns 1 on success,
           0 on failure.

               type **arr = NULL;
               type *elem = "whatever";
               size_t arr_size = 0;
               if (!rrd_add_ptr(&arr, &arr_size, elem))
                   handle_failure();

       rrd_add_ptr_chunk(void ***dest, size_t *dest_size, void *src, size_t *alloc, size_t chunk)
           Like "rrd_add_ptr", except the destination is allocated in chunks of "chunk".  "alloc"
           points to the number of entries allocated, whereas "dest_size" points to the number of
           valid pointers.  If more pointers are needed, "chunk" pointers are allocated and
           "alloc" is increased accordingly.  "alloc" must be >= "dest_size".

           This method improves performance on hosts with expensive "realloc()".

       rrd_add_strdup(char ***dest, size_t *dest_size, char *src)
           Like "rrd_add_ptr", except adds a "strdup" of the source string.

               char **arr = NULL;
               size_t arr_size = NULL;
               char *str  = "example text";
               if (!rrd_add_strdup(&arr, &arr_size, str))
                   handle_failure();

       rrd_add_strdup_chunk(char ***dest, size_t *dest_size, char *src, size_t *alloc, size_t
       chunk)
           Like "rrd_add_strdup", except the destination is allocated in chunks of "chunk".
           "alloc" points to the number of entries allocated, whereas "dest_size" points to the
           number of valid pointers.  If more pointers are needed, "chunk" pointers are allocated
           and "alloc" is increased accordingly.  "alloc" must be >= "dest_size".

       rrd_free_ptrs(void ***src, size_t *cnt)
           Free an array of pointers allocated by "rrd_add_ptr" or "rrd_add_strdup".  Also frees
           the array pointer itself.  On return, the source pointer will be NULL and the count
           will be zero.

               /* created as above */
               rrd_free_ptrs(&arr, &arr_size);
               /* here, arr == NULL && arr_size == 0 */

       rrd_mkdir_p(const char *pathname, mode_t mode)
           Create the directory named "pathname" including all of its parent directories (similar
           to "mkdir -p" on the command line - see mkdir(1) for more information). The argument
           "mode" specifies the permissions to use. It is modified by the process's "umask". See
           mkdir(2) for more details.

           The function returns 0 on success, a negative value else. In case of an error, "errno"
           is set accordingly. Aside from the errors documented in mkdir(2), the function may
           fail with the following errors:

           EINVAL
               "pathname" is "NULL" or the empty string.

           ENOMEM
               Insufficient memory was available.

           any error returned by stat(2)

           In contrast to mkdir(2), the function does not fail if "pathname" already exists and
           is a directory.

       rrd_scaled_duration (const char * token, unsigned long divisor, unsigned long * valuep)
           Parse a token in a context where it contains a count (of seconds or PDP instances), or
           a duration that can be converted to a count by representing the duration in seconds
           and dividing by some scaling factor.  For example, if a user would natively express a
           3 day archive of samples collected every 2 minutes, the sample interval can be
           represented by "2m" instead of 120, and the archive duration by "3d" (to be divided by
           120) instead of 2160 (3*24*60*60 / 120).  See more examples in "STEP, HEARTBEAT, and
           Rows As Durations" in rrdcreate.

           "token" must be a number with an optional single-character suffix encoding the scaling
           factor:

           "s" indicates seconds

           "m" indicates minutes.  The value is multiplied by 60.

           "h" indicates hours.  The value is multiplied by 3600 (or "60m").

           "d" indicates days.  The value is multiplied by 86400 (or "24h").

           "w" indicates weeks.  The value is multiplied by 604800 (or "7d").

           "M" indicates months.  The value is multiplied by 2678400 (or "31d").  (Note this
               factor accommodates the maximum number of days in a month.)

           "y" indicates years.  The value is multiplied by 31622400 (or "366d").  (Note this
               factor accommodates leap years.)

           "divisor" is a positive value representing the duration in seconds of an interval that
           the desired result counts.

           "valuep" is a pointer to where the decoded value will be stored if the conversion is
           successful.

           The initial characters of "token" must be the base-10 representation of a positive
           integer, or the conversion fails.

           If the remainder "token" is empty (no suffix), it is a count and no scaling is
           performed.

           If "token" has one of the suffixes above, the count is multiplied to convert it to a
           duration in seconds.  The resulting number of seconds is divided by "divisor" to
           produce a count of intervals each of duration "divisor" seconds.  If division would
           produce a remainder (e.g., "5m" (300 seconds) divided by "90s"), the conversion is
           invalid.

           If "token" has unrecognized trailing characters the conversion fails.

           The function returns a null pointer if the conversion was successful and "valuep" has
           been updated to the scaled value.  On failure, it returns a text diagnostic suitable
           for use in user error messages.

CLIENT FUNCTIONS

       The following functions are used to connected to an rrdcached instance, either via a unix
       or inet address, and create, update, or gather statistics about a specified RRD database
       file.

       There are two different interfaces: The rrd_client_ family of functions operate on a user-
       provided client object (rrd_client_t) and support multiple concurrent connections to
       rrdcache instances. The simpler rrdc_ family of functions handles connections
       transparently but can only be used for one connection at a time.

       All of the following functions and data types are specified in the "rrd_client.h" header
       file.

       rrd_client_new(const char *daemon_addr)
           Create a new client connection object. If specified, connect to the daemon at
           "daemon_addr". The connection can later be changed by calling rrd_client_connect.

       rrd_client_destroy(rrd_client_t *client)
           Close a client connection and destroy the object by freeing all dynamically allocated
           memory. After calling this function, "client" can no longer be used.

       rrd_client_connect(rrd_client_t *client, const char *daemon_addr)
       rrdc_connect(const char *daemon_addr)
           Connect to a running rrdcached instance, specified via "daemon_addr". Any previous
           connection will be closed. If "daemon_addr" is "NULL", it defaults to the value of the
           "ENV_RRDCACHED_ADDRESS" environment address.

       rrd_client_is_connected(rrd_client_t *client)
           Return a boolean int if the client is connected to the server.

       rrd_client_address(rrd_client_t *client)
           Returns the server address belonging to the current connection.

       rrdc_is_connected(const char *daemon_addr)
           Return a boolean int to determine if the client is connected to the rrdcache daemon
           specified by the "daemon_addr" parameter.

       rrd_client_ping(rrd_client_t *client)
       rrdc_ping
           Check the client connection by pinging the remote side.

       rrdc_is_any_connected
           Return a boolean int if any daemon connections are connected.

       rrd_client_disconnect(rrd_client_t *client)
       rrdc_disconnect
           Disconnect gracefully from the present daemon connection.

       rrd_client_update(rrd_client_t *client, const char *filename, int values_num, const char *
       const *values)
       rrdc_update(const char *filename, int values_num, const char * const *values)
           Update the RRD "filename" via the rrdcached. Where "values_num" is the number of
           values to update and "values" are the new values to add.

       rrd_client_info(rrd_client_t *client, const char *filename)
       rrdc_info(const char *filename)
           Grab rrd info of the RRD "filename" from the connected cache daemon.  This function
           returns an rrd_info_t structure of the following format:

               typedef struct rrd_blob_t {
                   unsigned long size; /* size of the blob */
                   unsigned char *ptr; /* pointer */
               } rrd_blob_t;

               typedef enum rrd_info_type { RD_I_VAL = 0,
                   RD_I_CNT,
                   RD_I_STR,
                   RD_I_INT,
                   RD_I_BLO
               } rrd_info_type_t;

               typedef union rrd_infoval {
                   unsigned long u_cnt;
                   rrd_value_t u_val;
                   char     *u_str;
                   int       u_int;
                   rrd_blob_t u_blo;
               } rrd_infoval_t;

               typedef struct rrd_info_t {
                   char     *key;
                   rrd_info_type_t type;
                   rrd_infoval_t value;
                   struct rrd_info_t *next;
               } rrd_info_t;

       rrd_client_last(rrd_client_t *client, const char *filename)
       rrdc_last(const char *filename)
           Grab the unix epoch of the last time RRD "filename" was updated.

       rrd_client_first(rrd_client_t *client, const char *filename, int rraindex)
       rrdc_first(const char *filename, int rraindex)
           Get the first value of the first sample of the RRD "filename", of the "rraindex" RRA
           (Round Robin Archive) index number.  The RRA index number can be determined by pulling
           the rrd_info_t off the RRD.

       rrd_client_create(rrd_client_t *client, const char *filename, unsigned long pdp_step,
       time_t last_up, int no_overwrite, int argc, const char **argv)
       rrdc_create(const char *filename, unsigned long pdp_step, time_t last_up, int
       no_overwrite, int argc, const char **argv)
           Create RRD database of path "filename".  The RRD will have a step size of "pfp_step",
           the unix epoch timestamp to start collecting data from. The number of data sources and
           RRAs "argc" and the definitions of the data sources and RRAs "argv". Lastly whether or
           not to overwrite an existing RRD if one is found with the same filename;
           "no_overwrite".

       rrdc_create_r2(rrd_client_t *client, const char *filename, unsigned long pdp_step, time_t
       last_up, int no_overwrite, const char **sources, const char *template, int argc, const
       char **argv)
       rrdc_create_r2(const char *filename, unsigned long pdp_step, time_t last_up, int
       no_overwrite, const char **sources, const char *template, int argc, const char **argv)
           Create an RRD database in the daemon. rrdc_create_r2 has the same parameters as
           rrdc_create with two added parameters of; "sources" and "template".

           where "template" is the file path to a RRD file template, with, the form defined in
           rrdcreate(1),

           The "sources" parameter defines series of file paths with data defined, to prefill the
           RRD with. See rrdcreate(1) for more details.

       rrd_client_flush(rrd_client_t *client, const char *filename)
       rrdc_flush(const char *filename)
           flush the currently RRD cached in the daemon specified via "filename".

       rrd_client_forget(rrd_client_t *client, const char *filename)
       rrdc_forget(const char *filename)
           Drop the cached data for the RRD file specified via "filename".

       rrdc_flush_if_daemon(const char *daemon_addr, const char *filename)
           Flush the specified RRD given by "filename" only if the daemon "daemon_addr" is up and
           connected.

       rrd_client_fetch(rrd_client_t *client, const char *filename, const char *cf, time_t
       *ret_start, time_t *ret_end, unsigned long *ret_step, unsigned long *ret_ds_num, char
       ***ret_ds_names, rrd_value_t **ret_data)
       rrdc_fetch(const char *filename, const char *cf, time_t *ret_start, time_t *ret_end,
       unsigned long *ret_step, unsigned long *ret_ds_num, char ***ret_ds_names, rrd_value_t
       **ret_data)
           Perform a fetch operation on the specified RRD Database given be "filename", where
           "cf" is the consolidation function, "ret_start" is the start time given by unix epoch,
           "ret_end" is the endtime. "ret_step" is the step size in seconds, "ret_ds_num" the
           number of data sources in the RRD, "ret_ds_names" the names of the data sources, and a
           pointer to an rrd_value_t object to shlep the data.

       rrdc_stats_get(rrd_client_t *client, rrdc_stats_t **ret_stats)
       rrdc_stats_get(rrdc_stats_t **ret_stats)
           Get stats from the connected daemon, via a linked list of the following structure:

               struct rrdc_stats_s {
                   const char *name;
                   uint16_t type;
                   #define RRDC_STATS_TYPE_GAUGE   0x0001
                   #define RRDC_STATS_TYPE_COUNTER 0x0002
                   uint16_t flags;
                   union {
                       uint64_t counter;
                       double   gauge;
                   } value;
                   struct rrdc_stats_s *next;
               };
               typedef struct rrdc_stats_s rrdc_stats_t;

       rrdc_stats_free(rrdc_stats_t *ret_stats)
           Free the stats struct allocated via rrdc_stats_get.

   SEE ALSO
       rrcached(1) rrdfetch(1) rrdinfo(1) rrdlast(1) rrdcreate(1) rrdupdate(1) rrdlast(1)

AUTHOR

       RRD Contributors <rrd-developers@lists.oetiker.ch>