Re: [Firebird-devel] Commit (un)certainity
> Mark Rotteveel wrote 06.01.2022 13:06: > > BTW: I think in most cases you should be able to infer from the socket > > error if the problem occurred on sending or on reading data (at least, > > when using blocking socket reads/writes, not sure about non-blocking). > >It is not true: > > https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf- > winsock2-send > > > The successful completion of a send function does not indicate that the > data was successfully delivered and received to the recipient. This function > only indicates the data was successfully sent. > > https://linux.die.net/man/3/send > > > Successful completion of a call to send() does not guarantee delivery of the > message. A return value of -1 indicates only locally-detected errors. Not being very familiar with client API functionality, I need to ask. There is no ACK response sent to the client when a message/request is received by the server for non-immediate response (ie. "execute SQL" vs. "get version")? Sean Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
Re: [Firebird-devel] Commit (un)certainity
>It is documented that successful return from function send() for TCP > doesn't > mean successful delivery of data to the target host, mere put them into > socket > buffer. >If op_commit is sent but network error appear during waiting for > response > there can be two cases: >1) op_commit packet is lost on its way to server; >2) op_response is lost on its way to client. > >In the first case the transaction on server is rolled back in the > latter - > committed successfully. > >Is there a way to handle such situation? Using of two round-trips > cannot > solve the problem, only shift point of uncertainty. > Two phase commit does solve the problem, at considerable expense. Cheers, Ann Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
Re: [Firebird-devel] Commit (un)certainity
Mark Rotteveel wrote 06.01.2022 13:06: BTW: I think in most cases you should be able to infer from the socket error if the problem occurred on sending or on reading data (at least, when using blocking socket reads/writes, not sure about non-blocking). It is not true: https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-send The successful completion of a send function does not indicate that the data was successfully delivered and received to the recipient. This function only indicates the data was successfully sent. https://linux.die.net/man/3/send Successful completion of a call to send() does not guarantee delivery of the message. A return value of -1 indicates only locally-detected errors. -- WBR, SD. Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
Re: [Firebird-devel] Commit (un)certainity
On 2022-01-05 21:48, Jiří Činčura wrote: Yes. You probably have the same problem in your provider, no? The problem exists there. Same as with fbclient. But I don't explicitly solve it, application developer is responsible for handling such scenario (if ever). I agree. If the application developer thinks this is a problem, they should switch to using 2-phase commits and having a scavenger to handle limbo transactions. BTW: I think in most cases you should be able to infer from the socket error if the problem occurred on sending or on reading data (at least, when using blocking socket reads/writes, not sure about non-blocking). Mark Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
Re: [Firebird-devel] Commit (un)certainity
>Yes. You probably have the same problem in your provider, no? The problem exists there. Same as with fbclient. But I don't explicitly solve it, application developer is responsible for handling such scenario (if ever). -- Mgr. Jiří Činčura https://www.tabsoverspaces.com/ Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
Re: [Firebird-devel] Commit (un)certainity
Em qua., 5 de jan. de 2022 17:14, Dimitry Sibiryakov escreveu: > Jiří Činčura wrote 05.01.2022 19:44: > > You're probably thinking about something in client library? > >Yes. You probably have the same problem in your provider, no? If no response or network error is returned, application will be stuck, will receive the error or will receive a timeout error. It looks like an application thing, not a driver thing. Adriano Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
Re: [Firebird-devel] Commit (un)certainity
Jiří Činčura wrote 05.01.2022 19:44: You're probably thinking about something in client library? Yes. You probably have the same problem in your provider, no? -- WBR, SD. Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
Re: [Firebird-devel] Commit (un)certainity
05.01.2022 15:03, Dimitry Sibiryakov wrote: Hello All. It is documented that successful return from function send() for TCP doesn't mean successful delivery of data to the target host, mere put them into socket buffer. If op_commit is sent but network error appear during waiting for response there can be two cases: 1) op_commit packet is lost on its way to server; 2) op_response is lost on its way to client. In the first case the transaction on server is rolled back in the latter - committed successfully. Is there a way to handle such situation? 2PC protocol was developed for this kind of problems. Using of two round-trips cannot solve the problem, only shift point of uncertainty. 2PC allows to know trasaction state and fix half-done commit. Regards, Vlad Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
Re: [Firebird-devel] Commit (un)certainity
One way to handle this is via manual inserts (and deletes) in a dedicated table. Something like: 1. Insert a row into the table at the beginning of each transaction. 2. If the connection fails during the commit, check for the presence of the corresponding row in the database. - If the row is present, continue normally, as the transaction was committed successfully - If the row is absent, use an execution strategy to retry the current operation. 3. If the commit is successful, delete the corresponding row to avoid the growth of the table. But this needs support on application level. You're probably thinking about something in client library? -- Mgr. Jiří Činčura https://www.tabsoverspaces.com/ Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
[Firebird-devel] Commit (un)certainity
Hello All. It is documented that successful return from function send() for TCP doesn't mean successful delivery of data to the target host, mere put them into socket buffer. If op_commit is sent but network error appear during waiting for response there can be two cases: 1) op_commit packet is lost on its way to server; 2) op_response is lost on its way to client. In the first case the transaction on server is rolled back in the latter - committed successfully. Is there a way to handle such situation? Using of two round-trips cannot solve the problem, only shift point of uncertainty. -- WBR, SD. Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
[Firebird-devel] Commit (un)certainity
Hello All. It is documented that successful return from function send() for TCP doesn't mean successful delivery of data to the target host, mere put them into socket buffer. If op_commit is sent but network error appear during waiting for response there can be two cases: 1) op_commit packet is lost on its way to server; 2) op_response is lost on its way to client. In the first case the transaction on server is rolled back in the latter - committed successfully. Is there a way to handle such situation? Using of two round-trips cannot solve the problem, only shift point of uncertainty. -- WBR, SD. Firebird-Devel mailing list, web interface at https://lists.sourceforge.net/lists/listinfo/firebird-devel
