Provided by: rrdtool_1.7.2-4ubuntu5_amd64 
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>