Overview of the

An
client application, such as a console or an adapter, utilizes the
to determine where
s are running. When a
starts, it registers with the broker:
  • Hostname of the machine it is running on
  • TCP port it is listening on.
    clients retrieve this information from the
    so that they can communicate with the
    .
    The
    registry maintains the following information:
  • Name of the
    , including the host and TCP port it is running on.
  • Status of each
    .
    The
    checks the status of each
    every five minutes by connecting to the host on which
    is running and determining if the
    process is running properly. If the
    is unable to connect or the process is not running, the
    changes the status of the
    to Dead.
    • Running
      indicates that the
      is able to communicate with the
      .
    • Dead
      indicates that the
      exited unexpectedly or is unreachable. When a
      properly shuts down, it notifies the
      and the
      removes it from its registry.
    • Unknown
      indicates that the
      was restarted and that it is querying its list of
      s to determine their state.
  • Process ID of each
    . This is the process ID assigned by the host’s operating system. In some cases when the
    is restarted, the process ID of each
    is set to zero to indicate the
    does not know the process ID of the
    .
  • Last time the state of the
    changed. This value is set when the
    registers with the
    and is updated if the
    determines that the
    is dead. When the
    restarts, it changes the status of
    s marked Unknown to Running or Dead.
    The
    changes the status of the
    to Dead when it cannot connect to the
    . However, the
    continues to try to connect to the
    every five minutes. If the
    succeeds in connecting to the
    , it changes its status back to Running.