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Pause the dbiterator when dumping the zone to the disk

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When we rewrote the zone dumping to use the separate threadpool, the
dumping would acquire the read lock for the whole time the zone dumping
process is dumping the zone.

When combined with incoming IXFR that tries to acquire the write lock on
the same rwlock, we would end up blocking all the other readers.

In this commit, we pause the dbiterator every time we get next record
and before start dumping it to the disk.
This commit is contained in:
Ondřej Surý 2021-06-04 09:22:09 +02:00
parent 7fef01201d
commit 7e59b8a4a1
1 changed files with 19 additions and 26 deletions
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45
lib/dns/masterdump.c
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@ -254,7 +254,6 @@ struct dns_dumpctx {
isc_mutex_t lock;
isc_refcount_t references;
atomic_bool canceled;
bool first;
bool do_date;
isc_stdtime_t now;
FILE *f;
@ -1578,7 +1577,6 @@ dumpctx_create(isc_mem_t *mctx, dns_db_t *db, dns_dbversion_t *version,
dctx->done = NULL;
dctx->done_arg = NULL;
dctx->task = NULL;
dctx->first = true;
atomic_init(&dctx->canceled, false);
dctx->file = NULL;
dctx->tmpfile = NULL;
@ -1737,7 +1735,6 @@ dumptostream(dns_dumpctx_t *dctx) {
char *bufmem;
dns_name_t *name;
dns_fixedname_t fixname;
isc_time_t start;
bufmem = isc_mem_get(dctx->mctx, initial_buffer_length);
@ -1745,32 +1742,24 @@ dumptostream(dns_dumpctx_t *dctx) {
name = dns_fixedname_initname(&fixname);
if (dctx->first) {
CHECK(writeheader(dctx));
CHECK(writeheader(dctx));
/*
* Fast format is not currently written incrementally,
* so we make the call to dns_db_serialize() here.
* If the database is anything other than an rbtdb,
* this should result in not implemented
*/
if (dctx->format == dns_masterformat_map) {
result = dns_db_serialize(dctx->db, dctx->version,
dctx->f);
goto cleanup;
}
result = dns_dbiterator_first(dctx->dbiter);
if (result != ISC_R_SUCCESS && result != ISC_R_NOMORE) {
goto cleanup;
}
dctx->first = false;
} else {
result = ISC_R_SUCCESS;
/*
* Fast format is not currently written incrementally,
* so we make the call to dns_db_serialize() here.
* If the database is anything other than an rbtdb,
* this should result in not implemented
*/
if (dctx->format == dns_masterformat_map) {
result = dns_db_serialize(dctx->db, dctx->version, dctx->f);
goto cleanup;
}
result = dns_dbiterator_first(dctx->dbiter);
if (result != ISC_R_SUCCESS && result != ISC_R_NOMORE) {
goto cleanup;
}
isc_time_now(&start);
while (result == ISC_R_SUCCESS) {
dns_rdatasetiter_t *rdsiter = NULL;
dns_dbnode_t *node = NULL;
@ -1790,6 +1779,10 @@ dumptostream(dns_dumpctx_t *dctx) {
}
dctx->tctx.neworigin = origin;
}
result = dns_dbiterator_pause(dctx->dbiter);
RUNTIME_CHECK(result == ISC_R_SUCCESS);
result = dns_db_allrdatasets(dctx->db, node, dctx->version,
dctx->now, &rdsiter);
if (result != ISC_R_SUCCESS) {