Module ngx_stream_upstream_module

Planning your ingress-nginx migration? Start here:
kubernetes.nginx.org.

english
русский
news
about
download
security
documentation
faq
books
community
enterprise
community forum (new)
x.com
blog
njs
ingress controller
gateway fabric

Module ngx_stream_upstream_module

Example Configuration
Directives
upstream
server
zone
state
hash
least_conn
least_time
random
resolver
resolver_timeout
Embedded Variables

The ngx_stream_upstream_module module (1.9.0)
is used to define groups of servers that can be referenced
by the proxy_pass
directive.

Example Configuration

upstream backend {
hash $remote_addr consistent;

server backend1.example.com:12345 weight=5;
server backend2.example.com:12345;
server unix:/tmp/backend3;

server backup1.example.com:12345 backup;
server backup2.example.com:12345 backup;
}

server {
listen 12346;
proxy_pass backend;
}

Dynamically configurable group with
periodic health checks is
available as part of our
commercial subscription:

resolver 10.0.0.1;

upstream dynamic {
zone upstream_dynamic 64k;

server backend1.example.com:12345 weight=5;
server backend2.example.com:12345 fail_timeout=5s slow_start=30s;
server 192.0.2.1:12345 max_fails=3;
server backend3.example.com:12345 resolve;
server backend4.example.com service=http resolve;

server backup1.example.com:12345 backup;
server backup2.example.com:12345 backup;
}

server {
listen 12346;
proxy_pass dynamic;
health_check;
}

Directives

Syntax:

upstream name { ... }

Default:

—

Context:

stream

Defines a group of servers.
Servers can listen on different ports.
In addition, servers listening on TCP and UNIX-domain sockets
can be mixed.

Example:

upstream backend {
server backend1.example.com:12345 weight=5;
server 127.0.0.1:12345 max_fails=3 fail_timeout=30s;
server unix:/tmp/backend2;
server backend3.example.com:12345 resolve;

server backup1.example.com:12345 backup;
}

By default, connections are distributed between the servers using a
weighted round-robin balancing method.
In the above example, each 7 connections will be distributed as follows:
5 connections go to backend1.example.com:12345
and one connection to each of the second and third servers.
If an error occurs during communication with a server, the connection will
be passed to the next server, and so on until all of the functioning
servers will be tried.
If communication with all servers fails, the connection will be closed.

Syntax:

server address [parameters];

Default:

—

Context:

upstream

Defines the address and other parameters
of a server.
The address can be specified as a domain name or IP address
with an obligatory port, or as a UNIX-domain socket path
specified after the “unix:” prefix.
A domain name that resolves to several IP addresses defines
multiple servers at once.

The following parameters can be defined:

weight=number

sets the weight of the server, by default, 1.

max_conns=number

limits the maximum number of simultaneous
connections to the proxied server (1.11.5).
Default value is zero, meaning there is no limit.
If the server group does not reside in the shared memory,
the limitation works per each worker process.

Prior to version 1.11.5, this parameter was available as part of our
commercial subscription.

max_fails=number

sets the number of unsuccessful attempts to communicate with the server
that should happen in the duration set by the fail_timeout
parameter to consider the server unavailable for a duration also set by the
fail_timeout parameter.
By default, the number of unsuccessful attempts is set to 1.
The zero value disables the accounting of attempts.
Here, an unsuccessful attempt is an error or timeout
while establishing a connection with the server.

fail_timeout=time

sets

the time during which the specified number of unsuccessful attempts to
communicate with the server should happen to consider the server unavailable;

and the period of time the server will be considered unavailable.

By default, the parameter is set to 10 seconds.

backup

marks the server as a backup server.
Connections to the backup server will be passed
when the primary servers are unavailable.

The parameter cannot be used along with the
hash and random load balancing methods.

down

marks the server as permanently unavailable.

resolve

monitors changes of the IP addresses
that correspond to a domain name of the server,
and automatically modifies the upstream configuration
without the need of restarting nginx.
The server group must reside in the shared memory.

In order for this parameter to work,
the resolver directive
must be specified in the
stream block
or in the corresponding upstream block.

Prior to version 1.27.3, this parameter was available only as part of our
commercial subscription.

service=name

enables resolving of DNS
SRV
records and sets the service name (1.9.13).
In order for this parameter to work, it is necessary to specify
the resolve parameter for the server
and specify a hostname without a port number.

If the service name does not contain a dot (“.”), then
the RFC-compliant name
is constructed
and the TCP protocol is added to the service prefix.
For example, to look up the
_http._tcp.backend.example.com SRV record,
it is necessary to specify the directive:

server backend.example.com service=http resolve;

If the service name contains one or more dots, then the name is constructed
by joining the service prefix and the server name.
For example, to look up the _http._tcp.backend.example.com
and server1.backend.example.com SRV records,
it is necessary to specify the directives:

server backend.example.com service=_http._tcp resolve;
server example.com service=server1.backend resolve;

Highest-priority SRV records
(records with the same lowest-number priority value)
are resolved as primary servers,
the rest of SRV records are resolved as backup servers.
If the backup parameter is specified for the server,
high-priority SRV records are resolved as backup servers,
the rest of SRV records are ignored.

Prior to version 1.27.3, this parameter was available only as part of our
commercial subscription.

Additionally,
the following parameters are available as part of our
commercial subscription:

slow_start=time

sets the time during which the server will recover its weight
from zero to a nominal value, when unhealthy server becomes
healthy,
or when the server becomes available after a period of time
it was considered unavailable.
Default value is zero, i.e. slow start is disabled.

The parameter cannot be used along with the
hash and random load balancing methods.

If there is only a single server in a group, max_fails,
fail_timeout and slow_start parameters
are ignored, and such a server will never be considered unavailable.

Syntax:

zone name [size];

Default:

—

Context:

upstream

Defines the name and size of the shared
memory zone that keeps the group’s configuration and run-time state that are
shared between worker processes.
Several groups may share the same zone.
In this case, it is enough to specify the size only once.

Additionally,
as part of our commercial subscription,
such groups allow changing the group membership
or modifying the settings of a particular server
without the need of restarting nginx.
The configuration is accessible via the
API module (1.13.3).

Prior to version 1.13.3,
the configuration was accessible only via a special location
handled by
upstream_conf.

Syntax:

state file;

Default:

—

Context:

upstream

This directive appeared in version 1.9.7.

Specifies a file that keeps the state
of the dynamically configurable group.

Examples:

state /var/lib/nginx/state/servers.conf; # path for Linux
state /var/db/nginx/state/servers.conf; # path for FreeBSD

The state is currently limited to the list of servers with their parameters.
The file is read when parsing the configuration and is updated each time
the upstream configuration is
changed.
Changing the file content directly should be avoided.
The directive cannot be used
along with the server directive.

Changes made during
configuration reload
or binary upgrade
can be lost.

This directive is available as part of our
commercial subscription.

Syntax:

hash key [consistent];

Default:

—

Context:

upstream

Specifies a load balancing method for a server group
where the client-server mapping is based on the hashed key value.
The key can contain text, variables,
and their combinations (1.11.2).
Usage example:

hash $remote_addr;

Note that adding or removing a server from the group
may result in remapping most of the keys to different servers.
The method is compatible with the
Cache::Memcached
Perl library.

If the consistent parameter is specified,
the ketama
consistent hashing method will be used instead.
The method ensures that only a few keys
will be remapped to different servers
when a server is added to or removed from the group.
This helps to achieve a higher cache hit ratio for caching servers.
The method is compatible with the
Cache::Memcached::Fast
Perl library with the ketama_points parameter set to 160.

Syntax:

least_conn;

Default:

—

Context:

upstream

Specifies that a group should use a load balancing method where a connection
is passed to the server with the least number of active connections,
taking into account weights of servers.
If there are several such servers, they are tried in turn using a
weighted round-robin balancing method.

Syntax:

least_time
connect |
first_byte |
last_byte
[inflight];

Default:

—

Context:

upstream

This directive appeared in version 1.7.11.

Specifies that a group should use a load balancing method where a connection
is passed to the server with the least average time and
least number of active connections, taking into account weights of servers.
If there are several such servers, they are tried in turn using a
weighted round-robin balancing method.

If the connect parameter is specified,
time to
connect
to the upstream server is used.
If the first_byte parameter is specified,
time to receive the
first byte of data is used.
If the last_byte is specified,
time to receive the
last byte of data is used.
If the inflight parameter is specified (1.11.6),
incomplete connections are also taken into account.

Prior to version 1.11.6,
incomplete connections were taken into account by default.

Prior to version 1.31.0,
this directive was available only as part of our
commercial subscription.

Syntax:

random [two [method]];

Default:

—

Context:

upstream

This directive appeared in version 1.15.1.

Specifies that a group should use a load balancing method where a connection
is passed to a randomly selected server, taking into account weights
of servers.

The optional two parameter
instructs nginx to randomly select
two
servers and then choose a server
using the specified method.
The default method is least_conn
which passes a connection to a server
with the least number of active connections.

The least_time method passes a connection to a server
with the least average time and least number of active connections.
If least_time=connect parameter is specified,
time to
connect
to the upstream server is used.
If least_time=first_byte parameter is specified,
time to receive the
first byte of data is used.
If least_time=last_byte is specified,
time to receive the
last byte of data is used.

The least_time method is available as a part of our
commercial subscription.

Syntax:

resolver
address ...
[valid=time]
[ipv4=on|off]
[ipv6=on|off]
[status_zone=zone];

Default:

—

Context:

upstream

This directive appeared in version 1.27.3.

Configures name servers used to resolve names of upstream servers
into addresses, for example:

resolver 127.0.0.1 [::1]:5353;

The address can be specified as a domain name or IP address,
with an optional port.
If port is not specified, the port 53 is used.
Name servers are queried in a round-robin fashion.

By default, nginx will look up both IPv4 and IPv6 addresses while resolving.
If looking up of IPv4 or IPv6 addresses is not desired,
the ipv4=off (1.23.1) or
the ipv6=off parameter can be specified.

By default, nginx caches answers using the TTL value of a response.
The optional valid parameter allows overriding it:

resolver 127.0.0.1 [::1]:5353 valid=30s;

To prevent DNS spoofing, it is recommended
configuring DNS servers in a properly secured trusted local network.

The optional status_zone parameter (1.17.5)
enables
collection
of DNS server statistics of requests and responses
in the specified zone.
The parameter is available as part of our
commercial subscription.

Since version 1.17.5 and prior to version 1.27.3,
this directive was available only as part of our
commercial subscription.

Syntax:

resolver_timeout time;

Default:

resolver_timeout 30s;

Context:

upstream

This directive appeared in version 1.27.3.

Sets a timeout for name resolution, for example:

resolver_timeout 5s;

Since version 1.17.5 and prior to version 1.27.3,
this directive was available only as part of our
commercial subscription.

Embedded Variables

The ngx_stream_upstream_module module
supports the following embedded variables:

$upstream_addr

keeps the IP address and port,
or the path to the UNIX-domain socket of the upstream server (1.11.4).
If several servers were contacted during proxying,
their addresses are separated by commas, e.g.
“192.168.1.1:12345, 192.168.1.2:12345, unix:/tmp/sock”.
If a server cannot be selected,
the variable keeps the name of the server group.

$upstream_bytes_received

number of bytes received from an upstream server (1.11.4).
Values from several connections
are separated by commas like addresses in the
$upstream_addr variable.

$upstream_bytes_sent

number of bytes sent to an upstream server (1.11.4).
Values from several connections
are separated by commas like addresses in the
$upstream_addr variable.

$upstream_connect_time

time to connect to the upstream server (1.11.4);
the time is kept in seconds with millisecond resolution.
Times of several connections
are separated by commas like addresses in the
$upstream_addr variable.

$upstream_first_byte_time

time to receive the first byte of data (1.11.4);
the time is kept in seconds with millisecond resolution.
Times of several connections
are separated by commas like addresses in the
$upstream_addr variable.

$upstream_last_addr

keeps the IP address or the path to the UNIX-domain socket
of the last selected upstream server (1.29.3).

This variable is available as part of our
commercial subscription.

$upstream_session_time

session duration in seconds with millisecond resolution (1.11.4).
Times of several connections
are separated by commas like addresses in the
$upstream_addr variable.