NAME: pglobalxact extension

SYNOPSIS:

#include<postgres.h>

PG_MODULE_MAGIC;

const char libname = LIBDIR "/pg_globalxact.so";

void * regfunc = load_external_function(libname, "tpc_register", true, NULL);

/* do some things */

/* In the transaction, if we have a libpq connection handle called conn */ regfunc(conn);

DESCRIPTION:

This extension provides services for doing destributed transactions within PostgreSQL and administrative tools for managing the review and recovery of distributed transactions when machines die between PREPARE and COMMIT/ROLLBACK stages.

For this to work, initial remote database connections must be registered into a transaction set. These sets are then stored in text files on disk because they must persist beyond a rollback or even, in some cases, a database restart.

The module has two classes of functions: c functions intended to be used by other extensions and SQL functions intended to be used by DBAs to view status of in-flight global transactions and engaging in various recovery functions.

This extension manages global transactions as "transaction sets" of local transactions on the running nodes. Right now, only PostgreSQL remote ends are supported though this could change over time.

The intended use is for C functions to be used to register remote transactions into the global transaction set, and then for local transaction becomes the control mechanism for the remote transactions. In terms of implementation, this means that the remote transactions go through a full two phase commit process as the local transaction commits or rolls back.

Recovery is guaranteed through transaction state files and a background worker whose job it is to retry COMMIT PREPARED or ROLLBACK PREPARED calls in order to bring things back into consistent states.

The SQL functions are intended to provide administrator access to the reconciliation etc process as well as allow human intervention when a remote node undergoes catastrophic failure and will not come back.

This library does not attempt to provide any assistance in global transaction deadlock detectoin or resolution. Nor does it provide any assistance on protecting against distributed read anomilies.

C FUNCTIONS

SQL FUNCTIONS

INTERNALS

DESIGN CHOICES

COPYRIGHT