Logging

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Craft’s application logs can help you confirm expected behavior and investigate issues. If you’ve ever encountered a cryptic error page on a live site and wondered what actually went wrong, the logs will have the complete story.

# Finding and Reading Log Files

By default, Craft writes log files to the storage/logs/ directory. Messages are split into a few different files, and are rotated daily:

  • console-[Y-m-d].log: logs generated from running console commands
  • queue-[Y-m-d].log: logs generated from running queue jobs
  • web-[Y-m-d].log: logs generated from front-end web requests

You can change where runtime artifacts are stored (including logs) using the CRAFT_STORAGE_PATH PHP constant.

Additionally, low-level PHP errors are logged to phperrors.log if allowed by your configuration. These messages are special, and bypass Craft’s logging system entirely.

All other messages follow the same format:

2022-07-15 00:00:04 [web.INFO] [yii\db\Connection::open] Opening DB connection: mysql:host=ddev-starter-blog-db;dbname=db;port=3306 {"memory":913536} 
Part Example Description
Timestamp 2022-07-15 00:00:04 Precise time that the log was created.
Target + Level [web.INFO] Type of request involved (web, console, queue), and log level (TRACE, INFO, WARNING, ERROR).
Category [yii\db\Connection::open] Yii convention that broadly defines the area of concern. Defaults to application, but may be the calling class or method or a plugin handle.
Message Opening DB connection: (...) Description explicitly passed to the logger.
Context {"memory":913536} Additional parameters that were captured along with the message.

Session and environment variables are printed after the last log line for the request, preceded by a Request context: message.

# What Gets Logged?

The types of messages you’ll find in a log file depend on the current environment, allowed logging level(s), installed plugins, and a host of other factors.

# Levels

Log volume generally increases as level (or “severity”) decreases—there are a ton of debugging messages emitted in development environments, but when only warnings and errors are logged in a live environment, you may go long periods of time without a single message.

Levels are a great way to summarize the substance of logs:

  • Error: Something happened that interfered with Craft’s expected behavior. Usually logged in the process of handling an exception.
  • Warning: Craft encountered an unusual (but recoverable) circumstance. Warnings often point to abuse, misuse, or misconfiguration.
  • Info: Messages emitted during normal operation. Oftentimes, these messages will correspond to things like failed validation, and include specifics that aren’t otherwise communicated to users.
  • Debug: Extraneous data that is likely only useful when actively investigating an issue with a feature or plugin.
  • Profiling: Normally excluded from logs. Profiling data is available to help identify low-level performance issues, like template rendering or database queries.

# Exceptions

Craft will also log uncaught exceptions. Exceptions can occur for all sorts of reasons, and will often use a specific class to reflect the nature of the issue. Those that extend yii\base\UserException (opens new window) are considered safe to display to a user, and will render this default view (or one matching your errorTemplatePrefix):

Default presentation of a 404 HTTP Exception

For security, other exceptions are hidden from the front-end, and only available by examining logs. When devMode is on, a stack trace will be output just after the exception’s message; otherwise, the stack trace is encoded as JSON and appended to the log message.

You can see a stack trace for any log message by increasing the traceLevel in your log configuration.

# Logs in Different Environments

What you see in your log files depends on the environment.

When you’re working locally with devMode enabled, logs are output in a verbose, multi-line format that’s human-readable. Any exceptions will include a stack trace.

[2022-04-15T17:00:11+00:00] web.INFO: Opening DB connection: pgsql:host=db;dbname=db;port=5432 {"trace":[],"memory":9646256,"category":"yii\\db\\Connection::open"}
[2022-04-15T17:00:11+00:00] web.WARNING: Some warning… {"trace":[],"memory":13577888,"category":"application"}
[2022-04-15T17:00:11+00:00] web.INFO: Request context
$_GET = []

$_POST = []
[…truncated] {"ip":"172.18.0.1"}

When devMode is off, log files are written in a machine-readable format that’s best for log aggregators. Each message will be represented on a single, longer line that includes context:

[2022-04-15T16:57:54+00:00] web.WARNING: Some warning… {"trace":[],"memory":13579752,"category":"application"}
[2022-04-15T16:57:54+00:00] web.WARNING: Request context  {"ip":"172.18.0.1","userId":1,"vars":{"_GET":[],"_POST":[],"_COOKIE":{"1031b8c41dfff97a311a7ac99863bdc5_username":"2756d05ef7521bdc1dac02da066e1658e3e16d6acc7360cfc6256cb1cec311cca:2:{i:0;s:41:\"1031b8c41dfff97a311a7ac99863bdc5_username\";i:1;s:5:\"admin\";}","CraftSessionId":"if0uq3uj36d8ek6n5o9eak2l04","1031b8c41dfff97a311a7ac99863bdc5_identity":"8ddb6a5ce28f3fb2d23567df9228ce31614d6b19572c4f60db3b4b5eae78f2a3a:2:{i:0;s:41:\"1031b8c41dfff97a311a7ac99863bdc5_identity\";i:1;s:159:\"[1,\"[\\\"QwoFhu6pBsTvSOkCXqNvu2_cIr16fde6AK1DHP7GLiyXmnv7qY5BscDi8sl_QRT9z2uGh051J7r9IkSawusrx-ijCLZWZ6bHB433\\\",null,\\\"d9667159e600aea00a68fcc215cc4f6e\\\"]\",3600]\";}","CRAFT_CSRF_TOKEN":"••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••"},"_FILES":[],"_SERVER":{"PATH":"/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin","HOSTNAME":"my-project.tld","PHP_DISPLAY_ERRORS":"on","PHP_MEMORY_LIMIT":"512M","PHP_MAX_EXECUTION_TIME":"5000","PHP_UPLOAD_MAX_FILESIZE":"512M","PHP_MAX_INPUT_VARS":"5000","PHP_POST_MAX_SIZE":"512M","PHP_OPCACHE_ENABLE":"0","PHP_OPCACHE_REVALIDATE_FREQ":"0","PHP_OPCACHE_VALIDATE_TIMESTAMPS":"0","XDEBUG_SESSION":"PHPSTORM","PHP_IDE_CONFIG":"serverName=my-project.tld","XDEBUG_CONFIG":"client_host=host.docker.internal client_port=9003","XDEBUG_MODE":"develop,debug","IMAGE_USER":"nitro","PHP_VERSION":"8.0","NVM_VERSION":"0.38.0","DEBIAN_FRONTEND":"noninteractive","HOME":"/home/nitro","LC_CTYPE":"C.UTF-8","SUPERVISOR_ENABLED":"1","SUPERVISOR_PROCESS_NAME":"php-fpm","SUPERVISOR_GROUP_NAME":"php-fpm","USER":"nitro","HTTP_X_FORWARDED_PROTO":"https","HTTP_X_FORWARDED_FOR":"172.18.0.1","HTTP_UPGRADE_INSECURE_REQUESTS":"1","HTTP_SEC_FETCH_USER":"?1","HTTP_SEC_FETCH_SITE":"none","HTTP_SEC_FETCH_MODE":"navigate","HTTP_SEC_FETCH_DEST":"document","HTTP_SEC_CH_UA_PLATFORM":"\"macOS\"","HTTP_SEC_CH_UA_MOBILE":"?0","HTTP_SEC_CH_UA":"\" Not A;Brand\";v=\"99\", \"Chromium\";v=\"100\", \"Google Chrome\";v=\"100\"","HTTP_COOKIE":"1031b8c41dfff97a311a7ac99863bdc5_username=2756d05ef7521bdc1dac02da066e1658e3e16d6acc7360cfc6256cb1cec311cca%3A2%3A%7Bi%3A0%3Bs%3A41%3A%221031b8c41dfff97a311a7ac99863bdc5_username%22%3Bi%3A1%3Bs%3A5%3A%22admin%22%3B%7D; 1031b8c41dfff97a311a7ac99863bdc5_identity=8ddb6a5ce28f3fb2d23567df9228ce31614d6b19572c4f60db3b4b5eae78f2a3a%3A2%3A%7Bi%3A0%3Bs%3A41%3A%221031b8c41dfff97a311a7ac99863bdc5_identity%22%3Bi%3A1%3Bs%3A159%3A%22%5B1%2C%22%5B%5C%22QwoFhu6pBsTvSOkCXqNvu2_cIr16fde6AK1DHP7GLiyXmnv7qY5BscDi8sl_QRT9z2uGh051J7r9IkSawusrx-ijCLZWZ6bHB433%5C%22%2Cnull%2C%5C%22d9667159e600aea00a68fcc215cc4f6e%5C%22%5D%22%2C3600%5D%22%3B%7D; CRAFT_CSRF_TOKEN=9779283c4e1eba389e1017adc948f01af0a22c04a007ab820e41e540b501e74ca%3A2%3A%7Bi%3A0%3Bs%3A16%3A%22CRAFT_CSRF_TOKEN%22%3Bi%3A1%3Bs%3A147%3A%22XBmAAP6UFlrOfMEOHl9coZnXbJKENF2LtqdsItB7%7C11c6df0a319dfd02ab5a74652e290bf2aa260e6423b903fc38fee0c76e1dbc06XBmAAP6UFlrOfMEOHl9coZnXbJKENF2LtqdsItB7%7C1%22%3B%7D","HTTP_CACHE_CONTROL":"max-age=0","HTTP_ACCEPT_LANGUAGE":"en-US,en;q=0.9","HTTP_ACCEPT_ENCODING":"gzip, deflate, br","HTTP_ACCEPT":"text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9","HTTP_USER_AGENT":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.88 Safari/537.36","HTTP_HOST":"my-project.tld","SCRIPT_FILENAME":"/app/web/index.php","REDIRECT_STATUS":"200","SERVER_NAME":"","SERVER_PORT":"80","SERVER_ADDR":"172.18.0.12","REMOTE_USER":"","REMOTE_PORT":"46122","REMOTE_ADDR":"172.18.0.19","SERVER_SOFTWARE":"nginx/1.18.0","GATEWAY_INTERFACE":"CGI/1.1","REQUEST_SCHEME":"http","SERVER_PROTOCOL":"HTTP/1.1","DOCUMENT_ROOT":"/app/web","DOCUMENT_URI":"/index.php","REQUEST_URI":"/","SCRIPT_NAME":"/index.php","CONTENT_LENGTH":"","CONTENT_TYPE":"","REQUEST_METHOD":"GET","QUERY_STRING":"","FCGI_ROLE":"RESPONDER","PHP_SELF":"/index.php","REQUEST_TIME_FLOAT":1650041873.980016,"REQUEST_TIME":1650041873,"PRIMARY_SITE_URL":"https://my-project.tld/","CRAFT_ENVIRONMENT":"dev","CRAFT_SECURITY_KEY":"•••","CRAFT_DEV_MODE":"0","CRAFT_DB_URL":"","CRAFT_DB_DATABASE":"db","CRAFT_DB_USER":"db","CRAFT_DB_PASSWORD":"•••••","CRAFT_DB_DRIVER":"pgsql","CRAFT_DB_SCHEMA":"public","CRAFT_DB_SERVER":"postgres-13-5432.database.nitro"},"_SESSION":{"bd62416aa8538ede709019a5e113eea5__flash":[],"1031b8c41dfff97a311a7ac99863bdc5__token":"••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••","1031b8c41dfff97a311a7ac99863bdc5__id":1,"__authKey":"••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••","1031b8c41dfff97a311a7ac99863bdc5__expire":1650045474,"__duration":3600}}}

# Tools

Log files are just plain text, but their growth can gradually become a problem for some programs. Let’s look at a few ways to monitor logs for new messages.

# Command Line

UNIX provides the tail command for printing files:

tail -f storage/logs/web-*.log

This will output new web logs as they’re written, and will continue to work even as files are rotated. You can clear any old output with Ctrl/Command + K.

To hunt for specific messages, pipe the output through grep (opens new window):

tail -f storage/logs/web-*.log | grep "specific message or category" -C 10

The -C flag preserves a few lines on either side of a message that matches. Some characters have special meaning in grep, and may need to be escaped.

# Console

MacOS comes with a utility called Console (opens new window), designed for log processing. When opening a file, it will automatically watch for new messages and can filter them by search terms.

# Log Drains

Some platforms will have built-in support for aggregating logs and “draining” them to first- and third-party tools. In these situations, the expectation is generally that logs are sent to stdout and stderr.

Docker operates in a similar way, making output streams available to the host via docker logs --follow my-container-name.

# Sensitive Information

To prevent leaking secrets into logs, Craft automatically redacts sensitive-sounding environment or “context” variable names, like “password”, “token”, and “key.” The final output ends up looking like this:

"CRAFT_DB_DATABASE":"db","CRAFT_DB_USER":"db","CRAFT_DB_PASSWORD":"•••••",

These keywords are customizable via the security component’s sensitiveKeywords property in config/app.php (opens new window):

<?php

return [
    'components' => [
        'security' => [
            'sensitiveKeywords' => [
                // Anything added here gets merged with the defaults:
                'private',
            ],
        ],
    ],
];

Craft does not attempt to redact the message content itself. It is your responsibility to prevent sensitive information from being explicitly logged, say, via interpolation in a message.

# Log Rotation

Logs are grouped by date without any specific size limit. The number of files is limited to 5 by default, per craft\log\MonologTarget::$maxFiles (opens new window).

For high-traffic environments, configuring logrotate (opens new window) or streaming your logs to stdout and stderr is recommended.

# Customizing Logs

Craft gives you fine-grained control over how logs are formatted and where they end up.

Configuration is handled via the log component, in config/app.php. If this is your first time dealing with app.php, we recommend reading a bit about application configuration.

# Monolog

Craft uses Monolog (opens new window) to standardize log output. The defaults used for creating the built-in web, console, and queue targets can be customized via the monologTargetConfig property:

<?php

use craft\helpers\App;
use Monolog\Formatter\LineFormatter;
use Psr\Log\LogLevel;
use yii\i18n\PhpMessageSource;
use yii\web\HttpException;

return [
    'components' => [
        'log' => [
            'monologTargetConfig' => [
                // Only log context in `devMode`
                'logContext' => App::devMode(),

                // Only export messages with `warning` severity and higher:
                'level' => LogLevel::WARNING,

                // Force single-line logs, even in `devMode`:
                'allowLineBreaks' => false,

                // Override message filtering to exclude *all* 400-level exceptions:
                // (This replaces the default exclusions, `PhpMessageSource:*` and `HttpException:404`)
                'except' => [
                    PhpMessageSource::class . ':*',
                    HttpException::class . ':4*',
                ],

                // Change the default log formatter and date format:
                'formatter' => new LineFormatter(
                    format: "%datetime% [%level_name%][%context.category%] %message% %context% %extra%\n",
                    dateFormat: DATE_ATOM
                ),
            ],
        ],
    ],
];

# Targets

Unless configured otherwise, all logs for a request will be written to the same file.

Additional targets (opens new window) can be defined to send your logs (or a subset of them, based on severity or category) to other destinations.

<?php

use craft\helpers\App;
use craft\log\MonologTarget;
use Psr\Log\LogLevel;
use yii\log\FileTarget;
use yii\web\HttpException;

return [
    'components' => [
        'log' => [
            'targets' => [
                // 1. Add a traditional Yii file target for auditing 404 errors that are normally excluded:
                [
                    'class' => FileTarget::class,
                    'logFile' => '@storage/logs/missing-pages.log',
                    'categories' => [
                        HttpException::class . ':404',
                    ],
                    'logVars' => [],
                ],

                // 2. Add a Monolog target for module-specific messages:
                [
                    'class' => MonologTarget::class,
                    'name' => 'custom-module',
                    'extractExceptionTrace' => !App::devMode(),
                    'allowLineBreaks' => App::devMode(),
                    'level' => App::devMode() ? LogLevel::INFO : LogLevel::WARNING,
                    'categories' => ['custom-module'],
                    'logContext' => false,
                ],
            ],
        ],
    ],
];

Here, we’re defining two new targets:

  1. A simple yii\log\FileTarget (opens new window) that only includes messages with the yii\web\HttpException:404 category. These are emitted by Yii, but excluded by Craft’s default targets.
  2. A custom craft\log\MonologTarget (opens new window) to siphon messages emitted by a custom module into a separate log file, and discards context info. Read about logging your own events to learn how to send a message here.

Our new targets don’t affect Craft’s normal logging behavior—the default targets are still configured. As a result, a single message may be dispatched to multiple targets; if you want to filter messages out of the default targets, you can use the categories and except properties within the monologTargetConfig, above. See the Yii documentation on messaging filtering (opens new window) for more information on how this works.

monologTargetConfig and the MonologTarget are the only places you should use PSR-3 Psr\Log\LogLevel constants—other Yii-compatible log targets should use yii\log\Logger (opens new window) constants.

The available options for each type of Target will differ, and may include things like API keys or hostnames for external services. Refer to the author’s documentation for specific requirements!

# stdout and stderr

Craft redirects all log output from Monolog targets to stdout and stderr when CRAFT_STREAM_LOG is set to true. This is common in load-balanced environments and servers with ephemeral filesystems, where log output is aggregated from multiple sources, or the sources themselves are not directly accessible.

# Trace Level

To see exception-like traces for all logs, set the log component’s traceLevel property (opens new window):

<?php
# config/app.php
return [
    'components' => [
        'log' => [
            // Include this many levels of the call stack:
            'traceLevel' => 5,
        ],
    ],
];

Keep in mind that non-zero traceLevel values can incur a performance hit as the system accumulates debugging data!

# Logging Your Own Events

You can log your own messages from a plugin or module.

# Using Craft’s Logger

Convenience methods are available for different severity levels:

  • Craft::trace() – verbose, fine-grained annotations—sometimes temporary—used for support or debugging
  • Craft::debug() – non-essential information that can be used for debugging issues
  • Craft::info() – standard level for informative contextual details
  • Craft::warning() – messages that indicate something problematic or unexpected even though everything continues to work
  • Craft::error() – most urgent level before an exception, used to indicate that something didn’t function properly

By default, Craft logs all levels when devMode is enabled. Otherwise, anything lower than warning will be ignored.

Logged messages should designate a message body, level, and optional category. Here, the we’re using the custom-module category, overriding the default of application:

// Short form, using a helper function for the `info` level:
Craft::info('My first log message!', 'custom-module');

// The equivalent call, with an explicit level:
Craft::getLogger()->log('My first log message!', Logger::LEVEL_INFO, 'custom-module');

These messages would be dispatched to the main log files (in environments where info-level messages are processed), as well as the custom MonologTarget we set up earlier! In both places, it will receive a [custom-module] designation:

2022-09-16 16:50:49 [web.INFO] [custom-module] My first log message! {"memory":1038928}

Anything that can be serialized as JSON can be logged.

# PSR-3 Logging

Craft 4 doesn’t require any changes to existing logging setups, but now accepts PSR-3 messages:

use samdark\log\PsrMessage;

// Traditional Yii2 Logging:
Craft::error('Some error…', 'Some category (logged as context.category)');

// PSR-3 Logging, with context and message substitutions:
Craft::error(new PsrMessage(
    'Some error, {psr3Replacement}',
    [
        'some' => 'context',
        'to' => ['be', 'serialized'],
        'psr3Replacement' => 'https://www.php-fig.org/psr/psr-3/'
    ],
));

Using the convenience methods will automatically translate Yii log levels to the most appropriate PSR-3 level when dispatched to a MonologTarget.

# Further Reading