Logging, Error Handling and Debugging

In the process of consuming message queue, you may encounter unexpected errors. Below is the list of key highlights of how to handle errors, work with logs and check unplanned issues happened during message processing.

Logs, Output, and Verbosity

Message Queue Consumer uses MonologBundle to output Logs. To output message with any of logging levels/priorities, you should inject LoggerInterface in your processor and log errors the same way as it is described in Logging with Monolog" Symfony doc. Consumer console command has different verbosity levels that determine the messages displayed in the output.

Console option	Output Errors
-q or --quiet	LogLevel::ERROR and higher
(none)	LogLevel::WARNING and higher
-v	LogLevel::NOTICE and higher
-vv	LogLevel::INFO and higher
-vvv	LogLevel::DEBUG and higher

All the LogLevel::ERROR logs and higher also will be printed to the prod.log file. You can change minimal log level that should be printed to the prod.log file using the oro:logger:level command which temporarily changes the configured logging level. For more details, see the Temporarily Decrease Log Level documentation.

Note

Keep in mind that prod.log is just an example. Your log file name may differ depending on your Monolog handlers configuration.

Processors

Sometimes, it is necessary to add your own data to log extra data. For more details on how to create your own processor and add the monolog.processor DIC tag to it, see the related Processors documentation.

Handlers

Consumer output is based on Monolog, so it supports a stack of handlers that can be used to write the log entries to different locations (e.g., files, database, Slack, etc). See more information in the related Symfony documentation.

It is useful when your production is configured with the real-time log service such as Google Stackdriver. Read more in the How to write logs to Stackdriver.

Formatters

To format the record before logging it to each logging handler, use a Formatter that implements Monolog\Formatter\FormatterInterface.

If your production is configured with a real-time log service (ELK Stack), read the related documentation on how to write logs to it.

Console Messages Output

Message Queue Consumer provides ConsoleHandler that listens to console events and writes log messages to the console output depending on the console verbosity. It uses a ConsoleFormatter to format the record before logging it. Record format pattern is described below:

"%datetime% %start_tag%%channel%.%level_name%%end_tag%: %message%%context%%extra%\n"

Consumer Heartbeat

An administrator must be informed about the state of consumers in the system (whether there is at least one alive).

This is covered by the Consumer Heartbeat functionality that works in the following way:

• On start and after every configured time period, each consumer calls the tick method of the ConsumerHeartbeat service that informs the system that the consumer is alive.

• The oro:cron:message-queue:consumer_heartbeat_check cron command is periodically executed to check consumers’ state. If no alive consumers found, the oro/message_queue_state socket message is sent notifying all logged-in users that the system may work incorrectly (because consumers are not available).

• The same check is also performed when a user logs in. This is done to notify users about the problem as soon as possible.

The check period can be changed in the application configuration file using the consumer_heartbeat_update_period option:

oro_message_queue:
    consumer:
        heartbeat_update_period: 20 #the update period was set to 20 minutes

The default value of the heartbeat_update_period option is 15 minutes.

To disable the Consumer Heartbeat functionality, set the heartbeat_update_period option to 0.

Consumer Interruption

Friendly Consumer Interruption

Sometimes, during the consuming and processing messages, it is necessary to interrupt consumer to avoid such cases as not actual cached data, maintenance mode or memory leaks. Also, it is better to limit messages or processing time during debugging or any other reason when the consumer should be stopped. Below is a list of friendly consumer interruption:

Output	Description
app.WARNING: Consuming interrupted. Queue: "oro.default", reason: Interrupt execution.	Consumer was interrupted with stop signal: SIGTERM, SIGQUIT or SIGINT
app.WARNING: Consuming interrupted. Queue: "oro.default", reason: The limit time has passed.	Passed time limit configured with command option --time-limit
app.WARNING: Consuming interrupted. Queue: "oro.default", reason: The message limit reached.	Passed message limit configured with command option --message-limit
app.WARNING: Consuming interrupted. Queue: "oro.default", reason: The memory limit reached.	Passed time limit configured with command option --memory-limit
app.WARNING: Consuming interrupted. Queue: "oro.default", reason: The cache was cleared.	Cache was cleared (it also will be triggered after saving System Configuration), more details here
app.WARNING: Consuming interrupted. Queue: "oro.default", reason: The cache was invalidated.	Schema was updated, and cache was cleared
app.WARNING: Consuming interrupted. Queue: "oro.default", reason: The Maintenance mode has been deactivated.	Maintenance mode was turned off

The normal interruption occurs only after processing a message. If an event was fired during a message processing, a consumer completes the message processing and interrupts after the processing is done.

Unfriendly Consumer Interruption

If the consumer is interrupted abruptly, check the prod.log file. It should contain the following message.

app.ERROR: Consuming interrupted, reason: Something went wrong.

The full exception stack trace will be printed in the console output.

To find out the reason for consumer interruption, use the Fingers Crossed Handler in the monolog configuration. It collects all logs in the buffer depending on the configured log level and prints them to prod.log if an error occurs (the error is triggered by the console.error event).

Note

All logs buffer collected before the error occurred will be erased before receiving the related message. The message will contain the logs record.

Example of Fingers Crossed Handler Configuration

To log into all environments, add the following code to config.yml. To log only in prod, add the code to config_prod.yml:

Note

Out of the box, the Fingers Crossed Handler is already enabled, and you don’t have to configure it manually.

config/config_prod.yml

 monolog:
     handlers:
         # ...
         main:
             type:         fingers_crossed
             action_level: error
             handler:      grouped
             buffer_size:  100

Interrupting Consumer from Code

Create consumption extension with its own logic:

src/Acme/Bundle/DemoBundle/Consumption/Extension/CustomExtension.php

namespace Oro\Component\MessageQueue\Consumption\Extension;

use Oro\Component\MessageQueue\Consumption\AbstractExtension;
use Oro\Component\MessageQueue\Consumption\Context;

class CustomExtension extends AbstractExtension
{
    /**
     * {@inheritdoc}
     */
    public function onPostReceived(Context $context)
    {
        // ... own logic

        if (!$context->isExecutionInterrupted()) {
            $context->setExecutionInterrupted(true);
            $context->setInterruptedReason('Message with reason of interruption.');
        }
    }
}

Declare service:

src/Acme/Bundle/DemoBundle/Resources/config/services.yml

 services:
     acme_demo.consumption.custom_extension:
         class: Acme\Bundle\DemoBundle\Consumption\Extension\CustomExtension
         public: false
         tags:
             - { name: 'oro_message_queue.consumption.extension', persistent: true }

Errors and Crashes

When the application is working, and consumer is configured, you may encounter some unforeseen errors. A few examples of common errors that may occur in the course of your application’s daily operations are listed below:

• Database related errors (connection errors, accessing errors, query errors, data errors)

• File system errors (permission errors, no disk space errors)

• Third-party integrations errors

If one listed error occurs, processor will return REQUEUE, and message will be redelivered.

Profiling

Below is a list of key variables that were added to extra and will be shown in the output.

Variable	Description
extension	Extension class which was caused by log message
processor	Processor that processes queue messages
message_id	Unique message ID
message_body	Message body
message_properties	List of message properties that were received from message broker
message_headers	List of message headers that were received from message broker
message_priority	Message priority (responsible for the order in which messages are processed)
memory_usage	Current memory usage
memory_taken	Memory usage difference (current memory usage minus memory usage at the beginning of current message processing)
peak_memory	Peak memory usage (maximum value of memory_usage from all previous log records related to current message processing)
elapsed_time	Time passed since the consumer started current message processing

Separate Message Queue Consumer Logs

If you want to log the consumer channel to a different file, create a new handler and configure it to log only messages from the consumer channel. You can add this to config.yml to log into all environments, or just config_prod.yml to log only in prod:

monolog:
 handlers:
   consumer_buffer:
       type:         fingers_crossed
       action_level: error
       handler:      consumer
       buffer_size:  100
       channels:     [ 'consumer' ] # The channels configuration only works for top-level handlers
   consumer:
       type:         stream
       path:         "%kernel.logs_dir%/consumer_%kernel.environment%.log"
       level:        debug

   # ...

   filtered:
       type:       filter
       min_level: info
       handler:   main
       channels:  [ '!consumer' ] # Exclude 'consumer' channel for main handlers chain

Third Party Logging Systems

• Writing Logs to Stackdriver

• Writing Logs to ELK Stack

For more information, see the following external resources:

• Monolog

• MonologBundle

• Symfony "Logging with Monolog"

• Symfony Verbosity Levels

• Symfony Logging Processors

• Symfony Logging Handlers

• Google Stackdriver

• ELK Stack: Elasticsearch, Logstash, Kibana