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ClickHouse® is a real-time analytics DBMS
9c7db6711b
Occasionally, 02479_mysql_connect_to_self fails on CI [1]. [1]: https://github.com/ClickHouse/ClickHouse/issues/50911 The problem was indeed query profiler and EINTR, but not in a way you may think. For such failures you may see the following trace in trace_log: contrib/openssl/crypto/bio/bss_sock.c:127::sock_read contrib/openssl/crypto/bio/bio_meth.c:121::bread_conv contrib/openssl/crypto/bio/bio_lib.c:285::bio_read_intern contrib/openssl/crypto/bio/bio_lib.c:311::BIO_read contrib/openssl/ssl/record/methods/tls_common.c:398::tls_default_read_n contrib/openssl/ssl/record/methods/tls_common.c:575::tls_get_more_records contrib/openssl/ssl/record/methods/tls_common.c:1122::tls_read_record contrib/openssl/ssl/record/rec_layer_s3.c:645::ssl3_read_bytes contrib/openssl/ssl/s3_lib.c:4527::ssl3_read_internal contrib/openssl/ssl/s3_lib.c:4551::ssl3_read contrib/openssl/ssl/ssl_lib.c:2343::ssl_read_internal contrib/openssl/ssl/ssl_lib.c:2357::SSL_read contrib/mariadb-connector-c/libmariadb/secure/openssl.c:729::ma_tls_read contrib/mariadb-connector-c/libmariadb/ma_tls.c:90::ma_pvio_tls_read contrib/mariadb-connector-c/libmariadb/ma_pvio.c:250::ma_pvio_read contrib/mariadb-connector-c/libmariadb/ma_pvio.c:297::ma_pvio_cache_read contrib/mariadb-connector-c/libmariadb/ma_net.c:373::ma_real_read contrib/mariadb-connector-c/libmariadb/ma_net.c:427::ma_net_read contrib/mariadb-connector-c/libmariadb/mariadb_lib.c:192::ma_net_safe_read contrib/mariadb-connector-c/libmariadb/mariadb_lib.c:2138::mthd_my_read_query_result contrib/mariadb-connector-c/libmariadb/mariadb_lib.c:2212::mysql_real_query src/Common/mysqlxx/Query.cpp:56::mysqlxx::Query::executeImpl() src/Common/mysqlxx/Query.cpp:73::mysqlxx::Query::use() src/Processors/Sources/MySQLSource.cpp:50::DB::MySQLSource::Connection::Connection() After which the connection will fail with: Code: 1000. DB::Exception: Received from localhost:9000. DB::Exception: mysqlxx::ConnectionLost: Lost connection to MySQL server during query (127.0.0.1:9004). (POCO_EXCEPTION) But, if you will take a look at ma_tls_read() you will see that it has proper retries for SSL_ERROR_WANT_READ (and EINTR is just a special case of it), but still, for some reason it fails. And the reason is the units of the read/write timeout, ma_tls_read() calls poll(read_timeout) in case of SSL_ERROR_WANT_READ, but, it incorrectly assume that the timeout is in milliseconds, but that timeout was in seconds, this bug had been fixed in [2], and now it works like a charm! [2]: https://github.com/ClickHouse/mariadb-connector-c/pull/17 I've verified it with patching openssl library: diff --git a/crypto/bio/bss_sock.c b/crypto/bio/bss_sock.c index 82f7be85ae..3d2f3926a0 100644 --- a/crypto/bio/bss_sock.c +++ b/crypto/bio/bss_sock.c @@ -124,7 +124,24 @@ static int sock_read(BIO *b, char *out, int outl) ret = ktls_read_record(b->num, out, outl); else # endif - ret = readsocket(b->num, out, outl); + { + static int i = 0; + static int j = 0; + if (!(++j % 5)) + { + fprintf(stderr, "sock_read: inject EAGAIN with ret=0\n"); + ret = 0; + errno = EAGAIN; + } + else if (!(++i % 3)) + { + fprintf(stderr, "sock_read: inject EAGAIN with ret=-1\n"); + ret = -1; + errno = EAGAIN; + } + else + ret = readsocket(b->num, out, outl); + } BIO_clear_retry_flags(b); if (ret <= 0) { if (BIO_sock_should_retry(ret)) And before this patch (well, not the patch itself, but the referenced patch in mariadb-connector-c) if you will pass read_write_timeout=1 it will fail: SELECT * FROM mysql('127.0.0.1:9004', system, one, 'default', '', SETTINGS connect_timeout = 100, connection_wait_timeout = 100, read_write_timeout=1) Code: 1000. DB::Exception: Received from localhost:9000. DB::Exception: mysqlxx::ConnectionLost: Lost connection to MySQL server during query (127.0.0.1:9004). (POCO_EXCEPTION) But after, it always works: $ ch benchmark -c10 -q "SELECT * FROM mysql('127.0.0.1:9004', system, one, 'default', '', SETTINGS connection_pool_size=1, connect_timeout = 100, connection_wait_timeout = 100, read_write_timeout=1)" ^CStopping launch of queries. SIGINT received. Queries executed: 478. localhost:9000, queries: 478, QPS: 120.171, RPS: 120.171, MiB/s: 0.001, result RPS: 120.171, result MiB/s: 0.001. 0.000% 0.014 sec. 10.000% 0.058 sec. 20.000% 0.065 sec. 30.000% 0.073 sec. 40.000% 0.079 sec. 50.000% 0.087 sec. 60.000% 0.089 sec. 70.000% 0.091 sec. 80.000% 0.095 sec. 90.000% 0.100 sec. 95.000% 0.102 sec. 99.000% 0.105 sec. 99.900% 0.140 sec. 99.990% 0.140 sec. Signed-off-by: Azat Khuzhin <a.khuzhin@semrush.com> |
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ClickHouse® is an open-source column-oriented database management system that allows generating analytical data reports in real-time.
How To Install (Linux, macOS, FreeBSD)
curl https://clickhouse.com/ | sh
Useful Links
- Official website has a quick high-level overview of ClickHouse on the main page.
- ClickHouse Cloud ClickHouse as a service, built by the creators and maintainers.
- Tutorial shows how to set up and query a small ClickHouse cluster.
- Documentation provides more in-depth information.
- YouTube channel has a lot of content about ClickHouse in video format.
- Slack and Telegram allow chatting with ClickHouse users in real-time.
- Blog contains various ClickHouse-related articles, as well as announcements and reports about events.
- Code Browser (github.dev) with syntax highlighting, powered by github.dev.
- Contacts can help to get your questions answered if there are any.
Monthly Release & Community Call
Every month we get together with the community (users, contributors, customers, those interested in learning more about ClickHouse) to discuss what is coming in the latest release. If you are interested in sharing what you've built on ClickHouse, let us know.
- v24.6 Community Call - Jul 2
Upcoming Events
Keep an eye out for upcoming meetups and events around the world. Somewhere else you want us to be? Please feel free to reach out to tyler <at> clickhouse <dot> com. You can also peruse ClickHouse Events for a list of all upcoming trainings, meetups, speaking engagements, etc.
- AWS Summit in DC - Jun 26
- ClickHouse Meetup in Amsterdam - Jun 27
- ClickHouse Meetup in Paris - Jul 9
- ClickHouse Cloud - Live Update Call - Jul 9
- ClickHouse Meetup @ Ramp - New York City - Jul 9
- AWS Summit in New York - Jul 10
- ClickHouse Meetup @ Klaviyo - Boston - Jul 11
Recent Recordings
- Recent Meetup Videos: Meetup Playlist Whenever possible recordings of the ClickHouse Community Meetups are edited and presented as individual talks. Current featuring "Modern SQL in 2023", "Fast, Concurrent, and Consistent Asynchronous INSERTS in ClickHouse", and "Full-Text Indices: Design and Experiments"
- Recording available: v24.4 Release Call All the features of 24.4, one convenient video! Watch it now!
Interested in joining ClickHouse and making it your full-time job?
We are a globally diverse and distributed team, united behind a common goal of creating industry-leading, real-time analytics. Here, you will have an opportunity to solve some of the most cutting-edge technical challenges and have direct ownership of your work and vision. If you are a contributor by nature, a thinker and a doer - we’ll definitely click!
Check out our current openings here: https://clickhouse.com/company/careers
Can't find what you are looking for, but want to let us know you are interested in joining ClickHouse? Email careers@clickhouse.com!