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vere: refactors epoc loading, adds fallback to previous when bad
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@joemfb
joemfb committed Oct 7, 2023
1 parent b9e39ba commit d7ea982
Showing 1 changed file with 137 additions and 54 deletions.
191 changes: 137 additions & 54 deletions pkg/vere/disk.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1423,6 +1423,86 @@ u3_disk_kindly(u3_disk* log_u, c3_d eve_d)
}
}

typedef enum {
_epoc_good = 0, // load successfully
_epoc_gone = 1, // version missing, total failure
_epoc_fail = 2, // transient failure (?)
_epoc_void = 3, // empty event log (cheaper to recover?)
_epoc_late = 4 // format from the future
} _epoc_kind;

/* _disk_epoc_load(): load existing epoch, enumerating failures
*/
static _epoc_kind
_disk_epoc_load(u3_disk* log_u, c3_d lat_d)
{
// check latest epoc version
//
{
c3_c ver_c[8];
c3_w ver_w;
if ( c3n == _disk_epoc_meta(log_u, lat_d, "epoc",
sizeof(ver_c) - 1, ver_c) )
{
fprintf(stderr, "disk: failed to load epoch 0i%" PRIc3_d " version\r\n",
lat_d);

return _epoc_gone;
}

if ( 1 != sscanf(ver_c, "%d", &ver_w) ) {
fprintf(stderr, "disk: failed to parse epoch version: '%s'\r\n", ver_c);
return _epoc_fail;
}

if ( U3D_VER1 != ver_w ) {
fprintf(stderr, "disk: unknown epoch version: '%s', expected '%d'\r\n",
ver_c, U3D_VER1);
return _epoc_late;
}

log_u->ver_w = ver_w;
}

// set path to latest epoch
c3_c epo_c[8193];
snprintf(epo_c, 8192, "%s/0i%" PRIc3_d, log_u->com_u->pax_c, lat_d);

// initialize latest epoch's db
if ( 0 == (log_u->mdb_u = u3_lmdb_init(epo_c, siz_i)) ) {
fprintf(stderr, "disk: failed to initialize database at %s\r\n",
epo_c);
return _epoc_fail;
}

fprintf(stderr, "disk: loaded epoch 0i%" PRIc3_d "\r\n", lat_d);

// get first/last event numbers from lmdb
c3_d fir_d, las_d;
if ( c3n == u3_lmdb_gulf(log_u->mdb_u, &fir_d, &las_d) ) {
fprintf(stderr, "disk: failed to get first/last event numbers\r\n");
u3_lmdb_exit(log_u->mdb_u);
log_u->mdb_u = 0;
return _epoc_fail;
}

if ( (c3n == u3_Host.ops_u.nuu )
&& !fir_d
&& !las_d
&& (c3n == u3_disk_read_meta(log_u->mdb_u, 0, 0, 0)) )
{
u3_lmdb_exit(log_u->mdb_u);
log_u->mdb_u = 0;
return _epoc_void;
}

// initialize dun_d/sen_d values
log_u->dun_d = ( 0 != las_d ) ? las_d : lat_d;
log_u->sen_d = log_u->dun_d;

return _epoc_good;
}

/* u3_disk_init(): load or create pier directories and event log.
*/
u3_disk*
Expand Down Expand Up @@ -1561,71 +1641,74 @@ u3_disk_init(c3_c* pax_c, u3_disk_cb cb_u)
return 0;
}

// check latest epoc version
//
c3_o try_o = c3n;

try_init:
{
c3_c ver_c[8];
c3_w ver_w;
if ( c3n == _disk_epoc_meta(log_u, lat_d, "epoc",
sizeof(ver_c) - 1, ver_c) )
{
fprintf(stderr, "disk: failed to load epoch version\r\n");
c3_free(log_u);
return 0;
}
_epoc_kind kin_e = _disk_epoc_load(log_u, lat_d);

if ( 1 != sscanf(ver_c, "%d", &ver_w) ) {
fprintf(stderr, "disk: failed to parse epoch version: '%s'\r\n", ver_c);
c3_free(log_u);
return 0;
}
switch ( kin_e ) {
case _epoc_good: {
// mark the latest epoch directory
log_u->epo_d = lat_d;

if ( U3D_VER1 != ver_w ) {
fprintf(stderr, "disk: unknown epoch version: '%s', expected '%d'\r\n",
ver_c, U3D_VER1);
c3_free(log_u);
return 0;
}
// mark the log as live
log_u->liv_o = c3y;

log_u->ver_w = ver_w;
}
#if defined(DISK_TRACE_JAM) || defined(DISK_TRACE_CUE)
u3t_trace_open(pax_c);
#endif

// set path to latest epoch
c3_c epo_c[8193];
snprintf(epo_c, 8192, "%s/0i%" PRIc3_d, log_c, lat_d);
return log_u;
} break;

// initialize latest epoch's db
if ( 0 == (log_u->mdb_u = u3_lmdb_init(epo_c, siz_i)) ) {
fprintf(stderr, "disk: failed to initialize database at '%s' '%s' '%s'\r\n", pax_c, log_c, epo_c);
c3_free(log_u);
return 0;
}
fprintf(stderr, "disk: loaded epoch 0i%" PRIc3_d "\r\n", lat_d);
case _epoc_void: // XX could handle more efficiently

// get first/last event numbers from lmdb
c3_d fir_d, las_d;
if ( c3n == u3_lmdb_gulf(log_u->mdb_u, &fir_d, &las_d) ) {
fprintf(stderr, "disk: failed to get first/last event numbers\r\n");
// XX dispose mdb_u
c3_free(log_u);
return 0;
}
case _epoc_gone: {
// XX if there is no version number, the epoc is invalid
// backup and try previous

// initialize dun_d/sen_d values
log_u->dun_d = ( 0 != las_d ) ? las_d : lat_d;
log_u->sen_d = log_u->dun_d;
if ( c3y == try_o ) {
fprintf(stderr, "multiple bad epochs, bailing out\r\n");
c3_free(log_u);
return 0;
}

// mark the latest epoch directory
log_u->epo_d = lat_d;
c3_z len_z = u3_disk_epoc_list(log_u, 0);

// mark the log as live
log_u->liv_o = c3y;
}
if ( len_z <= 1 ) {
fprintf(stderr, "only epoch is bad, bailing out\r\n");
c3_free(log_u);
return 0;
}

c3_d* sot_d = c3_malloc(len_z * sizeof(*sot_d));
u3_disk_epoc_list(log_u, sot_d);

#if defined(DISK_TRACE_JAM) || defined(DISK_TRACE_CUE)
u3t_trace_open(pax_c);
#endif
fprintf(stderr, "disk: latest epoch is 0i%" PRIc3_d " is bogus; "
"falling back to previous at 0i%" PRIc3_d "\r\n",
lat_d, sot_d[1]);

u3_disk_epoc_kill(log_u, lat_d);

lat_d = sot_d[1];
try_o = c3y;
c3_free(sot_d);
goto try_init;
} break;

case _epoc_fail: {
fprintf(stderr, "failed to load epoch\r\n");
c3_free(log_u);
return 0;
} break;

return log_u;
case _epoc_late: {
fprintf(stderr, "upgrade runtime version\r\n");
c3_free(log_u);
return 0;
}
}
}
}
}

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