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Make asynchronous replica re-initialization reliable #8324

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Nov 25, 2024
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Make asynchronous replica re-initialization reliable #8324

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83 changes: 59 additions & 24 deletions src/remote/server/ReplServer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -586,17 +586,20 @@ namespace
return true;
}

enum ActionType { REPLICATE, REPLAY, FAST_FORWARD };

void replicate(Target* target,
TransactionList& transactions,
FB_UINT64 sequence, ULONG offset,
ULONG length, const UCHAR* data,
bool rewind)
ActionType action)
{
const Block* const header = (Block*) data;

const auto traNumber = header->traNumber;

if (!rewind || !traNumber || transactions.exist(traNumber))
if (action == REPLICATE ||
(action == REPLAY && (!traNumber || transactions.exist(traNumber))))
{
target->replicate(sequence, offset, length, data);
}
Expand All @@ -609,7 +612,7 @@ namespace
if (transactions.find(traNumber, pos))
transactions.remove(pos);
}
else if (!rewind)
else if (action != REPLAY)
{
transactions.clear();
}
Expand All @@ -618,7 +621,7 @@ namespace
{
fb_assert(traNumber);

if (!rewind && !transactions.exist(traNumber))
if (action != REPLAY && !transactions.exist(traNumber))
transactions.add(ActiveTransaction(traNumber, sequence));
}
}
Expand Down Expand Up @@ -751,6 +754,7 @@ namespace
const FB_UINT64 max_sequence = queue.back()->header.hdr_sequence;
FB_UINT64 next_sequence = 0;
const bool restart = target->isShutdown();
auto action = REPLICATE;

for (auto segment : queue)
{
Expand All @@ -768,21 +772,48 @@ namespace
const FB_UINT64 db_sequence = target->initReplica();
const FB_UINT64 last_db_sequence = control.getDbSequence();

if (sequence <= db_sequence)
{
target->verbose("Deleting segment %" UQUADFORMAT " due to fast forward", sequence);
segment->remove();
continue;
}

if (db_sequence != last_db_sequence)
{
target->verbose("Resetting replication to continue from segment %" UQUADFORMAT, db_sequence + 1);
control.saveDbSequence(db_sequence);
transactions.clear();
control.saveComplete(db_sequence, transactions);
last_sequence = db_sequence;
last_offset = 0;
if (sequence == db_sequence + 1)
{
if (const auto oldest = findOldest(transactions))
{
const TraNumber oldest_trans = oldest->tra_id;
const FB_UINT64 oldest_sequence = oldest ? oldest->sequence : 0;
target->verbose("Resetting replication to continue from segment %" UQUADFORMAT
" (new OAT: %" UQUADFORMAT " in segment %" UQUADFORMAT ")",
db_sequence + 1, oldest_trans, oldest_sequence);
}
else
{
target->verbose("Resetting replication to continue from segment %" UQUADFORMAT,
db_sequence + 1);
}

control.saveDbSequence(db_sequence);
return PROCESS_SHUTDOWN; // this enforces restart from OAT
}

if (action != FAST_FORWARD)
{
if (segment != queue.front())
{
fb_assert(false);
return PROCESS_SHUTDOWN;
}

if (db_sequence > max_sequence)
{
target->verbose("Database sequence has been changed to %" UQUADFORMAT
", waiting for appropriate segment", db_sequence);
return PROCESS_SUSPEND;
}

target->verbose("Database sequence has been changed to %" UQUADFORMAT
", preparing for replication reset", db_sequence);

action = FAST_FORWARD;
}
}

// If no new segments appeared since our last attempt,
Expand Down Expand Up @@ -857,17 +888,18 @@ namespace

if (blockLength)
{
const bool rewind = (sequence < last_sequence ||
const bool replay = (sequence < last_sequence ||
(sequence == last_sequence && (!last_offset || totalLength < last_offset)));
if (action != FAST_FORWARD)
action = replay ? REPLAY : REPLICATE;

UCHAR* const data = buffer.getBuffer(length);
memcpy(data, &header, sizeof(Block));

if (read(file, data + sizeof(Block), blockLength) != blockLength)
raiseError("Journal file %s read failed (error %d)", segment->filename.c_str(), ERRNO);

replicate(target, transactions, sequence, totalLength,
length, data, rewind);
replicate(target, transactions, sequence, totalLength, length, data, action);
}

totalLength += length;
Expand All @@ -886,7 +918,10 @@ namespace
oldest_sequence = oldest ? oldest->sequence : 0;
next_sequence = sequence + 1;

string extra;
string actionName, extra;
actionName = (action == FAST_FORWARD) ? "scanned" :
(action == REPLAY) ? "replayed" : "replicated";

if (oldest)
{
const TraNumber oldest_trans = oldest->tra_id;
Expand All @@ -898,8 +933,8 @@ namespace
extra = "deleting";
}

target->verbose("Segment %" UQUADFORMAT " (%u bytes) is replicated in %s, %s",
sequence, totalLength, interval.c_str(), extra.c_str());
target->verbose("Segment %" UQUADFORMAT " (%u bytes) is %s in %s, %s",
sequence, totalLength, actionName.c_str(), interval.c_str(), extra.c_str());

if (!oldest_sequence)
segment->remove();
Expand All @@ -921,8 +956,8 @@ namespace
break;

target->verbose("Deleting segment %" UQUADFORMAT " as no longer needed", sequence);

segment->remove();

} while (pos < queue.getCount());
}
}
Expand Down
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