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https://issues.apache.org/jira/browse/THRIFT-4668?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16695573#comment-16695573
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ASF GitHub Bot commented on THRIFT-4668:
----------------------------------------
lshgdut commented on issue #1631: THRIFT-4668: make socket backlog configurable
for python
URL: https://github.com/apache/thrift/pull/1631#issuecomment-440920684
The value of `socket.SOMAXCONN` depends on different operate systems:
- on Window 7, it is `2147483647`
- on Centos or Debian, it is `128`, even I have set a different value to
`/proc/sys/net/core/somaxconn`
According to `Python-2.7.14/Modules/socketmodule.c`:
```c
4967 /* Maximum number of connections for "listen" */
4968: #ifdef SOMAXCONN
4969: PyModule_AddIntConstant(m, "SOMAXCONN", SOMAXCONN);
4970 #else
4971: PyModule_AddIntConstant(m, "SOMAXCONN", 5); /* Common value */
4972 #endif
```
The value of `SOMAXCONN` depend on system macro `SOMAXCONN`:
- on Window 7, I can not explain why it is 2147483647
- on linux, `SOMAXCONN` is defined in '/usr/include/bits/socket.h +144',
hard code to 128
Linux set `SOMAXCONN` macro to` core.sysctl_somaxconn` first, then check
the sysctl value of 'net.core.somaxconn' existing or not and override it if
possible.
When socket listening, if `backlog` is greater than SOMAXCONN, the kernel
will take the value of `min(backlog, SOMAXCONN)`. Here is linux kernel code
below:
```c
// From linux-3.10.0-693.25.4.el7/net/socket.c +1534
/*
* Perform a listen. Basically, we allow the protocol to do anything
* necessary for a listen, and if that works, we mark the socket as
* ready for listening.
*/
SYSCALL_DEFINE2(listen, int, fd, int, backlog)
{
struct socket *sock;
int err, fput_needed;
int somaxconn;
sock = sockfd_lookup_light(fd, &err, &fput_needed);
if (sock) {
somaxconn = sock_net(sock->sk)->core.sysctl_somaxconn;
if ((unsigned int)backlog > somaxconn)
backlog = somaxconn;
err = security_socket_listen(sock, backlog);
if (!err)
err = sock->ops->listen(sock, backlog);
fput_light(sock->file, fput_needed);
}
return err;
}
```
So doesn't it need to check the value of `_backlog` or not? May be a warning
better?
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> make socket backlog configurable for python
> -------------------------------------------
>
> Key: THRIFT-4668
> URL: https://issues.apache.org/jira/browse/THRIFT-4668
> Project: Thrift
> Issue Type: Improvement
> Components: Python - Library
> Affects Versions: 0.11.0
> Reporter: lsh
> Priority: Minor
> Labels: patch
>
> The backlog parameter of socket.listen was hard coded, so I can't customize
> it in my code.
> Adding `setBacklog` to `TServerSocket` can resolve my problem. :)
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