[python] Cleanup ThreadPool with atexit rather than __del__

Created by: fabianvf

This removes the __del__ function from the generated Python client, and replaces it with a cleanup function. When a ThreadPool is created, the cleanup function is registered with the atexit module.

This fixes #5093 (closed), where the API client could hang indefinitely at garbage collection.

Related to https://github.com/swagger-api/swagger-codegen/pull/10002

PR checklist

• Read the contribution guidelines.
• If contributing template-only or documentation-only changes which will change sample output, build the project before.
• Run the shell script(s) under ./bin/ (or Windows batch scripts under.\bin\windows) to update Petstore samples related to your fix. This is important, as CI jobs will verify all generator outputs of your HEAD commit, and these must match the expectations made by your contribution. You only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the code or mustache templates for a language ({LANG}) (e.g. php, ruby, python, etc).
• File the PR against the correct branch: master, 4.3.x, 5.0.x. Default: master.
• Copy the technical committee to review the pull request if your PR is targeting a particular programming language.

cc @taxpon @frol @mbohlool @cbornet @kenjones-cisco @tomplus @Jyhess @slash-arun @spacether

modules/openapi-generator/src/main/resources/python/python-experimental/README_common.mustache

@@ -7,18 +7,20 @@ from pprint import pprint
 {{> python_doc_auth_partial}}
 # Defining host is optional and default to {{{basePath}}}
 configuration.host = "{{{basePath}}}"
-# Create an instance of the API class
-api_instance = {{{packageName}}}.{{{classname}}}({{{packageName}}}.ApiClient(configuration))
-{{#allParams}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}{{^required}} (optional){{/required}}{{#defaultValue}} (default to {{{.}}}){{/defaultValue}}
-{{/allParams}}
+# Enter a context with an instance of the API client
+with {{{packageName}}}.ApiClient(configuration) as api_client:
+    # Create an instance of the API class
+    api_instance = {{{packageName}}}.{{{classname}}}(api_client)
+    {{#allParams}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}{{^required}} (optional){{/required}}{{#defaultValue}} (default to {{{.}}}){{/defaultValue}}
+    {{/allParams}}
 
-try:
-{{#summary}}    # {{{.}}}
-{{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}({{#allParams}}{{#required}}{{paramName}}{{/required}}{{^required}}{{paramName}}={{paramName}}{{/required}}{{#hasMore}}, {{/hasMore}}{{/allParams}}){{#returnType}}
-    pprint(api_response){{/returnType}}
-except {{{packageName}}}.ApiException as e:
-    print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
-{{/-first}}{{/operation}}{{/operations}}{{/-first}}{{/apis}}{{/apiInfo}}
+    try:
+    {{#summary}}    # {{{.}}}
+    {{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}({{#allParams}}{{#required}}{{paramName}}{{/required}}{{^required}}{{paramName}}={{paramName}}{{/required}}{{#hasMore}}, {{/hasMore}}{{/allParams}}){{#returnType}}
+        pprint(api_response){{/returnType}}
+    except {{{packageName}}}.ApiException as e:
+        print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
+    {{/-first}}{{/operation}}{{/operations}}{{/-first}}{{/apis}}{{/apiInfo}}
 ```
 
 ## Documentation for API Endpoints

modules/openapi-generator/src/main/resources/python/python-experimental/api_client.mustache

@@ -3,6 +3,7 @@
 from __future__ import absolute_import
 
 import json
+import atexit
 import mimetypes
 from multiprocessing.pool import ThreadPool
 import os
@@ -74,11 +75,19 @@ class ApiClient(object):
         # Set default User-Agent.
         self.user_agent = '{{#httpUserAgent}}{{{.}}}{{/httpUserAgent}}{{^httpUserAgent}}OpenAPI-Generator/{{{packageVersion}}}/python{{/httpUserAgent}}'
 
-    def __del__(self):
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.close()
+
+    def close(self):
         if self._pool:
             self._pool.close()
             self._pool.join()
             self._pool = None
+            if hasattr(atexit, 'unregister'):
+                atexit.unregister(self.close)
 
     @property
     def pool(self):
@@ -86,6 +95,7 @@ class ApiClient(object):
          avoids instantiating unused threadpool for blocking clients.
         """
         if self._pool is None:
+            atexit.register(self.close)
             self._pool = ThreadPool(self.pool_threads)
         return self._pool
 

modules/openapi-generator/src/main/resources/python/python-experimental/api_doc_example.mustache

@@ -7,51 +7,55 @@ from pprint import pprint
 {{#hasAuthMethods}}
 # Defining host is optional and default to {{{basePath}}}
 configuration.host = "{{{basePath}}}"
-# Create an instance of the API class
-api_instance = {{{packageName}}}.{{{classname}}}({{{packageName}}}.ApiClient(configuration))
+# Enter a context with an instance of the API client
+with {{{packageName}}}.ApiClient(configuration) as api_client:
+    # Create an instance of the API class
+    api_instance = {{{packageName}}}.{{{classname}}}(api_client)
 {{/hasAuthMethods}}
 {{^hasAuthMethods}}
-# Create an instance of the API class
-api_instance = {{{packageName}}}.{{{classname}}}()
+# Enter a context with an instance of the API client
+with {{{packageName}}}.ApiClient(configuration) as api_client:
+    # Create an instance of the API class
+    api_instance = {{{packageName}}}.{{{classname}}}(api_client)
 {{/hasAuthMethods}}
-{{#requiredParams}}{{^defaultValue}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}
-{{/defaultValue}}{{/requiredParams}}{{#optionalParams}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}{{^required}} (optional){{/required}}{{#defaultValue}} if omitted the server will use the default value of {{{defaultValue}}}{{/defaultValue}}
-{{/optionalParams}}
-{{#requiredParams}}
-{{^hasMore}}
+    {{#requiredParams}}{{^defaultValue}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}
+    {{/defaultValue}}{{/requiredParams}}{{#optionalParams}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}{{^required}} (optional){{/required}}{{#defaultValue}} if omitted the server will use the default value of {{{defaultValue}}}{{/defaultValue}}
+    {{/optionalParams}}
+    {{#requiredParams}}
+    {{^hasMore}}
 
-# example passing only required values which don't have defaults set
-try:
-{{#summary}}    # {{{.}}}
-{{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}({{#requiredParams}}{{^defaultValue}}{{paramName}}{{#hasMore}}, {{/hasMore}}{{/defaultValue}}{{/requiredParams}}){{#returnType}}
-    pprint(api_response){{/returnType}}
-except {{{packageName}}}.ApiException as e:
-    print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
-{{/hasMore}}
-{{/requiredParams}}
-{{#optionalParams}}
-{{^hasMore}}
+    # example passing only required values which don't have defaults set
+    try:
+    {{#summary}}    # {{{.}}}
+    {{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}({{#requiredParams}}{{^defaultValue}}{{paramName}}{{#hasMore}}, {{/hasMore}}{{/defaultValue}}{{/requiredParams}}){{#returnType}}
+        pprint(api_response){{/returnType}}
+    except {{{packageName}}}.ApiException as e:
+        print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
+    {{/hasMore}}
+    {{/requiredParams}}
+    {{#optionalParams}}
+    {{^hasMore}}
 
-# example passing only required values which don't have defaults set
-# and optional values
-try:
-{{#summary}}    # {{{.}}}
-{{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}({{#requiredParams}}{{^defaultValue}}{{paramName}}, {{/defaultValue}}{{/requiredParams}}{{#optionalParams}}{{paramName}}={{paramName}}{{#hasMore}}, {{/hasMore}}{{/optionalParams}}){{#returnType}}
-    pprint(api_response){{/returnType}}
-except {{{packageName}}}.ApiException as e:
-    print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
-{{/hasMore}}
-{{/optionalParams}}
-{{^requiredParams}}
-{{^optionalParams}}
+    # example passing only required values which don't have defaults set
+    # and optional values
+    try:
+    {{#summary}}    # {{{.}}}
+    {{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}({{#requiredParams}}{{^defaultValue}}{{paramName}}, {{/defaultValue}}{{/requiredParams}}{{#optionalParams}}{{paramName}}={{paramName}}{{#hasMore}}, {{/hasMore}}{{/optionalParams}}){{#returnType}}
+        pprint(api_response){{/returnType}}
+    except {{{packageName}}}.ApiException as e:
+        print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
+    {{/hasMore}}
+    {{/optionalParams}}
+    {{^requiredParams}}
+    {{^optionalParams}}
 
-# example, this endpoint has no required or optional parameters
-try:
-{{#summary}}    # {{{.}}}
-{{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}(){{#returnType}}
-    pprint(api_response){{/returnType}}
-except {{{packageName}}}.ApiException as e:
-    print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
-{{/optionalParams}}
-{{/requiredParams}}
+    # example, this endpoint has no required or optional parameters
+    try:
+    {{#summary}}    # {{{.}}}
+    {{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}(){{#returnType}}
+        pprint(api_response){{/returnType}}
+    except {{{packageName}}}.ApiException as e:
+        print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
+    {{/optionalParams}}
+    {{/requiredParams}}
 ```

modules/openapi-generator/src/main/resources/python/api_client.mustache

@@ -2,6 +2,7 @@
 {{>partial_header}}
 from __future__ import absolute_import
 
+import atexit
 import datetime
 from dateutil.parser import parse
 import json
@@ -75,11 +76,19 @@ class ApiClient(object):
         self.user_agent = '{{#httpUserAgent}}{{{.}}}{{/httpUserAgent}}{{^httpUserAgent}}OpenAPI-Generator/{{{packageVersion}}}/python{{/httpUserAgent}}'
         self.client_side_validation = configuration.client_side_validation
 
-    def __del__(self):
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        self.close()
+
+    def close(self):
         if self._pool:
             self._pool.close()
             self._pool.join()
             self._pool = None
+            if hasattr(atexit, 'unregister'):
+                atexit.unregister(self.close)
 
     @property
     def pool(self):
@@ -87,6 +96,7 @@ class ApiClient(object):
          avoids instantiating unused threadpool for blocking clients.
         """
         if self._pool is None:
+            atexit.register(self.close)
             self._pool = ThreadPool(self.pool_threads)
         return self._pool
 

modules/openapi-generator/src/main/resources/python/api_doc_example.mustache

@@ -8,22 +8,26 @@ from pprint import pprint
 {{#hasAuthMethods}}
 # Defining host is optional and default to {{{basePath}}}
 configuration.host = "{{{basePath}}}"
-# Create an instance of the API class
-api_instance = {{{packageName}}}.{{{classname}}}({{{packageName}}}.ApiClient(configuration))
-{{#allParams}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}{{^required}} (optional){{/required}}{{#defaultValue}} (default to {{{.}}}){{/defaultValue}}
-{{/allParams}}
+# Enter a context with an instance of the API client
+with {{{packageName}}}.ApiClient(configuration) as api_client:
+    # Create an instance of the API class
+    api_instance = {{{packageName}}}.{{{classname}}}(api_client)
+    {{#allParams}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}{{^required}} (optional){{/required}}{{#defaultValue}} (default to {{{.}}}){{/defaultValue}}
+    {{/allParams}}
 {{/hasAuthMethods}}
 {{^hasAuthMethods}}
-# Create an instance of the API class
-api_instance = {{{packageName}}}.{{{classname}}}()
-{{#allParams}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}{{^required}} (optional){{/required}}{{#defaultValue}} (default to {{{.}}}){{/defaultValue}}
-{{/allParams}}
+# Enter a context with an instance of the API client
+with {{{packageName}}}.ApiClient() as api_client:
+    # Create an instance of the API class
+    api_instance = {{{packageName}}}.{{{classname}}}(api_client)
+    {{#allParams}}{{paramName}} = {{{example}}} # {{{dataType}}} | {{{description}}}{{^required}} (optional){{/required}}{{#defaultValue}} (default to {{{.}}}){{/defaultValue}}
+    {{/allParams}}
 {{/hasAuthMethods}}
 
-try:
-{{#summary}}    # {{{.}}}
-{{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}({{#allParams}}{{#required}}{{paramName}}{{/required}}{{^required}}{{paramName}}={{paramName}}{{/required}}{{#hasMore}}, {{/hasMore}}{{/allParams}}){{#returnType}}
-    pprint(api_response){{/returnType}}
-except ApiException as e:
-    print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
+    try:
+    {{#summary}}    # {{{.}}}
+    {{/summary}}    {{#returnType}}api_response = {{/returnType}}api_instance.{{{operationId}}}({{#allParams}}{{#required}}{{paramName}}{{/required}}{{^required}}{{paramName}}={{paramName}}{{/required}}{{#hasMore}}, {{/hasMore}}{{/allParams}}){{#returnType}}
+        pprint(api_response){{/returnType}}
+    except ApiException as e:
+        print("Exception when calling {{classname}}->{{operationId}}: %s\n" % e)
 ```