///

### DNS

Now let's focus on all the actual HTTPS parts.

First, the browser would check with the **DNS servers** what is the **IP for the domain**, in this case, `someapp.example.com`.

The DNS servers would tell the browser to use some specific **IP address**. That would be the public IP address used by your server, that you configured in the DNS servers.

<img src="/img/deployment/https/https01.svg">

### TLS Handshake Start

There are many situations in which you need to notify an error to a client that is using your API.

This client could be a browser with a frontend, a code from someone else, an IoT device, etc.

You could need to tell the client that:

* The client doesn't have enough privileges for that operation.
* The client doesn't have access to that resource.
* The item the client was trying to access doesn't exist.
* etc.

      val pkcs8Bytes =
        pkcs8Base64Text.decodeBase64()
          ?: throw IllegalArgumentException("failed to decode private key")

      // The private key doesn't tell us its type but it's okay because the certificate knows!
      val keyType =
        when (certificate.publicKey) {
          is ECPublicKey -> "EC"
          is RSAPublicKey -> "RSA"

        type = TYPE_PING,
        flags = if (ack) FLAG_ACK else FLAG_NONE,
      )
      sink.writeInt(payload1)
      sink.writeInt(payload2)
      sink.flush()
    }
  }

  /**
   * Tell the peer to stop creating streams and that we last processed `lastGoodStreamId`, or zero
   * if no streams were processed.
   *
   * @param lastGoodStreamId the last stream ID processed, or zero if no streams were processed.

   * correctly requests of varying weight (permits), /no matter/ what the actual function is - so we
   * can tweak the latter freely. (The only requirement, obviously, is that we can compute its
   * integrals).
   *
   * Note well that if, for this function, we chose a horizontal line, at height of exactly (1/QPS),
   * then the effect of the function is non-existent: we serve storedPermits at exactly the same

Actually, all (or most) of the web frameworks work in this same way.

You never call those functions directly. They are called by your framework (in this case, **FastAPI**).

With the Dependency Injection system, you can also tell **FastAPI** that your *path operation function* also "depends" on something else that should be executed before your *path operation function*, and **FastAPI** will take care of executing it and "injecting" the results.

        br.addItem("Limit Size");
        br.addElement(limitSize);
        final String msg = br.buildExceptionMessage();
        throw new Forced404NotFoundException(msg, UserMessages.empty()); // heavy attack!? so give no page to tell wasted action
    }

    protected void setupServletFileUpload(final JakartaServletDiskFileUpload upload, final HttpServletRequest request) {
        upload.setHeaderCharset(Charset.forName(request.getCharacterEncoding()));

### Existing properties in existing classes

            //
            // 2. not to cancel any Future the user returned from an AsyncCallable
            //
            // We promise this because, once we cancel that Future, we would no longer be able to
            // tell when any underlying work it is doing is done. Thus, we might start a new task
            // while that underlying work is still running.
            //
            // So that is why we cancel only in the case of CAS success.

Additionally, eventually consistency means we will often get some final requests trickle in before all clients are aware the Pod is shutting down.

Finally, we SHOULD tell our (HBONE) peers we are shutting down.
This can help ensure that clients do not hold onto pooled connections for too long.