Provided by: libpmempool-dev_1.6.1-1ubuntu1_amd64 bug

NAME

       libpmempool - persistent memory pool management library

SYNOPSIS

              #include <libpmempool.h>
              cc -std=gnu99 ... -lpmempool -lpmem

   Library API versioning:
              const char *pmempool_check_version(
                  unsigned major_required,
                  unsigned minor_required);

   Error handling:
              const char *pmempool_errormsg(void);

   Other library functions:
       A description of other libpmempool functions can be found on the following manual pages:

       · health check functions: pmempool_check_init(3)

       · pool set synchronization and transformation: pmempool_sync(3)

       · pool set management functions: pmempool_rm(3)

       · toggle or query pool set features: pmempool_feature_query(3)

DESCRIPTION

       libpmempool  provides a set of utilities for off-line analysis and manipulation of a pool.
       A pool in this manpage means a pmemobj pool, pmemblk pool, pmemlog  pool  or  BTT  layout,
       independent  of  the  underlying storage.  Some libpmempool functions are required to work
       without any impact on the pool but some may create a new or modify an existing pool.

       libpmempool is for applications that need high reliability  or  built-in  troubleshooting.
       It may be useful for testing and debugging purposes also.

       libpmempool   introduces   functionality   of  pool  set  health  check,  synchronization,
       transformation and removal.

CAVEATS

       libpmempool relies on the library destructor being called from the main thread.  For  this
       reason,  all  functions that might trigger destruction (e.g.  dlclose(3)) should be called
       in the main thread.  Otherwise some of the resources associated with that thread might not
       be cleaned up properly.

       libpmempool requires the -std=gnu99 compilation flag to build properly.

LIBRARY API VERSIONING

       This  section  describes  how  the library API is versioned, allowing applications to work
       with an evolving API.

       The pmempool_check_version() function is used to see if the installed libpmempool supports
       the version of the library API required by an application.  The easiest way to do this for
       the application is to supply the compile-time version information, supplied by defines  in
       <libpmempool.h>, like this:

              reason = pmempool_check_version(PMEMPOOL_MAJOR_VERSION,
                                              PMEMPOOL_MINOR_VERSION);
              if (reason != NULL) {
                  /* version check failed, reason string tells you why */
              }

       Any  mismatch  in  the  major version number is considered a failure, but a library with a
       newer minor version number will pass this check  since  increasing  minor  versions  imply
       backwards compatibility.

       An  application  can also check specifically for the existence of an interface by checking
       for the version where that interface was introduced.  These  versions  are  documented  in
       this  man  page  as follows: unless otherwise specified, all interfaces described here are
       available in version 1.0 of the library.  Interfaces added after version 1.0 will  contain
       the text introduced in version x.y in the section of this manual describing the feature.

       When  the  version  check  performed by pmempool_check_version() is successful, the return
       value is NULL.  Otherwise the return value is a static string describing  the  reason  for
       failing  the  version  check.  The string returned by pmempool_check_version() must not be
       modified or freed.

DEBUGGING AND ERROR HANDLING

       If an error is detected during the call to a libpmempool  function,  the  application  may
       retrieve  an error message describing the reason for the failure from pmempool_errormsg().
       This function returns a pointer to a static  buffer  containing  the  last  error  message
       logged  for  the  current  thread.   If  errno  was  set,  the error message may include a
       description of the corresponding error code as returned by strerror(3).  The error message
       buffer  is thread-local; errors encountered in one thread do not affect its value in other
       threads.  The buffer is never cleared by any library function; its content is  significant
       only  when  the  return  value of the immediately preceding call to a libpmempool function
       indicated an error, or if errno was set.  The application must  not  modify  or  free  the
       error  message  string,  but  it  may  be  modified  by  subsequent calls to other library
       functions.

       Two versions of libpmempool are typically available on a development system.   The  normal
       version,  accessed  when a program is linked using the -lpmempool option, is optimized for
       performance.  That version skips checks that impact performance and never logs  any  trace
       information or performs any run-time assertions.

       A  second  version  of  libpmempool,  accessed  when  a  program  uses the libraries under
       /usr/lib/pmdk_debug, contains run-time assertions and trace points.  The  typical  way  to
       access   the  debug  version  is  to  set  the  environment  variable  LD_LIBRARY_PATH  to
       /usr/lib/pmdk_debug  or  /usr/lib64/pmdk_debug,  as  appropriate.   Debugging  output   is
       controlled  using  the following environment variables.  These variables have no effect on
       the non-debug version of the library.

       · PMEMPOOL_LOG_LEVEL

       The value of PMEMPOOL_LOG_LEVEL enables trace points in the debug version of the  library,
       as follows:

       · 0  -  This is the default level when PMEMPOOL_LOG_LEVEL is not set.  No log messages are
         emitted at this level.

       · 1 - Additional details on any errors detected are logged (in addition to  returning  the
         errno-based   errors   as   usual).    The  same  information  may  be  retrieved  using
         pmempool_errormsg().

       · 2 - A trace of basic operations is logged.

       · 3 - Enables a very verbose amount of function call tracing in the library.

       · 4 - Enables voluminous and fairly obscure tracing information that is likely only useful
         to the libpmempool developers.

       Unless PMEMPOOL_LOG_FILE is set, debugging output is written to stderr.

       · PMEMPOOL_LOG_FILE

       Specifies the name of a file where all logging information should be written.  If the last
       character in the name is “-”, the PID of the current process will be appended to the  file
       name  when the log file is created.  If PMEMPOOL_LOG_FILE is not set, output is written to
       stderr.

              NOTE: On Debian/Ubuntu systems, this extra debug version of the library is  shipped
              in  the respective -debug Debian package and placed in the /usr/lib/$ARCH/pmdk_dbg/
              directory.

EXAMPLE

       The following example illustrates how the libpmempool API is used.   The  program  detects
       the type and checks consistency of given pool.  If there are any issues detected, the pool
       is automatically repaired.

              #include <stddef.h>
              #include <unistd.h>
              #include <stdlib.h>
              #include <stdio.h>
              #include <libpmempool.h>

              #define PATH "./pmem-fs/myfile"
              #define CHECK_FLAGS (PMEMPOOL_CHECK_FORMAT_STR|PMEMPOOL_CHECK_REPAIR|\
                                   PMEMPOOL_CHECK_VERBOSE)

              int
              main(int argc, char *argv[])
              {
                  PMEMpoolcheck *ppc;
                  struct pmempool_check_status *status;
                  enum pmempool_check_result ret;

                  /* arguments for check */
                  struct pmempool_check_args args = {
                      .path       = PATH,
                      .backup_path    = NULL,
                      .pool_type  = PMEMPOOL_POOL_TYPE_DETECT,
                      .flags      = CHECK_FLAGS
                  };

                  /* initialize check context */
                  if ((ppc = pmempool_check_init(&args, sizeof(args))) == NULL) {
                      perror("pmempool_check_init");
                      exit(EXIT_FAILURE);
                  }

                  /* perform check and repair, answer 'yes' for each question */
                  while ((status = pmempool_check(ppc)) != NULL) {
                      switch (status->type) {
                      case PMEMPOOL_CHECK_MSG_TYPE_ERROR:
                          printf("%s\n", status->str.msg);
                          break;
                      case PMEMPOOL_CHECK_MSG_TYPE_INFO:
                          printf("%s\n", status->str.msg);
                          break;
                      case PMEMPOOL_CHECK_MSG_TYPE_QUESTION:
                          printf("%s\n", status->str.msg);
                          status->str.answer = "yes";
                          break;
                      default:
                          pmempool_check_end(ppc);
                          exit(EXIT_FAILURE);
                      }
                  }

                  /* finalize the check and get the result */
                  ret = pmempool_check_end(ppc);
                  switch (ret) {
                      case PMEMPOOL_CHECK_RESULT_CONSISTENT:
                      case PMEMPOOL_CHECK_RESULT_REPAIRED:
                          return 0;
                      default:
                          return 1;
                  }
              }

       See <http://pmem.io/pmdk/libpmempool> for more examples using the libpmempool API.

ACKNOWLEDGEMENTS

       libpmempool builds on the persistent memory programming model recommended by the SNIA  NVM
       Programming Technical Work Group: <http://snia.org/nvmp>

SEE ALSO

       dlclose(3),     pmempool_check_init(3),     pmempool_feature_query(3),     pmempool_rm(3),
       pmempool_sync(3), strerror(3), libpmem(7), libpmemblk(7), libpmemlog(7), libpmemobj(7) and
       <http://pmem.io>**