Add instrumentation for Celery (#780)

Ported from the DataDog instrumentation.

Co-authored-by: Diego Hurtado <ocelotl@users.noreply.github.com>
Co-authored-by: Mauricio Vásquez <mauricio@kinvolk.io>
Co-authored-by: alrex <alrex.boten@gmail.com>

.pylintrc

@@ -226,7 +226,7 @@ dummy-variables-rgx=_+$|(_[a-zA-Z0-9_]*[a-zA-Z0-9]+?$)|dummy|^ignored_|^unused_
 
 # Argument names that match this expression will be ignored. Default to name
 # with leading underscore.
-ignored-argument-names=_.*|^ignored_|^unused_
+ignored-argument-names=_.*|^ignored_|^unused_|^kwargs|^args
 
 # Tells whether we should check for unused import in __init__ files.
 init-import=no

tox.ini

@@ -147,6 +147,10 @@ envlist =
     py3{4,5,6,7,8}-test-ext-redis
     pypy3-test-ext-redis
 
+    ; opentelemetry-ext-celery
+    py3{5,6,7,8}-test-ext-celery
+    pypy3-test-ext-celery
+
     ; opentelemetry-ext-system-metrics
     py3{4,5,6,7,8}-test-ext-system-metrics
     ; ext-system-metrics intentionally excluded from pypy3
@@ -224,6 +228,7 @@ changedir =
   test-opentracing-shim: ext/opentelemetry-ext-opentracing-shim/tests
   test-ext-sqlalchemy: ext/opentelemetry-ext-sqlalchemy/tests
   test-ext-redis: ext/opentelemetry-ext-redis/tests
+  test-ext-celery: ext/opentelemetry-ext-celery/tests
   test-ext-system-metrics: ext/opentelemetry-ext-system-metrics/tests
 
 commands_pre =
@@ -240,6 +245,8 @@ commands_pre =
 
   getting-started: pip install -e {toxinidir}/opentelemetry-instrumentation -e {toxinidir}/ext/opentelemetry-ext-requests -e {toxinidir}/ext/opentelemetry-ext-wsgi -e {toxinidir}/ext/opentelemetry-ext-flask
 
+  celery: pip install {toxinidir}/ext/opentelemetry-ext-celery[test]
+
   grpc: pip install {toxinidir}/ext/opentelemetry-ext-grpc[test]
 
   wsgi,flask,django,asgi,pyramid,starlette: pip install {toxinidir}/tests/util
@@ -388,6 +395,7 @@ deps =
   psycopg2-binary ~= 2.8.4
   sqlalchemy ~= 1.3.16
   redis ~= 3.3.11
+  celery ~= 4.0, != 4.4.4
 
 changedir =
   ext/opentelemetry-ext-docker-tests/tests
@@ -397,6 +405,7 @@ commands_pre =
               -e {toxinidir}/opentelemetry-sdk \
               -e {toxinidir}/opentelemetry-instrumentation \
               -e {toxinidir}/tests/util \
+              -e {toxinidir}/ext/opentelemetry-ext-celery \
               -e {toxinidir}/ext/opentelemetry-ext-dbapi \
               -e {toxinidir}/ext/opentelemetry-ext-mysql \
               -e {toxinidir}/ext/opentelemetry-ext-psycopg2 \