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Phorum 5 performance notes

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Several of Phorum's options have a tradeoff effect: enabling more

features can slow Phorum down. This document describes which options

these are and tries to explain the performance cost of each one.

Which options you should turn off to improve performance depends

on the way you use your Phorum installation.

Table of contents:

1. Global Settings

   1.1 DNS Lookups

   1.2 Count New Private Messages

   1.3 Enable Moderator Notifications

   1.4 Track User Usage

2. Forum Settings

   2.1 Email Messages to Moderators

   2.2 Allow Email Notification

   2.3 Count Views

   2.4 Show New Count in Forum List

   2.5 Ban List

   2.6 Censor List

   2.7 Move Threads on Reply

   2.8 Check for duplicates

1. Global Settings

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 1.1 DNS Lookups

 ---------------

    DNS lookups cause Phorum to display DNS entries (hostnames) instead

    of IP addresses on posts. It also will enable checking if mail

    addresses point to valid domains.

    On a forum with a lot of posts, enabling this will result in a

    significant number of queries to your DNS server. Phorum's performance

    will slow down while a query is running, as it will wait for the result

    of the query.

    If your DNS server is slow, this may give the impression to your users

    that posting a message is very slow. If that is the case, you should

    turn DNS lookups off. If you have access to a fast DNS server or only

    have a few regular posters, you should be able to leave it on.

 1.2 Count New Private Messages

 ------------------------------

    If enabled, this option will alert users when they have new private

    messages. On every page a logged in user visits, Phorum will check

    to see if they have new private messages.

    If you have a large number of active users at one time with a large

    number of private messages, this query can start to slow down your

    database. Turning it off may help performance, but will also remove

    the notification users get when they receive a new private message.

    You can also enable userdata caching under "Cache Settings" to

    improve performance.

 1.3 Enable Moderator Notifications

 ----------------------------------

    Similar to the Count New Private Messages option, this option will

    alert users who are also moderators when they have a new item that

    requires their attention.

    The performance hit of this feature is basically nothing for users

    without moderator permissions, as Phorum will never perform the checks.

    Moderators will suffer a small performance hit, depending on what type

    of moderator they are.

    Administrators will suffer a larger performance hit, as they are

    effectively moderators of every type, so all of the checks will be

    performed.

 1.4 Track User Usage

 --------------------

    This option controls how often Phorum will record when a user was last

    active. Setting this to be more frequent results in more accurate last

    activity data, but also causes more database writes.

    The "Constantly" setting will record the users activity on every page

    hit by any logged in user, resulting in a dramatic increase in the number

    of database writes. In most databases, a write is much slower then a

    read, so this can dramatically reduce performance. This setting is not

    recommended, except for installations with very few users, or very

    powerful hardware.

    If you are using a module that actively requires this data (such as the

    Online Users module), the setting "Once per 5 minutes" is the best

    setting, as the data will be too out of date if you update the data

    less frequently.

    If you are not using such a module, "Once per day" or "Once per hour" are

    highly recommended over the other options. "Never" disables this function

    entirely, and is recommended if you simply don't care to know if a user

    is active or not.

    Note: the option "Cache User Data" should be disabled if you have this

    feature set to "Once per 5 minutes" or "Constantly", as the caching

    will not be of much use.

2. Forum Settings

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 2.1 Email Messages to Moderators

 --------------------------------

    If enabled, every post in the forum will be emailed to the forum's

    moderators. Administrators are automatically moderators in every forum,

    and will also get the emails.

    This option should not directly affect Phorum's performance, but when

    a post is made, it will cause some emails to be created. If you have a

    large number of moderators and a lot of posts being made by users, this

    can generate a significant amount of email traffic.

    The traffic should only be a problem on very large forums or if you have

    a slow mail server. In other cases, it should not cause significant

    performance issues.

 2.2 Allow Email Notification

 ----------------------------

    This option has similar issues to the Email Messages to Moderators

    setting, except the recipients of the emails are users who have

    selected the option to have replies in a followed thread emailed to

    them.

    If a large number of users is using this feature in a busy thread, it

    can affect performance. If only few users are using this feature, it

    will not cause significant performance issues.

 2.3 Count Views

 ---------------

    If enabled, this feature records the number of views each post gets.

    For every post read, the counter will be incremented in the database.

    On a busy forum, this will result in a tremendous number of database

    writes, dramatically slowing down performance.

    Enabling this feature is not recommended for high traffic forums,

    unless you have very powerful hardware.

 2.4 Show New Count in Forum List

 --------------------------------

    If enabled, the count of new messages for each forum will appear in

    index.php. While quite handy, this has to run several queries per

    listed forum. If there are many forums on the index.php page, there

    could be a significant performance hit.

 2.5 Ban List

 ------------

    The ban list is a list of words that are banned when posting a message.

    There is a small performance penalty for searching for the banned words,

    but only when posting.

 2.6 Censor List

 ---------------

    The censor list is a list of filtered words, that is checked on every

    post read. Because it is checked far more often than the ban list, a

    large censor list will affect performance much more.

 2.7 Move Threads on Reply

 -------------------------

    "Move Threads on Reply" means that a thread which gets a new reply causes

    the topic to be moved to the top of the forum, hence the topics are

    sorted by their last reply and not by their first post in the message

    list.

    In Flat-mode there is no performance hit. In Threaded-mode it causes

    a large overhead because of the complexity of the sorting and the

    counting of posts on a page.

 2.8 Check for duplicates

 ------------------------

    "Check for duplicates" runs one additional query while posting to check

    if that post has been made before. That query should be fast and just

    a small overhead.