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#################################################
Overview of Firebird Client Library Thread-Safety
#################################################
The thread-safety properties of the standard Firebird client library
vary according to the following:
+ Firebird version
+ operating system
+ Firebird server architecture (SuperServer, Classic, Embedded)
+ underlying connection protocol (embedded vs. local vs. IPC vs.
remote)
Determining whether the client library you're using is thread-safe can
be quite confusing. This document aims to reduce that confusion by
defining what thread-safety means in the context of the Firebird
client library, then presenting a table that specifies which client
library configurations are thread-safe.
Note that this document deals only with the *standard* Firebird client
library that underlies the Firebird C API. It has *no relevance* to
the clean-slate reimplementations in access libraries such as Jaybird.
Definition of "Thread-Safety"
=============================
Currently, the highest level of concurrency supported by any version
of the Firebird client library is *thread-safety at the connection
level*.
When we say that the Firebird client library is *thread-safe at the
connection level*, we mean that it is safe to use a particular
connection in only one thread at a time, although the same connection
can be manipulated by different threads in a serial fashion, and
different connections can be manipulated by different threads in
parallel.
For example, in a multithreaded application server, it is safe for a
particular connection to be leased from a connection pool by Thread A,
used, and returned to the pool for later lease by Thread B. It is not
safe for Thread A and Thread B to use the same connection at the same
time.
Thread-Safety Table
===================
+------------+---------+-----------------+----------------+--------------------+
| FB Version | OS | FB Architecture | Remote / Local | Thread-Safe? |
+============+=========+=================+================+====================+
| 1.0.3 | Windows | SuperServer | Local | No |
| | | +----------------+--------------------+
| | | | Remote | Yes |
| | +-----------------+----------------+--------------------+
| | | Classic | Local | No such config. |
| | | +----------------+--------------------+
| | | | Remote | No such config. |
| | +-----------------+----------------+--------------------+
| | | Embedded | Local | No such config. |
| | | +----------------+--------------------+
| | | | Remote | No such config. |
| +---------+-----------------+----------------+--------------------+
| | Linux | SuperServer | Local | No such config. |
| | | +----------------+--------------------+
| | | | Remote | No |
| | +-----------------+----------------+--------------------+
| | | Classic | Local | No |
| | | +----------------+--------------------+
| | | | Remote | No |
+------------+---------+-----------------+----------------+--------------------+
| 1.5 | Windows | SuperServer | Local | No |
| | | +----------------+--------------------+
| | | | Remote | Yes |
| | +-----------------+----------------+--------------------+
| | | Classic | Local | No such config. |
| | | +----------------+--------------------+
| | | | Remote | Yes |
| | +-----------------+----------------+--------------------+
| | | Embedded | Local | Yes |
| | | +----------------+--------------------+
| | | | Remote | No such config. |
| +---------+-----------------+----------------+--------------------+
| | Linux | SuperServer | Local | No such config. |
| | | +----------------+--------------------+
| | | | Remote | Yes |
| | +-----------------+----------------+--------------------+
| | | Classic | Local | No |
| | | +----------------+--------------------+
| | | | Remote | No |
+------------+---------+-----------------+----------------+--------------------+
| 2.0/2.1 | Windows | SuperServer | Local | Yes |
| | | +----------------+--------------------+
| | | | Remote | Yes |
| | +-----------------+----------------+--------------------+
| | | Classic | Local | Yes |
| | | +----------------+--------------------+
| | | | Remote | Yes |
| | +-----------------+----------------+--------------------+
| | | Embedded | Local | Yes |
| | | +----------------+--------------------+
| | | | Remote | No such config. |
| +---------+-----------------+----------------+--------------------+
| | Linux | SuperServer | Local | No such config. |
| | | +----------------+--------------------+
| | | | Remote | Yes |
| | +-----------------+----------------+--------------------+
| | | Classic | Local | No |
| | | +----------------+--------------------+
| | | | Remote | No |
+------------+---------+-----------------+----------------+--------------------+
This document was written by David Rushby, with assistance from Dmitry
Yemanov. Errors are attributable to Rushby rather than Yemanov.
|
