C#によるPDFバッチ処理：ドキュメントワークフローを大規模に自動化する

using IronPdf;
using System;
using System.IO;
using System.Threading.Tasks;
using System.Threading;
using System.Collections.Concurrent;

string inputFolder = "input/";
string outputFolder = "output/";
string errorLogPath = "error-log.txt";

Directory.CreateDirectory(outputFolder);

string[] htmlFiles = Directory.GetFiles(inputFolder, "*.html");
var renderer = new ChromePdfRenderer();
var errorLog = new ConcurrentBag<string>();

int processed = 0;
int failed = 0;
int retried = 0;

const int maxRetries = 3;

var options = new ParallelOptions
{
    MaxDegreeOfParallelism = Environment.ProcessorCount / 2
};

Parallel.ForEach(htmlFiles, options, htmlFile =>
{
    string fileName = Path.GetFileNameWithoutExtension(htmlFile);
    string outputPath = Path.Combine(outputFolder, $"{fileName}.pdf");
    int attempt = 0;
    bool success = false;

    while (attempt < maxRetries && !success)
    {
        attempt++;
        try
        {
            using var pdf = renderer.RenderHtmlFileAsPdf(htmlFile);
            pdf.SaveAs(outputPath);
            success = true;
            Interlocked.Increment(ref processed);

            if (attempt > 1)
            {
                Interlocked.Increment(ref retried);
                Console.WriteLine($"[OK] {fileName}.pdf (succeeded on attempt {attempt})");
            }
            else
            {
                Console.WriteLine($"[OK] {fileName}.pdf");
            }
        }
        catch (Exception ex) when (IsTransientException(ex) && attempt < maxRetries)
        {
            // Transient error - wait and retry with exponential backoff
            int delayMs = (int)Math.Pow(2, attempt) * 500;
            Console.WriteLine($"[RETRY] {fileName}: {ex.Message} (attempt {attempt}, waiting {delayMs}ms)");
            Thread.Sleep(delayMs);
        }
        catch (Exception ex)
        {
            // Non-transient error or max retries exceeded
            Interlocked.Increment(ref failed);
            string errorMessage = $"{DateTime.Now:yyyy-MM-dd HH:mm:ss} | {fileName} | {ex.GetType().Name} | {ex.Message}";
            errorLog.Add(errorMessage);
            Console.WriteLine($"[ERROR] {fileName}: {ex.Message}");
        }
    }
});

// Write error log
if (errorLog.Count > 0)
{
    File.WriteAllLines(errorLogPath, errorLog);
}

Console.WriteLine($"\nBatch complete:");
Console.WriteLine($"  Processed: {processed}");
Console.WriteLine($"  Failed: {failed}");
Console.WriteLine($"  Retried: {retried}");
if (failed > 0)
{
    Console.WriteLine($"  Error log: {errorLogPath}");
}

// Helper to identify transient exceptions worth retrying
bool IsTransientException(Exception ex)
{
    return ex is IOException ||
           ex is OutOfMemoryException ||
           ex.Message.Contains("timeout", StringComparison.OrdinalIgnoreCase) ||
           ex.Message.Contains("locked", StringComparison.OrdinalIgnoreCase);
}

Imports IronPdf
Imports System
Imports System.IO
Imports System.Threading
Imports System.Collections.Concurrent

Module Program
    Sub Main()
        Dim inputFolder As String = "input/"
        Dim outputFolder As String = "output/"
        Dim errorLogPath As String = "error-log.txt"

        Directory.CreateDirectory(outputFolder)

        Dim htmlFiles As String() = Directory.GetFiles(inputFolder, "*.html")
        Dim renderer As New ChromePdfRenderer()
        Dim errorLog As New ConcurrentBag(Of String)()

        Dim processed As Integer = 0
        Dim failed As Integer = 0
        Dim retried As Integer = 0

        Const maxRetries As Integer = 3

        Dim options As New ParallelOptions With {
            .MaxDegreeOfParallelism = Environment.ProcessorCount \ 2
        }

        Parallel.ForEach(htmlFiles, options, Sub(htmlFile)
                                                 Dim fileName As String = Path.GetFileNameWithoutExtension(htmlFile)
                                                 Dim outputPath As String = Path.Combine(outputFolder, $"{fileName}.pdf")
                                                 Dim attempt As Integer = 0
                                                 Dim success As Boolean = False

                                                 While attempt < maxRetries AndAlso Not success
                                                     attempt += 1
                                                     Try
                                                         Using pdf = renderer.RenderHtmlFileAsPdf(htmlFile)
                                                             pdf.SaveAs(outputPath)
                                                             success = True
                                                             Interlocked.Increment(processed)

                                                             If attempt > 1 Then
                                                                 Interlocked.Increment(retried)
                                                                 Console.WriteLine($"[OK] {fileName}.pdf (succeeded on attempt {attempt})")
                                                             Else
                                                                 Console.WriteLine($"[OK] {fileName}.pdf")
                                                             End If
                                                         End Using
                                                     Catch ex As Exception When IsTransientException(ex) AndAlso attempt < maxRetries
                                                         ' Transient error - wait and retry with exponential backoff
                                                         Dim delayMs As Integer = CInt(Math.Pow(2, attempt)) * 500
                                                         Console.WriteLine($"[RETRY] {fileName}: {ex.Message} (attempt {attempt}, waiting {delayMs}ms)")
                                                         Thread.Sleep(delayMs)
                                                     Catch ex As Exception
                                                         ' Non-transient error or max retries exceeded
                                                         Interlocked.Increment(failed)
                                                         Dim errorMessage As String = $"{DateTime.Now:yyyy-MM-dd HH:mm:ss} | {fileName} | {ex.GetType().Name} | {ex.Message}"
                                                         errorLog.Add(errorMessage)
                                                         Console.WriteLine($"[ERROR] {fileName}: {ex.Message}")
                                                     End Try
                                                 End While
                                             End Sub)

        ' Write error log
        If errorLog.Count > 0 Then
            File.WriteAllLines(errorLogPath, errorLog)
        End If

        Console.WriteLine(vbCrLf & "Batch complete:")
        Console.WriteLine($"  Processed: {processed}")
        Console.WriteLine($"  Failed: {failed}")
        Console.WriteLine($"  Retried: {retried}")
        If failed > 0 Then
            Console.WriteLine($"  Error log: {errorLogPath}")
        End If
    End Sub

    ' Helper to identify transient exceptions worth retrying
    Function IsTransientException(ex As Exception) As Boolean
        Return TypeOf ex Is IOException OrElse
               TypeOf ex Is OutOfMemoryException OrElse
               ex.Message.Contains("timeout", StringComparison.OrdinalIgnoreCase) OrElse
               ex.Message.Contains("locked", StringComparison.OrdinalIgnoreCase)
    End Function
End Module

using IronPdf;
using System;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using System.Threading;
using System.Collections.Generic;

string inputFolder = "input/";
string outputFolder = "output/";
string checkpointPath = "checkpoint.txt";
string errorLogPath = "errors.txt";

Directory.CreateDirectory(outputFolder);

// Load checkpoint - files already processed successfully
var completedFiles = new HashSet<string>();
if (File.Exists(checkpointPath))
{
    completedFiles = new HashSet<string>(File.ReadAllLines(checkpointPath));
    Console.WriteLine($"Resuming from checkpoint: {completedFiles.Count} files already processed");
}

// Get files to process (excluding already completed)
string[] allFiles = Directory.GetFiles(inputFolder, "*.html");
string[] filesToProcess = allFiles
    .Where(f => !completedFiles.Contains(Path.GetFileName(f)))
    .ToArray();

Console.WriteLine($"Files to process: {filesToProcess.Length} (skipping {completedFiles.Count} already done)");

var renderer = new ChromePdfRenderer();
var checkpointLock = new object();
int processed = 0;
int failed = 0;

var options = new ParallelOptions
{
    MaxDegreeOfParallelism = Environment.ProcessorCount / 2
};

Parallel.ForEach(filesToProcess, options, htmlFile =>
{
    string fileName = Path.GetFileName(htmlFile);
    string baseName = Path.GetFileNameWithoutExtension(htmlFile);
    string outputPath = Path.Combine(outputFolder, $"{baseName}.pdf");

    try
    {
        using var pdf = renderer.RenderHtmlFileAsPdf(htmlFile);
        pdf.SaveAs(outputPath);

        // Record success in checkpoint (thread-safe)
        lock (checkpointLock)
        {
            File.AppendAllText(checkpointPath, fileName + Environment.NewLine);
        }

        Interlocked.Increment(ref processed);
        Console.WriteLine($"[OK] {baseName}.pdf");
    }
    catch (Exception ex)
    {
        Interlocked.Increment(ref failed);

        // Log error for review
        lock (checkpointLock)
        {
            File.AppendAllText(errorLogPath,
                $"{DateTime.Now:yyyy-MM-dd HH:mm:ss} | {fileName} | {ex.Message}{Environment.NewLine}");
        }

        Console.WriteLine($"[ERROR] {fileName}: {ex.Message}");
    }
});

Console.WriteLine($"\nBatch complete:");
Console.WriteLine($"  Newly processed: {processed}");
Console.WriteLine($"  Failed: {failed}");
Console.WriteLine($"  Total completed: {completedFiles.Count + processed}");
Console.WriteLine($"  Checkpoint saved to: {checkpointPath}");

Imports IronPdf
Imports System
Imports System.IO
Imports System.Linq
Imports System.Threading.Tasks
Imports System.Threading
Imports System.Collections.Generic

Module Program
    Sub Main()
        Dim inputFolder As String = "input/"
        Dim outputFolder As String = "output/"
        Dim checkpointPath As String = "checkpoint.txt"
        Dim errorLogPath As String = "errors.txt"

        Directory.CreateDirectory(outputFolder)

        ' Load checkpoint - files already processed successfully
        Dim completedFiles As New HashSet(Of String)()
        If File.Exists(checkpointPath) Then
            completedFiles = New HashSet(Of String)(File.ReadAllLines(checkpointPath))
            Console.WriteLine($"Resuming from checkpoint: {completedFiles.Count} files already processed")
        End If

        ' Get files to process (excluding already completed)
        Dim allFiles As String() = Directory.GetFiles(inputFolder, "*.html")
        Dim filesToProcess As String() = allFiles _
            .Where(Function(f) Not completedFiles.Contains(Path.GetFileName(f))) _
            .ToArray()

        Console.WriteLine($"Files to process: {filesToProcess.Length} (skipping {completedFiles.Count} already done)")

        Dim renderer As New ChromePdfRenderer()
        Dim checkpointLock As New Object()
        Dim processed As Integer = 0
        Dim failed As Integer = 0

        Dim options As New ParallelOptions With {
            .MaxDegreeOfParallelism = Environment.ProcessorCount \ 2
        }

        Parallel.ForEach(filesToProcess, options, Sub(htmlFile)
                                                      Dim fileName As String = Path.GetFileName(htmlFile)
                                                      Dim baseName As String = Path.GetFileNameWithoutExtension(htmlFile)
                                                      Dim outputPath As String = Path.Combine(outputFolder, $"{baseName}.pdf")

                                                      Try
                                                          Using pdf = renderer.RenderHtmlFileAsPdf(htmlFile)
                                                              pdf.SaveAs(outputPath)
                                                          End Using

                                                          ' Record success in checkpoint (thread-safe)
                                                          SyncLock checkpointLock
                                                              File.AppendAllText(checkpointPath, fileName & Environment.NewLine)
                                                          End SyncLock

                                                          Interlocked.Increment(processed)
                                                          Console.WriteLine($"[OK] {baseName}.pdf")
                                                      Catch ex As Exception
                                                          Interlocked.Increment(failed)

                                                          ' Log error for review
                                                          SyncLock checkpointLock
                                                              File.AppendAllText(errorLogPath,
                                                                                 $"{DateTime.Now:yyyy-MM-dd HH:mm:ss} | {fileName} | {ex.Message}{Environment.NewLine}")
                                                          End SyncLock

                                                          Console.WriteLine($"[ERROR] {fileName}: {ex.Message}")
                                                      End Try
                                                  End Sub)

        Console.WriteLine(vbCrLf & "Batch complete:")
        Console.WriteLine($"  Newly processed: {processed}")
        Console.WriteLine($"  Failed: {failed}")
        Console.WriteLine($"  Total completed: {completedFiles.Count + processed}")
        Console.WriteLine($"  Checkpoint saved to: {checkpointPath}")
    End Sub
End Module

using IronPdf;
using System;
using System.IO;
using System.Threading.Tasks;
using System.Threading;
using System.Diagnostics;

string inputFolder = "input/";
string outputFolder = "output/";

Directory.CreateDirectory(outputFolder);

string[] htmlFiles = Directory.GetFiles(inputFolder, "*.html");
var renderer = new ChromePdfRenderer();

Console.WriteLine($"Processing {htmlFiles.Length} files with {Environment.ProcessorCount} CPU cores");

int processed = 0;
var stopwatch = Stopwatch.StartNew();

// Configure parallelism based on system resources
// Rule of thumb: ProcessorCount / 2 for memory-intensive operations
var options = new ParallelOptions
{
    MaxDegreeOfParallelism = Math.Max(1, Environment.ProcessorCount / 2)
};

Console.WriteLine($"Max parallelism: {options.MaxDegreeOfParallelism}");

// Use Parallel.ForEach for CPU-bound batch operations
Parallel.ForEach(htmlFiles, options, htmlFile =>
{
    string fileName = Path.GetFileNameWithoutExtension(htmlFile);
    string outputPath = Path.Combine(outputFolder, $"{fileName}.pdf");

    try
    {
        // Render HTML to PDF
        using var pdf = renderer.RenderHtmlFileAsPdf(htmlFile);
        pdf.SaveAs(outputPath);

        int current = Interlocked.Increment(ref processed);

        // Progress reporting every 10 files
        if (current % 10 == 0)
        {
            double elapsed = stopwatch.Elapsed.TotalSeconds;
            double rate = current / elapsed;
            double remaining = (htmlFiles.Length - current) / rate;
            Console.WriteLine($"Progress: {current}/{htmlFiles.Length} ({rate:F1} files/sec, ~{remaining:F0}s remaining)");
        }
    }
    catch (Exception ex)
    {
        Console.WriteLine($"[ERROR] {fileName}: {ex.Message}");
    }
});

stopwatch.Stop();
double totalRate = processed / stopwatch.Elapsed.TotalSeconds;

Console.WriteLine($"\nComplete:");
Console.WriteLine($"  Files processed: {processed}/{htmlFiles.Length}");
Console.WriteLine($"  Total time: {stopwatch.Elapsed.TotalSeconds:F1}s");
Console.WriteLine($"  Average rate: {totalRate:F1} files/sec");
Console.WriteLine($"  Time per file: {stopwatch.Elapsed.TotalMilliseconds / processed:F0}ms");

// Memory monitoring helper (call between chunks for large batches)
void CheckMemoryPressure()
{
    const long memoryThreshold = 4L * 1024 * 1024 * 1024; // 4 GB
    long currentMemory = GC.GetTotalMemory(forceFullCollection: false);

    if (currentMemory > memoryThreshold)
    {
        Console.WriteLine($"Memory pressure detected ({currentMemory / 1024 / 1024}MB), forcing GC...");
        GC.Collect();
        GC.WaitForPendingFinalizers();
        GC.Collect();
    }
}

Imports IronPdf
Imports System
Imports System.IO
Imports System.Threading.Tasks
Imports System.Threading
Imports System.Diagnostics

Module Program
    Sub Main()
        Dim inputFolder As String = "input/"
        Dim outputFolder As String = "output/"

        Directory.CreateDirectory(outputFolder)

        Dim htmlFiles As String() = Directory.GetFiles(inputFolder, "*.html")
        Dim renderer As New ChromePdfRenderer()

        Console.WriteLine($"Processing {htmlFiles.Length} files with {Environment.ProcessorCount} CPU cores")

        Dim processed As Integer = 0
        Dim stopwatch As Stopwatch = Stopwatch.StartNew()

        ' Configure parallelism based on system resources
        ' Rule of thumb: ProcessorCount / 2 for memory-intensive operations
        Dim options As New ParallelOptions With {
            .MaxDegreeOfParallelism = Math.Max(1, Environment.ProcessorCount \ 2)
        }

        Console.WriteLine($"Max parallelism: {options.MaxDegreeOfParallelism}")

        ' Use Parallel.ForEach for CPU-bound batch operations
        Parallel.ForEach(htmlFiles, options, Sub(htmlFile)
                                                 Dim fileName As String = Path.GetFileNameWithoutExtension(htmlFile)
                                                 Dim outputPath As String = Path.Combine(outputFolder, $"{fileName}.pdf")

                                                 Try
                                                     ' Render HTML to PDF
                                                     Using pdf = renderer.RenderHtmlFileAsPdf(htmlFile)
                                                         pdf.SaveAs(outputPath)
                                                     End Using

                                                     Dim current As Integer = Interlocked.Increment(processed)

                                                     ' Progress reporting every 10 files
                                                     If current Mod 10 = 0 Then
                                                         Dim elapsed As Double = stopwatch.Elapsed.TotalSeconds
                                                         Dim rate As Double = current / elapsed
                                                         Dim remaining As Double = (htmlFiles.Length - current) / rate
                                                         Console.WriteLine($"Progress: {current}/{htmlFiles.Length} ({rate:F1} files/sec, ~{remaining:F0}s remaining)")
                                                     End If
                                                 Catch ex As Exception
                                                     Console.WriteLine($"[ERROR] {fileName}: {ex.Message}")
                                                 End Try
                                             End Sub)

        stopwatch.Stop()
        Dim totalRate As Double = processed / stopwatch.Elapsed.TotalSeconds

        Console.WriteLine(vbCrLf & "Complete:")
        Console.WriteLine($"  Files processed: {processed}/{htmlFiles.Length}")
        Console.WriteLine($"  Total time: {stopwatch.Elapsed.TotalSeconds:F1}s")
        Console.WriteLine($"  Average rate: {totalRate:F1} files/sec")
        Console.WriteLine($"  Time per file: {stopwatch.Elapsed.TotalMilliseconds / processed:F0}ms")

        ' Memory monitoring helper (call between chunks for large batches)
        CheckMemoryPressure()
    End Sub

    Sub CheckMemoryPressure()
        Const memoryThreshold As Long = 4L * 1024 * 1024 * 1024 ' 4 GB
        Dim currentMemory As Long = GC.GetTotalMemory(forceFullCollection:=False)

        If currentMemory > memoryThreshold Then
            Console.WriteLine($"Memory pressure detected ({currentMemory \ 1024 \ 1024}MB), forcing GC...")
            GC.Collect()
            GC.WaitForPendingFinalizers()
            GC.Collect()
        End If
    End Sub
End Module