Cleanest way to write retry logic

Question

Occasionally I have a need to retry an operation several times before giving up   My code is like   int retries   3  while true      try       DoSomething        break     success      catch       if --retries    0  throw      else Thread Sleep 1000           I would like to rewrite this in a general retry function like   TryThreeTimes DoSomething     Is it possible in C    What would be the code for the TryThreeTimes   method

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I m a fan of recursion and extension methods  so here are my two cents   public static void InvokeWithRetries this Action  this  ushort numberOfRetries        try                this              catch               if  numberOfRetries    0              throw           InvokeWithRetries  this  --numberOfRetries

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Use Polly  https   github com App-vNext Polly-Samples  Here is a retry-generic I use with Polly  public T Retry lt T gt  Func lt T gt  action  int retryCount   0        PolicyResult lt T gt  policyResult   Policy       Handle lt Exception gt          Retry retryCount        ExecuteAndCapture lt T gt  action        if  policyResult Outcome    OutcomeType Failure                throw policyResult FinalException             return policyResult Result      Use it like this  var result   Retry      gt  MyFunction     3

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For those who want to have both the option to retry on any exception or explicitly set the exception type  use this    public class RetryManager        public void Do Action action                       TimeSpan interval                       int retries   3                Try lt object  Exception gt       gt                action                return null             interval  retries              public T Do lt T gt  Func lt T gt  action                       TimeSpan interval                       int retries   3                return Try lt T  Exception gt                 action               interval               retries              public T Do lt E  T gt  Func lt T gt  action                          TimeSpan interval                          int retries   3  where E   Exception               return Try lt T  E gt                 action               interval               retries              public void Do lt E gt  Action action                          TimeSpan interval                          int retries   3  where E   Exception               Try lt object  E gt       gt                action                return null             interval  retries              private T Try lt T  E gt  Func lt T gt  action                          TimeSpan interval                          int retries   3  where E   Exception               var exceptions   new List lt E gt              for  int retry   0  retry  lt  retries  retry                          try                               if  retry  gt  0                      Thread Sleep interval                   return action                              catch  E ex                                exceptions Add ex                                    throw new AggregateException exceptions

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Update after 6 years  now I consider that the approach below is pretty bad  To create a retry logic we should consider to use a library like Polly     My async implementation of the retry method   public static async Task lt T gt  DoAsync lt T gt  Func lt dynamic gt  action  TimeSpan retryInterval  int retryCount   3                var exceptions   new List lt Exception gt              for  int retry   0  retry  lt  retryCount  retry                          try                               return await action   ConfigureAwait false                             catch  Exception ex                                exceptions Add ex                              await Task Delay retryInterval  ConfigureAwait false                     throw new AggregateException exceptions           Key points  I used  ConfigureAwait false   and Func lt dynamic gt  instead Func lt T gt

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Building on the previous work  I thought about enhancing the retry logic in three ways    Specifying what exception type to catch retry   This is the primary enhacement as retrying for any exception is just plain wrong   Not nesting the last try in a try catch  achieving slightly better performance Making it an Action extension method  static class ActionExtensions     public static void InvokeAndRetryOnException lt T gt   this Action action  int retries  TimeSpan retryDelay  where T   Exception         if  action    null        throw new ArgumentNullException  action         while  retries--  gt  0               try                 action             return                catch  T                  Thread Sleep  retryDelay                       action              The method can then be invoked like so  anonymous methods can be used as well  of course    new Action  AMethodThatMightThrowIntermittentException      InvokeAndRetryOnException lt IntermittentException gt   2  TimeSpan FromSeconds  1

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This is possibly a bad idea  First  it is emblematic of the maxim  the definition of insanity is doing the same thing twice and expecting different results each time   Second  this coding pattern does not compose well with itself  For example   Suppose your network hardware layer resends a packet three times on failure  waiting  say  a second between failures    Now suppose the software layer resends an notification about a failure three times on packet failure   Now suppose the notification layer reactivates the notification three times on an notification delivery failure   Now suppose the error reporting layer reactivates the notification layer three times on a notification failure   And now suppose the web server reactivates the error reporting three times on error failure   And now suppose the web client resends the request three times upon getting an error from the server   Now suppose the line on the network switch that is supposed to route the notification to the administrator is unplugged  When does the user of the web client finally get their error message   I make it at about twelve minutes later    Lest you think this is just a silly example  we have seen this bug in customer code  though far  far worse than I ve described here  In the particular customer code  the gap between the error condition happening and it finally being reported to the user was several weeks because so many layers were automatically retrying with waits  Just imagine what would happen if there were ten retries instead of three   Usually the right thing to do with an error condition is report it immediately and let the user decide what to do   If the user wants to create a policy of automatic retries  let them create that policy at the appropriate level in the software abstraction

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The Transient Fault Handling Application Block provides an extensible collection of retry strategies including    Incremental   Fixed interval  Exponential back-off   It also includes a collection of error detection strategies for cloud-based services   For more information see this chapter of the Developer s Guide   Available via NuGet  search for  topaz

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Exponential backoff is a good retry strategy than simply trying  x number of times   You can use a library like Polly to implement it

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I d implement this   public static bool Retry int maxRetries  Func lt bool  bool gt  method        while  maxRetries  gt  0                if  method maxRetries    1                         return true                    maxRetries--            return false              I wouldn t use exceptions the way they re used in the other examples   It seems to me that if we re expecting the possibility that a method won t succeed  its failure isn t an exception   So the method I m calling should return true if it succeeded  and false if it failed   Why is it a Func lt bool  bool gt  and not just a Func lt bool gt    So that if I want a method to be able to throw an exception on failure  I have a way of informing it that this is the last try     So I might use it with code like   Retry 5  delegate bool lastIteration                 do stuff        if   succeeded  amp  amp  lastIteration                     throw new InvalidOperationException                      return succeeded           or  if   Retry 5  delegate bool lastIteration                 do stuff        return succeeded              Console WriteLine  Well  that didn t work         If passing a parameter that the method doesn t use proves to be awkward  it s trivial to implement an overload of Retry that just takes a Func lt bool gt  as well

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I had the need to pass some parameter to my method to retry  and have a result value  so i need an expression   I build up this class that does the work  it is inspired to the the LBushkin s one  you can use it like this    static void Main string   args           one shot     var res   Retry lt string gt  Do      gt  retryThis  try    4  TimeSpan FromSeconds 2   fix           delayed execute     var retry   new Retry lt string gt       gt  retryThis  try    4  TimeSpan FromSeconds 2   fix       var res2   retry Execute       static void fix         Console WriteLine  oh  no  Fix and retry          static string retryThis string tryThis        Console WriteLine  Let s try           throw new Exception tryThis      public class Retry lt TResult gt        Expression lt Func lt TResult gt  gt   Method      int  NumRetries      TimeSpan  RetryTimeout      Action  OnFailureAction       public Retry Expression lt Func lt TResult gt  gt  method  int numRetries  TimeSpan retryTimeout  Action onFailureAction                 Method   method           NumRetries   numRetries           OnFailureAction   onFailureAction           RetryTimeout   retryTimeout             public TResult Execute                 TResult result   default TResult           while   NumRetries  gt  0                        try                               result    Method Compile                      break                            catch                                OnFailureAction                     NumRetries--                  if   NumRetries  lt   0  throw     improved to avoid silent failure                 Thread Sleep  RetryTimeout                                   return result             public static TResult Do Expression lt Func lt TResult gt  gt  method  int numRetries  TimeSpan retryTimeout  Action onFailureAction                var retry   new Retry lt TResult gt  method  numRetries  retryTimeout  onFailureAction           return retry Execute              ps  the LBushkin s solution does one more retry  D

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Allowing for functions and retry messages  public static T RetryMethod lt T gt  Func lt T gt  method  int numRetries  int retryTimeout  Action onFailureAction     Guard IsNotNull method   method                 T retval   default T    do       try           retval   method         return retval          catch           onFailureAction          if  numRetries  lt   0  throw     improved to avoid silent failure       Thread Sleep retryTimeout          while  numRetries--  gt  0     return retval

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I would add the following code to the accepted answer  public static class Retry lt TException gt  where TException   Exception   ability to pass the exception type                 same code as the accepted answer               public static T Do lt T gt  Func lt T gt  action  TimeSpan retryInterval  int retryCount   3                        var exceptions   new List lt Exception gt                  for  int retry   0  retry  lt  retryCount  retry                                  try                                       return action                                      catch  TException ex    Usage of the exception type                                       exceptions Add ex                       Thread Sleep retryInterval                                                throw new AggregateException String Format  Failed to excecute after  0  attempt s    retryCount   exceptions                     Basically the above code is making the Retry class generic so you can pass the type of the exception you want to catch for retry   Now use it almost in the same way but specifying the exception type  Retry lt EndpointNotFoundException gt  Do      gt  SomeFunctionThatCanFail    TimeSpan FromSeconds 1

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I know this answer is very old but I just wanted to comment on this because I have run into issues using these while  do  whatever statement with counters    Over the years I have settled on a better approach I think  That is to use some sort of event aggregation like a reactive extensions  Subject  or the like  When a try fails  you simply publish an event saying the try failed  and have the aggregator function re-schedule the event  This allows you much more control over the retry without polluting the call itself with a bunch of retry loops and what not  Nor are you tying up a single thread with a bunch of thread sleeps

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public void TryThreeTimes Action action        var tries   3      while  true            try               action                break     success            catch               if  --tries    0                  throw              Thread Sleep 1000                       Then you would call   TryThreeTimes DoSomething        or alternatively     TryThreeTimes      gt  DoSomethingElse withLocalVariable        A more flexible option   public void DoWithRetry Action action  TimeSpan sleepPeriod  int tryCount   3        if  tryCount  lt   0          throw new ArgumentOutOfRangeException nameof tryCount         while  true            try               action                break     success            catch               if  --tryCount    0                  throw              Thread Sleep sleepPeriod                      To be used as   DoWithRetry DoSomething  TimeSpan FromSeconds 2   tryCount  10       A more modern version with support for async await   public async Task DoWithRetryAsync Func lt Task gt  action  TimeSpan sleepPeriod  int tryCount   3        if  tryCount  lt   0          throw new ArgumentOutOfRangeException nameof tryCount         while  true            try               await action                return     success            catch               if  --tryCount    0                  throw              await Task Delay sleepPeriod                      To be used as   await DoWithRetryAsync DoSomethingAsync  TimeSpan FromSeconds 2   tryCount  10

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Keep it simple with C  6 0  public async Task lt T gt  Retry lt T gt  Func lt T gt  action  TimeSpan retryInterval  int retryCount        try               return action              catch when  retryCount    0                await Task Delay retryInterval           return await Retry action  retryInterval  --retryCount

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I needed a method that supports cancellation  while I was at it  I added support for returning intermediate failures   public static class ThreadUtils       public static RetryResult Retry          Action target          CancellationToken cancellationToken          int timeout   5000          int retries   0                CheckRetryParameters timeout  retries          var failures   new List lt Exception gt             while  cancellationToken IsCancellationRequested                        try                               target                    return new RetryResult failures                             catch  Exception ex                                failures Add ex                              if  retries  gt  0                                retries--                  if  retries    0                                        throw new AggregateException                        Retry limit reached  see InnerExceptions for details                         failures                                                if  cancellationToken WaitHandle WaitOne timeout                                 break                                   failures Add new OperationCancelledException               The Retry Operation was cancelled              throw new AggregateException  Retry was cancelled    failures              private static void CheckRetryParameters int timeout  int retries                if  timeout  lt  1                        throw new ArgumentOutOfRangeException                        if  retries  lt  0                        throw new ArgumentOutOfRangeException                           public class RetryResult   IEnumerable lt Exception gt                private readonly IEnumerable lt Exception gt  failureExceptions          private readonly int failureCount            protected internal RetryResult               ICollection lt Exception gt  failureExceptions                          this failureExceptions   failureExceptions               this failureCount   failureExceptions Count                        public int FailureCount               get   return this failureCount               public IEnumerator lt Exception gt  GetEnumerator                 return this failureExceptions GetEnumerator               System Collections IEnumerator          System Collections IEnumerable GetEnumerator                 return this GetEnumerator              You can use the Retry function like this  retry 3 times with a 10 second delay but without cancellation   try       var result   ThreadUtils Retry          SomeAction           CancellationToken None          10000          3           it worked     result FailureCount    but failed this many times first    catch  AggregationException ex          oops  3 retries wasn t enough      Or  retry eternally every five seconds  unless cancelled   try       var result   ThreadUtils Retry          SomeAction           someTokenSource Token           it worked     result FailureCount    but failed this many times first    catch  AggregationException ex          operation was cancelled before success      As you can guess  In my source code I ve overloaded the Retry function to support the differing delgate types I desire to use

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int retries   3  while  true        try                 Do Somthing         break            catch  Exception ex                if  --retries    0              return Request BadRequest ApiUtil GenerateRequestResponse false   3 Times tried it failed do to       ex Message  new JObject              else             System Threading Thread Sleep 100

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Implemented LBushkin s answer in the latest fashion       public static async Task Do Func lt Task gt  task  TimeSpan retryInterval  int maxAttemptCount   3                var exceptions   new List lt Exception gt             for  int attempted   0  attempted  lt  maxAttemptCount  attempted                          try                               if  attempted  gt  0                                        await Task Delay retryInterval                                      await task                    return                            catch  Exception ex                                exceptions Add ex                                   throw new AggregateException exceptions              public static async Task lt T gt  Do lt T gt  Func lt Task lt T gt  gt  task  TimeSpan retryInterval  int maxAttemptCount   3                var exceptions   new List lt Exception gt             for  int attempted   0  attempted  lt  maxAttemptCount  attempted                          try                               if  attempted  gt  0                                        await Task Delay retryInterval                                     return await task                              catch  Exception ex                                exceptions Add ex                                   throw new AggregateException exceptions             and to use it   await Retry Do  TaskFunction   retryInterval  retryAttempts     whereas the function  TaskFunction  can either be Task lt T gt  or just Task

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This method allows retries on certain exception types  throws others immediately    public static void DoRetry      List lt Type gt  retryOnExceptionTypes      Action actionToTry      int retryCount   5      int msWaitBeforeEachRety   300        for  var i   0  i  lt  retryCount    i                try                       actionToTry                break                    catch  Exception ex                           Retries exceeded                Throws on last iteration of loop             if  i    retryCount - 1  throw                  Is type retryable              var exceptionType   ex GetType                if   retryOnExceptionTypes Contains exceptionType                                 throw                                Wait before retry             Thread Sleep msWaitBeforeEachRety                     public static void DoRetry      Type retryOnExceptionType      Action actionToTry      int retryCount   5      int msWaitBeforeEachRety   300            gt  DoRetry new List lt Type gt   retryOnExceptionType   actionToTry  retryCount  msWaitBeforeEachRety     Example usage   DoRetry typeof IOException        gt        using  var fs   new FileStream requestedFilePath  FileMode Create  FileAccess Write                 fs Write entryBytes  0  entryBytes Length

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Here s an async await version that aggregates exceptions and supports cancellation        lt seealso href  https   docs microsoft com en-us azure architecture patterns retry   gt  protected static async Task lt T gt  DoWithRetry lt T gt   Func lt Task lt T gt  gt  action  CancellationToken cancelToken  int maxRetries   3         var exceptions   new List lt Exception gt          for   int retries   0   cancelToken IsCancellationRequested  retries             try               return await action   ConfigureAwait  false              catch   Exception ex                 exceptions Add  ex                 if   retries  lt  maxRetries                   await Task Delay  500  cancelToken   ConfigureAwait  false      ease up a bit             else                 throw new AggregateException   Retry limit reached   exceptions                   exceptions Add  new OperationCanceledException  cancelToken          throw new AggregateException   Retry loop was canceled   exceptions

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Or how about doing it a bit neater      int retries   3  while  retries  gt  0      if  DoSomething            retries   0        else         retries--          I believe throwing exceptions should generally be avoided as a mechanism unless your a passing them between boundaries  such as building a library other people can use    Why not just have the DoSomething   command return true if it was successful and false otherwise   EDIT  And this can be encapsulated inside a function like others have suggested as well   Only problem is if you are not writing the DoSomething   function yourself

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public delegate void ThingToTryDeletage     public static void TryNTimes ThingToTryDelegate  int N  int sleepTime       while true             try                 ThingToTryDelegate            catch                if  --N    0  throw            else Thread Sleep time

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Retry helper  a generic java implementation that contains both returnable and void type retries   import java util function Supplier  import org slf4j Logger  import org slf4j LoggerFactory   public class RetryHelper     private static final Logger log   LoggerFactory getLogger RetryHelper class     private int retryWaitInMS    private int maxRetries     public RetryHelper         this retryWaitInMS   300      this maxRetries   3         public RetryHelper int maxRetry        this maxRetries   maxRetry      this retryWaitInMS   300         public RetryHelper int retryWaitInSeconds  int maxRetry        this retryWaitInMS   retryWaitInSeconds      this maxRetries   maxRetry         public  lt T gt  T retryAndReturn Supplier lt T gt  supplier        try         return supplier get          catch  Exception var3          return this retrySupplier supplier                public void retry Runnable runnable        try         runnable run          catch  Exception var3          this retrySupplier    - gt            runnable run            return null                          private  lt T gt  T retrySupplier Supplier lt T gt  supplier        log error  Failed  lt TASK gt   will be retried     this maxRetries     times         int retryCounter   0       while retryCounter  lt  this maxRetries          try           return supplier get            catch  Exception var6              retryCounter          log error   lt TASK gt  failed on retry      retryCounter     of     this maxRetries     with error      var6 getMessage             if  retryCounter  gt   this maxRetries              log error  Max retries exceeded               throw var6                     try             Thread sleep  long this retryWaitInMS             catch  InterruptedException var5              var5 printStackTrace                                 return supplier get           public int getRetryWaitInMS         return this retryWaitInMS         public int getMaxRetries         return this maxRetries           Usage       try         returnValue   new RetryHelper   retryAndReturn    - gt  performSomeTask args            or no return type        new RetryHelper   retry    - gt  mytask args          catch Exception ex         log error e getMessage           throw new CustomException

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Blanket catch statements that simply retry the same call can be dangerous if used as a general exception handling mechanism  Having said that  here s a lambda-based retry wrapper that you can use with any method  I chose to factor the number of retries and the retry timeout out as parameters for a bit more flexibility   public static class Retry       public static void Do          Action action          TimeSpan retryInterval          int maxAttemptCount   3                Do lt object gt       gt                        action                return null             retryInterval  maxAttemptCount              public static T Do lt T gt           Func lt T gt  action          TimeSpan retryInterval          int maxAttemptCount   3                var exceptions   new List lt Exception gt              for  int attempted   0  attempted  lt  maxAttemptCount  attempted                          try                               if  attempted  gt  0                                        Thread Sleep retryInterval                                     return action                              catch  Exception ex                                exceptions Add ex                                   throw new AggregateException exceptions             You can now use this utility method to perform retry logic   Retry Do      gt  SomeFunctionThatCanFail    TimeSpan FromSeconds 1      or   Retry Do SomeFunctionThatCanFail  TimeSpan FromSeconds 1      or   int result   Retry Do SomeFunctionWhichReturnsInt  TimeSpan FromSeconds 1   4     Or you could even make an async overload

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You might also consider adding the exception type you want to retry for   For instance is this a timeout exception you want to retry   A database exception   RetryForExcpetionType DoSomething  typeof TimeoutException   5  1000    public static void RetryForExcpetionType Action action  Type retryOnExceptionType  int numRetries  int retryTimeout        if  action    null          throw new ArgumentNullException  action        if  retryOnExceptionType    null          throw new ArgumentNullException  retryOnExceptionType        while  true                try                       action                return                    catch Exception e                        if  --numRetries  lt   0     retryOnExceptionType IsAssignableFrom e GetType                     throw               if  retryTimeout  gt  0                  System Threading Thread Sleep retryTimeout                       You might also note that all of the other examples have a similar issue with testing for retries    0 and either retry infinity or fail to raise exceptions when given a negative value   Also Sleep -1000  will fail in the catch blocks above   Depends on how  silly  you expect people to be but defensive programming never hurts

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Do it simple in C   Java or other languages     internal class ShouldRetryHandler       private static int RETRIES MAX NUMBER   3      private static int numberTryes       public static bool shouldRetry             var statusRetry   false           if  numberTryes lt  RETRIES MAX NUMBER                numberTryes                statusRetry   true                log msg - gt   retry number    numberTryes                     else               statusRetry   false                log msg - gt   reached retry number limit                      return statusRetry            and use it in your code very simple    void simpleMethod          some code      if ShouldRetryHandler shouldRetry           do some repetitive work               some code             or you can use it in recursive methods   void recursiveMethod          some code      if ShouldRetryHandler shouldRetry         recursiveMethod                  some code

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I ve written a small class based on answers posted here  Hopefully it will help someone  https   github com natenho resiliency  using System  using System Threading        lt summary gt      Classe utilit  ria para suporte a resili  ncia      lt  summary gt  public sealed class Resiliency            lt summary gt          Define o valor padr  o de n  mero de tentativas          lt  summary gt      public static int DefaultRetryCount   get  set              lt summary gt          Define o valor padr  o  em segundos  de tempo de espera entre tentativas          lt  summary gt      public static int DefaultRetryTimeout   get  set              lt summary gt          Inicia a parte est  tica da resili  ncia  com os valores padr  es          lt  summary gt      static Resiliency                 DefaultRetryCount   3          DefaultRetryTimeout   0                  lt summary gt          Executa uma  lt see cref  Action   gt  e tenta novamente DefaultRetryCount vezes  quando for disparada qualquer  lt see cref  Exception   gt            lt  summary gt           lt param name  action  gt A    o a ser realizada lt  param gt           lt remarks gt Executa uma vez e realiza outras DefaultRetryCount tentativas em caso de exce    o  N  o aguarda para realizar novas tentativa  lt  remarks gt      public static void Try Action action                Try lt Exception gt  action  DefaultRetryCount  TimeSpan FromMilliseconds DefaultRetryTimeout   null                   lt summary gt          Executa uma  lt see cref  Action   gt  e tenta novamente determinado n  mero de vezes quando for disparada qualquer  lt see cref  Exception   gt            lt  summary gt           lt param name  action  gt A    o a ser realizada lt  param gt           lt param name  retryCount  gt N  mero de novas tentativas a serem realizadas lt  param gt           lt param name  retryTimeout  gt Tempo de espera antes de cada nova tentativa lt  param gt      public static void Try Action action  int retryCount  TimeSpan retryTimeout                Try lt Exception gt  action  retryCount  retryTimeout  null                   lt summary gt          Executa uma  lt see cref  Action   gt  e tenta novamente determinado n  mero de vezes quando for disparada qualquer  lt see cref  Exception   gt            lt  summary gt           lt param name  action  gt A    o a ser realizada lt  param gt           lt param name  retryCount  gt N  mero de novas tentativas a serem realizadas lt  param gt           lt param name  retryTimeout  gt Tempo de espera antes de cada nova tentativa lt  param gt           lt param name  tryHandler  gt Permitindo manipular os crit  rios para realizar as tentativas lt  param gt      public static void Try Action action  int retryCount  TimeSpan retryTimeout  Action lt ResiliencyTryHandler lt Exception gt  gt  tryHandler                Try lt Exception gt  action  retryCount  retryTimeout  tryHandler                   lt summary gt          Executa uma  lt see cref  Action   gt  e tenta novamente por at   DefaultRetryCount vezes quando for disparada qualquer  lt see cref  Exception   gt            lt  summary gt           lt param name  action  gt A    o a ser realizada lt  param gt           lt param name  tryHandler  gt Permitindo manipular os crit  rios para realizar as tentativas lt  param gt           lt remarks gt Executa uma vez e realiza outras DefaultRetryCount tentativas em caso de exce    o  Aguarda DefaultRetryTimeout segundos antes de realizar nova tentativa  lt  remarks gt      public static void Try Action action  Action lt ResiliencyTryHandler lt Exception gt  gt  tryHandler                Try lt Exception gt  action  DefaultRetryCount  TimeSpan FromSeconds DefaultRetryTimeout   null                   lt summary gt          Executa uma  lt see cref  Action   gt  e tenta novamente determinado n  mero de vezes quando for disparada qualquer  lt see cref  TException   gt            lt  summary gt           lt param name  action  gt A    o a ser realizada lt  param gt           lt remarks gt Executa uma vez e realiza outras DefaultRetryCount tentativas em caso de exce    o  Aguarda DefaultRetryTimeout segundos antes de realizar nova tentativa  lt  remarks gt      public static void Try lt TException gt  Action action  where TException   Exception               Try lt TException gt  action  DefaultRetryCount  TimeSpan FromSeconds DefaultRetryTimeout   null                   lt summary gt          Executa uma  lt see cref  Action   gt  e tenta novamente determinado n  mero de vezes quando for disparada qualquer  lt see cref  TException   gt            lt  summary gt           lt param name  action  gt A    o a ser realizada lt  param gt           lt param name  retryCount  gt  lt  param gt      public static void Try lt TException gt  Action action  int retryCount  where TException   Exception               Try lt TException gt  action  retryCount  TimeSpan FromSeconds DefaultRetryTimeout   null                   lt summary gt          Executa uma  lt see cref  Action   gt  e tenta novamente determinado n  mero de vezes quando for disparada qualquer  lt see cref  Exception   gt            lt  summary gt           lt param name  action  gt A    o a ser realizada lt  param gt           lt param name  retryCount  gt  lt  param gt           lt param name  retryTimeout  gt  lt  param gt      public static void Try lt TException gt  Action action  int retryCount  TimeSpan retryTimeout  where TException   Exception               Try lt TException gt  action  retryCount  retryTimeout  null                   lt summary gt          Executa uma  lt see cref  Action   gt  e tenta novamente determinado n  mero de vezes quando for disparada qualquer  lt see cref  Exception   gt            lt  summary gt           lt param name  action  gt A    o a ser realizada lt  param gt           lt param name  tryHandler  gt Permitindo manipular os crit  rios para realizar as tentativas lt  param gt           lt remarks gt Executa uma vez e realiza outras DefaultRetryCount tentativas em caso de exce    o  Aguarda DefaultRetryTimeout segundos antes de realizar nova tentativa  lt  remarks gt      public static void Try lt TException gt  Action action  Action lt ResiliencyTryHandler lt TException gt  gt  tryHandler  where TException   Exception               Try action  DefaultRetryCount  TimeSpan FromSeconds DefaultRetryTimeout   tryHandler                   lt summary gt          Executa uma  lt see cref  Action   gt  e tenta novamente determinado n  mero de vezes quando for disparada uma  lt see cref  Exception   gt  definida no tipo gen  rico          lt  summary gt           lt param name  action  gt A    o a ser realizada lt  param gt           lt param name  retryCount  gt N  mero de novas tentativas a serem realizadas lt  param gt           lt param name  retryTimeout  gt Tempo de espera antes de cada nova tentativa lt  param gt           lt param name  tryHandler  gt Permitindo manipular os crit  rios para realizar as tentativas lt  param gt           lt remarks gt Constru  do a partir de v  rias ideias no post  lt seealso cref  http   stackoverflow com questions 156DefaultRetryCount191 c-sharp-cleanest-way-to-write-retry-logic   gt  lt  remarks gt      public static void Try lt TException gt  Action action  int retryCount  TimeSpan retryTimeout  Action lt ResiliencyTryHandler lt TException gt  gt  tryHandler  where TException   Exception               if  action    null              throw new ArgumentNullException nameof action             while  retryCount--  gt  0                        try                               action                    return                            catch  TException ex                                  Executa o manipulador de exception                 if  tryHandler    null                                        var callback   new ResiliencyTryHandler lt TException gt  ex  retryCount                       tryHandler callback                         A propriedade que aborta pode ser alterada pelo cliente                     if  callback AbortRetry                          throw                                       Aguarda o tempo especificado antes de tentar novamente                 Thread Sleep retryTimeout                                      Na   ltima tentativa  qualquer exception ser   lan  ada de volta ao chamador         action                   lt summary gt      Permite manipular o evento de cada tentativa da classe de  lt see cref  Resiliency   gt       lt  summary gt  public class ResiliencyTryHandler lt TException gt  where TException   Exception        region Properties           lt summary gt          Op    o para abortar o ciclo de tentativas          lt  summary gt      public bool AbortRetry   get  set              lt summary gt           lt see cref  Exception   gt  a ser tratada          lt  summary gt      public TException Exception   get  private set              lt summary gt          Identifca o n  mero da tentativa atual          lt  summary gt      public int CurrentTry   get  private set          endregion       region Constructors           lt summary gt          Instancia um manipulador de tentativa     utilizado internamente         por  lt see cref  Resiliency   gt  para permitir que o cliente altere o         comportamento do ciclo de tentativas          lt  summary gt      public ResiliencyTryHandler TException exception  int currentTry                Exception   exception          CurrentTry   currentTry              endregion

User · Answer

You should try Polly  It s a  NET library written by me that allows developers to express transient exception handling policies such as Retry  Retry Forever  Wait and Retry or Circuit Breaker in a fluent manner   Example  Policy      Handle lt SqlException gt  ex   gt  ex Number    1205       Or lt ArgumentException gt  ex   gt  ex ParamName     example        WaitAndRetry 3  retryAttempt   gt  TimeSpan FromSeconds 3        Execute      gt  DoSomething

User · Answer

I ve implemented an async version of the accepted answer like so - and it seems to work nicely - any comments            public static async Task DoAsync              Action action              TimeSpan retryInterval              int maxAttemptCount   3                        DoAsync lt object gt       gt                                action                    return null                 retryInterval  maxAttemptCount                      public static async Task lt T gt  DoAsync lt T gt               Func lt Task lt T gt  gt  action              TimeSpan retryInterval              int maxAttemptCount   3                        var exceptions   new List lt Exception gt                  for  int attempted   0  attempted  lt  maxAttemptCount  attempted                                  try                                       if  attempted  gt  0                                                Thread Sleep retryInterval                                             return await action                                      catch  Exception ex                                        exceptions Add ex                                               throw new AggregateException exceptions                And  call it simply like this   var result   await Retry DoAsync      gt  MyAsyncMethod    TimeSpan FromSeconds 5   4

[c#] Cleanest way to write retry logic?

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