trace_file.c

#include "postgres.h"
#include <sys/stat.h>
#include "utils/guc.h"
#include "miscadmin.h"

#include "trace_file.h"

static char* traceFileName = "trace_file.txt";

char *dataDir;

int traceFileLimit = 16; // limit in megabytes


size_t currentSize = 0;

FILE* traceFile = NULL;

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


void
TraceFileDeclareGucVariables(void)
{
    DefineCustomIntVariable("pg_uprobe.trace_file_limit",
                             "trace session data limit in megabytes",
                             NULL,
                             &traceFileLimit,
                             16,
                             1,
                             32 * 1024,
                             PGC_SUSET,
                             GUC_UNIT_MB,
                             NULL,
                             NULL,
                             NULL);


    DefineCustomStringVariable("pg_uprobe.trace_file_name",
                               "file name for trace session data",
                               NULL,
                               &traceFileName,
                               "trace_file.txt",
                               PGC_SUSET,
                               0,
                               NULL, NULL, NULL);

    DefineCustomStringVariable("pg_uprobe.data_dir",
                               "dir for file pg_uprobe.trace_file_name and other pg_uprobe files",
                               NULL,
                               &dataDir,
                               "./pg_uprobe/",
                               PGC_SUSET,
                               0,
                               CheckDataDirValue, NULL, NULL);
}


bool
OpenTraceSessionFile(bool throwOnError)
{
    char path[4096];
    int error;
    sprintf(path, "%s%s_%d", dataDir, traceFileName, MyProcPid);

    traceFile = fopen(path, "w");
    error = errno;

    if (traceFile == NULL && throwOnError)
        elog(ERROR, "can't open file %s for trace session data: %s", path, strerror(error));
    else if (traceFile == NULL)
        elog(LOG, "can't open file %s for trace session data: %s", path, strerror(error));

    currentSize = 0;
    return traceFile != NULL;
}


void
CloseTraceSessionFile(void)
{
    if (traceFile == NULL)
        return;

    fclose(traceFile);
    traceFile = NULL;
    currentSize = 0;
}


static bool
CheckDataDirValue(char** newval, void** extra, GucSource source)
{
    struct stat st;
    size_t		size;


    if (*newval == NULL || *newval[0] == '\0')
    {
        GUC_check_errdetail("pg_uprobe data can't be empty or null");
        return false;
    }

    size = strlen(*newval);

    if (size + 128 >= MAXPGPATH)
    {
        GUC_check_errdetail("pg_uprobe data dir too long.");
        return false;
    }

    if ((*newval)[size - 1] != '/')
    {
        *newval = guc_realloc(ERROR, *newval, size + 2);
        (*newval)[size] = '/';
        (*newval)[size + 1] = '\0';
    }

    if (stat(*newval, &st) != 0 || !S_ISDIR(st.st_mode))
    {
        GUC_check_errdetail("Specified pg_uprobe data dir does not exist.");
        return false;
    }

    return true;
}