Created
April 14, 2023 12:42
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Building Resilient Feature Flags That "Fail Open" In ColdFusion
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| <cfscript> | |
| apiResponse = serializeJson({ | |
| // ... truncated .... | |
| featureFlags: { | |
| canSeeDuplicate: true // This feature is now ENABLED for this user! | |
| } | |
| }); | |
| </cfscript> |
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| <cfscript> | |
| apiResponse = serializeJson({ | |
| // ... truncated .... | |
| featureFlags: { | |
| // ... the concept of this flag has been removed from the server ... | |
| } | |
| }); | |
| </cfscript> |
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| // If the feature flag is TRUE(thy), show the duplicate button. | |
| if ( response.featureFlags.canSeeDuplicate ) { | |
| contactDuplicate.style.display = "block"; | |
| } |
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| // Show the feature any time the flag is not EXPLICITLY FALSE! | |
| if ( response.featureFlags.canSeeDuplicate !== false ) { | |
| contactDuplicate.style.display = "block"; | |
| } |
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| <cfscript> | |
| apiResponse = serializeJson({ | |
| featureFlags: { | |
| // 2023-04-14: This feature no longer exists in the application. | |
| // Leaving this response hard-coded so that long-running client | |
| // code doesn't accidentally turn something on. We can delete this | |
| // line in a few months after we know that all clients have likely | |
| // refreshed their client-side bundles. | |
| canSeeDuplicate: false | |
| } | |
| }); | |
| </cfscript> |
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| <cfscript> | |
| // IMAGINE: This is an API response to a request from the Single-Page Application. | |
| apiResponse = serializeJson({ | |
| contact: { | |
| id: 4, | |
| name: "Jo Jo Bananas", | |
| email: "jojo.b@example.com", | |
| role: "Admin" | |
| }, | |
| // As part of the response, we are going to include some feature flags that | |
| // determine which features are enabled / visible in the client-side interface. | |
| // Imagine that we are in the middle of building a "duplication" feature. And, we | |
| // only want to show the option to "duplicate" if this feature flag is enabled. | |
| featureFlags: { | |
| canSeeDuplicate: false // User cannot see this feature... yet! | |
| } | |
| }); | |
| </cfscript> | |
| <!--- ------------------------------------------------------------------------------ ---> | |
| <!--- ------------------------------------------------------------------------------ ---> | |
| <!--- Imagine that this is a ColdFusion Server / Single-Page Application (SPA) ---> | |
| <!--- divide. And, that the following code is part of a LONG RUNNING PROCESS. ---> | |
| <!--- ------------------------------------------------------------------------------ ---> | |
| <!--- ------------------------------------------------------------------------------ ---> | |
| <!doctype html> | |
| <html lang="en"> | |
| <head> | |
| <title> | |
| Single-Page Application (SPA) | |
| </title> | |
| <link rel="stylesheet" type="text/css" href="./main.css" /> | |
| </head> | |
| <body> | |
| <h1 id="contactName"> | |
| {{ name }} | |
| </h1> | |
| <p id="contactEmail"> | |
| {{ email }} | |
| </p> | |
| <p id="contactRole"> | |
| {{ role }} | |
| </p> | |
| <p class="tools"> | |
| <a href="./edit.cfm"> | |
| Edit Contact | |
| </a> | |
| <a href="./delete.cfm"> | |
| Delete Contact | |
| </a> | |
| <!--- | |
| Note that the "duplicate" feature DEFAULTS to being HIDDEN (display: none). | |
| It will only be turned-on if the feature flag is enabled. | |
| ---> | |
| <a id="contactDuplicate" href="./duplicate.cfm" style=" display: none ; "> | |
| Duplicate Contact | |
| </a> | |
| </p> | |
| <!--- IMAGINE: Controller for the Single-Page Application (SPA) view. ---> | |
| <script type="text/javascript"> | |
| (function applyApiResponse( response ) { | |
| // Reconcile the view with the API response. | |
| contactName.textContent = response.contact.name; | |
| contactEmail.textContent = response.contact.email; | |
| contactRole.textContent = response.contact.role; | |
| // If the feature flag is TRUE(thy), show the duplicate button. | |
| if ( response.featureFlags.canSeeDuplicate ) { | |
| contactDuplicate.style.display = "block"; | |
| } | |
| })(JSON.parse( "<cfoutput>#encodeForJavaScript( apiResponse )#</cfoutput>" )); | |
| </script> | |
| </body> | |
| </html> |
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