basic_archive.c File Reference

#include "postgres.h"
#include <sys/stat.h>
#include <sys/time.h>
#include <unistd.h>
#include "archive/archive_module.h"
#include "common/int.h"
#include "miscadmin.h"
#include "storage/copydir.h"
#include "storage/fd.h"
#include "utils/guc.h"

Include dependency graph for basic_archive.c:

Go to the source code of this file.

Macros
#define	CMP_BUF_SIZE   (4096)

Functions
	PG_MODULE_MAGIC_EXT (.name="basic_archive",.version=PG_VERSION)
static bool	basic_archive_configured (ArchiveModuleState *state)
static bool	basic_archive_file (ArchiveModuleState *state, const char *file, const char *path)
static bool	check_archive_directory (char **newval, void **extra, GucSource source)
static bool	compare_files (const char *file1, const char *file2)
void	_PG_init (void)
const ArchiveModuleCallbacks *	_PG_archive_module_init (void)

Variables
static char *	archive_directory = NULL
static const ArchiveModuleCallbacks	basic_archive_callbacks

Macro Definition Documentation

CMP_BUF_SIZE

#define CMP_BUF_SIZE   (4096)

Function Documentation

_PG_archive_module_init()

const ArchiveModuleCallbacks * _PG_archive_module_init

(

void

)

Definition at line 85 of file basic_archive.c.

{
    return &basic_archive_callbacks;
}

References basic_archive_callbacks.

_PG_init()

void _PG_init

(

void

)

Definition at line 65 of file basic_archive.c.

{
    DefineCustomStringVariable("basic_archive.archive_directory",
                               "Archive file destination directory.",
                               NULL,
                               &archive_directory,
                               "",
                               PGC_SIGHUP,
                               0,
                               check_archive_directory, NULL, NULL);
 
    MarkGUCPrefixReserved("basic_archive");
}

References archive_directory, check_archive_directory(), DefineCustomStringVariable(), MarkGUCPrefixReserved(), and PGC_SIGHUP.

basic_archive_configured()

static bool basic_archive_configured ( ArchiveModuleState *  state )

static

Definition at line 138 of file basic_archive.c.

{
    if (archive_directory != NULL && archive_directory[0] != '\0')
        return true;
 
    arch_module_check_errdetail("%s is not set.",
                                "basic_archive.archive_directory");
    return false;
}

References arch_module_check_errdetail, and archive_directory.

basic_archive_file()

static bool basic_archive_file ( ArchiveModuleState *  state, const char *  file, const char *  path  )

static

Definition at line 154 of file basic_archive.c.

{
    char        destination[MAXPGPATH];
    char        temp[MAXPGPATH + 256];
    struct stat st;
    struct timeval tv;
    uint64      epoch;          /* milliseconds */
 
    ereport(DEBUG3,
            (errmsg("archiving \"%s\" via basic_archive", file)));
 
    snprintf(destination, MAXPGPATH, "%s/%s", archive_directory, file);
 
    /*
     * First, check if the file has already been archived.  If it already
     * exists and has the same contents as the file we're trying to archive,
     * we can return success (after ensuring the file is persisted to disk).
     * This scenario is possible if the server crashed after archiving the
     * file but before renaming its .ready file to .done.
     *
     * If the archive file already exists but has different contents,
     * something might be wrong, so we just fail.
     */
    if (stat(destination, &st) == 0)
    {
        if (compare_files(path, destination))
        {
            ereport(DEBUG3,
                    (errmsg("archive file \"%s\" already exists with identical contents",
                            destination)));
 
            fsync_fname(destination, false);
            fsync_fname(archive_directory, true);
 
            return true;
        }
 
        ereport(ERROR,
                (errmsg("archive file \"%s\" already exists", destination)));
    }
    else if (errno != ENOENT)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not stat file \"%s\": %m", destination)));
 
    /*
     * Pick a sufficiently unique name for the temporary file so that a
     * collision is unlikely.  This helps avoid problems in case a temporary
     * file was left around after a crash or another server happens to be
     * archiving to the same directory.
     */
    gettimeofday(&tv, NULL);
    if (pg_mul_u64_overflow((uint64) 1000, (uint64) tv.tv_sec, &epoch) ||
        pg_add_u64_overflow(epoch, (uint64) (tv.tv_usec / 1000), &epoch))
        elog(ERROR, "could not generate temporary file name for archiving");
 
    snprintf(temp, sizeof(temp), "%s/%s.%s.%d." UINT64_FORMAT,
             archive_directory, "archtemp", file, MyProcPid, epoch);
 
    /*
     * Copy the file to its temporary destination.  Note that this will fail
     * if temp already exists.
     */
    copy_file(path, temp);
 
    /*
     * Sync the temporary file to disk and move it to its final destination.
     * Note that this will overwrite any existing file, but this is only
     * possible if someone else created the file since the stat() above.
     */
    (void) durable_rename(temp, destination, ERROR);
 
    ereport(DEBUG1,
            (errmsg("archived \"%s\" via basic_archive", file)));
 
    return true;
}

References archive_directory, compare_files(), copy_file(), DEBUG1, DEBUG3, durable_rename(), elog, epoch, ereport, errcode_for_file_access(), errmsg(), ERROR, fsync_fname(), gettimeofday(), MAXPGPATH, MyProcPid, pg_add_u64_overflow(), pg_mul_u64_overflow(), snprintf, stat, and UINT64_FORMAT.

check_archive_directory()

static bool check_archive_directory ( char **  newval, void **  extra, GucSource  source  )

static

Definition at line 96 of file basic_archive.c.

{
    struct stat st;
 
    /*
     * The default value is an empty string, so we have to accept that value.
     * Our check_configured callback also checks for this and prevents
     * archiving from proceeding if it is still empty.
     */
    if (*newval == NULL || *newval[0] == '\0')
        return true;
 
    /*
     * Make sure the file paths won't be too long.  The docs indicate that the
     * file names to be archived can be up to 64 characters long.
     */
    if (strlen(*newval) + 64 + 2 >= MAXPGPATH)
    {
        GUC_check_errdetail("Archive directory too long.");
        return false;
    }
 
    /*
     * Do a basic sanity check that the specified archive directory exists. It
     * could be removed at some point in the future, so we still need to be
     * prepared for it not to exist in the actual archiving logic.
     */
    if (stat(*newval, &st) != 0 || !S_ISDIR(st.st_mode))
    {
        GUC_check_errdetail("Specified archive directory does not exist.");
        return false;
    }
 
    return true;
}

References GUC_check_errdetail, MAXPGPATH, newval, S_ISDIR, stat::st_mode, and stat.

Referenced by _PG_init().

compare_files()

static bool compare_files ( const char *  file1, const char *  file2  )

static

Definition at line 238 of file basic_archive.c.

{
#define CMP_BUF_SIZE (4096)
    char        buf1[CMP_BUF_SIZE];
    char        buf2[CMP_BUF_SIZE];
    int         fd1;
    int         fd2;
    bool        ret = true;
 
    fd1 = OpenTransientFile(file1, O_RDONLY | PG_BINARY);
    if (fd1 < 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open file \"%s\": %m", file1)));
 
    fd2 = OpenTransientFile(file2, O_RDONLY | PG_BINARY);
    if (fd2 < 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open file \"%s\": %m", file2)));
 
    for (;;)
    {
        int         nbytes = 0;
        int         buf1_len = 0;
        int         buf2_len = 0;
 
        while (buf1_len < CMP_BUF_SIZE)
        {
            nbytes = read(fd1, buf1 + buf1_len, CMP_BUF_SIZE - buf1_len);
            if (nbytes < 0)
                ereport(ERROR,
                        (errcode_for_file_access(),
                         errmsg("could not read file \"%s\": %m", file1)));
            else if (nbytes == 0)
                break;
 
            buf1_len += nbytes;
        }
 
        while (buf2_len < CMP_BUF_SIZE)
        {
            nbytes = read(fd2, buf2 + buf2_len, CMP_BUF_SIZE - buf2_len);
            if (nbytes < 0)
                ereport(ERROR,
                        (errcode_for_file_access(),
                         errmsg("could not read file \"%s\": %m", file2)));
            else if (nbytes == 0)
                break;
 
            buf2_len += nbytes;
        }
 
        if (buf1_len != buf2_len || memcmp(buf1, buf2, buf1_len) != 0)
        {
            ret = false;
            break;
        }
        else if (buf1_len == 0)
            break;
    }
 
    if (CloseTransientFile(fd1) != 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not close file \"%s\": %m", file1)));
 
    if (CloseTransientFile(fd2) != 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not close file \"%s\": %m", file2)));
 
    return ret;
}

References CloseTransientFile(), CMP_BUF_SIZE, ereport, errcode_for_file_access(), errmsg(), ERROR, OpenTransientFile(), PG_BINARY, and read.

Referenced by basic_archive_file().

PG_MODULE_MAGIC_EXT()

PG_MODULE_MAGIC_EXT	(	.	name = "basic_archive",
		.	version = PG_VERSION
	)

Variable Documentation

archive_directory

char* archive_directory = NULL

static

Definition at line 45 of file basic_archive.c.

Referenced by _PG_init(), basic_archive_configured(), and basic_archive_file().

basic_archive_callbacks

const ArchiveModuleCallbacks basic_archive_callbacks

static

Initial value:

= {
    .startup_cb = NULL,
    .check_configured_cb = basic_archive_configured,
    .archive_file_cb = basic_archive_file,
    .shutdown_cb = NULL
}

Definition at line 52 of file basic_archive.c.

Referenced by _PG_archive_module_init().