You stand in line while several (let's say 8) cashiers that at the same time are cooks take the orders from the people in front of you.

Everyone before you is waiting for their burgers to be ready before leaving the counter because each of the 8 cashiers goes and prepares the burger right away before getting the next order.

<img src="/img/async/parallel-burgers/parallel-burgers-01.png" class="illustration">

  ITER_END=$((NUM_CLUSTERS-1))
  for i in $(seq 0 "$ITER_END"); do
    for j in $(seq 0 "$ITER_END"); do
      if [[ "${j}" -gt "${i}" ]]; then
        NETWORK_ID_I="${CLUSTER_NETWORK_ID[i]}"
        NETWORK_ID_J="${CLUSTER_NETWORK_ID[j]}"
        if [[ "$NETWORK_ID_I" == "$NETWORK_ID_J" ]]; then
          POD_TO_POD_AND_SERVICE_CONNECTIVITY=1
        else
          POD_TO_POD_AND_SERVICE_CONNECTIVITY=0
        fi

    if (cacheCandidate != null && cacheResponse == null) {
      // The cache candidate wasn't applicable. Close it.
      cacheCandidate.body.closeQuietly()
    }

    // If we're forbidden from using the network and the cache is insufficient, fail.
    if (networkRequest == null && cacheResponse == null) {
      return Response.Builder()
        .request(chain.request())
        .protocol(Protocol.HTTP_1_1)

  /**
   * Returns a view of {@code network} with the direction (if any) of every edge reversed. All other
   * properties remain intact, and further updates to {@code network} will be reflected in the view.
   */
  public static <N, E> Network<N, E> transpose(Network<N, E> network) {
    if (!network.isDirected()) {
      return network; // the transpose of an undirected network is an identical network
    }

### Single Container

If you have a simple setup, with a **single container** that then starts multiple **worker processes** (or also just one process), then you could run those previous steps in the same container, right before starting the process with the app. The official Docker image supports this internally.

## Previous Steps Before Starting

There are many cases where you want to perform some steps **before starting** your application.

For example, you might want to run **database migrations**.

But in most cases, you will want to perform these steps only **once**.

So, you will want to have a **single process** to perform those **previous steps**, before starting the application.

Without a data validation system, you would have to do all the checks by hand, in code.

These features are what Marshmallow was built to provide. It is a great library, and I have used it a lot before.

But it was created before there existed Python type hints. So, to define every <abbr title="the definition of how data should be formed">schema</abbr> you need to use specific utils and classes provided by Marshmallow.

   * are running concurrently.
   *
   * <p>{@linkplain Executor#execute executed} tasks have a happens-before order as defined in the
   * Java Language Specification. Tasks execute with the same happens-before order that the function
   * calls to {@link Executor#execute `execute()`} that submitted those tasks had.
   *

      # have a shared root CA for this model to work.
      enabled: false
      # Should be set to the name of the cluster this installation will run in. This is required for sidecar injection
      # to properly label proxies
      clusterName: ""

    # Network defines the network this cluster belong to. This name
    # corresponds to the networks in the map of mesh networks.
    network: ""

  the system can't tell whether it has access to the network required by these
  operations.

  Offline mode really means anticipating a lack of network connectivity, and as
  a result turning off certain services provided by m2 and providing a coherent
  way of predicting and reporting when network-related failures will take place.
  It means warning users that since the network is missing, certain features and