DocSpace-buildtools/common/ASC.Common/Caching/RabbitMQCache.cs

// (c) Copyright Ascensio System SIA 2010-2022
//
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// You can redistribute it and/or modify it under the terms
// of the GNU Affero General Public License (AGPL) version 3 as published by the Free Software
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// to the effect that Ascensio System SIA expressly excludes the warranty of non-infringement of
// any third-party rights.
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namespace ASC.Common.Caching;

[Singletone]
public class RabbitMQCache<T> : IDisposable, ICacheNotify<T> where T : IMessage<T>, new()
{
    private IConnection _connection;
    private readonly IConnectionFactory _connectionFactory;

    private IModel _consumerChannel;
    private readonly Guid _instanceId;
    private readonly string _exchangeName;
    private readonly string _queueName;

    private readonly ILogger _logger;
    private readonly ConcurrentDictionary<string, List<Action<T>>> _actions;

    private readonly object _lock = new object();
    private bool _disposed;

    public RabbitMQCache(IConfiguration configuration, ILogger<RabbitMQCache<T>> logger)
    {
        _logger = logger;
        _instanceId = Guid.NewGuid();
        _exchangeName = $"asc:cache_notify:event_bus:{typeof(T).FullName}";
        _queueName = $"asc:cache_notify:queue:{typeof(T).FullName}:{_instanceId}";
        _actions = new ConcurrentDictionary<string, List<Action<T>>>();

        var rabbitMQConfiguration = configuration.GetSection("rabbitmq").Get<RabbitMQSettings>();

        _connectionFactory = new ConnectionFactory
        {
            HostName = rabbitMQConfiguration.HostName,
            UserName = rabbitMQConfiguration.UserName,
            Password = rabbitMQConfiguration.Password
        };

        _connection = _connectionFactory.CreateConnection();
        _consumerChannel = CreateConsumerChannel();

        StartBasicConsume();
    }

    private IModel CreateConsumerChannel()
    {
        TryConnect();

        _logger.TraceCreatingRabbitMQ();

        var channel = _connection.CreateModel();

        channel.ExchangeDeclare(exchange: _exchangeName, type: ExchangeType.Fanout);
        channel.QueueDeclare(queue: _queueName,
            durable: false,
            exclusive: false,
            autoDelete: true,
            arguments: null);

        channel.QueueBind(_queueName, _exchangeName, string.Empty, null);

        channel.CallbackException += (sender, ea) =>
        {
            _logger.WarningRecreatingRabbitMQ(ea.Exception);

            _consumerChannel.Dispose();
            _consumerChannel = CreateConsumerChannel();

            StartBasicConsume();

        };

        return channel;
    }

    private void StartBasicConsume()
    {
        _logger.TraceStartingRabbitMQ();

        if (_consumerChannel != null)
        {
            var consumer = new EventingBasicConsumer(_consumerChannel);

            consumer.Received += OnMessageReceived;

            _consumerChannel.BasicConsume(queue: _queueName, autoAck: true, consumer: consumer);
        }
        else
        {
            _logger.ErrorStartBasicConsumeCanNotCall();
        }
    }


    private void TryConnect()
    {
        lock (_lock)
        {
            if (IsConnected)
            {
                return;
            }

            _connection = _connectionFactory.CreateConnection();
            _connection.ConnectionShutdown += (s, e) => TryConnect();
            _connection.CallbackException += (s, e) => TryConnect();
            _connection.ConnectionBlocked += (s, e) => TryConnect();
        }
    }


    public bool IsConnected => _connection != null && _connection.IsOpen && !_disposed;

    private void OnMessageReceived(object sender, BasicDeliverEventArgs e)
    {
        var body = e.Body.Span.ToArray();

        var parser = new MessageParser<T>(() => new T());

        var data = body.Take(body.Length - 1);

        var obj = parser.ParseFrom(data.ToArray());

        var action = (CacheNotifyAction)body[body.Length - 1];

        if (_actions.TryGetValue(GetKey(action), out var onchange) && onchange != null)
        {
            Parallel.ForEach(onchange, a => a(obj));
        }
    }

    public void Publish(T obj, CacheNotifyAction action)
    {
        var objAsByteArray = obj.ToByteArray();

        var body = new byte[objAsByteArray.Length + 1];

        objAsByteArray.CopyTo(body, 0);

        body[body.Length - 1] = (byte)action;

        _consumerChannel.BasicPublish(
                             exchange: _exchangeName,
                             routingKey: string.Empty,
                             mandatory: true,
                             basicProperties: _consumerChannel.CreateBasicProperties(),
                             body: body);
    }

    public Task PublishAsync(T obj, CacheNotifyAction action)
    {
        Publish(obj, action);

        return Task.CompletedTask;
    }


    public void Subscribe(Action<T> onchange, CacheNotifyAction action)
    {
        _actions.GetOrAdd(GetKey(action), new List<Action<T>>())
            .Add(onchange);
    }

    public void Unsubscribe(CacheNotifyAction action)
    {
        _actions.TryRemove(GetKey(action), out _);
    }

    private string GetKey(CacheNotifyAction cacheNotifyAction)
    {
        return $"asc:channel:{cacheNotifyAction}:{typeof(T).FullName}".ToLower();
    }

    public void Dispose()
    {
        if (_disposed)
        {
            return;
        }

        _consumerChannel?.Dispose();
        _connection.Dispose();

        _disposed = true;
    }
}

public class RabbitMQSettings
{
    public string HostName { get; set; }
    public string UserName { get; set; }
    public string Password { get; set; }

}