Wire compression causes sporadic "Error reading data from the connection."
errors.
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Key: CORE-6468
URL: http://tracker.firebirdsql.org/browse/CORE-6468
Project: Firebird Core
Issue Type: Bug
Components: Engine
Affects Versions: 3.0.7
Environment: Firebird 3.0.7, Windows 10
Reporter: michalk1
Attachments: TestCase.zip
I came across this problem infrequently since first FB 3 versions. Now I
finally found that it is related to WireCompression and was able to create a
relatively reproducible test case. It consists of a repeated run of a long sql
statement, with commits between them. It is easier to spot the error when the
test is run concurrently from more consoles.
Steps to reproduce:
1) Make a copy of a employee.fdb (or any other database) database, for example
to "C:\Tmp\employee.fdb".
2) Modify firebird.conf to enable client wire compression (WireCompression =
true).
3) Unzip test case script files (TestMain.sql and TestCmd.sql), say to
"C:\Tmp\". TestCmd.sql is the command itself followed by a commit, TestMain.sql
is there just to call it repeatedly.
3) Run several command line consoles (two should be enough), and in each of
them, execute the sql script in isql:
isql -user SYSDBA -password masterkey localhost:C:\Tmp\employee.fdb -i
"C:\Tmp\TestMain.sql"
4) Sooner or later in some of the consoles (you may run the script repeatedly
of from more consoles) you should spot the errors. The first one is always
"Error reading data from the connection.". Following "Error writing data from
the connection." are just consequence of the already dropped connection.
Clues:
- Disabling wire compression results in no errors at all.
- Short sql statement are less likely to be affected, may be there is even a
threshold under which the error doesn't occur. Contents of the long sql
statement probably doesn't matter, just it's length.
- When the error arises, other connections continue to run (at least for some
time), which means that the problem is not caused by a server crash. It is just
the single connection that drops out.
- So far i couldn't reproduce the problem against Linux server, it may be
Windows specific.
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