ARES_SET_SERVER_STATE_CALLBACK
Section: C Library Functions (3)
Updated: 26 Apr 2024
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NAME
ares_set_server_state_callback - Function for setting a server state callback
SYNOPSIS
#include <ares.h>
typedef void (*ares_server_state_callback)(const char *server_string,
ares_bool_t success,
int flags,
void *data);
void ares_set_server_state_callback(ares_channel_t *channel,
ares_server_state_callback callback,
void *user_data);
DESCRIPTION
The
ares_set_server_state_callback(3) function sets a callback function
callback in the given ares channel handle
channel that is invoked
whenever a query on the channel completes. This includes both successful and
unsuccessful queries (including hard errors and timeouts). The callback
function is invoked with a number of parameters describing the query, as
follows.
The server_string parameter indicates the DNS server that was used for
the query, given as a string with the same format returned by
ares_get_servers_csv(3).
The success parameter indicates whether the query succeeded or not. It is
set to ARES_TRUE on success and ARES_FALSE on failure.
The flags parameter is a bitmask of flags describing various aspects of
the query (for example whether the query used UDP or TCP). These are described
below.
The data parameter is a reference to the custom user data user_data
that was passed to ares_set_server_state_callback(3) when setting the
server state callback.
The server state callback can be used by applications to monitor the state of
the DNS servers used by an ares channel. For example, it can be used to track
metrics about the numbers and types of queries sent to each server or to
detect when a server is uncontactable or unhealthy.
FLAGS
- ARES_SERV_STATE_UDP
-
Indicates that the query was tried over UDP.
- ARES_SERV_STATE_TCP
-
Indicates that the query was tried over TCP.
AVAILABILITY
This function was first introduced in -ares version 1.29.0.
SEE ALSO
ares_get_servers_csv(3)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- FLAGS
-
- AVAILABILITY
-
- SEE ALSO
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