Entry<K, V> entry = firstEntry();
    if (entry == null) {
      throw new NoSuchElementException();
    } else {
      return entry.getKey();
    }
  }

  @Override
  @ParametricNullness
  public K lastKey() {
    Entry<K, V> entry = lastEntry();
    if (entry == null) {
      throw new NoSuchElementException();
    } else {
      return entry.getKey();
    }
  }

  @Override

    target_match:
      severity: 'warning'
    equal: ['alertname', 'dev', 'instance']
```

This sample configuration uses a `webhook` at http://127.0.0.1:8010/webhook to post the alerts.
Start the AlertManager and it listens on port `9093` by default. Make sure your webhook is up and listening for the alerts.

## Configure Prometheus to use AlertManager

Add below section to your `prometheus.yml`
```yaml
alerting:
  alertmanagers:

)

// Server - extended http.Server supports multiple addresses to serve and enhanced connection handling.
type Server struct {
	http.Server
	Addrs         []string      // addresses on which the server listens for new connection.
	TCPOptions    TCPOptions    // all the configurable TCP conn specific configurable options.
	listenerMutex sync.Mutex    // to guard 'listener' field.

    return Iterables.<@Nullable Entry<K, V>>getFirst(descendingMap().entrySet(), null);
  }

  /**
   * A sensible definition of {@link #lastKey} in terms of {@code lastEntry}. If you override {@code
   * lastEntry}, you may wish to override {@code lastKey} to forward to this implementation.
   */
  protected K standardLastKey() {
    Entry<K, V> entry = lastEntry();
    if (entry == null) {

    return Iterables.<@Nullable Entry<K, V>>getFirst(descendingMap().entrySet(), null);
  }

  /**
   * A sensible definition of {@link #lastKey} in terms of {@code lastEntry}. If you override {@code
   * lastEntry}, you may wish to override {@code lastKey} to forward to this implementation.
   */
  protected K standardLastKey() {
    Entry<K, V> entry = lastEntry();
    if (entry == null) {

    Entry<K, V> entry = firstEntry();
    if (entry == null) {
      throw new NoSuchElementException();
    } else {
      return entry.getKey();
    }
  }

  @Override
  @ParametricNullness
  public K lastKey() {
    Entry<K, V> entry = lastEntry();
    if (entry == null) {
      throw new NoSuchElementException();
    } else {
      return entry.getKey();
    }
  }

  @Override

proxy["Proxy on http://0.0.0.0:9999/api/v1/app"]
server["Server on http://127.0.0.1:8000/app"]

browser --> proxy
proxy --> server
```

/// tip

The IP `0.0.0.0` is commonly used to mean that the program listens on all the IPs available in that machine/server.

///

The docs UI would also need the OpenAPI schema to declare that this API `server` is located at `/api/v1` (behind the proxy). For example:

    @Override
    @ParametricNullness
    public K firstKey() {
      return sortedMap().firstKey();
    }

    @Override
    @ParametricNullness
    public K lastKey() {
      return sortedMap().lastKey();
    }

    @Override
    public SortedMap<K, Collection<V>> headMap(@ParametricNullness K toKey) {
      return new SortedAsMap(sortedMap().headMap(toKey));
    }

      return standardFirstKey();
    }

    @Override
    public SortedMap<K, V> headMap(K toKey) {
      return standardHeadMap(toKey);
    }

    @Override
    public K lastKey() {
      return standardLastKey();
    }

    @Override
    public SortedMap<K, V> tailMap(K fromKey) {
      return standardTailMap(fromKey);
    }
  }

    return comparator;
  }

  @Override
  public @Nullable K firstKey() {
    return sortedDelegate.firstKey();
  }

  @Override
  public @Nullable K lastKey() {
    return sortedDelegate.lastKey();
  }

  @Nullable K higher(K k) {
    Iterator<K> iterator = keySet().tailSet(k).iterator();
    while (iterator.hasNext()) {
      K tmp = iterator.next();