Impala Startup Options for Client Connections

Use the following flags to control client connections to Impala when starting Impala Daemon coordinator. If a configuration field exists in Cloudera Manager, the field name is shown in parenthesis next to the flag name.

If the Cloudera Manager interface does not yet have a form field for an option, the Advanced category page for each daemon includes one or more Safety Valve fields where you can enter option names directly.

--accepted_client_cnxn_timeout

Controls how Impala treats new connection requests if it has run out of the number of threads configured by --fe_service_threads.

If --accepted_client_cnxn_timeout > 0, new connection requests are rejected if Impala can't get a server thread within the specified (in seconds) timeout.

If --accepted_client_cnxn_timeout=0, i.e. no timeout, clients wait indefinitely to open the new session until more threads are available.

The default timeout is 5 minutes.

The timeout applies only to client facing thrift servers, i.e., HS2 and Beeswax servers.

--disconnected_session_timeout

When a HiveServer2 session has had no open connections for longer than this value, the session will be closed, and any associated queries will be unregistered.

Specify the value in hours.

The default value is 1 hour.

This flag does not apply to Beeswax clients. When a Beeswax client connection is closed, Impala closes the session associated with that connection.

--fe_service_threads (Impala Daemon Max Client)

Specifies the maximum number of concurrent client connections allowed. The default value is 64 with which 64 queries can run simultaneously.

If you have more clients trying to connect to Impala than the value of this setting, the later arriving clients have to wait for the duration specified by --accepted_client_cnxn_timeout. You can increase this value to allow more client connections. However, a large value means more threads to be maintained even if most of the connections are idle, and it could negatively impact query latency. Client applications should use the connection pool to avoid need for large number of sessions.

--idle_client_poll_time_s

The value of this setting specifies how frequently Impala polls to check if a client connection is idle and closes it if the connection is idle. A client connection is idle if all sessions associated with the client connection are idle.

By default, --idle_client_poll_time_s is set to 30 seconds.

If --idle_client_poll_time_s is set to 0, idle client connections stay open until explicitly closed by the clients.

The connection will only be closed if all the associated sessions are idle or closed. Sessions cannot be idle unless either the flag --idle_session_timeout or the IDLE_SESSION_TIMEOUT query option is set to greater than 0. If idle session timeout is not configured, a session cannot become idle by definition, and therefore its connection stays open until the client explicitly closes it.

--max_cookie_lifetime_s

Impala uses cookies for authentication when clients connect via HiveServer2 over HTTP. Use the --max_cookie_lifetime_s startup flag to control how long generated cookies are valid for.

Specify the value in seconds.

The default value is 1 day.

Setting the flag to 0 disables cookie support.

When an unexpired cookie is successfully verified, the user name contained in the cookie is set on the connection.

Each impalad uses its own key to generate the signature, so clients that reconnect to a different impalad have to re-authenticate.

On a single impalad, cookies are valid across sessions and connections.

--beeswax_port (Impala Daemon Beeswax Port)

Specifies the port for clients to connect to Impala daemon via the Beeswax protocol.

You can disable the Beeswax end point for clients by setting the flag to 0.

--hs2_http_port (Impala Daemon HiveServer2 HTTP Port)

Specifies the port for clients to connect to Impala daemon over HTTP.

You can disable the HTTP end point for clients by setting the flag to 0.

To enable TLS/SSL for HiveServer2 HTTP endpoint, use --ssl_server_certificate and --ssl_private_key.

--hs2_port (Impala Daemon HiveServer2 Port)

Specifies the port for clients to connect to Impala daemon via the HiveServer2 protocol.

You can disable the binary HiveServer2 end point for clients by setting the flag to 0.

--ping_expose_webserver_url

Controls whether PingImpalaService, PingImpalaHS2Service RPC calls should expose the debug web url to the client or not.

By default this flag is set to true so that the users will not see an empty string when the debug web UI is not available. If the flag is set to false, the RPC calls will return an empty string instead of the real url signalling that the debug web UI is not available.