postgresql/src/backend/utils/misc/ps_status.c

/*--------------------------------------------------------------------
 * ps_status.c
 *
 * Routines to support changing the ps display of PostgreSQL backends
 * to contain some useful information. Differs wildly across
 * platforms.
 *
 * $Header: /cvsroot/pgsql/src/backend/utils/misc/ps_status.c,v 1.3 2001/03/20 22:31:54 momjian Exp $
 *
 * Copyright 2000 by PostgreSQL Global Development Group
 * various details abducted from various places
 *--------------------------------------------------------------------
 */

#include "postgres.h"

#include <unistd.h>


#ifdef HAVE_SYS_PSTAT_H
# include <sys/pstat.h>			/* for HP-UX */
#endif
#ifdef HAVE_PS_STRINGS
# include <machine/vmparam.h>	/* for old BSD */
# include <sys/exec.h>
#endif

#include "miscadmin.h"

#include "utils/ps_status.h"

extern char **environ;


/*------
 * Alternative ways of updating ps display:
 *
 * PS_USE_SETPROCTITLE
 *     use the function setproctitle(const char *, ...)
 *     (newer BSD systems)
 * PS_USE_PSTAT
 *     use the pstat(PSTAT_SETCMD, )
 *     (HPUX)
 * PS_USE_PS_STRINGS
 *     assign PS_STRINGS->ps_argvstr = "string"
 *     (some BSD systems)
 * PS_USE_CHANGE_ARGV
 *     assign argv[0] = "string"
 *     (some other BSD systems)
 * PS_USE_CLOBBER_ARGV
 *     write over the argv and environment area
 *     (most SysV-like systems)
 * PS_USE_NONE
 *     don't update ps display
 *     (This is the default, as it is safest.)
 */
#if defined(HAVE_SETPROCTITLE)
# define PS_USE_SETPROCTITLE
#elif defined(HAVE_PSTAT) && defined(PSTAT_SETCMD)
# define PS_USE_PSTAT
#elif defined(HAVE_PS_STRINGS)
# define PS_USE_PS_STRINGS 
#elif defined(BSD) || defined(__bsdi__) || defined(__hurd__)
# define PS_USE_CHANGE_ARGV
#elif defined(__linux__) || defined(_AIX4) || defined(_AIX3) || defined(__sgi) || (defined(sun) && !defined(BSD)) || defined(ultrix) || defined(__ksr__) || defined(__osf__) || defined(__QNX__) || defined(__svr4__) || defined(__svr5__)
# define PS_USE_CLOBBER_ARGV
#else
# define PS_USE_NONE
#endif


/* Different systems want the buffer padded differently */
#if defined(_AIX3) || defined(__linux__) || defined(__QNX__) || defined(__svr4__)
# define PS_PADDING '\0'
#else
# define PS_PADDING ' '
#endif


#ifndef PS_USE_CLOBBER_ARGV
/* all but one options need a buffer to write their ps line in */
#define PS_BUFFER_SIZE 256
static char ps_buffer[PS_BUFFER_SIZE];
static const size_t ps_buffer_size = PS_BUFFER_SIZE;

#else  /* PS_USE_CLOBBER_ARGV */
static char * ps_buffer; /* will point to argv area */
static size_t ps_buffer_size; /* space determined at run time */
#endif /* PS_USE_CLOBBER_ARGV */

static size_t ps_buffer_fixed_size; /* size of the constant prefix */



/*
 * Call this once at backend start.
 */
void
init_ps_display(int argc, char *argv[],
				const char * username, const char * dbname,
				const char * host_info)
{
#ifndef PS_USE_NONE
    Assert(username);
    Assert(dbname);

	/* no ps display for stand-alone backend */
    if (!IsUnderPostmaster)
        return;

# ifdef PS_USE_CHANGE_ARGV
	argv[0] = ps_buffer;
	argv[1] = NULL;
# endif /* PS_USE_CHANGE_ARGV */

# ifdef PS_USE_CLOBBER_ARGV
    /*
     * If we're going to overwrite the argv area, count the space.
     */
	{
		char * end_of_area = NULL;
		char **new_environ;
		int i;

		/*
		 * check for contiguous argv strings
		 */
		for (i = 0; i < argc; i++)
			if (i == 0 || end_of_area + 1 == argv[i])
				end_of_area = argv[i] + strlen(argv[i]);

		/*
		 * check for contiguous environ strings following argv
		 */
		for (i = 0; end_of_area != NULL && environ[i] != NULL; i++)
			if (end_of_area + 1 == environ[i])
				end_of_area = environ[i] + strlen(environ[i]);

		if (end_of_area == NULL)
		{
			ps_buffer = NULL;
			ps_buffer_size = 0;
		}
		else
		{
			ps_buffer = argv[0];
			ps_buffer_size = end_of_area - argv[0] - 1;
		}
		argv[1] = NULL;

		/*
		 * move the environment out of the way
		 */
		for (i = 0; environ[i] != NULL; i++)
			;
		new_environ = malloc(sizeof (char *) * (i + 1));
		for (i = 0; environ[i] != NULL; i++)
		new_environ[i] = strdup(environ[i]);
		new_environ[i] = NULL;
		environ = new_environ;
	}
# endif /* PS_USE_CLOBBER_ARGV */

	/*
	 * Make fixed prefix
	 */
# ifdef PS_USE_SETPROCTITLE
	/* apparently setproctitle() already adds a `progname:' prefix to
	 * the ps line */
	snprintf(ps_buffer, ps_buffer_size,
			 "%s %s %s ",
			 username, dbname, host_info);
# else
	snprintf(ps_buffer, ps_buffer_size,
			 "postgres: %s %s %s ",
			 username, dbname, host_info);
# endif

    ps_buffer_fixed_size = strlen(ps_buffer);
#endif /* not PS_USE_NONE */
}



/*
 * Call this to update the ps status display to a fixed prefix plus an
 * indication of what you're currently doing passed in the argument.
 */
void
set_ps_display(const char * value)
{
#ifndef PS_USE_NONE
	/* no ps display for stand-alone backend */
	if (!IsUnderPostmaster)
		return;

# ifdef PS_USE_CLOBBER_ARGV
	/* If ps_buffer is a pointer, it might still be null */
	if (!ps_buffer)
		return;
# endif

	/* Update ps_buffer to contain both fixed part and value */
	StrNCpy(ps_buffer + ps_buffer_fixed_size, value,
			ps_buffer_size - ps_buffer_fixed_size);

	/* Transmit new setting to kernel, if necessary */

# ifdef PS_USE_SETPROCTITLE
	setproctitle("%s", ps_buffer);
# endif

# ifdef PS_USE_PSTAT
		{
			union pstun pst;

			pst.pst_command = ps_buffer;
			pstat(PSTAT_SETCMD, pst, strlen(ps_buffer), 0, 0);
		}
# endif /* PS_USE_PSTAT */

# ifdef PS_USE_PS_STRINGS
		PS_STRINGS->ps_nargvstr = 1;
		PS_STRINGS->ps_argvstr = ps_buffer;
# endif /* PS_USE_PS_STRINGS */

# ifdef PS_USE_CLOBBER_ARGV
		{
			char * cp;
			/* pad unused memory */
			for(cp = ps_buffer + strlen(ps_buffer);
				cp < ps_buffer + ps_buffer_size;
				cp++)
				*cp = PS_PADDING;
		}
# endif /* PS_USE_CLOBBER_ARGV */

#endif /* not PS_USE_NONE */
}


/*
 * Returns what's currently in the ps display, in case someone needs
 * it.  Note that only the variable part is returned.
 */
const char *
get_ps_display(void)
{
#ifdef PS_USE_CLOBBER_ARGV
	/* If ps_buffer is a pointer, it might still be null */
	if (!ps_buffer)
		return "";
#endif

	return ps_buffer + ps_buffer_fixed_size;
}