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  • Rails, Rake, moving a folder to a new location

    - by Sam
    I need to move a folder from a plugin to the main app/views. I guess using rake to do this with the following command is the easiest way: require 'fileutils' FileUtils.mv('/vendor/plugins/easy_addresses/lib/app/views', '/app/views/') I'm just not sure where to tell script where to look and where to place the folder. The file I want to move is in the following location: `vender/plugins/easy_addresses/lib/app/views/easy_addresses easy_ addresses is the name of the folder in views that I want to move to my_app/app/views/

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  • Windows scheduled task not running

    - by Ravi Kumar Singh
    I have several SQL server backups on a server. I have created a batch file which then copies these to network drives. These are mapped to the server, and it works properly. Now, I've created a scheduled task to do this. If I select "run the task when logged in", I can test the task. It works fine. However I cannot test it with the other option "run task if logged in or not". I've read that testing this task is not possible manually. However the task runs when we log off the server automatically.

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  • Why is Windows Task Scheduler trying to launch multiple instances?

    - by Paul H
    We have a number of Windows Scheduled tasks that run on one Server 2008 Webserver (not R2) which is in a cluster. We recently moved from an original webserver Cluster to a new webserver Cluser (Server 2008 - not R2). The new webserver (in the cluster) running the Windows Tasks is setup the same as on the original we believe. BUT we now find that on the new Windows Server the Windows Task Scheduler seems to want to instantly start each task three times. If we set the option to queue up a new task we get: Event ID 324 Task Scheduler queued instance "{9a1a8411-b042-45ff-8e6b-89874df230d7}" of task "\Client Reporting" and will launch it as soon as instance "{2bcc3df6-ea3b-4453-90c2-75b8b1946388}" completes. If we set the option to stop an existing task we get: Event ID 323 Task Scheduler stopped instance "{e685a910-b32b-414e-85fd-96bbe54314a2}" of task "\Client Reporting" in order to launch new instance "{4db66265-1f51-4ede-8535-ac7c3cb5c4c1}" . Ticked settings: Allow task to be run on demand. Run task as soon as possible after a scheduled start is missed. Stop the task if running for longer than 1 hour. If the running task does not end when requested force it to stop. Start the task only if the computer is on AC power. Stop the task if the computer switches to battery power. Selected option: If the task is already running - stop the existing instance. Note: We moved the tasks from one server to another in the cluster to see if it the Task Scheduler on the particular server we'd picked causing the problem. Same behaviour. Could it be something to do with the build of the new servers? We have very similar tasks set up on another server cluster that work OK without all this multiple starting. Comparing those tasks to the ones here - there does not seem to be anything obviously different in terms of settings available to us through the options within the Task Scheduler. Trigger: The task is scheduled to be triggered daily, once an hour - and to be stopped if it exceeds this time. Action: Runs a .bat file. What could be causing this/where we can look to see what logic is causing the tasks to start multiple times in this way?

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  • task scheduler - run interactively as any user with admin credentials

    - by Force Flow
    I'm trying to deploy a scheduled task with a GPO. The task is set to run at login and executes a batch file, which then executes an EXE file. However, I also need it to be interactive and run with admin privledges to bypass the UAC prompt for a username and password when the exe file runs. I created the task for "Vista and later". I've tried running the task as mydoman\administrator and as NT AUTHORITY\Authenticated users with "run only when user is logged in" and "run with highest privledges" selected. If I log in as anyone but administrator, the task does run in the background, as I can see the cmd.exe process running in task manager as mydomain\administrator. Only if I log in as administrator do I then see the cmd window with the batch script running. How can I get the cmd window to display no matter which user logs in?

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  • Windows Task Scheduler won't let me uncheck "Wake the computer" option for a backup task

    - by KdawgUD
    I have a problem with my windows 7 laptop automatically waking after I put it to sleep and then I find it later with the battery drained. I tracked down the culprit using the "powercfg -lastwake" command to be a Backup task in the "Windows Server" section of the task scheduler. I have tried unchecking the "Wake the computer to run this task" checkbox for this task, but after I do this and reboot, the box is always rechecked again. How can I make this setting persist? I have full admin rights to this laptop, but it is on a domain. Edit: I looked into the domain policy settings as suggested by Dave below and did not find any policies related to scheduled task settings. Any other ideas?

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  • Unique task queue task names only for active duration

    - by antony.trupe
    I want to guarantee that a task is not in a task queue more then once, so I generate a unique name based on it's payload. But, that task name is reserved for up to 7 days, which is not what I want; I only want it reserved for the duration the task is queued; it could be immediately re-queued. Once a Task with name N is written, any subsequent attempts to insert a Task named N will fail. Eventually (at least seven days after the task successfully executes), the task will be deleted and the name N can be reused. Is there a way to check if the named task is already in the queue then add it if it's not? Or a totally different approach?

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  • Task ownership with Wordpress - CSS - Designer or Developer?

    - by Syed Absar
    We have a dispute regarding who owns which tasks when it comes to the CSS on our live site. Our designer argues that he is not responsible to log-in to word press and modify the css or use ftp for any changes because that's not his job description while developer argues that since it is css, it belongs to designer and that he is to update the changes to the server and then compare and correct the output. I'd like experienced people working in professional development environment to put a light on this scenario. I'm not sure if this is the right place to ask this question, or is there a separate forum for business development or project management specific questions?

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  • Process runs slower as a scheduled task than it does interactively

    - by Charlie
    I have a scheduled task which is very CPU- and IO-intensive, and takes about four hours to run (building source code, if you're curious). The task is a Powershell script which spawns various sub-processes to do its work. When I run the same process interactively from a Powershell prompt, as the same user account, it runs in about two and a half hours. The task is running on Windows Server 2008 R2. What I want to know is why it takes so much longer to run as a scheduled task - more than an hour longer. One thing I noticed is that the task scheduler runs at Below-Normal priority, so when my task starts, it inherits the same lowered priority. However, I've updated the script to set the Powershell process priority back to Normal, and it still takes just as long. Anybody have an idea what could be different between the two scenarios? I've ruled out differences in processor and IO load - this task is the only thing the system is used for, so there's nothing else running that could be competing for resources.

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  • What does this rake db:seed error mean?

    - by Kenji Kina
    I've been trying to solve this problem for a couple of hours but I can't seem to understand what's going on. I'm using Rails 3 beta, and want to seed some data to the database. However, when I try to seed some values through db:seed, I get this error: rake aborted! Attribute(#81402440) expected, got Array(#69024170) The seeds.rb is: DataType.delete_all DataType.create( :name => 'String' ) And I got these classes: class DataType < ActiveRecord::Base has_many :attributes end class Attribute < ActiveRecord::Base belongs_to :data_types end While the migration definition for DataType is merely: class CreateDataTypes < ActiveRecord::Migration def self.up create_table :data_types do |t| t.string :name t.timestamps end end def self.down drop_table :data_types end end Can anyone tell me what I'm doing wrong?

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  • legitimacy of the tasks in the task scheduler

    - by Eyad
    Is there a way to know the source and legitimacy of the tasks in the task scheduler in windows server 2008 and 2003? Can I check if the task was added by Microsoft (ie: from sccm) or by a 3rd party application? For each task in the task scheduler, I want to verify that the task has not been created by a third party application. I only want to allow standards Microsoft Tasks and disable all other non-standards tasks. I have created a PowerShell script that goes through all the xml files in the C:\Windows\System32\Tasks directory and I was able to read all the xml task files successfully but I am stuck on how to validate the tasks. Here is the script for your reference: Function TaskSniper() { #Getting all the fils in the Tasks folder $files = Get-ChildItem "C:\Windows\System32\Tasks" -Recurse | Where-Object {!$_.PSIsContainer}; [Xml] $StandardXmlFile = Get-Content "Edit Me"; foreach($file in $files) { #constructing the file path $path = $file.DirectoryName + "\" + $file.Name #reading the file as an XML doc [Xml] $xmlFile = Get-Content $path #DS SEE: http://social.technet.microsoft.com/Forums/en-US/w7itprogeneral/thread/caa8422f-6397-4510-ba6e-e28f2d2ee0d2/ #(get-authenticodesignature C:\Windows\System32\appidpolicyconverter.exe).status -eq "valid" #Display something $xmlFile.Task.Settings.Hidden } } Thank you

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  • How can I make Ruby rake display the full backtrace on uncaught exception

    - by Martinos
    As you may know rake swallows the full backtrace on uncaught exception. If I want to have a full backtrace, I need to add the --trace option. I find this very annoying because some of my tasks take long time to run (up to 6 hours), when it crashes I don't have any debugging info. I need to run it again with the --trace. On top of that, the system may not be in the same state as when the error occurred, so it may not show afterward. I always have to add --trace on any tasks. This displasy stuff that I don't want to see when the task is executed. Is there a way to change this default behaviour? (which I don't think is useful at all)

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  • rake db:create gives some problem when used from limited account

    - by Xinxua
    I am using mysql 5.1 and mysql gems version is 2.73 This is giving the following error message when I try to run it from a limited account in my XP. If try it using the admin account, it works fine. I think this is wierd because it cannot be the problem of mysql gem. (in F:/Temp/wassup) !!! The bundled mysql.rb driver has been removed from Rails 2.2. Please install the mysql gem and try again: gem install mysql. rake aborted! 5: Access is denied. - C:/Program Files/Ruby/lib/ruby/gems/1.8/gems/mysql-2.7. 3-x86-mswin32/ext/mysql.so (See full trace by running task with --trace) I need to work from the limited account. Can anyone let me know why is this happening?

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  • Recursive wildcards in Rake?

    - by Roger Lipscombe
    Follow up to this question about GNU make: I've got a directory, flac, containing .FLAC files. I've got a corresponding directory, mp3 containing MP3 files. If a FLAC file is newer than the corresponding MP3 file (or the corresponding MP3 file doesn't exist), then I want to run a bunch of commands to convert the FLAC file to an MP3 file, and copy the tags across. The kicker: I need to search the flac directory recursively, and create corresponding subdirectories in the mp3 directory. The directories and files can have spaces in the names, and are named in UTF-8. It turns out that this won't work in make, because of the spaces in the directories and filenames, so I'm wondering how to do it in rake instead...

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  • Task Scheduler permissions error for some jobs

    - by MaseBase
    I have recently moved to a 64-bit Windows Server 2008 R2. I setup my Scheduled Tasks to run under one user (TaskUser) specifically created for the scheduler and most run just fine. However some of them do not run under TaskUser but will for my own credentials. Here is the Event Log entry I found, which from my research points me to believe that it doesn't have permissions, but it does. It also has the option "Run with highest privileges" checked on. I have seen this particular checkbox work wonders on some tasks, but I have a number of them that it's not helping for. The error is ERROR_ELEVATION_REQUIRED but the user is a member of the administrators group and has folder/file permission and is set to "Run with highest privileges" Log Name: Microsoft-Windows-UAC/Operational Source: Microsoft-Windows-UAC Date: 4/27/2010 2:21:44 PM Event ID: 1 Task Category: (1) Level: Error Keywords: User: LIVE\TaskUser Computer: www2 Description: The process failed to handle ERROR_ELEVATION_REQUIRED during the creation of a child process. Event Xml: <Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event"> <System> <Provider Name="Microsoft-Windows-UAC" Guid="{E7558269-3FA5-46ED-9F4D-3C6E282DDE55}" /> <EventID>1</EventID> <Version>0</Version> <Level>2</Level> <Task>1</Task> <Opcode>0</Opcode> <Keywords>0x8000000000000000</Keywords> <TimeCreated SystemTime="2010-04-27T21:21:44.407053800Z" /> <EventRecordID>19</EventRecordID> <Correlation /> <Execution ProcessID="2460" ThreadID="5960" /> <Channel>Microsoft-Windows-UAC/Operational</Channel> <Computer>www2</Computer> <Security UserID="S-1-5-21-4017510424-2083581016-1307463562-1640" /> </System> <EventData></EventData> </Event> The errors shown in the Task Scheduler History tab display these results and states This operation requires an interactive window station. (0x800705B3) EventID 103 Task Scheduler failed to launch action "F:\App\Path\ConsoleApp.exe" in instance "{1a6d3450-b85a-40c0-b3db-72b98c1aa395}" of task "\taskFolder\taskName". Additional Data: Error Value: 2147943859. EventID 203 Task Scheduler failed to start instance "{1a6d3450-b85a-40c0-b3db-72b98c1aa395}" of "\taskFolder\taskName" task for user "LIVE\TaskUser" . Additional Data: Error Value: 2147943859.

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  • Parallelism in .NET – Part 18, Task Continuations with Multiple Tasks

    - by Reed
    In my introduction to Task continuations I demonstrated how the Task class provides a more expressive alternative to traditional callbacks.  Task continuations provide a much cleaner syntax to traditional callbacks, but there are other reasons to switch to using continuations… Task continuations provide a clean syntax, and a very simple, elegant means of synchronizing asynchronous method results with the user interface.  In addition, continuations provide a very simple, elegant means of working with collections of tasks. Prior to .NET 4, working with multiple related asynchronous method calls was very tricky.  If, for example, we wanted to run two asynchronous operations, followed by a single method call which we wanted to run when the first two methods completed, we’d have to program all of the handling ourselves.  We would likely need to take some approach such as using a shared callback which synchronized against a common variable, or using a WaitHandle shared within the callbacks to allow one to wait for the second.  Although this could be accomplished easily enough, it requires manually placing this handling into every algorithm which requires this form of blocking.  This is error prone, difficult, and can easily lead to subtle bugs. Similar to how the Task class static methods providing a way to block until multiple tasks have completed, TaskFactory contains static methods which allow a continuation to be scheduled upon the completion of multiple tasks: TaskFactory.ContinueWhenAll. This allows you to easily specify a single delegate to run when a collection of tasks has completed.  For example, suppose we have a class which fetches data from the network.  This can be a long running operation, and potentially fail in certain situations, such as a server being down.  As a result, we have three separate servers which we will “query” for our information.  Now, suppose we want to grab data from all three servers, and verify that the results are the same from all three. With traditional asynchronous programming in .NET, this would require using three separate callbacks, and managing the synchronization between the various operations ourselves.  The Task and TaskFactory classes simplify this for us, allowing us to write: var server1 = Task.Factory.StartNew( () => networkClass.GetResults(firstServer) ); var server2 = Task.Factory.StartNew( () => networkClass.GetResults(secondServer) ); var server3 = Task.Factory.StartNew( () => networkClass.GetResults(thirdServer) ); var result = Task.Factory.ContinueWhenAll( new[] {server1, server2, server3 }, (tasks) => { // Propogate exceptions (see below) Task.WaitAll(tasks); return this.CompareTaskResults( tasks[0].Result, tasks[1].Result, tasks[2].Result); }); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This is clean, simple, and elegant.  The one complication is the Task.WaitAll(tasks); statement. Although the continuation will not complete until all three tasks (server1, server2, and server3) have completed, there is a potential snag.  If the networkClass.GetResults method fails, and raises an exception, we want to make sure to handle it cleanly.  By using Task.WaitAll, any exceptions raised within any of our original tasks will get wrapped into a single AggregateException by the WaitAll method, providing us a simplified means of handling the exceptions.  If we wait on the continuation, we can trap this AggregateException, and handle it cleanly.  Without this line, it’s possible that an exception could remain uncaught and unhandled by a task, which later might trigger a nasty UnobservedTaskException.  This would happen any time two of our original tasks failed. Just as we can schedule a continuation to occur when an entire collection of tasks has completed, we can just as easily setup a continuation to run when any single task within a collection completes.  If, for example, we didn’t need to compare the results of all three network locations, but only use one, we could still schedule three tasks.  We could then have our completion logic work on the first task which completed, and ignore the others.  This is done via TaskFactory.ContinueWhenAny: var server1 = Task.Factory.StartNew( () => networkClass.GetResults(firstServer) ); var server2 = Task.Factory.StartNew( () => networkClass.GetResults(secondServer) ); var server3 = Task.Factory.StartNew( () => networkClass.GetResults(thirdServer) ); var result = Task.Factory.ContinueWhenAny( new[] {server1, server2, server3 }, (firstTask) => { return this.ProcessTaskResult(firstTask.Result); }); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, instead of working with all three tasks, we’re just using the first task which finishes.  This is very useful, as it allows us to easily work with results of multiple operations, and “throw away” the others.  However, you must take care when using ContinueWhenAny to properly handle exceptions.  At some point, you should always wait on each task (or use the Task.Result property) in order to propogate any exceptions raised from within the task.  Failing to do so can lead to an UnobservedTaskException.

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  • Task Scheduler Disable Google Updater Error

    - by muntoo
    Whenever I try to disable GoogleUpdateTaskUser in Vista using Task Scheduler, I get the following: --------------------------- Task Scheduler --------------------------- Not enough quota is available to process this command.GoogleUpdateTaskMachineUA --------------------------- OK --------------------------- After clicking OK: --------------------------- Task Scheduler --------------------------- This task could not be modified as requested. --------------------------- OK --------------------------- I tried this with all the "GoogleUpdate" stuff you can see in the picture below. Any ideas? THIS confirms it should work.

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  • Creating a task that runs at incorrect login credentials

    - by GDA
    I'm trying to set up a personalized security option on my computer to take a picture using the webcam whenever someone tries to log onto my computer using an incorrect password. I've set up the task in the task scheduler, and I can get it to pass, but then the problem begins. When the task passes, it triggers like a million times and keeps going until I disable the task. Does anybody know why it might be doing that and how to make it not?

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  • Adding Mysql Columns in Rails Rake

    - by Gigg
    I have a rake file that does a series of calculations on a database. Basically it adds usage on equipment regularly. At the end of the day it needs to add that days total to a monthly total table and update that same table. i use the following simple concepts: To get data from the database is pretty simple: @usages = Usage.find(:all) time = Time.new for usage in @usages sql = ActiveRecord::Base.connection To insert it into the database: sql.execute "INSERT (or UPDATE) into usages ## add values and options as per MySQL But how do I: take a column from a database, add all of its values together that have a common value in another column, (i.e. if column x == value y) and then insert it into another column in another table, say dailyusages? I have tried these options: task (:monthly => :environment) do @dailyusages = Dailyusage.find(:all) for dailyusage in @dailyusages sql = ActiveRecord::Base.connection time = Time.new device = monthlyusages.device month = time.month if device == dailyusages.device ##&& month == dailyusages.month total = (dailyusage.total.sum.to_i) @monthlyusages = Monthlyusage.find(:all) for monthlyusage in @monthlyusages sql = ActiveRecord::Base.connection old_total = monthlyusage.total.to_i new_total = (old_total + total) sql.execute "UPDATE monthlyusages ( year, month, total, device ) values('#{time.year}', '#{time.month}', '#{total}', '#{dailyusage.device}' )" end I obviously have uncommented options and tried all sorts of things. Any help would really save me a load of trouble. Thanks in advance. (** BTW - I am new to rails, so go easy on me **)

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  • Albacore msbuild task problem

    - by Dejan
    Just updated albacore to version 0.14 and ran into a major problem. My current environment is: Ruby 1.9.1 Rake 0.8.7 Albacore 0.1.4 The problem is that as of now all my rake build throw a funny little exception: undefined method 'push' for #<Enumerator:0x???????> So far I have traced the problem to albacore msbuild.rb line 38 and 26. To be honest I just don't have a clue why this is happening. As a little help here is the rake task that is turning my hear Grey :) desc "Build solution" msbuild :build => :prepareOutput do |msb| msb.properties :configuration => :Release msb.targets :Clean, :Build msb.solution = "../xxx/xxx/xxx.sln" end

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  • "The user account does not have permission to run this task"

    - by Ken
    I'm trying to get a scheduled task to run on Windows Server 2008. It has been working fine for months, and then hung, so I killed it, and now I can't get it to start. (In case it's not obvious, I'm not a Windows sysadmin by any stretch of the imagination. I inherited responsibility for this system, more or less.) The error it gives is: "The user account does not have permission to run this task". The task's "author" is "A". The task's "When running the task, use the following user account:" is "B". And my user is "C". All of A, B, C are members of the Administrators group, so I'm a bit puzzled as to why it thinks I don't have permissions to run this. Ideas?

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  • Windows XP Task Management: no execution

    - by Ice09
    Hi, we used the following scenario sucessfully over a long period of time: Remotely log onto a Win XP server, which is used by one user most/all of time Schedule a task using the "task planner" Task was run at "almost" each scheduled point of time (seldom it did not start, presumably when someone else was logged in). For some time now, we share the server with several users. Even though I checked an option for running independently of the logged in user, this option does not seem to work. Now, the task is seldom executed, not seldom not executed. Now, the question is: is there some other option I can't see which disables the execution OR, even better, is there some other tool which we can use for task scheduling on Win XP servers with several different users?

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  • Understanding C# async / await (2) Awaitable / Awaiter Pattern

    - by Dixin
    What is awaitable Part 1 shows that any Task is awaitable. Actually there are other awaitable types. Here is an example: Task<int> task = new Task<int>(() => 0); int result = await task.ConfigureAwait(false); // Returns a ConfiguredTaskAwaitable<TResult>. The returned ConfiguredTaskAwaitable<TResult> struct is awaitable. And it is not Task at all: public struct ConfiguredTaskAwaitable<TResult> { private readonly ConfiguredTaskAwaiter m_configuredTaskAwaiter; internal ConfiguredTaskAwaitable(Task<TResult> task, bool continueOnCapturedContext) { this.m_configuredTaskAwaiter = new ConfiguredTaskAwaiter(task, continueOnCapturedContext); } public ConfiguredTaskAwaiter GetAwaiter() { return this.m_configuredTaskAwaiter; } } It has one GetAwaiter() method. Actually in part 1 we have seen that Task has GetAwaiter() method too: public class Task { public TaskAwaiter GetAwaiter() { return new TaskAwaiter(this); } } public class Task<TResult> : Task { public new TaskAwaiter<TResult> GetAwaiter() { return new TaskAwaiter<TResult>(this); } } Task.Yield() is a another example: await Task.Yield(); // Returns a YieldAwaitable. The returned YieldAwaitable is not Task either: public struct YieldAwaitable { public YieldAwaiter GetAwaiter() { return default(YieldAwaiter); } } Again, it just has one GetAwaiter() method. In this article, we will look at what is awaitable. The awaitable / awaiter pattern By observing different awaitable / awaiter types, we can tell that an object is awaitable if It has a GetAwaiter() method (instance method or extension method); Its GetAwaiter() method returns an awaiter. An object is an awaiter if: It implements INotifyCompletion or ICriticalNotifyCompletion interface; It has an IsCompleted, which has a getter and returns a Boolean; it has a GetResult() method, which returns void, or a result. This awaitable / awaiter pattern is very similar to the iteratable / iterator pattern. Here is the interface definitions of iteratable / iterator: public interface IEnumerable { IEnumerator GetEnumerator(); } public interface IEnumerator { object Current { get; } bool MoveNext(); void Reset(); } public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IDisposable, IEnumerator { T Current { get; } } In case you are not familiar with the out keyword, please find out the explanation in Understanding C# Covariance And Contravariance (2) Interfaces. The “missing” IAwaitable / IAwaiter interfaces Similar to IEnumerable and IEnumerator interfaces, awaitable / awaiter can be visualized by IAwaitable / IAwaiter interfaces too. This is the non-generic version: public interface IAwaitable { IAwaiter GetAwaiter(); } public interface IAwaiter : INotifyCompletion // or ICriticalNotifyCompletion { // INotifyCompletion has one method: void OnCompleted(Action continuation); // ICriticalNotifyCompletion implements INotifyCompletion, // also has this method: void UnsafeOnCompleted(Action continuation); bool IsCompleted { get; } void GetResult(); } Please notice GetResult() returns void here. Task.GetAwaiter() / TaskAwaiter.GetResult() is of such case. And this is the generic version: public interface IAwaitable<out TResult> { IAwaiter<TResult> GetAwaiter(); } public interface IAwaiter<out TResult> : INotifyCompletion // or ICriticalNotifyCompletion { bool IsCompleted { get; } TResult GetResult(); } Here the only difference is, GetResult() return a result. Task<TResult>.GetAwaiter() / TaskAwaiter<TResult>.GetResult() is of this case. Please notice .NET does not define these IAwaitable / IAwaiter interfaces at all. As an UI designer, I guess the reason is, IAwaitable interface will constraint GetAwaiter() to be instance method. Actually C# supports both GetAwaiter() instance method and GetAwaiter() extension method. Here I use these interfaces only for better visualizing what is awaitable / awaiter. Now, if looking at above ConfiguredTaskAwaitable / ConfiguredTaskAwaiter, YieldAwaitable / YieldAwaiter, Task / TaskAwaiter pairs again, they all “implicitly” implement these “missing” IAwaitable / IAwaiter interfaces. In the next part, we will see how to implement awaitable / awaiter. Await any function / action In C# await cannot be used with lambda. This code: int result = await (() => 0); will cause a compiler error: Cannot await 'lambda expression' This is easy to understand because this lambda expression (() => 0) may be a function or a expression tree. Obviously we mean function here, and we can tell compiler in this way: int result = await new Func<int>(() => 0); It causes an different error: Cannot await 'System.Func<int>' OK, now the compiler is complaining the type instead of syntax. With the understanding of the awaitable / awaiter pattern, Func<TResult> type can be easily made into awaitable. GetAwaiter() instance method, using IAwaitable / IAwaiter interfaces First, similar to above ConfiguredTaskAwaitable<TResult>, a FuncAwaitable<TResult> can be implemented to wrap Func<TResult>: internal struct FuncAwaitable<TResult> : IAwaitable<TResult> { private readonly Func<TResult> function; public FuncAwaitable(Func<TResult> function) { this.function = function; } public IAwaiter<TResult> GetAwaiter() { return new FuncAwaiter<TResult>(this.function); } } FuncAwaitable<TResult> wrapper is used to implement IAwaitable<TResult>, so it has one instance method, GetAwaiter(), which returns a IAwaiter<TResult>, which wraps that Func<TResult> too. FuncAwaiter<TResult> is used to implement IAwaiter<TResult>: public struct FuncAwaiter<TResult> : IAwaiter<TResult> { private readonly Task<TResult> task; public FuncAwaiter(Func<TResult> function) { this.task = new Task<TResult>(function); this.task.Start(); } bool IAwaiter<TResult>.IsCompleted { get { return this.task.IsCompleted; } } TResult IAwaiter<TResult>.GetResult() { return this.task.Result; } void INotifyCompletion.OnCompleted(Action continuation) { new Task(continuation).Start(); } } Now a function can be awaited in this way: int result = await new FuncAwaitable<int>(() => 0); GetAwaiter() extension method As IAwaitable shows, all that an awaitable needs is just a GetAwaiter() method. In above code, FuncAwaitable<TResult> is created as a wrapper of Func<TResult> and implements IAwaitable<TResult>, so that there is a  GetAwaiter() instance method. If a GetAwaiter() extension method  can be defined for Func<TResult>, then FuncAwaitable<TResult> is no longer needed: public static class FuncExtensions { public static IAwaiter<TResult> GetAwaiter<TResult>(this Func<TResult> function) { return new FuncAwaiter<TResult>(function); } } So a Func<TResult> function can be directly awaited: int result = await new Func<int>(() => 0); Using the existing awaitable / awaiter - Task / TaskAwaiter Remember the most frequently used awaitable / awaiter - Task / TaskAwaiter. With Task / TaskAwaiter, FuncAwaitable / FuncAwaiter are no longer needed: public static class FuncExtensions { public static TaskAwaiter<TResult> GetAwaiter<TResult>(this Func<TResult> function) { Task<TResult> task = new Task<TResult>(function); task.Start(); return task.GetAwaiter(); // Returns a TaskAwaiter<TResult>. } } Similarly, with this extension method: public static class ActionExtensions { public static TaskAwaiter GetAwaiter(this Action action) { Task task = new Task(action); task.Start(); return task.GetAwaiter(); // Returns a TaskAwaiter. } } an action can be awaited as well: await new Action(() => { }); Now any function / action can be awaited: await new Action(() => HelperMethods.IO()); // or: await new Action(HelperMethods.IO); If function / action has parameter(s), closure can be used: int arg0 = 0; int arg1 = 1; int result = await new Action(() => HelperMethods.IO(arg0, arg1)); Using Task.Run() The above code is used to demonstrate how awaitable / awaiter can be implemented. Because it is a common scenario to await a function / action, so .NET provides a built-in API: Task.Run(): public class Task2 { public static Task Run(Action action) { // The implementation is similar to: Task task = new Task(action); task.Start(); return task; } public static Task<TResult> Run<TResult>(Func<TResult> function) { // The implementation is similar to: Task<TResult> task = new Task<TResult>(function); task.Start(); return task; } } In reality, this is how we await a function: int result = await Task.Run(() => HelperMethods.IO(arg0, arg1)); and await a action: await Task.Run(() => HelperMethods.IO());

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  • How do I start IRB console from a rake task?

    - by Michael Lang
    I'm trying to write a rake task that will set up an environment mirroring my project. task :environment do require 'rubygems' require 'sequel' # require 'my_projects_special_files' end task :foo => [:environment] do require 'irb' IRB.start end Leads to irb complaining that "foo" doesn't exist (the name of the task) 10:28:01:irb_test rake foo --trace (in /Users/mwlang/projects/personal/rake/irb_test) ** Invoke foo (first_time) ** Invoke environment (first_time) ** Execute environment ** Execute foo rake aborted! No such file or directory - foo /opt/local/lib/ruby/1.8/irb/input-method.rb:68:in `initialize' /opt/local/lib/ruby/1.8/irb/input-method.rb:68:in `open' /opt/local/lib/ruby/1.8/irb/input-method.rb:68:in `initialize' /opt/local/lib/ruby/1.8/irb/context.rb:80:in `new' /opt/local/lib/ruby/1.8/irb/context.rb:80:in `initialize' /opt/local/lib/ruby/1.8/irb.rb:92:in `new' /opt/local/lib/ruby/1.8/irb.rb:92:in `initialize' /opt/local/lib/ruby/1.8/irb.rb:57:in `new' /opt/local/lib/ruby/1.8/irb.rb:57:in `start' /Users/mwlang/projects/personal/rake/irb_test/Rakefile:9

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  • How to call a Thor task multiple times?

    - by deepak
    Thor like Rake (and Make) has task management. If I call a task multiple times, it will effectively call the task only once. How can I call a task multiple times? I tried modifying the @_invocations hash, but that did not work: require 'csv' require './config/environment' class MisReport < Thor desc "all", "generate mysql and postgres mis" def all generate("pg_mis_report", "pg") generate("mysql_mis_report", "mysql") end desc "generate", "generate mis report" def generate(file_name = "mis_report_#{Time.now.to_s(:number)}", connection = "postgres") if connection == "pg" puts "== postgres database" ActiveRecord::Base.establish_connection :development_mysql else puts "== mysql database" ActiveRecord::Base.establish_connection :development end # generate MIS puts puts "mis file is at: #{file_path}" end end

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