Ddtrace

This release includes the removal of service sending, this should resolve many of the 400s that are being returned from the Agent resulting in an unfriendly `ERROR` message and giving the impression that the tracer is failing. (757)

Improvements
- [core] Make writing services a no-op (735)
- [tests] upgrade flake8 to 3.5.0 (743)
- remove flake8 ignores and fix issues (744)

Read the [full changeset](https://github.com/DataDog/dd-trace-py/compare/v0.17.0...v0.17.1) and the [release milestone](https://github.com/DataDog/dd-trace-py/milestone/31?closed=1).
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New features
- [redis] add support for redis 3.0.0 (716)
- [core] Allow DD_AGENT_HOST and DD_TRACE_AGENT_PORT env variables (708)
- [core] Add global tracer tags (702)
- [core] Trace http headers (647)

Improvements
- [docs] add Flask configuration documentation (734)
- Add long_description to setup.py (728)
- [tests] pin version of redis-py-cluster for 'tox -e wait' (725)
- [requests] Add another split_by_domain test (713)
- [docs] Add kombu references (711)
- [ci] Use small circleci resource class for all jobs (710)
- [requests] patch Session.send instead of Session.request (707)
- [ci] reorganize CircleCI workflows (705)
- [elasticsearch] add support for elasticsearch{1,2,5} packages (701)
- [tests] add base test case classes and rewrite tracer tests (689)
- [dbapi] Trace db fetch and session methods (664)

Bugfixes
- [elasticsearch] add alias for default _perform_request (737)
- [tests] Pin pytest to 3.x.x and redis to 2.10.x for rediscluster (727)
- [django] Use a set instead of list for cache_backends to avoid duplicates (726 -- thanks wenbochang)
- [tests] fix broken redis check (722)
- [docs] Fix broken flask link (712)
- [mongodb] Fix pymongo query metadata (706)

Read the [full changeset](https://github.com/DataDog/dd-trace-py/compare/v0.16.0...v0.17.0) and the [release milestone](https://github.com/DataDog/dd-trace-py/milestone/29?closed=1).
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New Integrations
* [jinja2] Add jinja2 integration (649 -- thanks mgu)
* [kombu] add Kombu integration (515 -- thanks tebriel)
* [grpc] Add grpc client support. (641)
* [gevent] Support gevent 1.3 (663)
* [flask] rewrite Flask integration (667)

Bug Fixes
* [mysqldb] Fix mysqldb monkey patch (623 -- thanks benjamin-lim)
* [requests] exclude basic auth from service name (646 -- thanks snopoke)

Improvements
* [core] Add IntegrationConfig helper class (684)
* [core] add support for integration span hooks (679)
* [httplib, requests] Sanitize urls in span metadata (688)
* [tests] ensure we are running tests.contrib.test_utils (678)
* [celery] [bottle] Add span type information for celery and bottle. (636)
* [ci] Reorganize autopatch test calls (670)
* [core] initial support for partial flushes (668)
* [django] Remove query from django db span's tag sql.query (659)
* [tests] Make CI faster by disabling dist and install in autopatching tests (654)
* [core] Trace http headers (647)
* [django] Infer span resource name when internal error handler is used (645)
* [elasticsearch] Make constant organization consistent with other integrations (628)

Read the [full changeset](https://github.com/DataDog/dd-trace-py/compare/v0.15.0...v0.16.0) and the [release milestone](https://github.com/DataDog/dd-trace-py/milestone/28?closed=1).

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**New integrations**

- Add [rediscluster](https://pypi.org/project/redis-py-cluster/) integration (#533, 637)
- Add [Vertica](https://github.com/vertica/vertica-python) Integration (#634)

**Bug fixes**

- [django] Fix minimum Django version for user.is_authenticated property (626 -- thanks browniebroke)

**Improvements**

- [celery] Add retry reason metadata to spans (630)
- [core] Update config to allow configuration before patching (650)
- [core] Add Tracer API to retrieve the root Span (625)
- [core] Fixed `HTTPConnection` leaking (542 -- thanks mackeyja92)
- [django] Allow Django cache to be seen as a different service. (629)
- [gevent] Patch modules on first import (632)
- [gevent] Add support for gevent.pool.Pool and gevent.pool.Group (600)
- [redis] Removed unused tag (627)
- [requests] Patch modules on first import (632)
- [tests] Add Span.span_type tests (633)
- [tests] Update the integrations libraries versions to the latest possible. (607)
- [tests] CircleCI run tests in the new alpine-based test runner (638)
- [tests] Add test cases for API._put (640)
- [tests] Skip flaky TestWorkers.test_worker_multiple_traces test case (643)
- [tests] Remove tests for not supported gevent 1.3 (644)

Read the [full changeset](https://github.com/DataDog/dd-trace-py/compare/v0.14.1...v0.15.0) and the [release milestone](https://github.com/DataDog/dd-trace-py/milestone/25?closed=1).
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**Bug fixes**
- [opentracer] Activate span context on extract (606, 608)
- [opentracer] Fix "does not provide the extra opentracing" (611, 616)

**Improvements**
- [docs] Clarify debug mode (610)
- [docs] Fix docstring for `Tracer.set_tags` (612 -- thanks goodspark)
- [docs] Add priority sampling to ddtrace-run usage (621)
- [circleci] Imrpve python docs deployment strategy (615)
- [tests] Refactor tox.ini file (609)
- [tests] Improve performance of tests execution (605)

Read the [full changeset](https://github.com/DataDog/dd-trace-py/compare/v0.14.0...v0.14.1) and the [release milestone](https://github.com/DataDog/dd-trace-py/milestone/27?closed=1).
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**OpenTracing**

In this release we are happy to introduce the beta for the long-awaited OpenTracing compatible API layer for `ddtrace`!

Support for `opentracing>=2.0.0` is provided in this release. Namely, the following are supported:

- `start_span`/`start_active_span`
- `inject` and `extract` functionality
- `baggage`, through `set_baggage_item` and `get_baggage_item`
- compatible tags from the [OpenTracing specification](https://github.com/opentracing/specification/blob/b193756f1fe646b79ef4f901bed92c0e72845440/semantic_conventions.md#standard-span-tags-and-log-fields)
- scope manager support
- seamless integration with the Datadog tracer when using `ddtrace-run`

For setup information and usage see [our docs for the Datadog OpenTracing tracer](http://pypi.datadoghq.com/trace/docs/installation_quickstart.html#opentracing).


**CI Improvements**

Also included in this release are some optimizations to our CI which should get things running a bit quicker.

Thanks labbati!



Read the [full changeset](https://github.com/DataDog/dd-trace-py/compare/v0.13.1...v0.14.0) and the [release milestone](https://github.com/DataDog/dd-trace-py/milestone/20?closed=1).
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