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Update Trace API spec

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doc/README.performance_monitoring
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Performance analysis with Firebird.
Document version 0.1
Document version 0.2
Created by Nickolay Samofatov
Performance monitoring framework is consisted of 2 parts:
@ -9,43 +9,55 @@ Performance monitoring framework is consisted of 2 parts:
Trace API.
Trace API allows to plug a monitoring module into the engine and notify it
of processes happening there. List of analysis plugins is specified in
firebird.conf parameter TracePlugins. Each trace plugin receives notifications
on each database attached as a call of procedure having following signature:
Trace API allows to plug a monitoring module into the engine and notify it of
processes happening there. List of analysis plugins is specified in firebird.conf
parameter TracePlugins. Each trace plugin receives notifications on each database
opened by the engine as a call of procedure having following signature:
ISC_STATUS trace_attach(ISC_STATUS* status, TraceDatabase* db);
NTRACE_BOOLEAN trace_attach(const char* db_filename, const TracePlugin** plugin);
Conceptually db is the database trace interface, but it is implemented as a
structure of function pointers and void* object pointer.
Conceptually TracePlugin is the plugin trace interface. It is implemented as a
structure of function pointers and void* object pointer to be passed as first
argument for each function.
Given this interface plugin may install hooks for particular events and receive
notifications on them. In fact, set of hooks is also implemented as a structure
with function pointers.
notifications for them. If plugin has interest in some kind of events for given
database it sets plugin pointer to a structure containing non-null hook function
pointers and returns NTRACE_TRUE value. Otherwise it should return NTRACE_FALSE.
See ntrace.h module for definitions of these structures and events supported.
One category of hooks receives the same parameters as corresponding Y-Valve
(public API) methods plus internal objects identifiers, generated PLANs for
statements and performance counters. One more hook receives performance
statistics for each procedure execution.
Each hook function returns boolean value indicating success or failure. When hook
function fails engine collects error message from plugin in the same thread
context as hook was called, writes message to firebird.log and stops calling
hooks for this particular database and trace plugin.
See jrd/ntrace.h module for definitions of structures and events supported.
Default analysis module.
Reference implementation of analysis plugin is centered around a concept of
performance snapshot. Snapshot detail may vary, but in any case it contains
information on all activities performed by server during a given period of time,
possibly in aggregated form. All snapshots may be compared to allow quanititive
measurements of performance improvements due to various optimization activities
or changes in user applications and infrastucture.
information on all activities performed by server for database during a given
period of time, possibly in aggregated form. All snapshots may be compared to
allow quanititive measurements of performance improvements due to various
optimization activities or changes in user applications and infrastucture.
Snapshot data is collected by trace module in raw form in a binary log file and
then may be loaded into a stats database using ntrace utility.
Stored snapshots may contain data on usage of indices, statements executed,
their plans and performance counters, IO statistics and other performance data.
Stored snapshots may contain data on usage of indices, statements executed, their
plans and performance counters, IO statistics and other performance data.
Level of detail for information collected is set up in analysis trace module
configuration file on per-database basis.
Default analysis module does not have GUI and only provides a database with
data on server activities and some stored procedures to use and maintain it.
Default analysis module does not have GUI and only provides a database with data
on server activities and some stored procedures to use and maintain it.
It is expected that third parties develop GUI tools, custom trace modules and
statistics tools to statisfy rich client needs.