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073bb52648
The scope of this change is limited to removing the Cloudera copyright from the Impala shell banner and replacing it with a conref to a generic message with no reference to Cloudera or CDH version numbers. Change-Id: I1f6a3175cd34c434e3e6bccd99665b021287a768 Reviewed-on: http://gerrit.cloudera.org:8080/6138 Reviewed-by: John Russell <jrussell@cloudera.com> Tested-by: Impala Public Jenkins
219 lines
8.2 KiB
XML
219 lines
8.2 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd">
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<concept id="connecting">
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<title>Connecting to impalad through impala-shell</title>
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<titlealts audience="PDF"><navtitle>Connecting to impalad</navtitle></titlealts>
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<prolog>
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<metadata>
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<data name="Category" value="Impala"/>
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<data name="Category" value="impala-shell"/>
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<data name="Category" value="Network"/>
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<data name="Category" value="DataNode"/>
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<data name="Category" value="Developers"/>
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<data name="Category" value="Data Analysts"/>
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</metadata>
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</prolog>
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<conbody>
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<!--
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TK: This would be a good theme for a tutorial topic.
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Lots of nuances to illustrate through sample code.
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-->
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<p>
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Within an <cmdname>impala-shell</cmdname> session, you can only issue queries while connected to an instance
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of the <cmdname>impalad</cmdname> daemon. You can specify the connection information:
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<ul>
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<li>
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Through command-line options when you run the <cmdname>impala-shell</cmdname> command.
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</li>
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<li>
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Through a configuration file that is read when you run the <cmdname>impala-shell</cmdname> command.
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</li>
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<li>
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During an <cmdname>impala-shell</cmdname> session, by issuing a <codeph>CONNECT</codeph> command.
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</li>
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</ul>
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See <xref href="impala_shell_options.xml"/> for the command-line and configuration file options you can use.
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</p>
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<p>
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You can connect to any DataNode where an instance of <cmdname>impalad</cmdname> is running,
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and that host coordinates the execution of all queries sent to it.
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</p>
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<p>
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For simplicity during development, you might always connect to the same host, perhaps running <cmdname>impala-shell</cmdname> on
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the same host as <cmdname>impalad</cmdname> and specifying the hostname as <codeph>localhost</codeph>.
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</p>
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<p>
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In a production environment, you might enable load balancing, in which you connect to specific host/port combination
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but queries are forwarded to arbitrary hosts. This technique spreads the overhead of acting as the coordinator
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node among all the DataNodes in the cluster. See <xref href="impala_proxy.xml"/> for details.
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</p>
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<p>
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<b>To connect the Impala shell during shell startup:</b>
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</p>
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<ol>
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<li>
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Locate the hostname of a DataNode within the cluster that is running an instance of the
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<cmdname>impalad</cmdname> daemon. If that DataNode uses a non-default port (something
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other than port 21000) for <cmdname>impala-shell</cmdname> connections, find out the
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port number also.
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</li>
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<li>
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Use the <codeph>-i</codeph> option to the
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<cmdname>impala-shell</cmdname> interpreter to specify the connection information for
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that instance of <cmdname>impalad</cmdname>:
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<codeblock>
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# When you are logged into the same machine running impalad.
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# The prompt will reflect the current hostname.
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$ impala-shell
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# When you are logged into the same machine running impalad.
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# The host will reflect the hostname 'localhost'.
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$ impala-shell -i localhost
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# When you are logged onto a different host, perhaps a client machine
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# outside the Hadoop cluster.
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$ impala-shell -i <varname>some.other.hostname</varname>
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# When you are logged onto a different host, and impalad is listening
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# on a non-default port. Perhaps a load balancer is forwarding requests
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# to a different host/port combination behind the scenes.
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$ impala-shell -i <varname>some.other.hostname</varname>:<varname>port_number</varname>
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</codeblock>
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</li>
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</ol>
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<p>
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<b>To connect the Impala shell after shell startup:</b>
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</p>
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<ol>
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<li>
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Start the Impala shell with no connection:
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<codeblock>$ impala-shell</codeblock>
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<p>
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You should see a prompt like the following:
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</p>
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<codeblock>Welcome to the Impala shell. Press TAB twice to see a list of available commands.
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...
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<ph conref="../shared/ImpalaVariables.xml#impala_vars/ShellBanner"/>
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[Not connected] > </codeblock>
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</li>
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<li>
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Locate the hostname of a DataNode within the cluster that is running an instance of the
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<cmdname>impalad</cmdname> daemon. If that DataNode uses a non-default port (something
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other than port 21000) for <cmdname>impala-shell</cmdname> connections, find out the
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port number also.
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</li>
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<li>
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Use the <codeph>connect</codeph> command to connect to an Impala instance. Enter a command of the form:
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<codeblock>[Not connected] > connect <varname>impalad-host</varname>
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[<varname>impalad-host</varname>:21000] ></codeblock>
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<note>
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Replace <varname>impalad-host</varname> with the hostname you have configured for any DataNode running
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Impala in your environment. The changed prompt indicates a successful connection.
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</note>
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</li>
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</ol>
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<p>
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<b>To start <cmdname>impala-shell</cmdname> in a specific database:</b>
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</p>
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<p>
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You can use all the same connection options as in previous examples.
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For simplicity, these examples assume that you are logged into one of
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the DataNodes that is running the <cmdname>impalad</cmdname> daemon.
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</p>
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<ol>
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<li>
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Find the name of the database containing the relevant tables, views, and so
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on that you want to operate on.
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</li>
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<li>
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Use the <codeph>-d</codeph> option to the
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<cmdname>impala-shell</cmdname> interpreter to connect and immediately
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switch to the specified database, without the need for a <codeph>USE</codeph>
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statement or fully qualified names:
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<codeblock>
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# Subsequent queries with unqualified names operate on
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# tables, views, and so on inside the database named 'staging'.
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$ impala-shell -i localhost -d staging
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# It is common during development, ETL, benchmarking, and so on
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# to have different databases containing the same table names
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# but with different contents or layouts.
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$ impala-shell -i localhost -d parquet_snappy_compression
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$ impala-shell -i localhost -d parquet_gzip_compression
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</codeblock>
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</li>
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</ol>
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<p>
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<b>To run one or several statements in non-interactive mode:</b>
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</p>
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<p>
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You can use all the same connection options as in previous examples.
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For simplicity, these examples assume that you are logged into one of
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the DataNodes that is running the <cmdname>impalad</cmdname> daemon.
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</p>
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<ol>
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<li>
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Construct a statement, or a file containing a sequence of statements,
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that you want to run in an automated way, without typing or copying
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and pasting each time.
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</li>
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<li>
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Invoke <cmdname>impala-shell</cmdname> with the <codeph>-q</codeph> option to run a single statement, or
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the <codeph>-f</codeph> option to run a sequence of statements from a file.
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The <cmdname>impala-shell</cmdname> command returns immediately, without going into
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the interactive interpreter.
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<codeblock>
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# A utility command that you might run while developing shell scripts
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# to manipulate HDFS files.
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$ impala-shell -i localhost -d database_of_interest -q 'show tables'
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# A sequence of CREATE TABLE, CREATE VIEW, and similar DDL statements
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# can go into a file to make the setup process repeatable.
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$ impala-shell -i localhost -d database_of_interest -f recreate_tables.sql
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</codeblock>
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</li>
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</ol>
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</conbody>
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</concept>
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