GEODE-8480: Add txmanager check in tx example

[alb3rtobr]

No description provided.

[pdxcodemonkey]

Did you find an issue that was fixed by this? What is the repro case? Can we add a simple test that shows the problem? The changes look fine, but it's difficult to judge correctness or whether there's a product issue since it doesn't modify any product code.

[alb3rtobr]

I was running a test consisting on killing a Geode server while a C++ client with several threads was executing transactions. I observed that most of the times, the client died after killing the server with following error in logs:

[error 2020/09/01 10:31:05.977905 CEST alb3rtobr-XPS:7395 139697166743296] Unexpected exception during completing transaction : illegal State
terminate called after throwing an instance of 'apache::geode::client::Exception'
terminate called recursively
  what():  : illegal State

I was not sure about what was happening, but I had the feeling that I was doing something wrong, because I would not expect that the client was dying in this scenario. When I was taking a look at the transaction page in the Geode documentation, I realized that in Java, the transaction example includes the call to the exists() method (link to the doc) before performing rollback.

if(txManager.exists()) {
    txManager.rollback();
}     

I added the call to the function to my C++ client and the problem was solved. After that the client was showing some exceptions when one of the server was killed, but the client was not dying. So I felt that calling to this exists()method was something to be done in transactions and that it was missing from the C++ documentation.

[pdxcodemonkey]

Please add a test that reproduces the problem, if you can. If it's too much work, file a separate Jira work item for the test and I'll approve/merge this. Thanks!

[alb3rtobr]

Dont worry, I think its not needed to split this in two different tickets, I will try to write a test when I find time. Im moving this PR to draft in the meanwhile.

[alb3rtobr]

There you are a test that shows the problem. I have divided the code in two commits. In the first one, the test fails with the following error:

$ ctest -R TransactionsTest -j1
Test project /home/alb3rtobr/CLionProjects/Nordix/geode-native/build/cppcache/integration/test
    Start 61: TransactionsTest.ExceptionWhenRollingBackTx
1/1 Test #61: TransactionsTest.ExceptionWhenRollingBackTx ...***Exception: Child aborted 21.41 sec

0% tests passed, 1 tests failed out of 1

Total Test time (real) =  23.72 sec

The following tests FAILED:
	 61 - TransactionsTest.ExceptionWhenRollingBackTx (Child aborted)
Errors while running CTest

But after changing the code to call transactionManager->exists() before executing the rollback (the second commit), the test case works fine.

[alb3rtobr]

PR rebased to fix conflict with CMakeLists.txt

[codecov-commenter]

Codecov Report

Merging #648 into develop will increase coverage by 0.26%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop     #648      +/-   ##
===========================================
+ Coverage    73.95%   74.21%   +0.26%     
===========================================
  Files          644      644              
  Lines        51132    51132              
===========================================
+ Hits         37813    37948     +135     
+ Misses       13319    13184     -135     

Impacted Files	Coverage Δ
cppcache/src/ThinClientStickyManager.cpp	77.88% <0.00%> (-10.58%)	⬇️
...test/testThinClientPoolExecuteHAFunctionPrSHOP.cpp	91.20% <0.00%> (-3.71%)	⬇️
cppcache/src/ClientMetadataService.cpp	64.98% <0.00%> (-0.92%)	⬇️
cppcache/src/ClientMetadata.cpp	65.16% <0.00%> (-0.57%)	⬇️
cppcache/src/ThinClientLocatorHelper.cpp	85.71% <0.00%> (-0.40%)	⬇️
cppcache/src/ExecutionImpl.cpp	67.69% <0.00%> (-0.39%)	⬇️
cppcache/src/TcrConnection.cpp	72.48% <0.00%> (-0.32%)	⬇️
cppcache/src/ThinClientRedundancyManager.cpp	75.62% <0.00%> (-0.32%)	⬇️
cppcache/src/TcrMessage.cpp	85.62% <0.00%> (+0.31%)	⬆️
cppcache/src/ThinClientPoolDM.cpp	75.48% <0.00%> (+0.35%)	⬆️
... and 15 more

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