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25. Tracing python-oracledb — python-oracledb 3.4.0b1 documentation

There are multiple approaches for application tracing and monitoring:

• End-to-end database tracing attributes such as Connection.action and Connection.module are supported in the python-oracledb Thin and Thick modes. Using these attributes is recommended since they aid application monitoring and troubleshooting.

• You can subclass python-oracledb classes and implement your own driver API call tracing and logging. Also, the standard Python tracing capabilities can be used.

• The Java Debug Wire Protocol (JDWP) for debugging PL/SQL can be used. See Debugging PL/SQL with the Java Debug Wire Protocol.

• Instrumentation libraries such as OpenTelemetry allow sophisticated monitoring, see Using python-oracledb with OpenTelemetry.

• Python-oracledb in Thick mode can dump a trace of SQL statements executed. See Low Level SQL Tracing.

• The unique connection identifiers that appear in connection error messages, and in Oracle Database traces and logs, can be used to resolve connectivity errors. See Using Connection Identifiers.

Oracle Database end-to-end application tracing simplifies diagnosing application code flow and performance problems in multi-tier or multi-user environments.

The connection attributes Connection.client_identifier, Connection.clientinfo, Connection.dbop, Connection.module, and Connection.action set metadata for end-to-end tracing. The values can be queried from data dictionary and dynamic performance views to monitor applications, or you can use tracing utilities. Values may appear in logs and audit trails.

Also see Connection Metadata and Application Contexts for information about setting Application Contexts.

The Connection.client_identifier attribute is typically set to the name (or identifier) of the actual end user initiating a query. This allows the database to distinguish, and trace, end users for applications that connect using a common database username. It can also be used by Oracle Virtual Private Database (VPD) policies to automatically limit data access. Oracle Database’s DBMS_MONITOR package can take advantage of the client identifer to enable statistics and tracing at an individual level.

The Connection.module and Connection.action attributes can be set to user-chosen, descriptive values identifying your code architecture.

After attributes are set, the values are sent to the database when the next round-trip to the database occurs, for example when the next SQL statement is executed.

The attribute values will remain set in connections released back to a connection pool. When the application re-acquires a connection from the pool, it should initialize the values to a desired state before using that connection.

The example below shows setting the action, module, and client identifier attributes on a connection object, and then querying a view to see the recorded values. The example both sets and queries the values, but typically monitoring is done externally to the application.

# Set the tracing metadata
connection.client_identifier = "pythonuser"
connection.action = "Query Session tracing parameters"
connection.module = "End-to-end Demo"

for row in cursor.execute("""
        SELECT username, client_identifier, module, action
        FROM V$SESSION
        WHERE sid = SYS_CONTEXT('USERENV', 'SID')"""):
    print(row)

The output will be like:

('SYSTEM', 'pythonuser', 'End-to-end Demo', 'Query Session tracing parameters')

The values can also be manually set by calling DBMS_APPLICATION_INFO procedures or DBMS_SESSION.SET_IDENTIFIER. These incur round-trips to the database which reduces application scalability:

BEGIN
    DBMS_SESSION.SET_IDENTIFIER('pythonuser');
    DBMS_APPLICATION_INFO.set_module('End-to-End Demo');
    DBMS_APPLICATION_INFO.set_action(action_name => 'Query Session tracing parameters');
END;

The Connection.dbop attribute can be used for Real-Time SQL Monitoring, see Monitoring Database Operations. The value will be shown in the DBOP_NAME column of the V$SQL_MONITOR view:

connection.dbop = "my op"

for row in cursor.execute("""
        SELECT dbop_name
        FROM V$SQL_MONITOR
        WHERE sid = SYS_CONTEXT('USERENV', 'SID')"""):
    print(row)

The Java Debug Wire Protocol (JDWP) for debugging PL/SQL can be used with python-oracledb.

Python-oracledb applications that call PL/SQL can step through that PL/SQL code using JDWP in a debugger. This allows Python and PL/SQL code to be debugged in the same debugger environment. You can enable PL/SQL debugging in python-oracledb as follows:

• In python-oracledb Thin or Thick modes, set the ORA_DEBUG_JDWP environment variable to host=hostname;port=portnum indicating where the PL/SQL debugger is running. Then run the application.

• In python-oracledb Thin mode, you can alternatively set the connection parameter debug_jdwp during connection. This variable defaults to the value of the ORA_DEBUG_JDWP environment variable.

See the documentation on DBMS_DEBUG_JDWP, the video PL/SQL debugging with Visual Studio and Visual Studio Code, and the blog post Debugging PL/SQL with Visual Studio Code (and more).

The Thick mode of python-oracledb is implemented using the ODPI-C wrapper on top of the Oracle Client libraries. The ODPI-C tracing capability can be used to log executed python-oracledb statements to the standard error stream. Before executing Python, set the environment variable DPI_DEBUG_LEVEL to 16 in your terminal window.

On Linux, you might use:

export DPI_DEBUG_LEVEL=16

On Windows, this could be done with:

After setting the variable, run the Python Script, for example on Linux:

python end-to-endtracing.py 2> log.txt

For an application that does a single query, the log file might contain a tracing line consisting of the prefix ‘ODPI’, a thread identifier, a timestamp, and the SQL statement executed:

ODPI [23389068] 2025-06-25 12:07:55.405: ODPI-C 5.5.1
ODPI [23389068] 2025-06-25 12:07:55.405: debugging messages initialized at level 16
ODPI [23389068] 2025-06-25 12:08:01.363: SQL select name from jobs

See ODPI-C Debugging for documentation on DPI_DEBUG_LEVEL.

A unique connection identifier (CONNECTION_ID) is generated for each connection to the Oracle Database. The connection identifier is shown in some Oracle Network error messages and logs, which helps in better tracing and diagnosing of connection failures. For example:

DPY-6005: cannot connect to database (CONNECTION_ID=m0PfUY6hYSmWPcgrHZCQIQ==)

Depending on the Oracle Database version in use, the information that is shown in logs varies.

You can define a prefix value which is added to the beginning of the CONNECTION_ID value. This prefix aids in identifying the connections from a specific application.

See Troubleshooting Oracle Net Services for more information on connection identifiers.

Python-oracledb Thin mode

In python-oracledb Thin mode, you can specify a prefix using the connection_id_prefix parameter when creating standalone connections or pooled connections, or alternatively set a prefix when calling oracledb.ConnectParams() or oracledb.PoolParams(). For example:

connection = oracledb.connect(user="hr", password=userpwd,
                              dsn="localhost/orclpdb",
                              connection_id_prefix="MYAPP")

If this connection to the database fails, MYAPP is added as a prefix to the CONNECTION_ID value shown in the error message, for example:

DPY-6005: cannot connect to database (CONNECTION_ID=MYAPPm0PfUY6hYSmWPcgrHZCQIQ==).

Python-oracledb Thick mode

In python-oracledb Thick mode, you can specify the connection identifier prefix in the connection string or connect descriptor. For example:

mydb = (DESCRIPTION =
         (ADDRESS_LIST= (ADDRESS=...) (ADDRESS=...))
         (CONNECT_DATA=
            (SERVICE_NAME=sales.us.example.com)
            (CONNECTION_ID_PREFIX=MYAPP)
         )
       )

Several methods for tracing bind variable values can be used. When tracing bind variable values, be careful not to leak information and create a security problem.

In Oracle Database, the view V$SQL_BIND_CAPTURE can capture bind information. Tracing with Oracle Database’s DBMS_MONITOR package may also be useful.

You can additionally subclass python-oracledb classes and log any bind values.

OpenTelemetry can also be used, see Using python-oracledb with OpenTelemetry.

This section shows some of the Oracle Database views useful for tracing and monitoring python-oracledb. Other views and columns not described here also contain useful information, such as the Database Resident Connection Pooling (DRCP) views discussed in Monitoring DRCP, and the views discussed in Oracle Database End-to-End Tracing and Tracing Bind Values.

The following table shows sample values for some V$SESSION columns. You may see other values if you have changed the defaults using the Defaults object before connecting, set the equivalent connection or pool creation parameters, or set the attribute Connection.module as shown in Oracle Database End-to-End Tracing.

Column

Sample Thin mode value

Sample Thick mode value

MACHINE

“myusername-mac”

“myusername-mac”

MODULE

The value of Python’s sys.executable, such as /Users/myusername/.pyenv/versions/3.13.3/bin/python

Similar to python@myusername-mac (TNS V1-V3)

OSUSER

“myusername”

“myusername”

PROGRAM

The value of Python’s sys.executable, such as /Users/myusername/.pyenv/versions/3.13.3/bin/python

Similar to python@myusername-mac (TNS V1-V3)

TERMINAL

“unknown”

Similar to ttys001

The following table shows sample values for some V$SESSION_CONNECT_INFO columns. You may see other values if you have changed the defaults using the Defaults object before connecting, set the equivalent connection or pool creation parameters, or set the driver_name parameter in oracledb.init_oracle_client().

Column

Sample Thin mode value

Sample Thick mode value

CLIENT_DRIVER

“python-oracledb thn : 3.2.0”

“python-oracledb thk : 3.2.0”

CLIENT_OCI_LIBRARY

“Unknown”

The Oracle Client or Instant Client type, such as “Full Instant Client”

CLIENT_VERSION

“3.2.0.0.0” (the python-oracledb version number with an extra .0.0)

The Oracle Client library version number

OSUSER

“myusername”

“myusername”

The OpenTelemetry observability framework is useful for monitoring applications and identifying bottlenecks. Python-oracledb conforms to the Python DB API specification allowing standard Python modules for OpenTelemetry to be used to instrument your applications.

OpenTelemetry’s backend trace exporters can provide graphic and intuitive representation of OpenTelemetry trace information. Visual exporters include Zipkin, Jaeger, and Prometheus. Simple tracing can also be directed to the console by making use of the exporter ConsoleSpanExporter from the opentelemetry-sdk package.

For details on using OpenTelemetry in Python, see Python OpenTelemetry documentation.

This example shows a python-oracledb application using OpenTelemetry’s ConsoleSpanExporter exporter to display trace information to the console.

Installing OpenTelemetry Modules

For this example, install:

python -m pip install opentelemetry-sdk opentelemetry-api opentelemetry-instrumentation-dbapi

Sample Application

This simple application performs two queries in a custom span. It also sets the service name and system attributes to user-chosen values. It uses the capture_parameters option to enable bind variable tracing.

Warning

The trace integration setting capture_parameters=True captures bind variable values and is a security risk.

The sample code is:

import oracledb

from opentelemetry import trace
from opentelemetry.sdk.trace import TracerProvider
from opentelemetry.sdk.trace.export import (
    BatchSpanProcessor,
    ConsoleSpanExporter,
)
from opentelemetry.sdk.resources import Resource

user = "hr"
password = userpwd
host = "dbhost.example.com"
service_name = "orclpdb"

resource = Resource(attributes={
    "service.name": service_name,   # displayed as a resource attribute "service.name"
})

provider = TracerProvider(resource=resource)
processor = BatchSpanProcessor(ConsoleSpanExporter())
provider.add_span_processor(processor)
trace.set_tracer_provider(provider)

from opentelemetry.instrumentation.dbapi import trace_integration

trace_integration(
    oracledb,
    connect_method_name="connect",
    database_system="oracle",  # displayed as attribute "db.system"
    capture_parameters=True,   # displayed as attribute "db.statement.parameters"
                               # WARNING: this shows bind variable values
)

connection = oracledb.connect(user=user, password=password,
                              host=host, service_name=service_name)

with connection.cursor() as cursor:
    tracer = trace.get_tracer("HR-tracer-name")
    with tracer.start_as_current_span("HR-span-1") as span:
        sql = "select city from locations where location_id = :1"
        for r, in cursor.execute(sql, [2200]):
            print(r)
        sql = "select 'Hello World!' from dual"
        for r, in cursor.execute(sql):
            print(r)

Sample Output

The sample output will be like:

Sydney
Hello World!
{
    "name": "select",
    "context": {
        "trace_id": "0xb24817cd2ea38ffa523c2ee2778508f7",
        "span_id": "0xacfd82ed60e8976d",
        "trace_state": "[]"
    },
    "kind": "SpanKind.CLIENT",
    "parent_id": "0x19027598c301cfac",
    "start_time": "2025-05-29T08:40:10.194645Z",
    "end_time": "2025-05-29T08:40:10.209815Z",
    "status": {
        "status_code": "UNSET"
    },
    "attributes": {
        "db.system": "oracle",
        "db.name": "",
        "db.statement": "select city from locations where location_id = :1",
        "db.statement.parameters": "[2200]"
    },
    "events": [],
    "links": [],
    "resource": {
        "attributes": {
            "service.name": "orclpdb1"
        },
        "schema_url": ""
    }
}
{
    "name": "select",
    "context": {
        "trace_id": "0xb24817cd2ea38ffa523c2ee2778508f7",
        "span_id": "0x376dff430f66b14f",
        "trace_state": "[]"
    },
    "kind": "SpanKind.CLIENT",
    "parent_id": "0x19027598c301cfac",
    "start_time": "2025-05-29T08:40:10.210799Z",
    "end_time": "2025-05-29T08:40:10.214694Z",
    "status": {
        "status_code": "UNSET"
    },
    "attributes": {
        "db.system": "oracle",
        "db.name": "",
        "db.statement": "select 'Hello World!' from dual"
    },
    "events": [],
    "links": [],
    "resource": {
        "attributes": {
            "service.name": "orclpdb1"
        },
        "schema_url": ""
    }
}
{
    "name": "HR-span-1",
    "context": {
        "trace_id": "0xb24817cd2ea38ffa523c2ee2778508f7",
        "span_id": "0x19027598c301cfac",
        "trace_state": "[]"
    },
    "kind": "SpanKind.INTERNAL",
    "parent_id": null,
    "start_time": "2025-05-29T08:40:10.194536Z",
    "end_time": "2025-05-29T08:40:10.214732Z",
    "status": {
        "status_code": "UNSET"
    },
    "attributes": {},
    "events": [],
    "links": [],
    "resource": {
        "attributes": {
            "service.name": "orclpdb1"
        },
        "schema_url": ""
    }
}

The two query results precede OpenTelemetry’s tracing. The tracing then shows:

• The start and end time of each operation.

• Each “select” trace block’s association to the span “HR-span-1” via their parent_id values, which match the span’s span_id value.

• The bind variable value 2200 in the attribute db.statement.parameters. Warning: it is a security risk to monitor bind variable values this way. Keep the capture_parameters option set to False.

• The system and service name as set in the application.

The Python OpenTelemetry modules allow further customization for tracing. See their documentation for more information.

When a graphical provider is used instead of ConsoleSpanExporter, the database query relationships and timings are easier to analyze.

The boolean attributes Connection.thin and ConnectionPool.thin can be used to show the current mode of a python-oracledb connection or pool, respectively. The method oracledb.is_thin_mode() can also be used, but review its usage notes about when its return value may change.

For example, to show the mode used by a connection:

The python-oracledb version can be shown with oracledb.__version__:

print(oracledb.__version__)

Version and mode information can also be seen in the Oracle Database data dictionary table V$SESSION_CONNECT_INFO:

with connection.cursor() as cursor:
    sql = """SELECT UNIQUE client_driver
             FROM V$SESSION_CONNECT_INFO
             WHERE sid = SYS_CONTEXT('USERENV', 'SID')"""
    for r, in cursor.execute(sql):
        print(r)

In python-oracledb Thin mode, the output will be like:

python-oracledb thn : 3.2.0

In python-oracledb Thick mode, the output will be like:

python-oracledb thk : 3.2.0

Note that you may not see these values if you have set oracledb.defaults.driver_name or the driver_name parameter in oracledb.init_oracle_client().

Low level tracing is mostly useful to maintainers of python-oracledb.

• For python-oracledb Thin mode, packets can be traced by setting the environment variable PYO_DEBUG_PACKETS in your terminal window before running your application.

  For example, on Linux, you might use:

  export PYO_DEBUG_PACKETS=1
  

  On Windows you might set the variable like:

  Alternatively, the variable can be set in the application:

  import os
  os.environ["PYO_DEBUG_PACKETS"] = "1"
  import oracledb
  

  The output goes to stdout. The information logged is roughly similar to an Oracle Net trace of level 16, see Oracle Net Services TRACE_LEVEL_CLIENT.

• Python-oracledb Thick mode can be traced using:

  • DPI_DEBUG_LEVEL as documented in ODPI-C Debugging.

  • Oracle Call Interface (OCI) tracing as directed by Oracle Support.

  • Oracle Net services tracing as documented in Oracle Net Services Tracing Parameters.

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