Jaeger Bindings for Python OpenTracing API
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README.md

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Jaeger Bindings for Python OpenTracing API

This is a client-side library that can be used to instrument Python apps for distributed trace collection, and to send those traces to Jaeger. See the OpenTracing Python API for additional detail.

Contributing and Developing

Please see CONTRIBUTING.md.

Installation

pip install jaeger-client

Getting Started

import logging
import time
from jaeger_client import Config

if __name__ == "__main__":
    log_level = logging.DEBUG
    logging.getLogger('').handlers = []
    logging.basicConfig(format='%(asctime)s %(message)s', level=log_level)

    config = Config(
        config={ # usually read from some yaml config
            'sampler': {
                'type': 'const',
                'param': 1,
            },
            'logging': True,
        },  
        service_name='your-app-name',
        validate=True,
    )
    # this call also sets opentracing.tracer
    tracer = config.initialize_tracer()

    with tracer.start_span('TestSpan') as span:
        span.log_kv({'event': 'test message', 'life': 42})

        with tracer.start_span('ChildSpan', child_of=span) as child_span:
            span.log_kv({'event': 'down below'})

    time.sleep(2)   # yield to IOLoop to flush the spans - https://github.com/jaegertracing/jaeger-client-python/issues/50
    tracer.close()  # flush any buffered spans

Other Instrumentation

The opentracing-contrib project has a few modules that provide explicit instrumentation support for popular frameworks like Django and Flask.

At Uber we are mostly using the opentracing_instrumentation module that provides:

  • explicit instrumentation for HTTP servers, and
  • implicit (monkey-patched) instrumentation for several popular libraries like urllib2, redis, requests, some SQL clients, etc.

Initialization & Configuration

Note: do not initialize the tracer during import, it may cause a deadlock (see issues #31, #60). Instead define a function that returns a tracer (see example below) and call that function explicitly after all the imports are done.

Production

The recommended way to initialize the tracer for production use:

from jaeger_client import Config

def init_jaeger_tracer(service_name='your-app-name'):
    config = Config(config={}, service_name=service_name, validate=True)
    return config.initialize_tracer()

Note that the call initialize_tracer() also sets the opentracing.tracer global variable. If you need to create additional tracers (e.g., to create spans on the client side for remote services that are not instrumented), use the new_tracer() method.

Prometheus metrics

This module brings a Prometheus integration to the internal Jaeger metrics.
The way to initialize the tracer with Prometheus metrics:

from jaeger_client.metrics.prometheus import PrometheusMetricsFactory

config = Config(
        config={},
        service_name='your-app-name',
        validate=True,
        metrics_factory=PrometheusMetricsFactory(namespace='your-app-name')
)
tracer = config.initialize_tracer()

Development

For development, some parameters can be passed via config dictionary, as in the Getting Started example above. For more details please see the Config class.

WSGI

Applications running under WSGI usually fork multiple sub-processes to handle individual requests. When Jaeger tracer is initialized, it may start a new background thread. If the process later forks, it might cause issues or hang the application (due to exclusive lock on the interpreter). Therefore, it is recommended that the tracer is not initialized until after the child processes are forked. Depending on the WSGI framework you might be able to use @postfork decorator to delay tracer initialization (see also issues #31, #60).

Debug Traces (Forced Sampling)

Programmatically

The OpenTracing API defines a sampling.priority standard tag that can be used to affect the sampling of a span and its children:

from opentracing.ext import tags as ext_tags

span.set_tag(ext_tags.SAMPLING_PRIORITY, 1)

Via HTTP Headers

Jaeger Tracer also understands a special HTTP Header jaeger-debug-id, which can be set in the incoming request, e.g.

curl -H "jaeger-debug-id: some-correlation-id" http://myhost.com

When Jaeger sees this header in the request that otherwise has no tracing context, it ensures that the new trace started for this request will be sampled in the "debug" mode (meaning it should survive all downsampling that might happen in the collection pipeline), and the root span will have a tag as if this statement was executed:

span.set_tag('jaeger-debug-id', 'some-correlation-id')

This allows using Jaeger UI to find the trace by this tag.

Zipkin Compatibility

To use this library directly with other Zipkin libraries & backend, you can provide the configuration property propagation: 'b3' and the X-B3-* HTTP headers will be supported.

The B3 codec assumes it will receive lowercase HTTP headers, as this seems to be the standard in the popular frameworks like Flask and Django. Please make sure your framework does the same.

License

Apache 2.0 License.