Transaction::pointer Transaction::load (uint256 const& id)
{
std::string sql = "SELECT LedgerSeq,Status,RawTxn "
"FROM Transactions WHERE TransID='";
sql.append (to_string (id));
sql.append ("';");
boost::optional<std::uint64_t> ledgerSeq;
boost::optional<std::string> status;
Blob rawTxn;
{
auto db = getApp().getTxnDB ().checkoutDb ();
soci::blob sociRawTxnBlob (*db);
soci::indicator rti;
*db << sql, soci::into (ledgerSeq), soci::into (status),
soci::into (sociRawTxnBlob, rti);
if (!db->got_data () || rti != soci::i_ok)
return {};
convert(sociRawTxnBlob, rawTxn);
}
return Transaction::transactionFromSQL (
ledgerSeq, status, rawTxn, Validate::YES);
}
/// Retrieve the data for a given namespace and key.
Store::Status MemcachedStore::get_data(const std::string& table,
const std::string& key,
std::string& data,
uint64_t& cas,
SAS::TrailId trail)
{
Store::Status status = Store::Status::OK;
// Construct the fully qualified key.
std::string fqkey = table + "\\\\" + key;
const char* key_ptr = fqkey.data();
const size_t key_len = fqkey.length();
const std::vector<memcached_st*>& replicas = get_replicas(fqkey, Op::READ);
if (trail != 0)
{
SAS::Event start(trail, SASEvent::MEMCACHED_GET_START, 0);
start.add_var_param(fqkey);
SAS::report_event(start);
}
LOG_DEBUG("%d read replicas for key %s", replicas.size(), fqkey.c_str());
// Read from all replicas until we get a positive result.
memcached_return_t rc = MEMCACHED_ERROR;
bool active_not_found = false;
size_t failed_replicas = 0;
size_t ii;
// If we only have one replica, we should try it twice -
// libmemcached won't notice a dropped TCP connection until it tries
// to make a request on it, and will fail the request then
// reconnect, so the second attempt could still work.
size_t attempts = (replicas.size() == 1) ? 2 : replicas.size();
for (ii = 0; ii < attempts; ++ii)
{
size_t replica_idx;
if ((replicas.size() == 1) && (ii == 1))
{
if (rc != MEMCACHED_CONNECTION_FAILURE)
{
// This is a legitimate error, not a server failure, so we
// shouldn't retry.
break;
}
replica_idx = 0;
LOG_WARNING("Failed to read from sole memcached replica: retrying once");
}
else
{
replica_idx = ii;
}
// We must use memcached_mget because memcached_get does not retrieve CAS
// values.
LOG_DEBUG("Attempt to read from replica %d (connection %p)", replica_idx, replicas[replica_idx]);
rc = memcached_mget(replicas[replica_idx], &key_ptr, &key_len, 1);
if (memcached_success(rc))
{
// memcached_mget command was successful, so retrieve the result.
LOG_DEBUG("Fetch result");
memcached_result_st result;
memcached_result_create(replicas[replica_idx], &result);
memcached_fetch_result(replicas[replica_idx], &result, &rc);
if (memcached_success(rc))
{
// Found a record, so exit the read loop.
LOG_DEBUG("Found record on replica %d", replica_idx);
data.assign(memcached_result_value(&result), memcached_result_length(&result));
cas = (active_not_found) ? 0 : memcached_result_cas(&result);
// std::string::assign copies its arguments when used with a
// char*, so this is safe.
memcached_result_free(&result);
break;
}
else
{
// Free the result and continue the read loop.
memcached_result_free(&result);
}
}
if (rc == MEMCACHED_NOTFOUND)
{
// Failed to find a record on an active replica. Flag this so if we do
// find data on a later replica we can reset the cas value returned to
// zero to ensure a subsequent write will succeed.
LOG_DEBUG("Read for %s on replica %d returned NOTFOUND", fqkey.c_str(), replica_idx);
active_not_found = true;
}
else
{
// Error from this node, so consider it inactive.
LOG_DEBUG("Read for %s on replica %d returned error %d (%s)",
fqkey.c_str(), replica_idx, rc, memcached_strerror(replicas[replica_idx], rc));
++failed_replicas;
}
}
if (memcached_success(rc))
{
if (trail != 0)
{
SAS::Event got_data(trail, SASEvent::MEMCACHED_GET_SUCCESS, 0);
got_data.add_var_param(fqkey);
got_data.add_var_param(data);
got_data.add_static_param(cas);
SAS::report_event(got_data);
}
// Return the data and CAS value. The CAS value is either set to the CAS
// value from the result, or zero if an earlier active replica returned
// NOT_FOUND. This ensures that a subsequent set operation will succeed
// on the earlier active replica.
LOG_DEBUG("Read %d bytes from table %s key %s, CAS = %ld",
data.length(), table.c_str(), key.c_str(), cas);
}
else if (failed_replicas < replicas.size())
{
// At least one replica returned NOT_FOUND.
if (trail != 0)
{
SAS::Event not_found(trail, SASEvent::MEMCACHED_GET_NOT_FOUND, 0);
not_found.add_var_param(fqkey);
SAS::report_event(not_found);
}
LOG_DEBUG("At least one replica returned not found, so return NOT_FOUND");
status = Store::Status::NOT_FOUND;
}
else
{
// All replicas returned an error, so log the error and return the
// failure.
if (trail != 0)
{
SAS::Event err(trail, SASEvent::MEMCACHED_GET_ERROR, 0);
err.add_var_param(fqkey);
SAS::report_event(err);
}
LOG_ERROR("Failed to read data for %s from %d replicas",
fqkey.c_str(), replicas.size());
status = Store::Status::ERROR;
}
return status;
}
/// Retrieve the data for a given namespace and key.
Store::Status BaseMemcachedStore::get_data(const std::string& table,
const std::string& key,
std::string& data,
uint64_t& cas,
SAS::TrailId trail)
{
Store::Status status;
// Construct the fully qualified key.
std::string fqkey = table + "\\\\" + key;
const char* key_ptr = fqkey.data();
const size_t key_len = fqkey.length();
int vbucket = vbucket_for_key(fqkey);
const std::vector<memcached_st*>& replicas = get_replicas(vbucket, Op::READ);
if (trail != 0)
{
SAS::Event start(trail, SASEvent::MEMCACHED_GET_START, 0);
start.add_var_param(fqkey);
SAS::report_event(start);
}
TRC_DEBUG("%d read replicas for key %s", replicas.size(), fqkey.c_str());
// Read from all replicas until we get a positive result.
memcached_return_t rc = MEMCACHED_ERROR;
bool active_not_found = false;
size_t failed_replicas = 0;
size_t ii;
// If we only have one replica, we should try it twice -
// libmemcached won't notice a dropped TCP connection until it tries
// to make a request on it, and will fail the request then
// reconnect, so the second attempt could still work.
size_t attempts = (replicas.size() == 1) ? 2 : replicas.size();
for (ii = 0; ii < attempts; ++ii)
{
size_t replica_idx;
if ((replicas.size() == 1) && (ii == 1))
{
if (rc != MEMCACHED_CONNECTION_FAILURE)
{
// This is a legitimate error, not a server failure, so we
// shouldn't retry.
break;
}
replica_idx = 0;
TRC_WARNING("Failed to read from sole memcached replica: retrying once");
}
else
{
replica_idx = ii;
}
TRC_DEBUG("Attempt to read from replica %d (connection %p)",
replica_idx,
replicas[replica_idx]);
rc = get_from_replica(replicas[replica_idx], key_ptr, key_len, data, cas);
if (memcached_success(rc))
{
// Got data back from this replica. Don't try any more.
TRC_DEBUG("Read for %s on replica %d returned SUCCESS",
fqkey.c_str(),
replica_idx);
break;
}
else if (rc == MEMCACHED_NOTFOUND)
{
// Failed to find a record on an active replica. Flag this so if we do
// find data on a later replica we can reset the cas value returned to
// zero to ensure a subsequent write will succeed.
TRC_DEBUG("Read for %s on replica %d returned NOTFOUND", fqkey.c_str(), replica_idx);
active_not_found = true;
}
else
{
// Error from this node, so consider it inactive.
TRC_DEBUG("Read for %s on replica %d returned error %d (%s)",
fqkey.c_str(), replica_idx, rc, memcached_strerror(replicas[replica_idx], rc));
++failed_replicas;
}
}
if (memcached_success(rc))
{
if (data != TOMBSTONE)
{
if (trail != 0)
{
SAS::Event got_data(trail, SASEvent::MEMCACHED_GET_SUCCESS, 0);
got_data.add_var_param(fqkey);
got_data.add_var_param(data);
got_data.add_static_param(cas);
SAS::report_event(got_data);
}
// Return the data and CAS value. The CAS value is either set to the CAS
// value from the result, or zero if an earlier active replica returned
// NOT_FOUND. This ensures that a subsequent set operation will succeed
// on the earlier active replica.
if (active_not_found)
{
cas = 0;
}
TRC_DEBUG("Read %d bytes from table %s key %s, CAS = %ld",
data.length(), table.c_str(), key.c_str(), cas);
status = Store::OK;
}
else
{
if (trail != 0)
{
SAS::Event got_tombstone(trail, SASEvent::MEMCACHED_GET_TOMBSTONE, 0);
got_tombstone.add_var_param(fqkey);
got_tombstone.add_static_param(cas);
SAS::report_event(got_tombstone);
}
// We have read a tombstone. Return NOT_FOUND to the caller, and also
// zero out the CAS (returning a zero CAS makes the interface cleaner).
TRC_DEBUG("Read tombstone from table %s key %s, CAS = %ld",
table.c_str(), key.c_str(), cas);
cas = 0;
status = Store::NOT_FOUND;
}
// Regardless of whether we got a tombstone, the vbucket is alive.
update_vbucket_comm_state(vbucket, OK);
if (_comm_monitor)
{
_comm_monitor->inform_success();
}
}
else if (failed_replicas < replicas.size())
{
// At least one replica returned NOT_FOUND.
if (trail != 0)
{
SAS::Event not_found(trail, SASEvent::MEMCACHED_GET_NOT_FOUND, 0);
not_found.add_var_param(fqkey);
SAS::report_event(not_found);
}
TRC_DEBUG("At least one replica returned not found, so return NOT_FOUND");
status = Store::Status::NOT_FOUND;
update_vbucket_comm_state(vbucket, OK);
if (_comm_monitor)
{
_comm_monitor->inform_success();
}
}
else
{
// All replicas returned an error, so log the error and return the
// failure.
if (trail != 0)
{
SAS::Event err(trail, SASEvent::MEMCACHED_GET_ERROR, 0);
err.add_var_param(fqkey);
SAS::report_event(err);
}
TRC_ERROR("Failed to read data for %s from %d replicas",
fqkey.c_str(), replicas.size());
status = Store::Status::ERROR;
update_vbucket_comm_state(vbucket, FAILED);
if (_comm_monitor)
{
_comm_monitor->inform_failure();
}
}
return status;
}
