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From "Igor Sapego (Jira)" <j...@apache.org>
Subject [jira] [Updated] (IGNITE-13997) CPP Thin: Transactions can cause deadlock when client shared in multiple threads
Date Thu, 14 Jan 2021 16:49:00 GMT

     [ https://issues.apache.org/jira/browse/IGNITE-13997?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Igor Sapego updated IGNITE-13997:
---------------------------------
    Description: 
In our tests we have detected a deadlock when following piece of code is
executed for more than one thread on our application:

{code:cpp}
ClientTransactions transactions = client.ClientTransactions();
ClientTransaction tx = transactions.TxStart(PESSIMISTIC, READ_COMMITTED);

// This call should atomically get the current value for "key" and put
"value" instead, locking the "key" cache entry at the same time
auto oldValue = cache.GetAndPut(key, value);

// Only the thread able of locking "key" should reach this code. Others have
to wait for tx.Commit() to complete
cache.Put (key, newValue);

// After this call, other thread waiting in GetAndPut for "key" to be
released should be able of continuing
tx.Commit ();
{code}

The thread reaching "cache.Put (key, newValue);" call, gets blocked in
there, concretely in the lockGuard object created at the beginning of
DataChannel::InternalSyncMessage function (data_channel.cpp:108).  After
debugging, we realized that this lockGuard is owned by a different thread,
which is currently waiting on socket while executing GetAndPut function.
According to this, my guess is that data routing for C++ Thin Clients is not
multithread friendly.  

Reported in http://apache-ignite-users.70518.x6.nabble.com/Multithread-transactions-in-a-C-Thin-Client-td35145.html

  was:
In our tests we have detected a deadlock when following piece of code is
executed for more than one thread on our application:

{code:cpp}
ClientTransactions transactions = client.ClientTransactions();
ClientTransaction tx = transactions.TxStart(PESSIMISTIC, READ_COMMITTED);

// This call should atomically get the current value for "key" and put
"value" instead, locking the "key" cache entry at the same time
auto oldValue = cache.GetAndPut(key, value);

// Only the thread able of locking "key" should reach this code. Others have
to wait for tx.Commit() to complete
cache.Put (key, newValue);

// After this call, other thread waiting in GetAndPut for "key" to be
released should be able of continuing
tx.Commit ();
{code:cpp}

The thread reaching "cache.Put (key, newValue);" call, gets blocked in
there, concretely in the lockGuard object created at the beginning of
DataChannel::InternalSyncMessage function (data_channel.cpp:108).  After
debugging, we realized that this lockGuard is owned by a different thread,
which is currently waiting on socket while executing GetAndPut function.
According to this, my guess is that data routing for C++ Thin Clients is not
multithread friendly.  

Reported in http://apache-ignite-users.70518.x6.nabble.com/Multithread-transactions-in-a-C-Thin-Client-td35145.html


> CPP Thin: Transactions can cause deadlock when client shared in multiple threads
> --------------------------------------------------------------------------------
>
>                 Key: IGNITE-13997
>                 URL: https://issues.apache.org/jira/browse/IGNITE-13997
>             Project: Ignite
>          Issue Type: Bug
>          Components: thin client
>    Affects Versions: 2.9.1
>            Reporter: Igor Sapego
>            Priority: Major
>
> In our tests we have detected a deadlock when following piece of code is
> executed for more than one thread on our application:
> {code:cpp}
> ClientTransactions transactions = client.ClientTransactions();
> ClientTransaction tx = transactions.TxStart(PESSIMISTIC, READ_COMMITTED);
> // This call should atomically get the current value for "key" and put
> "value" instead, locking the "key" cache entry at the same time
> auto oldValue = cache.GetAndPut(key, value);
> // Only the thread able of locking "key" should reach this code. Others have
> to wait for tx.Commit() to complete
> cache.Put (key, newValue);
> // After this call, other thread waiting in GetAndPut for "key" to be
> released should be able of continuing
> tx.Commit ();
> {code}
> The thread reaching "cache.Put (key, newValue);" call, gets blocked in
> there, concretely in the lockGuard object created at the beginning of
> DataChannel::InternalSyncMessage function (data_channel.cpp:108).  After
> debugging, we realized that this lockGuard is owned by a different thread,
> which is currently waiting on socket while executing GetAndPut function.
> According to this, my guess is that data routing for C++ Thin Clients is not
> multithread friendly.  
> Reported in http://apache-ignite-users.70518.x6.nabble.com/Multithread-transactions-in-a-C-Thin-Client-td35145.html



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