Communication Library Parameters

tcp_keepalives_idle

Parameter description: Specifies the interval for transmitting keepalive signals on an OS that supports the TCP_KEEPIDLE socket option. If no keepalive signal is transmitted, the connection is in idle mode.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

• If the OS does not support TCP_KEEPIDLE, set this parameter to 0.
• The parameter is ignored on an OS where connections are established using the Unix domain socket.
• If this parameter is set to 0, the system value is used.
• This parameter is not shared among different sessions. That is, different session connections may have different values.
• The parameter value in the current session connection, not the value of the GUC copy, is displayed.

Value range: 0 to 3600. The unit is s.

Default value: 60

tcp_keepalives_interval

Parameter description: Specifies the response time before retransmission on an OS that supports the TCP_KEEPINTVL socket option.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

Value range: 0 to 180. The unit is s.

Default value:

• If the OS does not support TCP_KEEPINTVL, set this parameter to 0.
• The parameter is ignored on an OS where connections are established using the Unix domain socket.
• If this parameter is set to 0, the system value is used.
• This parameter is not shared among different sessions. That is, different session connections may have different values.
• The parameter value in the current session connection, not the value of the GUC copy, is displayed.

tcp_keepalives_count

Parameter description: Specifies the number of keepalive signals that can be waited before the GaussDB server is disconnected from the client on an OS that supports the TCP_KEEPCNT socket option.

This parameter is a USERSET parameter. Set it based on instructions provided in Table 1.

• If the OS does not support TCP_KEEPCNT, set this parameter to 0.
• The parameter is ignored on an OS where connections are established using the Unix domain socket.
• If this parameter is set to 0, the system value is used.
• This parameter is not shared among different sessions. That is, different session connections may have different values.
• The parameter value in the current session connection, not the value of the GUC copy, is displayed.

Value range: 0 to 100. 0 indicates that the connection is immediately broken if GaussDB does not receive a keepalived signal from the client.

Default value: 20

tcp_user_timeout

Parameter description: Specifies the maximum duration for which the transmitted data can remain in the unacknowledged state before the TCP connection is forcibly closed when the GaussDB sends data on the OS that supports the TCP_USER_TIMEOUT socket option.

This is a SIGHUP parameter. Set it based on instructions provided in Table 1.

• If the OS does not support the TCP_USER_TIMEOUT option, the value of this parameter does not take effect. The default value is 0.
• The parameter is ignored on an OS where connections are established using the Unix domain socket.

Value Range: 0 to 3600000. The unit is ms. The value 0 indicates that the value is set based on the OS.

Default value: 0

Note that the effective result of this parameter varies according to the OS kernel.

• For AArch64 EulerOS (Linux kernel version: 4.19), the timeout interval is the value of this parameter.
• For x86 EulerOS 2.5 (Linux kernel version: 3.10), the timeout interval is not the set value of this parameter but the maximum value in different ranges. That is, the maximum value of the total Linux TCP retransmission duration range to which the set value of tcp_user_timeout belongs. For example, if tcp_user_timeout is set to 40000, the actual total retransmission duration is 51 seconds.

  Table 1 Value of tcp_user_timeout for x86 EulerOS 2.5 (Linux kernel version: 3.10)

  Number of Linux TCP Retransmission Times	Total Linux TCP Retransmission Duration Range (s)	Example of tcp_user_timeout (ms)	Actual Linux TCP Retransmission Duration (s)
  1	(0.2,0.6]	400	0.6
  2	(0.6,1.4]	1000	1.4
  3	(1.4,3]	2000	3
  4	(3,6.2]	4000	6.2
  5	(6.2,12.6]	10000	12.6
  6	(12.6,25.4]	20000	25.4
  7	(25.4,51]	40000	51
  8	(51,102.2]	80000	102.2
  9	(102.2,204.6]	150000	204.6
  10	(204.6,324.6]	260000	324.6
  11	(324.6,444.6]	400000	444.6

  Note: The duration of each TCP retransmission increases exponentially with the number of retransmission times until it reaches 120s. When the duration of a TCP retransmission reaches 120s, the duration of each subsequent retransmission remains 120s.

comm_proxy_attr

Parameter description: Specifies the parameters related to the communication proxy library.

• This parameter applies only to the centralized ARM standalone system running EulerOS 2.9.
• This function takes effect when the thread pool is enabled, that is, enable_thread_pool is set to on.
• When setting this parameter, you need to set the GUC parameter local_bind_address to the IP address of the NIC of the libos_kni.
• Parameter template: comm_proxy_attr = '{enable_libnet:true, enable_dfx:false, numa_num:4, numa_bind:[[30,31],[62,63],[94,95],[126,127]]}'
• Parameters that need to be configured include:
  • enable_libnet: whether to enable the user-mode protocol. The options are as follows: true and false.
  • enable_dfx: whether to enable the communication proxy library view. The options are as follows: true and false.
  • numa_num: number of NUMA nodes in the system. 2P and 4P servers are supported. The value can be: 4 or 8.
  • numa_bind: core binding parameter of the agent thread. Each numa has two CPUs. There are a total of numa_num groups. The value range is as follows: [0, Number of CPUs – 1].

This parameter is a POSTMASTER parameter. Set it based on instructions provided in Table 1.

Value range: a string, consisting of one or more characters

Default value: none