NET library of activities and adding custom activities for other kinds of functionality. A Visual Studio tool called Workflow Designer helps visualize these workflows. Techopedia Explains Windows Workflow Foundation WF In Microsoft's "Guide to the Windows Workflow Documentation," the company explains that scalability and the ability to handle big workloads are paramount for server applications.
However, it is also critical to create a code base that is user-friendly and easy to maintain. Microsoft points out that approaches to scalability sometimes create complicated logic structures. Windows Workflow Foundation was created to allow creating more versatile, unified and scalable applications.
For example, Microsoft suggests creating unified applications that run on a single process to understand the value of scalable logic. Tutorials are available to help first-time users in creating custom applications in a step-by-step manner and in using the other important functions of the Windows Workflow Foundation.
Share this Term. Web Collaboration Elastic Computing. Tech moves fast! Q: How would I use the. NET routing service in AppFabric? NET routing service system. Q: How does the scale-out solutions offered by Windows Azure and the Microsoft.
How do I choose one or another? Because new or enhanced applications for both Strata and AppFabric are built using the Visual Studio development environment and the. NET Framework, this provides customers with the choice of building applications either on premises, in the cloud, or hybrid solutions offering the best of both worlds.
In the meantime, by building upon consistent programming models in. NET and using the breadth of interoperability found in the platform, this will enable you great flexibility and the power of choice in the future. AppFabric represents an evolutionary step in our vision towards providing frameworks, runtimes and tools that make it easier to build scalable applications by default. In the meantime, the more you apply the principles of scalability in writing applications today, the easier it will be for them to run on both the first version of AppFabric and on subsequent releases.
How does it relate to persistence provider scale-out? That feature exists to enable retries to recover from network errors, SQL failover and other recoverable errors like occasional deadlocks. This is not related to scale-out in any way. The WF4 workflow above uses Comment activities. The Comment activity was described in the Component-level Performance Comparisons section earlier in this article.
One of the clear trends to notice in this graph is that nesting has relatively minimal impact on memory usage in both WF3 and WF4. The most significant memory impact comes from the number of activities in a given workflow. Given the data from the sequence , complex depth 5 sequence 5, and complex depth 7 sequence 1 variations, it is clear that as the number of activities enters the thousands, the memory usage increase becomes more noticeable.
Measuring memory per workflow definition is divided into two different tests because of the available options for hosting workflows in WF3 and WF4. The tests are run in a different manner than the workflow complexity test in that a given workflow is instanced and executed only once per definition.
This is because the workflow definition and its host remain in memory for the lifetime of the AppDomain. The memory used by running a given workflow instance should be cleaned up during garbage collection. The migration guidance for WF4 contains more detailed information on the hosting options.
Creating many workflow definitions for a workflow definition test can be done in several ways. For instance, one could use code generation to create a set of workflows that are identical except in name and save each of those workflows into separate files.
This approach was taken for the console-hosted test. In WF3, the WorkflowRuntime class was used to run the workflow definitions.
WF4 can either use WorkflowApplication to create a single workflow instance or directly use WorkflowInvoker to run the activity as if it were a method call. WorkflowApplication is a host of a single workflow instance and has closer feature parity to WorkflowRuntime so that was used in this test.
The VirtualPathProvider handles the incoming request and responds with a "virtual file" that can be loaded from a database or, in this case, generated on the fly. It is therefore unnecessary to create physical files. The workflow definitions used in the console test were simple sequential workflows with a single activity.
The IIS-hosted case used workflows that start on receiving a message and end on sending a reply:. The following table shows the delta in working set between a single workflow definition and definitions:. Hosting workflow definitions in IIS consumes much more memory due to the WorkflowServiceHost , detailed WCF service artifacts, and the message processing logic associated with the host.
The XAML is stored as an embedded resource in the assembly and compiled during runtime to provide the implementation of the workflow. There is some overhead associated with this process. An example of one of the WF4 workflows is shown below:. There are many other factors that can affect memory consumption. The same advice for all managed programs still applies. In IIS-hosted environments, the WorkflowServiceHost object created for a workflow definition stays in memory until the application pool is recycled.
This should be kept in mind when writing extensions. Also, it is best to avoid "global" variables variables scoped to the whole workflow and limit the scope of variables wherever possible. The WF3 SQL persistence provider is a simple implementation that serializes the workflow instance and stores it in a blob. For this reason, the performance of this provider depends heavily on the size of the workflow instance.
In WF3, the instance size could increase for many reasons, as is discussed previously in this paper. Many customers choose not to use the default SQL persistence provider because storing a serialized instance in a database gives no visibility into the state of the workflow.
In order to find a particular workflow without knowing the workflow id, one would have to deserialize each persisted instance and examine the contents. Many developers prefer to write their own persistence providers to overcome this obstacle. The persistence tables expose certain information such as the active bookmarks and promotable properties. The new content-based correlation feature in WF4 would not perform well using the WF3 SQL persistence approach, which has driven some change in the organization of the persisted workflow instance.
This makes the job of the persistence provider more complex and puts extra stress on the database. Even with an improved feature set and better concurrency handling, the SQL persistence provider in WF4 is faster than the provider in WF3. To showcase this, two workflows that perform essentially the same operations in WF3 and WF4 are compared below. The two workflows are both created by a received message. After sending an initial reply, the workflow is persisted.
The same could be achieved in WF3 by marking an activity as "persist on close. The workflows are persisted but not unloaded. The TCP transport increases that factor to 3. The reason that WF4 throughput is greater is due to the faster workflow runtime.
The size of the serialized instance is low for both cases and is not a major contributing element in this situation. Both the WF3 and WF4 workflows in this test use an activity to explicitly indicate when persistence should occur. This has the benefit of persisting the workflow without unloading it. In WF3, it is also possible to persist using the TimeToUnload feature, but this unloads the workflow instance from memory. If a developer using WF3 wants to make sure a workflow persists at certain points, they either have to alter the workflow definition or pay the cost for unloading and re-loading the workflow instance.
This feature allows the workflow instance to be persisted on idle but stay in memory until the TimeToUnload threshold is met or execution is resumed. Be sure to include the following performance counters from the SQL database when performance testing workflow applications:. Workflow tracking can be used to track the progress of a workflow.
The information that is included in the tracking events is determined by a tracking profile. The more complex the tracking profile, the more expensive tracking becomes. WF3 shipped with a SQL-based tracking service. This service could work in batched and non-batched modes.
In non-batched mode, tracking events are written directly to the database. In batched mode, tracking events are collected into the same batch as the workflow instance state. The batched mode has the best performance for the widest range of workflow designs.
However, batching can have a negative performance impact if the workflow runs many activities without persisting and those activities are tracked. This would commonly happen in loops and the best way to avoid this scenario is to design large loops to contain a persistence point. Introducing a persistence point into a loop can negatively affect performance as well so it is important to measure the costs of each and come up with a balance.
WF4 is not shipped with a SQL tracking service. Recording tracking information to a SQL database can be handled better from an application server rather than built into the. ETW is a kernel-level, low-latency event system built into Windows. In addition to kernel events such as processor, disk, memory, and network usage, many applications leverage ETW as well.
ETW events are more powerful than performance counters in that events can be customized to the application. An event can contain text such as a workflow ID or an informational message. Also, events are categorized with bitmasks so that consuming a certain subset of events will have less performance impact than capturing all events.
Collection of tracking events can be separated to another process. This gives greater flexibility in how the events are recorded. The performance benefits to ETW tracking come with a drawback. ETW events can be lost if the system is under intense resource pressure.
The processing of events is not meant to block normal program execution and therefore it is not guaranteed that all ETW events will be broadcast to their subscribers. This makes ETW tracking great for health monitoring but not suitable for auditing.
A separate job drains the data from this table and reforms it into reporting tables that can be viewed on the AppFabric dashboard. This means that a batch of tracking events is handled independent of the workflow it came from and therefore does not have to wait for a persistence point before being recorded.
ETW events can be recorded with tools such as logman or xperf. The compact ETL file can be viewed with a tool like xperfview or converted to a more readable format, such as XML, with tracerpt.
In WF3, the only option for getting tracking events without a SQL database is to create a custom tracking service. Enabling workflow tracking will impact performance in varying degrees. The basic tracking profile, also used in AppFabric, is shown in this benchmark.
Also included is the cost of tracking only health monitoring events. These events are useful for troubleshooting problems and determining the average throughput of the system. Many customers that adopted Windows Workflow Foundation early will have in-house or third-party workflow definitions and custom activities for WF3. It is recommended that the Interop activity only be used when necessary. The following table shows the results of running a workflow containing five activities in a sequence in various configurations.
There is a notable performance increase to using Interop over straight WF3. However, when compared against WF4 activities, the increase is negligible. Heavy investments in performance for WF4 have paid off in many crucial areas. Individual workflow component performance is in some cases hundreds of times faster in WF4 compared to WF3 due to a leaner WF runtime. Latency numbers are significantly better as well. This means the performance penalty for using WF as opposed to hand-coding WCF orchestration services is very small considering the added benefits of using WF.
Health monitoring by means of workflow tracking now has very little overhead.
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