不使用mLab配置Heroku与MongoDB：能否在Heroku本地部署MongoDB？

Hey there! Great question—let me break this down for you clearly.

Short Answer #

Yes, technically you can spin up a MongoDB instance directly on a Heroku dyno, but it’s extremely not recommended for any production, or even semi-permanent, use cases. Here’s why this is such a bad idea:

Key Reasons to Avoid Self-Hosting MongoDB on Heroku #

• Ephemeral Filesystem: Heroku dynos use a temporary filesystem that resets every time the dyno restarts—and restarts happen all the time: daily automatically, during deployments, or when Heroku scales your app. Every restart will wipe all your MongoDB data clean. You could add an external persistent storage add-on, but that defeats the whole point of "local" deployment.
• Tight Resource Limits: Heroku dynos have strict CPU, memory, and bandwidth caps. MongoDB is a resource-hungry database, especially as your dataset grows. A standard dyno will struggle to handle even moderate traffic, leading to lag, crashes, or timeouts.
• No Built-In Reliability: Heroku doesn’t offer replication, failover, or automatic recovery for self-hosted databases on dynos. If your dyno goes down, your database goes down with it—no safety net.
• Maintenance Nightmare: You’ll be on the hook for managing backups, applying security patches, updating MongoDB versions, and scaling the instance yourself. That’s a ton of extra work compared to using a managed service.

What Developers Actually Do (And Why) #

Nearly everyone uses a managed MongoDB service like MongoDB Atlas (the successor to mLab) instead of self-hosting on Heroku. These services:

• Give you persistent, replicated storage that survives dyno restarts.
• Handle scaling, backups, and security out of the box.
• Offer way better performance and reliability than a dyno-hosted MongoDB instance.
• Integrate seamlessly with Heroku, so setup is quick and painless.

If You Really Want to Test It (For Throwaway Development Only) #

If you’re just experimenting and don’t care about keeping your data, you can test running MongoDB on a Heroku dyno. Here’s a quick outline:

1. Make sure MongoDB is included in your app’s setup (for Node.js, you’d add the relevant packages to package.json, but you’ll also need to install the MongoDB binary on the dyno).
2. Update your Procfile to start both your app and MongoDB:

   web: npm start
   worker: mongod --dbpath ./data
   

3. Deploy to Heroku—but remember: every time your dyno restarts, the ./data folder will be emptied. This is only useful for quick, disposable tests.

内容的提问来源于stack exchange，提问作者8195mike