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PointQueue.cs
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PointQueue.cs
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// Copyright (c) Rapid Software LLC. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using Npgsql;
using NpgsqlTypes;
using Scada.Data.Models;
using Scada.Log;
using Scada.Server.Lang;
using System;
using System.Collections.Generic;
using System.Threading;
namespace Scada.Server.Modules.ModArcPostgreSql.Logic
{
/// <summary>
/// Represents a queue for writing data points to a database.
/// <para>Представляет очередь для записи точек данных в базу данных.</para>
/// </summary>
internal class PointQueue
{
private readonly Queue<CnlDataPoint> dataQueue; // contains data points for writing
private readonly NpgsqlCommand command; // writes a data point
private readonly NpgsqlParameter cnlNumParam; // the channel number parameter
private readonly NpgsqlParameter timestampParam; // the timestamp parameter
private readonly NpgsqlParameter valParam; // the channel value parameter
private readonly NpgsqlParameter statParam; // the channel status parameter
/// <summary>
/// Initializes a new instance of the class.
/// </summary>
public PointQueue(int maxQueueSize, string insertSql)
{
dataQueue = new Queue<CnlDataPoint>(maxQueueSize);
command = new NpgsqlCommand(insertSql);
cnlNumParam = command.Parameters.Add("cnlNum", NpgsqlDbType.Integer);
timestampParam = command.Parameters.Add("timestamp", NpgsqlDbType.TimestampTz);
valParam = command.Parameters.Add("val", NpgsqlDbType.Double);
statParam = command.Parameters.Add("stat", NpgsqlDbType.Integer);
MaxQueueSize = maxQueueSize;
HasError = false;
ReturnOnError = false;
}
/// <summary>
/// Gets the maximum queue size.
/// </summary>
public int MaxQueueSize { get; }
/// <summary>
/// Gets a value indicating whether to return points to the queue in case of error.
/// </summary>
public bool ReturnOnError { get; set; }
/// <summary>
/// Gets the current queue size.
/// </summary>
public int Count
{
get
{
return dataQueue.Count;
}
}
/// <summary>
/// Gets a value indicating whether the queue is in error state.
/// </summary>
public bool HasError { get; private set; }
/// <summary>
/// Gets or sets the archive code.
/// </summary>
public string ArchiveCode { get; set; }
/// <summary>
/// Gets or sets the application log.
/// </summary>
public ILog AppLog { get; set; }
/// <summary>
/// Gets or sets the archive log.
/// </summary>
public ILog ArcLog { get; set; }
/// <summary>
/// Gets or sets the database connection.
/// </summary>
public NpgsqlConnection Connection { get; set; }
/// <summary>
/// Gets an object that can be used to synchronize access to the queue.
/// </summary>
public object SyncRoot
{
get
{
return this;
}
}
/// <summary>
/// Sets the command parameters according to the data point.
/// </summary>
private void SetCommandParams(CnlDataPoint point)
{
cnlNumParam.Value = point.CnlNum;
timestampParam.Value = point.Timestamp;
valParam.Value = point.Val;
statParam.Value = point.Stat;
}
/// <summary>
/// Enqueues a data point to the queue.
/// </summary>
public void EnqueuePoint(int cnlNum, DateTime timestamp, CnlData cnlData)
{
lock (dataQueue)
{
dataQueue.Enqueue(new CnlDataPoint(cnlNum, timestamp, cnlData));
}
}
/// <summary>
/// Enqueues a data point without locking the queue.
/// </summary>
public void EnqueueWithoutLock(int cnlNum, DateTime timestamp, CnlData cnlData)
{
dataQueue.Enqueue(new CnlDataPoint(cnlNum, timestamp, cnlData));
}
/// <summary>
/// Inserts or updates data points from the queue.
/// </summary>
public void InsertPoints()
{
if (Connection == null)
throw new InvalidOperationException("Connection must not be null.");
NpgsqlTransaction trans = null;
try
{
Connection.Open();
trans = Connection.BeginTransaction();
command.Connection = Connection;
command.Transaction = trans;
for (int i = 0; i < DbUtils.BundleSize; i++)
{
// retrieve a data point from the queue
CnlDataPoint point;
lock (dataQueue)
{
if (dataQueue.Count > 0)
point = dataQueue.Dequeue();
else
break;
}
try
{
// write the data point
SetCommandParams(point);
command.ExecuteNonQuery();
}
catch
{
// return the unwritten data point to the queue
if (ReturnOnError)
{
lock (dataQueue)
{
dataQueue.Enqueue(point);
}
}
throw;
}
}
if (dataQueue.Count == 0)
ArcLog?.WriteInfo(ServerPhrases.QueueBecameEmpty);
trans.Commit();
HasError = false;
}
catch (Exception ex)
{
DbUtils.SafeRollback(trans);
HasError = true;
AppLog?.WriteError(ex, ServerPhrases.ArchiveMessage, ArchiveCode, ServerPhrases.WriteDbError);
ArcLog?.WriteError(ex, ServerPhrases.WriteDbError);
Thread.Sleep(DbUtils.ErrorDelay);
}
finally
{
Connection.Close();
}
}
/// <summary>
/// Writes all data points from the queue.
/// </summary>
public void FlushPoints()
{
if (Connection == null)
throw new InvalidOperationException("Connection must not be null.");
if (dataQueue.Count == 0)
return;
NpgsqlTransaction trans = null;
try
{
Connection.Open();
trans = Connection.BeginTransaction();
command.Connection = Connection;
command.Transaction = trans;
lock (dataQueue)
{
while (dataQueue.Count > 0)
{
SetCommandParams(dataQueue.Dequeue());
command.ExecuteNonQuery();
}
}
ArcLog?.WriteInfo(ServerPhrases.QueueBecameEmpty);
trans.Commit();
HasError = false;
}
catch (Exception ex)
{
DbUtils.SafeRollback(trans);
HasError = true;
AppLog?.WriteError(ex, ServerPhrases.ArchiveMessage, ArchiveCode, ServerPhrases.WriteDbError);
ArcLog?.WriteError(ex, ServerPhrases.WriteDbError);
}
finally
{
Connection.Close();
}
}
/// <summary>
/// Removes excess points from the head of the queue.
/// </summary>
public void RemoveExcessPoints()
{
int lostCnt = 0;
lock (dataQueue)
{
while (dataQueue.Count > MaxQueueSize)
{
dataQueue.Dequeue();
lostCnt++;
}
}
if (lostCnt > 0)
{
string msg = string.Format(ServerPhrases.PointsWereLost, lostCnt);
AppLog?.WriteError(ServerPhrases.ArchiveMessage, ArchiveCode, msg);
ArcLog?.WriteError(msg);
}
}
}
}