Getting Started with Transients

Sal Ferrarello / @salcode

salcode.com/wcphilly19

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What's the temperature?

Caching

Current Temperature on Your Website

salcode.com/temp

Dark Sky
Web API

Web API ?

Website for a Computer

Web API ?

Website for a Computer

Dark Sky
Website for a Computer

https://api.darksky.net/forecast/abc123/40.6,-75.4

  $response = wp_remote_get( $url );
  $body     = wp_remote_retrieve_body($response);
  $weather  = json_decode( $body );
  $temp     = $weather->currently->temperature;

  $response = wp_remote_get( $url );

  $response = wp_remote_get( $url );
  $body     = wp_remote_retrieve_body($response);

  $response = wp_remote_get( $url );
  $body     = wp_remote_retrieve_body($response);
  $weather  = json_decode( $body );

  $response = wp_remote_get( $url );
  $body     = wp_remote_retrieve_body($response);
  $weather  = json_decode( $body );
  $temp     = $weather->currently->temperature;

function fe_get_wp_temp_api_call() {


  $response = wp_remote_get( $url );
  $body     = wp_remote_retrieve_body($response);
  $weather  = json_decode( $body );
  $temp     = $weather->currently->temperature;

  return $temp;
}

function fe_get_wp_temp_api_call() {

  // This is slow!
  $response = wp_remote_get( $url );
  $body     = wp_remote_retrieve_body($response);
  $weather  = json_decode( $body );
  $temp     = $weather->currently->temperature;

  return $temp;
}

function fe_get_wp_temp_f() {




  $temp = fe_get_wp_temp_api_call(); // SLOW.



  return $temp;
}

set_transient(
	$transient_key, // Unique key (max length 172).
	$value,         // Value to cache.
	$max_time       // Max time in seconds to keep.
);

get_transient( $transient_key );
// Returns the cached value or false.

function fe_get_wp_temp_f() {




  $temp = fe_get_wp_temp_api_call(); // SLOW.



  return $temp;
}

function fe_get_wp_temp_f() {




  $temp = fe_get_wp_temp_api_call(); // SLOW.

  set_transient('fe_wp_temp', $temp, 1800 );

  return $temp;
}

function fe_get_wp_temp_f() {

  $temp = get_transient( 'fe_wp_temp' );


  $temp = fe_get_wp_temp_api_call(); // SLOW.

  set_transient('fe_wp_temp', $temp, 1800 );

  return $temp;
}

function fe_get_wp_temp_f() {

  $temp = get_transient( 'fe_wp_temp' );
  if ( false !== $temp ) { return $temp; }

  $temp = fe_get_wp_temp_api_call(); // SLOW.

  set_transient('fe_wp_temp', $temp, 1800 );

  return $temp;
}

set_transient(
	$transient_key, // Unique key (max length 172).
	$value,         // Value to cache.
	$max_time       // Max time in seconds to keep.
);

get_transient( $transient_key );
// Returns the cached value or false.

Query Monitor Plugin

How much faster?

Getting a transient is approximately 1,000 times faster than a HTTP API Call.

How are Transients Stored

• In the options table (default)
• Persistent Object Cache (Redis, Memcached)

Transients in Options Table

Stores two values

• Value to be stored (e.g. temp)
• Timeout expiration as unix time stamp

Unix Time Stamp

Number of seconds since midnight January 1, 1970 UTC

e.g. 1570312800

Transients in Options Table

• _transient_{transient_key}
• _transient_timeout_{transient_key}

Transients in Options Table

• _transient_fe_wp_temp 
• _transient_timeout_fe_wp_temp     

Our Transients in the Options Table

Transients Manager Plugin

Expired Transients

Expired transients are deleted by get_transient()

Abandoned Transients

Abandoned transients are never deleted.

Transients Manager Plugin

Delete Transients

on Plugin Deactivation

When I Use Transients

• Remote API Calls
• Slow database queries

When I Don't Use Transients

When I Can't Recreate the Data

WordPress Time Constants

$max_time = 1800;

$max_time = 30 * MINUTE_IN_SECONDS;

Prefer Data Over HTML

Summary

• Use transients for slow code
• Transients may disappear unexpectedly
• Use Query Monitor Plugin
• Use Transients Manager Plugin
• Use WordPress Time Constants

Sal Ferrarello

salcode.com/wcphilly19

Resources

• Sal's example WordPress Current Temp Plugin
• JSONView Chrome Browser Extension
• Dark Sky Web API
• WordPress Query Monitor Plugin
• WordPress Transients Manager Plugin
• About WordPress Persistent Object Caching
• About Unix Time Stamp
• You should Delete Transients on Plugin Deactivation
• More on WordPress Transients

Image Credits

• Bus with blurred background
• String on finger
• Clouds
• Thermometer
• Unsure Face
• Office Computer