.- Backend -.

/ \

/ \

DTM ---- Backend ---- Coordinator

\ /

\ /

`- Backend -´

-- Informs the DTM about a global transaction

-- identified by the corresponding pairs of node:xid values.

dtm_begin_transaction(nodes integer[], xids integer[]) RETURNS void

-- Causes the backend to get a snapshot from the DTM

-- and merge it with the local snapshot.

dtm_get_snapshot() RETURNS void

----------

libdtm api

----------

// Sets up the host and port for DTM connection.

// The defaults are "127.0.0.1" and 5431.

void TuneToDtm(char *host, int port);

void DtmInitSnapshot(Snapshot snapshot);

// Starts a new global transaction of nParticipants size. Returns the

// transaction id, fills the 'snapshot' and 'gxmin' on success. 'gxmin' is the

// smallest xmin among all snapshots known to DTM. Returns INVALID_XID

// otherwise.

TransactionId DtmGlobalStartTransaction(int nParticipants, Snapshot snapshot, TransactionId *gxmin);

// Asks the DTM for a fresh snapshot. Fills the 'snapshot' and 'gxmin' on

// success. 'gxmin' is the smallest xmin among all snapshots known to DTM.

void DtmGlobalGetSnapshot(TransactionId xid, Snapshot snapshot, TransactionId *gxmin);

// Commits transaction only once all participants have called this function,

// does not change CLOG otherwise. Set 'wait' to 'true' if you want this call

// to return only after the transaction is considered finished by the DTM.

// Returns the status on success, or -1 otherwise.

XidStatus DtmGlobalSetTransStatus(TransactionId xid, XidStatus status, bool wait);

// Gets the status of the transaction identified by 'xid'. Returns the status

// on success, or -1 otherwise. If 'wait' is true, then it does not return

// until the transaction is finished.

XidStatus DtmGlobalGetTransStatus(TransactionId xid, bool wait);

// Reserves at least 'nXids' successive xids for local transactions. The xids

// reserved are not less than 'xid' in value. Returns the actual number of xids

// reserved, and sets the 'first' xid accordingly. The number of xids reserved

// is guaranteed to be at least nXids.

// In other words, *first ≥ xid and result ≥ nXids.

// Also sets the 'active' snapshot, which is used as a container for the list

// of active global transactions.

int DtmGlobalReserve(TransactionId xid, int nXids, TransactionId *first, Snapshot active);

--------------------

Backend-DTM Protocol

--------------------

The queries from backend to DTM should be formatted according to this syntax.

<char cmd><hex16 argc><hex16 argv[0]><hex16 argv[1]>...

<cmd> is a character representing a command.

<argc> is the number of arguments.

<argv[i]> are the arguments.

prevent DTM from using those values for global transactions. The

'snapshot' represent the list of currently active global transactions.

The DTM replies with:

'+'<hex16 min><hex16 max><snapshot> if reserved a range [min, max]

'-' on failure

for vote results calculation. The DTM also creates and returns the

The DTM replies with:

'+'<hex16 xid><snapshot> if transaction started successfully

'-' on failure

Asks the DTM about the status of the global transaction identified

If 'wait' is true, DTM will not reply until it considers the

The DTM replies with:

"+0" if not started

"+c" if committed

"+a" if aborted

"+?" if in progress

'-' if failed

Tells the DTM to vote for commit of the global transaction identified

by the given 'xid'.

Tells the DTM to vote againts commit of the global transaction

identified by the given 'xid'.

Tells the DTM to generate a snapshot for the global transaction

identified by the given 'xid'. The DTM will create a snapshot for every

participant, so when each of them asks for the snapshot it will reply

with the same snapshot. The DTM generates a fresh version if the same

client asks for a snapshot again for the same transaction.

The DTM replies with '+' followed by a snapshot in the form:

<hex16 gxmin><hex16 xmin><hex16 xmax><hex16 xcnt><hex16 xip[0]>...

Where 'gxmin' is the smallest xmin among all available snapshots.

In case of a failure, the DTM replies with '-'.

LIBUV_CFLAGS=-I"$(LIBUV_PREFIX)/include" -L"$(LIBUV_PREFIX)/lib"

bin/dtmd: obj/eventwrap.o obj/main.o obj/parser.o obj/clog.o obj/clogfile.o obj/util.o obj/transaction.o obj/snapshot.o | bindir objdir

$(CC) -o bin/dtmd $(CFLAGS) $(LIBUV_CFLAGS) \

obj/eventwrap.o obj/main.o obj/parser.o \

$(LIBUV_LDFLAGS)

obj/eventwrap.o: src/eventwrap.c | objdir

$(CC) -c -o obj/eventwrap.o $(CFLAGS) $(LIBUV_CFLAGS) src/eventwrap.c

check: bin/util-test bin/clog-test bin/parser-test

./check.sh util parser clog

bin/parser-test: obj/parser-test.o obj/parser.o | bindir

$(CC) -o bin/parser-test $(CFLAGS) obj/parser-test.o obj/parser.o

#define MAX_XID 0xdeadbeefcafebabe

typedef unsigned long long xid_t;

#define BITS_PER_NODE 4

#define MAX_NODES (1 << BITS_PER_NODE)