Databases
StackOverflow2013
Postsdbo
PORe-factor a ThreadPool.QueueUserWorkItem to Task Parallel Library
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PORe-factor a ThreadPool.QueueUserWorkItem to Task Parallel Library
    primarykey
    data
    text
    <p>Trying to re-factor a ThreadPool.QueueUserWorkItem to TPL and to be honest I don't know either very well (yet). </p> <p>In real life this will be an I/O operation. Query to Azure Table Storage on the PartitionKey so it should parallel effectively.</p> <p>See the method GetAllTPL() as it has the simple TPL I wrote. It passes this very simple test case. Is the TPL wrong and I just don't know it? Can I do that better? Anything that might make this simple test case fail when it is an actual Table query? </p> <p>ThreadPool.QueueUserWorkItem and TPL both produce the same correct answer for this very limited test case. Put stopwatch on a bigger (but still simplified) test case and TPL is just short of twice as fast as ThreadPool.QueueUserWorkItem. TPL seems to queue up in groups of 3 and ThreadPool.QueueUserWorkItem in groups of 2 running on just a P4 with hyper threading. Since thread.sleep is not real work that does not tell me a lot.</p> <p>The ThreadPool.QueueUserWorkItem is from a .NET 3.5 code sample (pre TPL). I am pretty sure TPL has a better option but I am new to TPL. Thanks</p> <pre><code>using System.Threading; using System.Threading.Tasks; namespace WaitForConsole { class Program { static void Main(string[] args) { string[] partitionKey = new string[] { "one", "two", "three", "four" }; IEnumerable&lt;string&gt; commonRowKeys = GetAllQWI(partitionKey); foreach (string commonRowKey in commonRowKeys) Console.WriteLine(commonRowKey); Console.ReadLine(); commonRowKeys = GetAllTPL(partitionKey); foreach (string commonRowKey in commonRowKeys) Console.WriteLine(commonRowKey); Console.ReadLine(); } public static IEnumerable&lt;string&gt; GetAllQWI(string[] partitionKey) { // this a a code sample from .NET 3.5 and it runs on 4.0 IEnumerable&lt;string&gt; finalResults = null; ManualResetEvent[] resetEvents = new ManualResetEvent[partitionKey.Length]; HashSet&lt;string&gt;[] rowKeys = new HashSet&lt;string&gt;[partitionKey.Length]; for (int i = 0; i &lt; rowKeys.Length; i++) { resetEvents[i] = new ManualResetEvent(false); ThreadPool.QueueUserWorkItem(new WaitCallback((object index) =&gt; { Console.WriteLine("GetAllQWI " + ((int)index).ToString()); rowKeys[(int)index] = TableQueryGetRowKeys(partitionKey[(int)index]); resetEvents[(int)index].Set(); }), i); } try { WaitHandle.WaitAll(resetEvents); Console.WriteLine("WaitAll done"); finalResults = (IEnumerable&lt;string&gt;)rowKeys[0]; foreach (var thisRowKeys in rowKeys) { finalResults = finalResults.Intersect(thisRowKeys); } } catch (Exception ex) { Console.WriteLine("WaitAll ex " + ex.Message); } return finalResults; } public static IEnumerable&lt;string&gt; GetAllTPL(string[] partitionKey) { // this is the conversion of the ThreadPool.QueueUserWorkItem to TPL // seems to be working but is this optimal IEnumerable&lt;string&gt; finalResults = null; HashSet&lt;string&gt;[] rowKeys = new HashSet&lt;string&gt;[partitionKey.Length]; // how to do this in TPL Parallel.For(0, partitionKey.Length, i =&gt; { Console.WriteLine("GetAllTPL " + i.ToString()); rowKeys[i] = TableQueryGetRowKeys(partitionKey[i]); }); // Do I need to do anything special to wait for all the tasks to finish? // Interesting that i is not necessarily in order but it does not need to be finalResults = (IEnumerable&lt;string&gt;)rowKeys[0]; foreach (var thisRowKeys in rowKeys) { finalResults = finalResults.Intersect(thisRowKeys); } return finalResults; } public static HashSet&lt;string&gt; TableQueryGetRowKeys(string partitionKey) { // in real life this is an Azure table query to get all rowKeys for a partitionKey Thread.Sleep(10000); if (DateTime.Now.Millisecond % 2 == 0) { return new HashSet&lt;string&gt; { "alph", "beta", "gamma", "delta" }; } else { return new HashSet&lt;string&gt; { "beta", "gamma", "delta", "epsilon" }; } } } } </code></pre> <p>Spent several hours to get this far. If TPL will do this then I will learn more about TPL and not learn ThreadPool.QueueUserWorkItem. It kind of scares me the TPL was so simple. Just want to check that I am not missing something. I got this TPL from a compute intensive sample. </p> <p>One post on SO about irregular results with TPL and Azure but in the end could not reproduce. <a href="https://stackoverflow.com/questions/3664083/can-parallel-foreach-be-used-safely-with-cloudtablequery">Can Parallel.ForEach be used safely with CloudTableQuery</a> </p> <p>Another post from the Azure team states TPL and Azure is OK <a href="https://stackoverflow.com/questions/3056628/windows-azure-parallelization-of-the-code">Windows Azure: Parallelization of the code</a></p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USCommunity
    1. USpaparazzo
    plurals
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PORe-factor a ThreadPool.QueueUserWorkItem to Task Parallel Library
      1. This table or related slice is empty.
      1. VTUpMod
    1. COHow do you expect to refactor code that you don't understand into new code that you don't understand? Even if we refactor it for you, how will you maintain it?
      singulars
      1. PORe-factor a ThreadPool.QueueUserWorkItem to Task Parallel Library
      1. USRobert Harvey
    2. CO@RobertHarvey Almost every question on SO is from someone that has zero to partial knowledge. This is not production code and I don't expect SO to maintain production code.
      singulars
      1. PORe-factor a ThreadPool.QueueUserWorkItem to Task Parallel Library
      1. USpaparazzo
    3. CO`Almost every question on SO is from someone that has zero to partial knowledge` -- That statement is demonstrably false. We expect people to come here with *some* knowledge. If you're asking from a framework of zero knowledge, your best approach is to read up on ThreadPool and the TPL, and then ask a question here if you get stuck.
      singulars
      1. PORe-factor a ThreadPool.QueueUserWorkItem to Task Parallel Library
      1. USRobert Harvey
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload