.. default-domain:: chpl

.. module:: ServerDaemon

ServerDaemon
============
**Usage**

.. code-block:: chapel

   use ServerDaemon;


or

.. code-block:: chapel

   import ServerDaemon;

.. enum:: enum ServerDaemonType { DEFAULT, INTEGRATION, METRICS, STATUS }

   .. enumconstant:: enum constant DEFAULT

   .. enumconstant:: enum constant INTEGRATION

   .. enumconstant:: enum constant METRICS

   .. enumconstant:: enum constant STATUS

.. data:: const sdLogger = new Logger(logLevel, logChannel)

.. data:: var serverDaemonTypes = try! getDaemonTypes()

.. function:: proc getDaemonTypes() throws

   *
   * Retrieves a list of 1..n ServerDaemonType objects generated 
   * from the comma-delimited list of ServerDaemonType strings
   * provided in the daemonTypes command-line parameter
   

.. function:: proc metricsEnabled()

   *
   * Returns a boolean indicating if Arkouda is configured to generate and
   * make available metrics via a dedicated metrics socket
   

.. function:: proc integrationEnabled()

   *
   * Returns a boolean indicating whether Arkouda is configured to 
   * register/deregister with an external system such as Kubernetes.
   

.. function:: proc multipleServerDaemons()

   *
   * Returns a boolean indicating if there are multiple ServerDaemons
   

.. function:: proc register(endpoint: ServiceEndpoint) throws

   *
   * Generates the Kubernetes app name for Arkouda, which varies based
   * upon which pod corresponds to Locale 0.
   

.. class:: ArkoudaServerDaemon

   *
   * The ArkoudaServerDaemon class defines the run and shutdown 
   * functions all derived classes must override
   

   .. attribute:: var st = new owned SymTab()

   .. attribute:: var shutdownDaemon = false

   .. attribute:: var port: int

   .. method:: proc run() throws

   .. method:: proc requestShutdown(user: string) throws

      *
      * Prompts the ArkoudaServerDaemon to initiate a shutdown, triggering
      * a change in state which will cause the derived ArkoudaServerDaemon
      * to (1) exit the daemon loop within the run function and (2) execute 
      * the shutdown function.
      

   .. method:: proc extractRequest(request: string): RequestMsg throws

      
      * Converts the incoming request JSON string into RequestMsg object.
      

   .. method:: proc shutdown() throws

      *
      * Encapsulates logic that is to be invoked once a ArkoduaSeverDaemon
      * has exited the daemon loop.
      

.. class:: DefaultServerDaemon : ArkoudaServerDaemon

   *
   * The DefaultServerDaemon class serves as the default Arkouda server
   * daemon which is run within the arkouda_server driver
   

   .. attribute:: var serverToken: string

   .. attribute:: var arkDirectory: string

   .. attribute:: var connectUrl: string

   .. attribute:: var reqCount: int = 0

   .. attribute:: var repCount: int = 0

   .. attribute:: var context: ZMQ.Context

   .. attribute:: var socket: ZMQ.Socket

   .. method:: proc init()

   .. method:: proc getConnectUrl(token: string) throws

   .. method:: proc printServerSplashMessage(token: string, arkDirectory: string) throws

   .. method:: proc createServerConnectionInfo() throws

      
      Creates the serverConnectionInfo file on arkouda_server startup
      

   .. method:: proc deleteServerConnectionInfo() throws

      
      Deletes the serverConnetionFile on arkouda_server shutdown
      

   .. method:: proc sendRepMsg(repMsg: ?t) throws where t == string || t == bytes

      
      Following processing of incoming message, sends a message back to the client.
      
      :arg repMsg: either a string or bytes to be sent
      

   .. method:: proc authenticateUser(token: string) throws

      
      Compares the token submitted by the user with the arkouda_server token. If the
      tokens do not match, or the user did not submit a token, an ErrorWithMsg is thrown.    
      
      :arg token: the submitted token string
      

   .. method:: override proc requestShutdown(user: string) throws

      
      Sets the shutdownDaemon boolean to true and sends the shutdown command to socket,
      which stops the arkouda_server listener thread and closes socket.
      

   .. method:: proc registerServerCommands()

      *
      * Register our server commands in the CommandMap
      * There are 3 general types
      * 1. Standard, required commands which adhere to the standard Message signature
      * 2. Specialized, required commands which do not adhere to the standard Message signature
      * 3. "Optional" modules which are included at compilation time via ServerModules.cfg
      

   .. method:: proc initArkoudaDirectory() throws

   .. method:: override proc shutdown() throws

      *
      * The overridden shutdown function calls exit(0) if there are multiple 
      * ServerDaemons configured for this Arkouda instance.
      

   .. method:: proc processMetrics(user: string, cmd: string, args: MessageArgs, elapsedTime: real, memUsed: uint) throws

   .. method:: proc processErrorMessageMetrics(user, cmd, err) throws

   .. method:: proc getErrorName(err)

   .. method:: proc processErrorMetrics(user, cmd, errName) throws

   .. method:: override proc run() throws

.. class:: MetricsServerDaemon : ArkoudaServerDaemon

   *
   * The MetricsServerDaemon provides a separate endpoint for gathering user, request, 
   * locale, and server-scoped metrics. The separate port lessens the possibility of
   * metrics requests being blocked by command requests.
   

   .. attribute:: var context: ZMQ.Context

   .. attribute:: var socket: ZMQ.Socket

   .. method:: proc init()

   .. method:: override proc run() throws

.. class:: ExternalIntegrationServerDaemon : DefaultServerDaemon

   *
   * The ExternalIntegrationServerDaemon class registers Arkouda with the
   * configured external system and then invokes ArkoudaServerDeamon.run()
   

   .. method:: override proc run() throws

      *
      * Overridden run function registers the ServerDaemon with an 
      * external system and then invokes the parent run function.
      

   .. method:: override proc shutdown() throws

      *
      * Overridden shutdown function deregisters Arkouda from an external
      * system and then invokes the parent shutdown() function.
      

.. class:: ServerStatusDaemon : ArkoudaServerDaemon

   *
   * The ServerStatusDaemon provides a non-blocking endpoint for retrieving 
   * server status via a separate, dedicated port to lessen the chances of 
   * blocking incoming status requests with command requests.
   

   .. attribute:: var context: ZMQ.Context

   .. attribute:: var socket: ZMQ.Socket

   .. method:: proc init()

   .. method:: override proc run() throws

.. function:: proc getServerDaemon(daemonType: ServerDaemonType): shared ArkoudaServerDaemon throws

.. function:: proc getServerDaemons() throws