Architecture

PdfAPI is hosted in IIS as a single ASP.NET Web API 2 application with no OWIN self-hosting and no WCF surface. Startup wires Web API configuration and an Autofac container before any request is served; every controller resolves a per-request PDF service and, where tracking applies, a per-request NHibernate unit of work against the Oracle IMG schema.

Hosting model

The service is hosted in IIS. Global.asax instantiates WebApiApplication : System.Web.HttpApplication, whose Application_Start runs the App_Start configuration classes, including WebApiConfig.Register(HttpConfiguration).

Aspect	Finding
Host	IIS (System.Web.HttpApplication) — no OWIN, no WCF, no self-host
Application class	WebApiApplication (PdfAPI\Global.asax.cs)
Startup call chain	Application_Start → LicenseHelper.LicenseSyncfusion() → AreaRegistration.RegisterAllAreas() → GlobalConfiguration.Configure(WebApiConfig.Register) → FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters) → RouteConfig.RegisterRoutes(RouteTable.Routes) → BundleConfig.RegisterBundles(BundleTable.Bundles) → build and configure the Autofac container (ContainerBuilder, RegisterControllers, RegisterApiControllers, IoCConfig.RegisterDependencies, builder.Build()) → assign DependencyResolver and GlobalConfiguration.Configuration.DependencyResolver
Virtual directory / app pool	Not determined from source**
Target framework	.NET Framework 4.6.2

Request pipeline

The following diagram shows how a request reaches a controller action and how the NHibernate unit of work is scoped for tracked operations.

flowchart TD
    CLIENT["Client request"] --> IIS["IIS + HttpApplication"]
    IIS --> HANDLER["ApiResponseHandler<br>DelegatingHandler"]
    HANDLER --> ROUTE["Attribute routing<br>MapHttpAttributeRoutes"]
    ROUTE --> CTRL["Controller : ApiController"]
    CTRL --> FACTORY["PdfServiceFactory.Create()<br>reads pdfapi.pdfservicetype"]
    FACTORY --> SVC["SyncfusionPdfService<br>or ActivePdfService"]
    SVC --> TRACK["PdfTrackingService"]
    TRACK --> UOW["NHibernate IUnitOfWork<br>IUnitOfWorkFactory(&quot;oracle&quot;)"]
    UOW --> DB["Oracle IMG schema"]
    SVC --> CORE["PdfAPI.Core / PdfApi.SyncFusionCore<br>format operations"]

Layer responsibilities

Layer	Type	Responsibility
WebApiApplication	System.Web.HttpApplication	Application start-up and configuration wiring
PdfAPI\App_Start\WebApiConfig.cs	Configuration	Message handler, formatter, route, and error-detail-policy configuration
ConvertController, ExtractController, MergeController, LegacyController, InfoController, ApiInfoController	System.Web.Http.ApiController	Request binding and delegation to the service layer; four of six controllers add per-action try/catch error handling
PdfServiceFactory / PdfService (abstract) / SyncfusionPdfService / ActivePdfService	Service layer	Selects and executes the PDF processor, coordinates tracking and incident email
PdfTrackingService	NHibernate	Persistence through IUnitOfWork against the Oracle IMG schema — the sole data-access component in the repository

Routing configuration

Aspect	Finding
MapHttpAttributeRoutes() called	Yes
Convention route templates	api/{controller}/{id} (DefaultApi, id optional) — registered but matched by no live action, because every action carries [Route]*
Route prefix / versioning	[RoutePrefix("v1")] (ConvertController, ExtractController, MergeController), [RoutePrefix("v1/legacy")] (LegacyController), [RoutePrefix("v1/info")] (InfoController); ApiInfoController has no [RoutePrefix]
Controller folder layout	All six controllers live in PdfAPI\Controllers\v1\; the folder name contributes nothing to the URL — only [RoutePrefix]/[Route] values do

Base controller

Every controller declares System.Web.Http.ApiController directly. There is no repository-local base controller (no ApiBase-style type), so no shared response construction, logging, or identity resolution is contributed by inheritance.

Controller	Base	Inherited behavior
ConvertController, ExtractController, MergeController, LegacyController, InfoController, ApiInfoController	ApiController	—

Composition root

Composition root location, as actually found in this repository: PdfAPI\App_Start\IocConfig.cs — the file name carries a lowercase c (IocConfig.cs), while the class it declares is IoCConfig with public static void RegisterDependencies(ContainerBuilder builder). This path was discovered behaviorally, not by filename convention: the Autofac API surface (new Autofac.ContainerBuilder(), builder.Build(), AutofacDependencyResolver, AutofacWebApiDependencyResolver, RegisterCommonDependencies() was searched across the whole solution closure and traced back from PdfAPI\Global.asax.cs → Application_Start. No Autofac.Module subclass, no RegisterAssemblyTypes, and no separate *.Dependencies or SAIF.DependencyMaps.* project exists in this repository.

Field	Value
Project	PdfAPI
File	PdfAPI\App_Start\IocConfig.cs
Entry method	IoCConfig.RegisterDependencies(ContainerBuilder)
Invoked from	PdfAPI\Global.asax.cs → Application_Start (after RegisterControllers/RegisterApiControllers, before builder.Build())
Resolver	Both AutofacDependencyResolver (MVC) and AutofacWebApiDependencyResolver (Web API) are assigned in Global.asax.cs
Autofac version	Not read from packages.config in this analysis pass — see Dependencies for package versions
Additional registration files	None

The container is built across PdfAPI\Global.asax.cs and PdfAPI\App_Start\IocConfig.cs together: Global.asax.cs creates the ContainerBuilder, registers MVC and Web API controllers by assembly scan, calls IoCConfig.RegisterDependencies(builder), builds the container, and assigns both dependency resolvers. IocConfig.cs calls builder.RegisterCommonDependencies(typeof(HttpApplication)) (from SAIF.Web.Mvc.Extensions) to supply ILogService, IEnvironmentService, and the named IUnitOfWorkFactory("oracle"), then layers on the two application-specific registrations below.

Registration	Lifetime	Resolved by	Purpose
builder.RegisterCommonDependencies(typeof(HttpApplication))	Determined inside the extension method — not visible in this repository**	All controllers and services	Supplies ILogService, IEnvironmentService, and IUnitOfWorkFactory("oracle")
IUnitOfWork (lambda over IUnitOfWorkFactory("oracle").GetUnitOfWork(DbConnectionManager.GetOracleConnectionString(IEnvironmentService, EnvironmentConfigKeys.OracleDatabase, "IMG")))	InstancePerRequest	PdfServiceFactory, PdfService, PdfTrackingService	NHibernate unit of work for the Oracle IMG schema
PdfServiceFactory (concrete type, no interface)	InstancePerRequest	ConvertController, ExtractController, MergeController, LegacyController, InfoController	Selects and constructs the PDF processor per request

IPdfService is not registered with Autofac; controllers receive PdfServiceFactory and call .Create() themselves, so the concrete processor is selected per request at runtime rather than by container configuration (BR-PDFAPI-003).

Error handling

Three mechanisms co-exist in this repository; they are not interchangeable, and one does not apply to API endpoints at all.

Mechanism	Registered in	Scope	Behavior
ApiResponseHandler (DelegatingHandler, package SAIF.Web.API)	config.MessageHandlers.Add(new ApiResponseHandler()); in PdfAPI\App_Start\WebApiConfig.cs	Global — every Web API request/response, including framework-produced failures	Wraps/post-processes the HTTP response for the whole service; the exact envelope shape is implemented inside the SAIF.Web.API package and is not visible in this repository**
Per-action try/catch + ILogService.LogException	ConvertController (both actions), ExtractController, MergeController, LegacyController	Per-action (5 of 13 endpoints)	The action swallows the exception, logs it, and returns Ok(new PdfResult("<message>", request)) — HTTP 200 with Status = Failed
MVC HandleErrorAttribute	filters.Add(new HandleErrorAttribute()); in PdfAPI\App_Start\FilterConfig.cs	MVC controllers only (GlobalFilters.Filters) — has no effect on any ApiController action	Not part of the API error contract

config.Filters is never populated — there is no Web API ExceptionFilterAttribute, no IExceptionHandler, and no IExceptionLogger. config.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.Always; applies in every environment, so an unhandled exception produces full framework exception detail (message, type, stack trace) before the response reaches ApiResponseHandler. That handler's final wrapping/post-processing and the actual client-visible envelope are not visible in this repository** (see Endpoints: Error response shape). InfoController (7 endpoints) and ApiInfoController (1 endpoint) have no try/catch, so their validation failures surface as framework errors rather than as a PdfResult.

API documentation surface

Aspect	Finding
Swagger / Swashbuckle	Active — via [assembly: PreApplicationStartMethod(typeof(SwaggerConfig), "Register")] in PdfAPI\App_Start\SwaggerConfig.cs; there is no explicit SwaggerConfig.Register() call in Application_Start
Exposed route	Not determined from source** — SwaggerConfig.Register() calls EnableSwagger(c => c.SingleApiVersion("v1", "PdfAPI")).EnableSwaggerUi(), with no custom RootUrl configured
Package and version	Swashbuckle / Swashbuckle.Core 5.3.2, WebActivatorEx 2.0

Telemetry

Aspect	Finding
Instrumentation	None found — a search for ConfigureOpenTelemetry( across the solution closure returned zero matches
Registered in	—

The only observability in force is logging through ILogService (LogException, TraceError, TraceWarn, TraceDebug) plus log4net 2.0.5, and a stray Console.WriteLine(result.ToString()) at the end of SyncfusionPdfService.FinalizeResult (see Tech debt).

Design constraints

• The NHibernate unit of work is scoped InstancePerRequest, so the transaction boundary for tracking writes is the HTTP request, not the business operation.
• PdfTrackingService is the sole data-access component; every controller and service reaches the database only through it.
• IncludeErrorDetailPolicy.Always produces framework exception detail before ApiResponseHandler runs, in every environment; the final client-visible envelope is unknown** (see Endpoints: Error response shape) — this is a design constraint with security implications regardless (see Tech debt).

Integration points

System	Type	Purpose
Oracle IMG schema	Database	Tracking record persistence for convert/merge requests
ActivePDF server (UNC working directory)	Downstream service	Alternate PDF processor, selected by pdfapi.pdfservicetype == "activepdf"
SMTP (mail.saif.com)	Downstream service	Failure incident email sent from PdfService.SendIncidentEmail

Related documentation

• API index
• Overview
• Endpoints
• Authentication and authorization
• Dependencies
• Configuration
• Operations and processes
• Business rules
• Data model
• Operational runbook
• Tech debt

Note: Statements marked with * were inferred from code structure, naming conventions, or contextual evidence where direct confirmation was not available in source artifacts. Statements marked with ** could not be confirmed; treat as unknown until verified.

Sources

• PdfAPI\Global.asax.cs
• PdfAPI\App_Start\WebApiConfig.cs
• PdfAPI\App_Start\IocConfig.cs
• PdfAPI\App_Start\SwaggerConfig.cs
• PdfAPI\App_Start\FilterConfig.cs
• PdfAPI\Services\PdfServiceFactory.cs
• PdfAPI\Services\PdfService.cs
• PdfAPI\Services\PdfTrackingService.cs
• PdfAPI\Services\Syncfusion\SyncfusionPdfService.cs
• PdfAPI\Services\ActivePdf\ActivePdfService.cs