Hangfire 1.5.5

Why?

Simple to use
Can be used in any type of .net application e.g. asp.net, win service, console etc
No need for windows scheduler
Mgmt and visibility of jobs via the library and dash board
Can monitor, review, re-run and track all background jobs
Will log start/complete job time
Will fire background job multiple times if it doesn't complete ok
Stores job definition in database
Only marks job as complete when last line of job has been execute ok
Background job can be simple (i.e. the job instruction and job execution are run in under teh same app) or distributed (i.e the job is run under another app)
e.g. WebAPI executes the job instruction to save the job definition to the database
e.g. Win Service executes the actual job
Removes ASP.NET issues e.g. running background threads can pose issues, multiple instances might fire job more than once, app domin and app pool recycling
Open source free to use for commercial use

Hangfire Jobs

Fire and forget jobs (one off jobs)
Delay jobs (fires after a delay)
Reocurring jobs (fires on a schedule)
Continuation jobs (fire after parent jobs)
Batch jobs (fires a batch of jobs)
Batch continuations (fires after a batch of jobs has completed)

Hangfire Architeture

Hangfire client (creates jobs)
Hangfire server (runs jobs)
Hangfire job storage (stores jobs)

Installing and Running Hangfire

Installing Hangfire using Nuget:

-- Installs; HangfireCore, Hangfire, HangfireSqlServer

Configuring Hangfire:

-- If using OWIN copy the Hangfire startup code from readme.txt to Startup.cs

-- If not using OWIN copy the Hangfire startup code from readme.txt to Global.asax

-- Also add using Hangfire; statement

-- What is the start up code:

--- GlobalConfiguration.Configuration is an extension method to tell hangfire the database connection name or database connection string to the Hangfire database

--- You need to create an empty Hangfire database, so when Hangfire starts up it will automatically create the database objects and required data

--- app.UseHangfireDashboard() starts up the dash board

--- app.UseHangfireServer() starts up the server that will get and run the jobs

--- Access the Hangfire dash board by the root url/hangfire

Coding a background job:

-- e.g. BackgroundJob.Enqueue(() => _service.DoSomething(entity.Id));

Hangfire Integration

Single process; run hangire client and server within same app
Web garden; multiple instances of simple process apps. The same jobs won't picked up)
Web farm; Web garden on multiple servers
Seperate service; hangfire client in seperate app from Hangfire sever (note that both apps need access background jobs code/project)
Seperate server; Serate service on different servers

Hangfire Pro Features

Batch jobs and chaining batch jobs is a pro feature
Allows complex workflows i.e. multiple continuations
Supports Redis storage
Allows windows performance counters to be used

Hangfire Background Jobs

Fire-and-forget (i.e. Enqueued job):

(starts a job straight away)

-- BackgroundJob.Enqueue()

--- The fire-and-forget enqueue method takes a lambda expression and store it as json in the Hangfire database

--- It serialises the method and parameter(s) into json

--- Creates a background job record/definition in the Hangfire database and queue

--- Returns to the caller immediately

Delayed (i.e. Scheduled job):

(starts a job later)

-- BackgroundJob.Schedule()

--- Specify using lambda and TimeSpan

--- Hangfire server queues scheduled jobs

--- If running hangfire Server in ASP.NET then configure to always run in IIS

Recurring (i.e. Recurring job):

(adds or updates a reocurring job)

-- AddOrUpdate() to create or update a recurring job

--- Specify by passing a job identifier, lambda expression and CRON type or expression

-- RemoveIfExists() to remove a job

--- Pass a job id

-- Trigger() to trigger a reocurring job immediately without impacting existign schedule

--- Specify by passing a job id

-- Stores a reocurring job to storage and checks every minute to see if it needs to run the job

Using batches

(is for hangfire Pro only, is a different Nuget package i.e. Hangfire.Pro)

-- BatchJob.StartNew()

--- Need to specific Configuration.Usebatches() in config

See pluralsight course and code for more info on batch jobs

Chainging batches

See pluralsight course and code

Complex workflows

See pluralsight course and code

Passing parameters

-- Supports passing of multiple parameters

-- Parameters are serialised (array, collections, custom objects)

-- Serialisation of parameters allows process boundaries to be passed

-- Reference parameters (i.e. pointers to memory locations) not supported. Ref and out not supported

-- It is more efficient to pass concrete vales e.g. ids rather than complex objects e.g. entity

-- The background job thread needs access to the parameter types to deserialize the json objects to .NET objects

Passing Dependancies

(How to pass dependant objects)

-- The JobActivator creates an instance using the default constructor

-- Can have a constructor for passing in instances for unit testing

-- Hangfire has extension packages for IoC (StructureMap wasn't listed need to check)

-- Dependancies must be instantiated using the default constructor or you must have a means of injecting those dependancies in

-- Hangfire.StructureMap NuGet package exists

Hangfire Dashboard

Is written as OWIN middleware
Can be hosted in console app or windows service
Requires:

-- Microsoft.Owin.Host.SystemWeb

-- OWIN startup class

-- app.UseHangfireDashboard()

Hangfire Dashboard Features

Servers

-- Shows number of worker threads available

-- Can configure server to use a number of threads

-- Shows queues the server is listening to

-- Can configure server to look at specific queues

Jobs
Retries

-- Default retries is 10 times

-- If backgroundjob throws an exception then it fails and will be retried

Recurring
Scheduled
Failed

-- After 10 job failures the job will be listed here

Awaiting

-- Are continuation jobs waiting on other jobs to complete

Succeeded

-- Can requeue a job to run again

Hangfire dashboard Configuration

Use app.UseHangfireDashboard(...) and pass DashboardOptions object to change config settings below

Creating a link
Changing the URL
Changing 'Back to site' link
Multiple dashboards

Pass a different SqlServerStorage(..) object to UseHangfireDashboard(..) to set multiple Hangfire sql server databases and dash boards

Logging

Supports Log4Net
Provides automatic logging
Can use ILogProvider and ILog for custom logging

Unit Testing

Provides IBackgroundJobClient to mock background jobs

Job Filters

Can be used to intercept events e.g. start/status of jobs
Inhereit from JobFilterAttribute and and interface e.g. IApplyStateFilter, IClientFilter, IElectStateFilter, IServerFilter, IEventsLogsFilter etc