The Flask Mega-Tutorial Part XVIII: Deployment on Heroku

This is the eighteenth installment of the Flask Mega-Tutorial series, in which I'm going to deploy Microblog to the Heroku cloud platform.

For your reference, below is a list of the articles in this series.

Note 1: If you are looking for the legacy version of this tutorial, it's here.

Note 2: If you would like to support my work on this blog, or just don't have patience to wait for weekly articles, I am offering the complete version of this tutorial packaged as an ebook or a set of videos. For more information, visit courses.miguelgrinberg.com.

In the previous article I showed you the "traditional" way to host a Python application, and I gave you two actual examples of deployment to Linux based servers. If you are not used to manage a Linux system, you probably thought that the amount of effort that needs to be put into the task was big, and that surely there must be an easier way.

In this chapter I'm going to show you a completely different approach, in which you rely on a third-party cloud hosting provider to perform most of the administration tasks, freeing you to spend more time working on your application.

Many cloud hosting providers offer a managed platform on which applications can run. All you need to provide to have your application deployed on these platforms is the actual application, because the hardware, operating system, scripting language interpreters, database, etc. are all managed by the service. This type of service is called Platform as a Service, or PaaS.

Sounds too good to be true, right?

I will look at deploying Microblog to Heroku, a popular cloud hosting service that is also very friendly for Python applications. I picked Heroku not only because it is popular, but also because it has a free service level that will allow you to follow me and do a complete deployment without spending any money.

The GitHub links for this chapter are: Browse, Zip, Diff.

Hosting on Heroku

Heroku was one of the first platform as a service providers. It started as a hosting option for Ruby based applications, but then grew to support many other languages like Java, Node.js and of course Python.

Deploying a web application to Heroku is done through the git version control tool, so you must have your application in a git repository. Heroku looks for a file called Procfile in the application's root directory for instructions on how to start the application. For Python projects, Heroku also expects a requirements.txt file that lists all the module dependencies that need to be installed. After the application is uploaded to Heroku's servers through git, you are essentially done and just need to wait a few seconds until the application is online. It's really that simple.

The different service tiers Heroku offers allow you to choose how much computing power and time you get for your application, so as your user base grows you will need to buy more units of computing, which Heroku calls "dynos".

Ready to try Heroku? Let's get started!

Creating Heroku account

Before you can deploy to Heroku you need to have an account with them. So visit heroku.com and create a free account. Once you have an account and log in to Heroku, you will have access to a dashboard, where all your applications are listed.

Installing the Heroku CLI

Heroku provides a command-line tool for interacting with their service called Heroku CLI, available for Windows, Mac OS X and Linux. The documentation includes installation instructions for all the supported platforms. Go ahead and install it on your system if you plan on deploying the application to test the service.

The first thing you should do once the CLI is installed is login to your Heroku account:

$ heroku login

Heroku CLI will ask you to enter your email address and your account password. Your authenticated status will be remembered in subsequent commands.

Setting Up Git

The git tool is core to the deployment of applications to Heroku, so you must install it on your system if you don't have it yet. If you don't have a package available for your operating system, you can visit the git site to download an installer.

There are a lot of reasons why using git for your projects makes sense. If you plan to deploy to Heroku, you have one more, because to deploy to Heroku, your application must be in a git repository. If you are going to do a test deployment for Microblog, you can clone the application from GitHub:

$ git clone https://github.com/miguelgrinberg/microblog
$ cd microblog
$ git checkout v0.18

The git checkout command selects the specific commit that has the application at the point in its history that corresponds to this chapter.

If you prefer to work with your own code instead of mine, you can transform your own project into a git repository by running git init . on the top-level directory (note the period after init, which tells git that you want to create the repository in the current directory).

Creating a Heroku Application

To register a new application with Heroku, you use the apps:create command from the root directory of the application, passing the application name as the only argument:

$ heroku apps:create flask-microblog
Creating flask-microblog... done
http://flask-microblog.herokuapp.com/ | https://git.heroku.com/flask-microblog.git

Heroku requires that applications have a unique name. The name flask-microblog that I used above is not going to be available to you because I'm using it, so you will need to pick a different name for your deployment.

The output of this command will include the URL that Heroku assigned to the application, and also its git repository. Your local git repository will be configured with an extra remote, called heroku. You can verify that it exists with the git remote command:

$ git remote -v
heroku  https://git.heroku.com/flask-microblog.git (fetch)
heroku  https://git.heroku.com/flask-microblog.git (push)

Depending on how you created your git repository, the output of the above command could also include another remote called origin.

The Ephemeral File System

The Heroku platform is different to other deployment platforms in that it features an ephemeral file system that runs on a virtualized platform. What does that mean? It means that at any time, Heroku can reset the virtual server on which your server runs back to a clean state. You cannot assume that any data that you save to the file system will persist, and in fact, Heroku recycles servers very often.

Working under these conditions introduces some problems for my application, which uses a few files:

  • The default SQLite database engine writes data in a disk file
  • Logs for the application are also written to the file system
  • The compiled language translation repositories are also written to local files

The following sections will address these three areas.

Working with a Heroku Postgres Database

To address the first problem, I'm going to switch to a different database engine. In Chapter 17 you saw me use a MySQL database to add robustness to the Ubuntu deployment. Heroku has a database offering of its own, based on the Postgres database, so I'm going to switch to that to avoid the file-based SQLite.

Databases for Heroku applications are provisioned with the same Heroku CLI. In this case I'm going to create a database on the free tier:

$ heroku addons:add heroku-postgresql:hobby-dev
Creating heroku-postgresql:hobby-dev on flask-microblog... free
Database has been created and is available
 ! This database is empty. If upgrading, you can transfer
 ! data from another database with pg:copy
Created postgresql-parallel-56076 as DATABASE_URL
Use heroku addons:docs heroku-postgresql to view documentation

The URL for the newly created database is stored in a DATABASE_URL environment variable that will be available when the application runs. This is very convenient, because the application already looks for the database URL in that variable.

Logging to stdout

Heroku expects applications to log directly to stdout. Anything the application prints to the standard output is saved and returned when you use the heroku logs command. So I'm going to add a configuration variable that indicates if I need to log to stdout or to a file like I've been doing. Here is the change in the configuration:

config.py: Option to log to stdout.

class Config(object):
    # ...
    LOG_TO_STDOUT = os.environ.get('LOG_TO_STDOUT')

Then in the application factory function I can check this configuration to know how to configure the application's logger:

app/__init__.py: Log to stdout or file.

def create_app(config_class=Config):
    # ...
    if not app.debug and not app.testing:
        # ...

        if app.config['LOG_TO_STDOUT']:
            stream_handler = logging.StreamHandler()
            if not os.path.exists('logs'):
            file_handler = RotatingFileHandler('logs/microblog.log',
                                               maxBytes=10240, backupCount=10)
                '%(asctime)s %(levelname)s: %(message)s '
                '[in %(pathname)s:%(lineno)d]'))

        app.logger.info('Microblog startup')

    return app

So now I need to set the LOG_TO_STDOUT environment variable when the application runs in Heroku, but not in other configurations. The Heroku CLI makes this easy, as it provides an option to set environment variables to be used at runtime:

$ heroku config:set LOG_TO_STDOUT=1
Setting LOG_TO_STDOUT and restarting flask-microblog... done, v4

Compiled Translations

The third aspect of Microblog that relies on local files is the compiled language translation files. The more direct option to ensure those files never disappear from the ephemeral file system is to add the compiled language files to the git repository, so that they become part of the initial state of the application once it is deployed to Heroku.

A more elegant option, in my opinion, is to include the flask translate compile command in the start up command given to Heroku, so that any time the server is restarted those files are compiled again. I'm going to go with this option, since I know that my start up procedure is going to require more than one command anyway, since I also need to run the database migrations. So for now, I will set this problem aside, and will revisit it later when I write the Procfile.

Elasticsearch Hosting

Elasticsearch is one of the many services that can be added to a Heroku project, but unlike Postgres, this is not a service provided by Heroku, but by third parties that partner with Heroku to provide add-ons. At the time I'm writing this, there are three different providers of an integrated Elasticsearch service.

Before you configure Elasticsearch, be aware that Heroku requires your account to have a credit card on file before any third party add-on is installed, even if you stay within their free tiers. If you prefer not to provide your credit card to Heroku, then skip this section. You will still be able to deploy the application, but the search functionality is not going to work.

Out of the Elasticsearch options that are available as add-ons, I decided to try SearchBox, which comes with a free starter plan. To add SearchBox to your account, you have to run the following command while being logged in to Heroku:

$ heroku addons:create searchbox:starter

This command will deploy an Elasticsearch service and leave the connection URL for the service in a SEARCHBOX_URL environment variable associated with your application. Once more keep in mind that this command will fail unless you add your credit card to your Heroku account.

If you recall from Chapter 16, my application looks for the Elasticsearch connection URL in the ELASTICSEARCH_URL variable, so I need to add this variable and set it to the connection URL assigned by SearchBox:

$ heroku config:get SEARCHBOX_URL
$ heroku config:set ELASTICSEARCH_URL=<your-elasticsearch-url>

Here I first asked Heroku to print the value of SEARCHBOX_URL, and then I added a new environment variable with the name ELASTICSEARCH_URL set to that same value.

Updates to Requirements

Heroku expects the dependencies to be in the requirements.txt file, exactly like I defined it in Chapter 15. But for the application to run on Heroku I need to add two new dependencies to this file.

Heroku does not provide a web server of its own. Instead, it expects the application to start its own web server on the port number given in the environment variable $PORT. Since the Flask development web server is not robust enough to use for production, I'm going to use gunicorn again, the server recommended by Heroku for Python applications.

The application will also be connecting to a Postgres database, and for that SQLAlchemy requires the psycopg2 package to be installed.

Both gunicorn and psycopg2 need to be added to the requirements.txt file.

The Procfile

Heroku needs to know how to execute the application, and for that it uses a file named Procfile in the root directory of the application. The format of this file is simple, each line includes a process name, a colon, and then the command that starts the process. The most common type of application that runs on Heroku is a web application, and for this type of application the process name should be web. Below you can see a Procfile for Microblog:

Procfile: Heroku Procfile.

web: flask db upgrade; flask translate compile; gunicorn microblog:app

Here I defined the command to start the web application as three commands in sequence. First I run a database migration upgrade, then I compile the language translations, and finally I start the server.

Because the first two sub-commands are based on the flask command, I need to add the FLASK_APP environment variable:

$ heroku config:set FLASK_APP=microblog.py
Setting FLASK_APP and restarting flask-microblog... done, v4
FLASK_APP: microblog.py

The application also relies on other environment varialbes, such as those that configure the email server or the token for the live translations. Those need to be added with addition heroku config:set commands.

The gunicorn command is simpler than what I used for the Ubuntu deployment, because this server has a very good integration with the Heroku environment. For example, the $PORT environment variable is honored by default, and instead of using the -w option to set the number of workers, heroku recommends adding a variable called WEB_CONCURRENCY, which gunicorn uses when -w is not provided, giving you the flexibility to control the number of workers without having to modify the Procfile.

Deploying the Application

All the preparatory steps are complete, so now it is time to run the deployment. To upload the application to Heroku's servers for deployment, the git push command is used. This is similar to how you push changes in your local git repository to GitHub or other remote git server.

And now I have reached the most interesting part, where I push the application to our Heroku hosting account. This is actually pretty simple, I just have to use git to push the application to the master branch of the Heroku git repository. There are a couple of variations on how to do this, depending on how you created your git repository. If you are using my v0.18 code, then you need to create a branch based on this tag, and push it as the remote master branch, as follows:

$ git checkout -b deploy
$ git push heroku deploy:master

If instead, you are working with your own repository, then your code is already in a master branch, so you first need to make sure that your changes are committed:

$ git commit -a -m "heroku deployment changes"

And then you can run the following to start the deployment:

$ git push heroku master

Regardless of how you push the branch, you should see the following output from Heroku:

$ git push heroku deploy:master
Counting objects: 247, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (238/238), done.
Writing objects: 100% (247/247), 53.26 KiB | 3.80 MiB/s, done.
Total 247 (delta 136), reused 3 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote: -----> Python app detected
remote: -----> Installing python-3.6.2
remote: -----> Installing pip
remote: -----> Installing requirements with pip
remote: -----> Discovering process types
remote:        Procfile declares types -> web
remote: -----> Compressing...
remote:        Done: 57M
remote: -----> Launching...
remote:        Released v5
remote:        https://flask-microblog.herokuapp.com/ deployed to Heroku
remote: Verifying deploy... done.
To https://git.heroku.com/flask-microblog.git
 * [new branch]      deploy -> master

The label heroku that we used in the git push command is the remote that was automatically added by the Heroku CLI when the application was created. The deploy:master argument means that I'm pushing the code from the local repository referenced by the deploy branch to the master branch on the Heroku repository. When you work with your own projects, you will likely be pushing with the command git push heroku master, which pushes your local master branch. Because of the way this project is structured, I'm pushing a branch that is not master, but the destination branch on the Heroku side always needs to be master as that is the only branch that Heroku accepts for deployment.

And that is it, the application should now be deployed at the URL that you were given in the output of the command that created the application. In my case, the URL was https://flask-microblog.herokuapp.com, so that is what I need to type to access the application.

If you want to see the log entries for the running application, use the heroku logs command. This can be useful if for any reason the application fails to start. If there were any errors, those will be in the logs.

Deploying Application Updates

To deploy a new version of the application, you just need to run a new git push command with the new code. This will repeat the deployment process, take the old deployment offline, and then replace it with the new code. The commands in the Procfile will run again as part of the new deployment, so any new database migrations or translations will be updated during the process.


  • #51 Larp said 2018-12-08T13:22:01Z

    Thanks for your reply, Miguel. Yes, I included the flask db upgrade command in the Procfile and also tried running heroku run flask db upgrade, but I still get the error that basically says relationship user does not exist.

    Anyway, I think this is because I deleted the migrations folder several commits ago. So when I generated the migrations folder again using the flask db init, flask migrate, flask upgrade workflow (right before committing and pushing to Heroku), this seemes to be what happens: the new migration script tries to create all the tables alphabetically and fails when in the process of creating a table that referenced another table further down the queue.

    For example, I have a 'company' table that included a field referencing the user.id column as foreign key.

    Since the script tries to create the 'company' table before the 'user' table, the create_table command fails.

    The error happens with the Postgres db provisioned from Heroku.

    But with the local SQLite database, this is fine. The db upgrade completes without issues in my local development environment.

    The problem is very similar to the below Stack Overflow question (where the asker uses a local Postgres db):


    The asker's solution is to modify the migration script's upgrade function by manually reordering the create_table commands so that parent tables precede their children.

    Is there another way around this?

    Thank you again, Miguel.

  • #52 Miguel Grinberg said 2018-12-08T14:17:29Z

    @Larp: looks like this is a known issue with Alembic. See https://github.com/sqlalchemy/alembic/issues/326.

  • #53 ALT said 2019-01-15T22:38:28Z

    Hi Miguel, thank you for the amazing tutorial. The application is successfully deployed but when I try to register user, I get 500 error. It looks to me that the problem might be with the Postgresql database. Do you have any idea on what I could try?

  • #54 Miguel Grinberg said 2019-01-16T09:41:59Z

    @ALT: you don't need to guess what the problem is. Use the "heroku logs" command to see the Flask output, including a stack trace for the 500 error.

  • #55 Jay Oceans said 2019-01-21T20:42:42Z

    Hi Miguel,

    I followed your directions for getting the app up on Heroku and that worked. However, my login attempts were failing for my account, then when I went back to try on my local host I am getting the following error:

    psycopg2.OperationalError: could not translate host name "jayoceans" to address: nodename nor servname provided, or not known

    Any advice?

  • #56 Miguel Grinberg said 2019-01-22T10:19:21Z

    @Jay: what is "jayoceans". Did you set that somewhere in your configuration? That needs to be a hostname.

  • #57 Mihika said 2019-03-01T08:46:08Z

    Hi Miguel,

    Thanks a lot for this tutorial. I followed the instructions here, and was able to deploy it on Heroku. However, when I am trying to register a new user, I get the following 500 error:

    (psycopg2.DataError) value too long for type character varying(64) [SQL: 'INSERT INTO "user" (username, email, password, about_me, last_seen) VALUES (%(username)s, %(email)s, %(password)s, %(about_me)s, %(last_seen)s) RETURNING "user".id'] [parameters: {'username': 'Mihika', 'email': 'mohta.mihika@gmail.com', 'password': 'pbkdf2:sha256:50000$cn0ire3I$af1654086af149c4b88fbb4d85d1442379aafbe16a8ebfc6dad19c90071f774f', 'about_me': None, 'last_seen': datetime.datetime(2019, 3, 1, 8, 15, 55, 679308)}] (Background on this error at: http://sqlalche.me/e/9h9h)

    Any idea on what could be going wrong? The app works perfectly on localhost and I am being able to register users normally.

    Also, is there any way to transfer all the users and their data from my sqlite database to the postgres db on Heroku?


  • #58 Miguel Grinberg said 2019-03-01T10:33:32Z

    @Mihika: it appears your password_hash column in the User model is set to 64 characters? That's too short, I have it set to 128.

    There is no built-in mechanism to transfer data between the two databases, that is not a common operation you'd want to do unless both databases are for tests or development. You'll never want development data copied to the production database, for example. In any case, you can transfer the data using export and import tools for the two database types. For example, you can export the sqlite data to a .csv file, then import that into Postgres.

  • #59 Mihika said 2019-03-05T06:29:43Z

    Hi Miguel,

    Thanks for your response. I changed the size of my password field and it is working perfectly now. However, I had to delete the sqlite database and the postgres db on Heroku and create the databases and migration scripts again for this to work. Am I missing something here, or is this the way to go about it? I had tried to generate a new migration script for the sqlite db, but eventually had to delete the db and create a new one.

    Why did the app not fail when running on localhost? Also, the way the app looks when running on localhost is slightly different from the way it looks on Heroku (on localhost all the fields appear bigger). Is there any reason for this difference in displays?


  • #60 Miguel Grinberg said 2019-03-05T10:07:32Z

    @Mihika: Welcome to the world of database implementation inconsistencies. :)

    The reason why it worked locally is that SQLite does not enforce field lengths, fields are variable lengths regardless of what you specify. On Postgres the lengths are enforced.

    The reason you could not migrate your SQLite database is that this database has very limited support for modifying existing columns. Changing lengths or types is not supported. Postgres does support this, so this change would have worked on that database.

    The display difference is odd. Maybe you have zoomed your browser in and that is why everything is larger? Some browsers remember your zoom settings.

  • #61 Mihika said 2019-03-05T15:57:22Z

    Hi Miguel,

    Thanks for the explanation. I remembered I had zoomed in for a presentation, and that is the reason the display for localhost was larger. After zooming out, it is displaying correctly now. Thanks a lot for the help!

  • #62 Harvey said 2019-03-11T07:33:23Z

    Does the name "user" postgresql keyword. When I push this tutorial to heroku, I try to access the tables through: heroku pg:psql micro:Database>\dt gives he the list of table like alembic_ version, followers,post, user. But when I query the tables user, it returns error. eg select * from user; Error near user.

  • #63 Miguel Grinberg said 2019-03-11T11:08:13Z

    @Harvey: try enclosing the table name in quotes.

  • #64 Ritesh said 2019-04-05T08:18:49Z

    Hi Miguel, Awesome Job with the tutorial..I'm facing issues deploying the app to Heroku:

    git push heroku master ...remote: Compressing source files... done. remote: Building source: remote: ! No default language could be detected for this app. remote: HINT: This occurs when Heroku cannot detect the buildpack to use for this application automatically. remote: See https://devcenter.heroku.com/articles/buildpacks remote: ! Push failed remote: Verifying deploy... remote: ! Push rejected to mldataplay. To https://git.heroku.com/xyz.git ! [remote rejected] master -> master (pre-receive hook declined) error: failed to push some refs to 'https://git.heroku.com/xyz.git'

  • #65 Miguel Grinberg said 2019-04-05T10:44:37Z

    @Ritesh: your local repository is missing one of the required files that Heroku uses to determine this is a Python project, either requirements.txt or Procfile.

  • #66 Jonathan George said 2019-05-24T23:49:38Z

    Hi Miguel,

    Im also having the same error when I try to deploy to heroku when i type the following git push heroku deploy:master Counting objects: 3999, done. Delta compression using up to 4 threads. Compressing objects: 100% (3906/3906), done. Writing objects: 100% (3999/3999), 16.83 MiB | 607.00 KiB/s, done. Total 3999 (delta 639), reused 0 (delta 0) remote: Compressing source files... done. remote: Building source: remote: remote: ! No default language could be detected for this app. remote: HINT: This occurs when Heroku cannot detect the buildpack to use for this application automatically. remote: See https://devcenter.heroku.com/articles/buildpacks remote: remote: ! Push failed remote: Verifying deploy... remote: remote: ! Push rejected to jg-micro-message. remote: To https://git.heroku.com/jg-micro-message.git ! [remote rejected] deploy -> master (pre-receive hook declined) error: failed to push some refs to 'https://git.heroku.com/jg-micro-message.git'

    my git repository is up to date, the only thing i would add is that i did not add search function to my project and I never got translate or email to work. I m not sure this would have any thing to do with why these errors are occurring though. any thought/help?

    thanks for your time and for this awesome project.

  • #67 Miguel Grinberg said 2019-05-25T07:19:33Z

    @Jonathan: do you have a requirements.txt file in the top-level of your repository?

  • #68 yfe said 2019-07-08T16:17:13Z

    Hello, I've deployed the app on Heroku, when I try to post something I get the following stacktrace:

    sqlalchemy.exc.ProgrammingError: (psycopg2.errors.DatatypeMismatch) column "timestamp" is of type integer but expression is of type timestamp without time zone 2019-07-08T16:14:19.161880+00:00 app[web.1]: LINE 1: ...post (body, timestamp, user_id) VALUES ('fsdfge', '2019-07-0... 2019-07-08T16:14:19.161881+00:00 app[web.1]: ^ 2019-07-08T16:14:19.161883+00:00 app[web.1]: HINT: You will need to rewrite or cast the expression. 2019-07-08T16:14:19.161885+00:00 app[web.1]: 2019-07-08T16:14:19.161886+00:00 app[web.1]: [SQL: INSERT INTO post (body, timestamp, user_id) VALUES (%(body)s, %(timestamp)s, %(user_id)s) RETURNING post.id] 2019-07-08T16:14:19.161888+00:00 app[web.1]: [parameters: {'body': 'fsdfge', 'timestamp': datetime.datetime(2019, 7, 8, 16, 14, 19, 153082), 'user_id': 3}] 2019-07-08T16:14:19.161890+00:00 app[web.1]: (Background on this error at: http://sqlalche.me/e/f405)

    Any idea on how to solve this please ?

  • #69 Miguel Grinberg said 2019-07-09T16:14:34Z

    @yfe: the error is telling you what's wrong. The timestamp column is of type integer, you are trying to write something that is not an integer there.

  • #70 James said 2019-08-05T08:14:18Z

    Thanks so much for this tutorial, it's been incredibly helpful. I've managed to deploy my app to Heroku, but I want to continue to develop locally to test and then later push to Heroku. However, whenever I try flask run, or flask db migrate I get this error; ... import fcntl ModuleNotFoundError: No module named 'fcntl

    Apparently this is linked to gunicorn, which cannot run on windows. Any suggestions to allow local development to continue?

  • #71 Miguel Grinberg said 2019-08-05T11:34:42Z

    @James: You should look at the complete stack trace of that error to determine where in your application you import gunicorn, and see if you can remove that dependency. Normally gunicorn is executed from the CLI, so you do not need to import it into your project.

  • #72 Debashish Palit said 2019-08-08T06:03:35Z

    Hi MIguel, My question is about Heroku deployment, but pertains to some info in your book on Flasky. I did not know where else to post my question, so I am putting it here. First of all, let me say that it is a wonderful book - I enjoyed it thoroughly. My problem is with using Werkzeug ProxyFix. I did not use it in my web-app that I deployed to Heroku - yet the external link in the password reset email is being generated (correctly) with https . I used only Flask-SSLify - so how did this happen? Is ProxyFix not required now? Thanks, Debashish

  • #73 Miguel Grinberg said 2019-08-08T20:26:24Z

    @Debashish: is the generated link on the email https or http? If you are getting an http link, everything will work because Flask-SSLify will redirect it to the https. If you are getting an https link directly, then I'm not sure, my expectation would be that Flask would have no way to know it is running on https unless you add ProxyFix.

  • #74 Debashish Palit said 2019-08-09T04:38:14Z

    The generated link on the email is https. But l haven't used ProxyFix. Maybe the reverse proxy used by the Heroku free tier is configured differently. I tried googling the topic without luck.

  • #75 Miguel Grinberg said 2019-08-09T08:51:55Z

    @Debashish: you can print request.environ and then see it in the heroku logs. the wsgi.url_scheme entry should tell you what gunicorn is sending down to the app. The HTTP_X_FORWARDED_PROTO entry will tell you what Heroku is sending, which is what ProxyFix uses to make a correction when wsgi.url_scheme is wrong.

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