operations.md 10 KB


title: "Operations" date: 2019-03-13T18:28:09-07:00 draft: false

weight: 2

Quick Start Wizard

The Quick Start wizard allows you to perform the following Hue setup operations by clicking the tab of each step or sequentially by clicking Next in each screen:

  1. Check Configuration validates your Hue configuration. It will note any potential misconfiguration and provide hints as to how to fix them. You can edit the configuration file described in the next section or use Cloudera Manager, if installed, to manage your changes.
  2. Examples contains links to install examples into the Hive, Impala, MapReduce, Spark, Oozie, Solr Dashboard and Pig Editor applications.
  3. Users contains a link to the User Admin application to create or import users and a checkbox to enable and disable collection of usage information.

Configuration

Displays a list of the installed Hue applications and their configuration. The location of the folder containing the Hue configuration files is shown at the top of the page. Hue configuration settings are in the hue.ini configuration file.

Click the tabs under Configuration Sections and Variables to see the settings configured for each application. For information on configuring these settings, see Hue Configuration in the Hue installation manual.

Hue ships with a default configuration that will work for pseudo-distributed clusters. If you are running on a real cluster, you must make a few changes to the hue.ini configuration file (/etc/hue/hue.ini when installed from the package version) or pseudo-distributed.ini in desktop/conf when in development mode). The following sections describe the key configuration options you must make to configure Hue.

To list all available configuration options, run: $ /usr/share/hue/build/env/bin/hue config_help | less This commands outlines the various sections and options in the configuration, and provides help and information on the default values.
To view the current configuration from within Hue, open: http:///hue/dump_config
Hue loads and merges all of the files with extension `.ini` located in the `/etc/hue` directory. Files that are alphabetically later take precedence.

Administration

Now that you've installed and started Hue, you can feel free to skip ahead to the <> section. Administrators may want to refer to this section for more details about managing and operating a Hue installation.

Configuration Validation

Hue can detect certain invalid configuration.

To view the configuration of a running Hue instance, navigate to http://myserver:8888/hue/dump_config, also accessible through the About application.

Server Logs

Displays the Hue Server log and allows you to download the log to your local system in a zip file.

Threads

Read more on the Threads and Metrics pages blog post

Threads page can be very helpful in debugging purposes. It includes a daemonic thread and the thread objects serving concurrent requests. The host name, thread name identifier and current stack frame of each are displayed. Those are useful when Hue “hangs”, sometimes in case of a request too CPU intensive. There is also a REST API to get the dump of Threads using 'desktop/debug/threads'

Metrics

Read more on the Threads and Metrics pages blog post

Hue uses the PyFormance Python library to collect the metrics. These metrics are represented as gauge, counters, meter, rate of events over time, histogram, statistical distribution of values. A REST API endpoint '/desktop/metrics/' to get all the metrics dump as json is also exposed

The below metrics of most concern to us are displayed on the page:

  • requests.active
  • requests.exceptions
  • requests.response-time
  • threads.daemon
  • threads.total
  • users
  • users.active

One of the most useful ones are the percentiles of response time of requests and the count of active users. Admins can either filter a particular property in all the metrics or select a particular metric for all properties

Process Hierarchy

A script called supervisor manages all Hue processes. The supervisor is a watchdog process -- its only purpose is to spawn and monitor other processes. A standard Hue installation starts and monitors the following processes:

  • runcpserver - a web server based on CherryPy that provides the core web functionality of Hue

If you have installed other applications into your Hue instance, you may see other daemons running under the supervisor as well.

You can see the supervised processes running in the output of ps -f -u hue:

UID        PID  PPID  C STIME TTY          TIME CMD
hue       8685  8679  0 Aug05 ?        00:01:39 /usr/share/hue/build/env/bin/python /usr/share/hue/build/env/bin/desktop runcpserver

Note that the supervisor automatically restarts these processes if they fail for any reason. If the processes fail repeatedly within a short time, the supervisor itself shuts down.

Logging

The Hue logs are found in /var/log/hue, or in a logs directory under your Hue installation root. Inside the log directory you can find:

  • An access.log file, which contains a log for all requests against the Hue web server.
  • A supervisor.log file, which contains log information for the supervisor process.
  • A supervisor.out file, which contains the stdout and stderr for the supervisor process.
  • A .log file for each supervised process described above, which contains the logs for that process.
  • A .out file for each supervised process described above, which contains the stdout and stderr for that process.

If users on your cluster have problems running Hue, you can often find error messages in these log files. If you are unable to start Hue from the init script, the supervisor.log log file can often contain clues.

Viewing Recent Log Messages

In addition to logging INFO level messages to the logs directory, the Hue web server keeps a small buffer of log messages at all levels in memory. You can view these logs by visiting http://myserver:8888/hue/logs. The DEBUG level messages shown can sometimes be helpful in troubleshooting issues.

Troubleshooting

To troubleshoot why Hue is slow or consuming high memory, admin can enable instrumentation by setting the instrumentation flag to True.

[desktop]
instrumentation=true
If django_debug_mode is enabled, instrumentation is automatically enabled. This flag appends the response time and the total peak memory used since Hue started for every logged request.

Instrumentation enabled

[17/Apr/2018 15:18:43 -0700] access       INFO     127.0.0.1 admin - "POST /jobbrowser/jobs/ HTTP/1.1" `returned in 97ms (mem: 135mb)`

Instrumentation not enabled

[23/Apr/2018 10:59:01 -0700] INFO     127.0.0.1 admin - "POST /jobbrowser/jobs/ HTTP/1.1" returned in 88ms

Database

Hue requires a SQL database to store small amounts of data, including user account information as well as history of job submissions and Hive queries. By default, Hue is configured to use the embedded database SQLite for this purpose, and should require no configuration or management by the administrator. However, MySQL is the recommended database to use. This section contains instructions for configuring Hue to access MySQL and other databases.

Inspecting the Database

The default SQLite database used by Hue is located in: /usr/share/hue/desktop/desktop.db. You can inspect this database from the command line using the sqlite3 program or typing `/usr/share/hue/build/env/bin/hue dbshell'. For example:

sqlite3 /usr/share/hue/desktop/desktop.db
SQLite version 3.6.22
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite> select username from auth_user;
admin
test
sample
sqlite>

It is strongly recommended that you avoid making any modifications to the database directly using SQLite, though this trick can be useful for management or troubleshooting.

Backing up the Database

If you use the default SQLite database, then copy the desktop.db file to another node for backup. It is recommended that you back it up on a regular schedule, and also that you back it up before any upgrade to a new version of Hue.

Configuring to Access Another Database

Although SQLite is the default database type, some advanced users may prefer to have Hue access an alternate database type. Note that if you elect to configure Hue to use an external database, upgrades may require more manual steps in the future.

The following instructions are for MySQL, though you can also configure Hue to work with other common databases such as PostgreSQL and Oracle.

Note that Hue has only been tested with SQLite and MySQL database backends.

Configuring to Store Data in MySQL

To configure Hue to store data in MySQL:

  1. Create a new database in MySQL and grant privileges to a Hue user to manage this database.

    mysql> create database hue;
    Query OK, 1 row affected (0.01 sec)
    mysql> grant all on hue.* to 'hue'@'localhost' identified by 'secretpassword';
    Query OK, 0 rows affected (0.00 sec)
    
  2. Shut down Hue if it is running.

  3. To migrate your existing data to MySQL, use the following command to dump the existing database data to a text file. Note that using the ".json" extension is required.

    /usr/share/hue/build/env/bin/hue dumpdata > $some-temporary-file.json
    
  4. Open the hue.ini file in a text editor. Directly below the [[database]] line, add the following options (and modify accordingly for your MySQL setup):

    host=localhost
    port=3306
    engine=mysql
    user=hue
    password=secretpassword
    name=hue
    
  5. As the Hue user, configure Hue to load the existing data and create the necessary database tables:

    /usr/share/hue/build/env/bin/hue syncdb --noinput
    mysql -uhue -psecretpassword -e "DELETE FROM hue.django_content_type;"
    /usr/share/hue/build/env/bin/hue loaddata $temporary-file-containing-dumped-data.json
    

Your system is now configured and you can start the Hue server as normal.