Unable to get JSON history output

[willfurnell]

Describe the bug

The following HTML is output at the end of the JSON when requesting the history of a service for a host

<b>Fatal error</b>:  Uncaught ErrorException: Uncaught ErrorException: session_name(): Cannot change session name when headers already sent in /usr/share/php/Icinga/Web/Session/Php72Session.php:20
Stack trace:
#0 [internal function]: Icinga\Application\ApplicationBootstrap-&gt;Icinga\Application\{closure}(2, 'session_name():...', '/usr/share/php/...', 20, Array)
#1 /usr/share/php/Icinga/Web/Session/Php72Session.php(20): session_name('Icingaweb2')
#2 /usr/share/php/Icinga/Web/Session/PhpSession.php(167): Icinga\Web\Session\Php72Session-&gt;open()
#3 /usr/share/php/Icinga/Web/Controller/ActionController.php(579): Icinga\Web\Session\PhpSession-&gt;write()
#4 /usr/share/php/Icinga/Web/Controller/ActionController.php(525): Icinga\Web\Controller\ActionController-&gt;shutdownSession()
#5 /usr/share/icingaweb2/modules/icingadb/application/controllers/ErrorController.php(58): Icinga\Web\Controller\ActionController-&gt;postDispatch()
#6 /usr/share/icinga-php/vendor/vendor/shardj/zf1-future/library/Zend/Controller/Action.php(521): Icinga\Module\Icingadb\C in <b>/usr/share/icinga-php/vendor/vendor/shardj/zf1-future/library/Zend/Controller/Plugin/Broker.php</b> on line <b>262</b><br />

Additionally, the full check history for the service is not returned either in the JSON that is output, just one check result as far as I can see.

To Reproduce

1. In your web browser, go to https://icinga/icingaweb2/icingadb/service/history?name=sshd-external-check&host.name=hostname&format=json and look at the output returned

OR

Run a cURL command like the following requesting JSON

curl -s -HContent-Type:application/json -HAccept:application/json -u api:api "https://icinga/icingaweb2/icingadb/service/history?name=service&host.name=hostname&format=json"

Expected behavior

Well formatted JSON, with the full check history is returned

Your Environment

Include as many relevant details about the environment you experienced the problem in.

• Icinga DB Web version (System - About): 1.1.1
• Icinga Web 2 version (System - About): 2.12.1
• Web browser: Firefox, cURL
• Icinga 2 version (icinga2 --version): r2.14.1-1
• Icinga DB version (icingadb --version): v1.1.1
• PHP version used (php --version): 7.3.33
• Server operating system and version: CentOS 7

[nilmerg]

This is very likely caused by #847.

The problem is that since then, the query results are fully loaded into memory and held there in full for a brief time. This causes an out of memory error on history views as there the number of resulting rows is usually very large.

To solve this, we may do one of the following things:

1. Query redis in exports again for each individual result. Pro: quickly done, Con: Bad performance
2. Fetch results in parts and query redis every nth number of them. Pro: Better performance, Con: Not easily done

I'd prefer 2) 😅

[nilmerg]

Or 3), don't query redis at all because it's unnecessary as no current state is required due to the results being of historical nature. 🤦‍♂️