NAME
pmtime, pmTimeConnect, pmTimeDisconnect, pmTimeRecv, pmTimeSendAck,
pmTimeShowDialog - time control functions for synchronizing the archive
position and update interval between one or more applications
C SYNOPSIS
#include <pcp/pmtime.h>
int pmTimeConnect(int port, pmTime *state)
int pmTimeDisconnect(int fd)
int pmTimeSendAck(int fd, struct timeval *fetchTime)
int pmTimeShowDialog(int fd, int show)
int pmTimeRecv(int fd, pmTime *state)
cc ... -lpcp_gui
DESCRIPTION
These functions form part of the Performance Metrics Applications
Programming Interface (PMAPI) and are intended to provide a uniform
mechanism for applications to both replay archive data and report live
data in a time synchronized manner.
The pmTime structure has the following fields:
typedef struct {
unsigned int magic;
unsigned int length;
pm_tctl_command command;
pm_tctl_source source;
pm_tctl_state state;
pm_tctl_mode mode;
struct timeval delta;
struct timeval position;
struct timeval start; /* archive only */
struct timeval end; /* archive only */
char data[0]; /* arbitrary length info (TZ) */
} pmTime;
In the simplest case, the application should call pmTimeConnect to
connect to the time control server, pmtime(1), and then repeatedly call
pmTimeRecv in the main loop of the application. On success,
pmTimeConnect returns a non-negative file descriptor. In applications
which have multiple threads of control, rather than simply blocking in
pmTimeRecv, the file descriptor may be used in calls to select(2). In
graphical applications, the file descriptor may be used to interface
with the event loop.
The port parameter to pmTimeConnect is the port number of the socket on
which the time control server is (or will be) listening for new
connections.
The state parameter to pmTimeConnect is used to initialize a new time
control server or to pass additional information to an existing time
control server. The start and finish fields indicate the chronological
bounds interesting to the application. The showdialog field indicates
whether the time control server should initially show or hide the
dialog. The position, delta, and data fields indicate the initial
archive position, update interval, time zone string and time zone label
string.
pmTimeRecv blocks until the time control server sends a command
message. It then updates the state parameter and returns one of the
PM_TCTL command identifiers.
The PM_TCTL_SET command indicates the application should seek to the
archive position (see pmSetMode(3)) returned in the position field of
the state parameter.
The PM_TCTL_STEP command indicates the application should perform an
update, i.e. advance (or rewind, if delta is negative) to the time
indicated by position and then fetch new metric values, update the
display or whatever. In order for several application to remain
synchronized, the time control server will wait until all applications
have acknowledged that they have completed the step command.
Applications should call pmTimeSendAck when the step command has been
processed. Note that PM_TCTL_STEP is the only command that requires an
explicit acknowledgement.
The PM_TCTL_VCRMODE command is used by the time control server to
indicate the current VCR mode.
The value is returned in the vcrmode field of the state parameter
passed to pmTimeRecv, and remains valid until the next PM_TCTL_VCRMODE
command is received.
The PM_TCTL_TZ command indicates the application should use a new time-
zone, as indicated in the tz and tzlabel fields of the state parameter.
The PM_TCTL_BOUNDS command is sent to all applications when the time
control server changes its chronological bounds. This may occur when a
new application connects to the time control server or the user changes
the bounds manually. Most applications will ignore this command.
The PM_TCTL_SHOWDIALOG command will be sent to all applications when
the visibility of the time control server changes. This allows
applications to alter the text in menus or buttons to reflect this
change. Applications may change the visibility of the time control
dialog using the pmTimeShowDialog function. The initial visibility is
determined when the time control dialog is first created by an
application calling pmTimeConnect with the showdialog field in the
state parameter set to the desired value.
The pmTimeDisconnect function may be used to close the command socket
to the time control server. This is useful when applications need to
change the connection mode, e.g. to divorce the current time control
server and connect to a new one.
SEE ALSO
pmtime(1), PMAPI(3) and pmSetMode(3).