will have to make sure that it's a single process running those previous steps *even* if afterwards, you start **multiple processes** (multiple workers) for the application itself. If those steps were run by **multiple processes**, they would **duplicate** the work by running it in **parallel**, and if the steps were something delicate like a database migration, they could cause conflicts with each other.

Of course, there are some cases where there's no problem in running the previous...

        valuesBuilder.add(requireNonNull(stream.readObject()));
      }
      ImmutableSet<Object> valueSet = valuesBuilder.build();
      if (valueSet.size() != valueCount) {
        throw new InvalidObjectException("Duplicate key-value pairs exist for key " + key);
      }
      builder.put(key, valueSet);
      tmpSize += valueCount;
    }

    ImmutableMap<Object, ImmutableSet<Object>> tmpMap;
    try {

			poolObjInfos[i] = pinfo
		}(i, pool, poolOpts[i])
	}
	wg.Wait()

	// Sort the objInfos such that we always serve latest
	// this is a defensive change to handle any duplicate
	// content that may have been created, we always serve
	// the latest object.
	sort.Slice(poolObjInfos, func(i, j int) bool {
		mtime1 := poolObjInfos[i].ObjInfo.ModTime
		mtime2 := poolObjInfos[j].ObjInfo.ModTime

  public <T> ClassSanityTester setDistinctValues(Class<T> type, T value1, T value2) {
    checkNotNull(type);
    checkNotNull(value1);
    checkNotNull(value2);
    checkArgument(!Objects.equal(value1, value2), "Duplicate value provided.");
    distinctValues.replaceValues(type, ImmutableList.of(value1, value2));
    setDefault(type, value1);
    return this;
  }

  /**

		if best.name > last {
			select {
			case <-ctxDone:
				return ctx.Err()
			case out <- *best:
				last = best.name
			}
		} else if serverDebugLog {
			console.Debugln("mergeEntryChannels: discarding duplicate", best.name, "<=", last)
		}
		// Replace entry we just sent.
		if err := selectFrom(bestIdx); err != nil {
			return err
		}
	}
}

// merge will merge other into m.

   *
   * @param services The services to manage
   * @throws IllegalArgumentException if not all services are {@linkplain State#NEW new} or if there
   *     are any duplicate services.
   */
  public ServiceManager(Iterable<? extends Service> services) {
    ImmutableList<Service> copy = ImmutableList.copyOf(services);
    if (copy.isEmpty()) {

   *
   * @param services The services to manage
   * @throws IllegalArgumentException if not all services are {@linkplain State#NEW new} or if there
   *     are any duplicate services.
   */
  public ServiceManager(Iterable<? extends Service> services) {
    ImmutableList<Service> copy = ImmutableList.copyOf(services);
    if (copy.isEmpty()) {

- kube-proxy: a configuration file specified via `--config` is now loaded with strict deserialization, which fails if the config file contains duplicate or unknown fields. This protects against accidentally running with config files that are malformed, mis-indented, or have typos in field names, and getting unexpected behavior. ([#82927](https://github.com/kubernetes/kubernetes/pull/82927), [@ob...

   * Section 7.2.1.2. The iteration order follows the lexicographical order. This means that the
   * first permutation will be in ascending order, and the last will be in descending order.
   *
   * <p>Duplicate elements are considered equal. For example, the list [1, 1] will have only one
   * permutation, instead of two. This is why the elements have to implement {@link Comparable}.
   *

        }
        return buf.toString().trim();
    }

    protected String replaceDuplicateHost(final String url) {
        try {
            // remove duplicate host
            final DuplicateHostHelper duplicateHostHelper = ComponentUtil.getDuplicateHostHelper();
            return duplicateHostHelper.convert(url);
        } catch (final Exception e) {
            return url;