Skip to main content

Suspend/resume a flow

Flows can be suspended until resume or cancel event(s) are received. This feature is most useful to implement approval steps but can be used flexibly for other purpose.


On WindmillHub you can find ready-to-use scripts that use this feature. For example:

Adding approval step

You can think of a scenario where only specific people can resume (or cancel) a flow. To achieve this they would need to receive personalized URL via some external communication channel (like email, SMS or chat message).

Important thing to remember is that a number of required approvals can be customized. This allows some flexibility for a cases where you either require approvals from all authorized people or only from one.

Required approvals

Approval script - Gmail example

Adding Gmail resource

Lets start with adding Gmail resource. From "Resources" view select "Connect an API" and then let's sign in with Google

Connect an API

Sign in with Google

You will be redirected to Google Accounts and asked to log in. After authentication you will be redirected back to Windmill.

Connection in progress

From now on, whenever you use this resource, Windmill script will send emails via Gmail on your behalf.

Reusing script from WindmillHub

Let's create a flow as described in the getting started section (go, typescript, python). Our first step will be approval script from WindmillHub

Approval step from Hub

Reuse Gmail script from Hub

Make sure to fill required fields, especially choose Gmail resource and define approver emails (this are email addresses of people that are authorized to resume a flow and this is where Windmill job will send resume URL).

Check how it works!

For the sake of this example let's add a "dummy" hello world script as a 2nd stop in our flow

Dummy script

We can test our flow now

Test flow

You can notice that after first step flow is suspended and is waiting for approval

Waiting for approval

Let's imagine that you are now the person that is authorized to resume a suspended flow. You should receive an email with URL that leads to webpage like this

Approval webpage

You can now resume a flow and see that the flow finished with "Success" status.

Finished flow

Cool, isn't it?

Notifying about approver(s) that resumed a flow - Slack example

In this example we're extending the flow with approval step from previous example. Windmill will send a notification as a message in Slack channel about approver(s) that resumed a flow.

Adding Slack resource

First lets add a Slack resource. From "Resources" view select "Connect an API" and then select Slack

Connect an API

Connect Slack resource

Allow Slack access

Connection in progress

Re-using script from WindmillHub

Now let's extend our existing flow (that already has an approval step) with a script that will use "The list of approvers" from the "Step Context"

Extend flow

Script from hub

Reuse Slack script

Step Context magic

This is where the magic begins - the "Step Context". You can notice that we have access to the list of approves from previous approval step.

The list of approvers

Now all we have to do is to inject this particular step context to the "approvers" argument of our script! There is more than one way of doing this, but this time we will use the UI feature. All you have to do is to click on "link" icon and then select "approvers"

Inject approvers 1

Inject approvers 2

Lets test it

Run the flow. Resume it ...

Resume flow

... and find the notification on Slack channel