TypeError: Converting circular structure to JSON

[Alireza-Hallajian]

I get the "Converting circular structure to JSON" error in my project, and I know it happens in one of my "res.send"s. But it doesn't happen every time the API is called, as I sometimes see it in my logs. The server is in production mode and there is no report about it from users.

Environment

• Inversify Version: 6.0.1
• Node.js 18.16.1
• Operating System and version: Ubuntu 22.04.2 LTS

Stack trace

TypeError: Converting circular structure to JSON
--> starting at object with constructor 'ServerResponse'
| property 'socket' -> object with constructor 'Socket'
--- property '_httpMessage' closes the circle
at JSON.stringify ()
at stringify (/home/lineage/workspace/posterity-refactored-backend/node_modules/express/lib/response.js:1150:12)
at ServerResponse.json (/home/lineage/workspace/posterity-refactored-backend/node_modules/express/lib/response.js:271:14)
at ServerResponse.send (/home/lineage/workspace/posterity-refactored-backend/node_modules/express/lib/response.js:162:21)
at InversifyExpressServer. (/home/lineage/workspace/posterity-refactored-backend/node_modules/inversify-express-utils/src/server.ts:273:25)
at step (/home/lineage/workspace/posterity-refactored-backend/node_modules/inversify-express-utils/lib/server.js:33:23)
at Object.next (/home/lineage/workspace/posterity-refactored-backend/node_modules/inversify-express-utils/lib/server.js:14:53)
at fulfilled (/home/lineage/workspace/posterity-refactored-backend/node_modules/inversify-express-utils/lib/server.js:5:58)
at processTicksAndRejections (node:internal/process/task_queues:95:5)

[ingluis-code]

I also have the same problem which does not happen every time and it does not interrupt the operation but it is very annoying.

[SzymonKaczorowski-Kainos]

I faced the same issue.

Based on my observation, the problem arises when the server's response is sent after connection is dropped and return res.sendStatus() syntax is used. In my case, I was able to resolve the issue by modifying the code as follows.

I changed this:

 public async healthCheck(req: Request, res: Response) {
    try {
      const results = await Promise.allSettled([
        checkDatabases(),
        [...]
      ]);
      [...]
      return res.sendStatus(200);
    } catch (error) {
      return res.sendStatus(500);
    }
  }

to this (removed return statement)

 public async healthCheck(req: Request, res: Response) {
    try {
      const results = await Promise.allSettled([
        checkDatabases(),
        [...]
      ]);
      [...]
       res.sendStatus(200);
    } catch (error) {
       res.sendStatus(500);
    }
  }

After this, I was no longer able to reproduce the issue. Not sure if this is expected behaviour.