Commit Graph

12 Commits

Author SHA1 Message Date
Azat Khuzhin
ed70ed6f71 Introduce connection_no_wait setting for MySQL engine.
This will allow to avoid superfluous sleep during query execution, since
this not only not desired behavoiur, but also may hang the server, since
if you will execute enough queries that will use MySQL database but will
not allow enough connections (or your MySQL server is too slow) then you
may run out of threads in the global thread pool.

Also note that right now it is possible to get deadlock when the mysql
pool is full, consider the following scenario:

- you have m1 and m2 mysql tables
- you have q1 and q2 queries, bot queries join m1 and m2
- q1 allocated connection for m1 but cannot allocate connection for m2
- q2 allocated connection for m2 but cannot allocate connection for m1
- but to resolve the lock one should give up on the locking while it is not possible right now...

And then you got no free threads and this:

    # grep -h ^202 /proc/$(pgrep clickhouse-serv)/task/*/syscall  | cut -d' ' -f2 | sort | uniq -c | sort -nr | head
       1554 0x7ffb60b92fe8 # mutex in mysqlxx::PoolWithFailover::get
       1375 0x7ffb9f1c4748 # mutex in ::PoolEntryHelper::~PoolEntryHelper from DB::MultiplexedConnections::invalidateReplica
       1160 0x7ffb612918b8 # mutex in mysqlxx::PoolWithFailover::get
         42 0x7ffb9f057984 # mutex in ThreadPoolImpl<std::__1::thread>::worker

    *NOTE: 202 is a `futex` with WAIT*

(Went with `syscall` because debugging 10k+ threads is not easy, and
eventually it may TRAP)
2021-09-02 22:23:37 +03:00
Alexey Milovidov
f063e44131 Whitespaces 2021-08-15 09:00:28 +03:00
Haavard Kvaalen
efa94c5735 Fix use after free in mysqlxx::Pool::tryGet()
tryGet() created an Entry object that referenced a Connection, but then
deleted the Connection just before the Entry went out of scope.
2021-03-04 16:51:27 +01:00
Alexander Kazakov
63b95c7451
MySQL dictionary source: A mechanism for retrying unexpected connection loss during communication with mysql server (#21237)
* Added a new type of Exception

for better recognition of connection failures

* Added more logging for mysql communication

* Retries on connection loss during query.

Make MySQL dictionary source resilient to unexpected loss of connection
during querying MySQL. This behavior is controlled with
".fail_on_connection_loss" config parameter, which defaults to false.

* Stripped some debugging leftover garbage

* Minor followup corrections

* Corrections after PR comments

* Yet more fixes
2021-02-27 11:18:28 +03:00
Alexander Kazakov
66f603512c
A followup correction to #19998 (#21221) 2021-02-26 11:42:37 +03:00
Alexander Kazakov
4bcaed98d8
Added "opt_reconnect" parameter to config for controlling MYSQL_OPT_RECONNECT option (#19998)
* Support for MYSQL_OPT_RECONNECT option

It can now be controlled by .opt_reconnect = {true|false} parameter in
the mysql replica config section
2021-02-26 09:49:49 +03:00
Alexander Kazakov
0e41af11c7
Fixed typo in message format (#17900) 2020-12-08 14:28:35 +03:00
Alexander Kazakov
81d9d3237f
In mysqlxx::Pool: fix for reconnection problem (#17681)
Remove stalled unrecoverable connections from myqsl connections pool
2020-12-03 23:36:10 +03:00
alesapin
16fa71a4c9 Missed comment 2020-10-08 20:46:59 +03:00
alesapin
70f2a3328d Better atomic operations on refcount 2020-10-08 20:45:18 +03:00
alexey-milovidov
c7863e1ac6
Clang Tidy, part 7 (#9799)
* Attempt to enable identifier naming check

* Attempt to enable identifier naming check, continue

* Progress on identifier names

* Adopt identifier names check

* Fixed error

* Merge with master

* Fixed build

* Fixed build

* Fixed build

* Fixed build

* Fixed build

* Fixed error

* Fixed error

* Fixed error
2020-03-23 05:12:31 +03:00
Ivan
b7ef5a699c
Move FastMemcpy to contribs (#9219)
* Get rid of non-existent vectorclass
* Move FastMemcpy to contribs
* Restore comments
* Disable FastMemcpy on non-Linux
* Fix cmake file
* Don't build FastMemcpy for ARM64
* Replace FastMemcpy submodule with its contents
* Fix cmake file
* Move widechar_width to contrib/
* Move sumbur to contrib/
* Move consistent-hashing to contrib/
* Fix UBSan tests
2020-03-13 01:26:16 +03:00