mirror of
https://github.com/mailscope/kumomta.git
synced 2026-10-29 09:46:15 +00:00
Wez Furlong
d3ba5ccd2c
To support distributed connection limits, adjust the way that connection limits are handled. Previously, we'd do a simple in-memory comparison with the limit to guide whether we had reached the limit. In a distributed/clustered scenario we need a shared understanding of the state of the connections, so we're moving to a lease-based model. Each connection is associated with a UUID. Each egress path maintains a set of connections and their UUIDs. When attempting to make a new connection, we can only proceed if the number of connections associated with an egress path is below the limit. When a connection is closed, its UUID is removed from the associated set. To handle crashes, kills and netsplits, the path -> uuid association is also accompanied by an expiration time beyond which it can be assumed that the lease is no longer valid. We compute that time based on the worst case timeout value for a single message send on the given pathway. Each time a connection is ready to obtain a new message, it will try to extend its lease by that same duration. This commit introduces these concepts and models them using an in-memory store for the single node case, and using redis for the cluster case. When your policy enables `kumo.configure_redis_throttles`, that same redis configuration is used to back to the connection limiting functionality. refs: https://github.com/KumoCorp/kumomta/issues/41
283 lines
8.7 KiB
Markdown
283 lines
8.7 KiB
Markdown
# `kumo.make_egress_path { PARAMS }`
|
|
|
|
Constructs a configuration object that specifies how traffic travelling the
|
|
path from a *source* to a *site* will behave.
|
|
|
|
This function should be called from the
|
|
[get_egress_path_config](../events/get_egress_path_config.md) event handler to provide the
|
|
configuration for the requested site.
|
|
|
|
The following keys are possible:
|
|
|
|
## connection_limit
|
|
|
|
Specifies the maximum number of concurrent connections that will be made from
|
|
the current MTA machine to the destination site.
|
|
|
|
```lua
|
|
kumo.on('get_egress_path_config', function(domain, source_name, site_name)
|
|
return kumo.make_egress_path {
|
|
connection_limit = 32,
|
|
}
|
|
end)
|
|
```
|
|
|
|
## consecutive_connection_failures_before_delay
|
|
|
|
Each time KumoMTA exhausts the full list of hosts for the destination it
|
|
increments a `consecutive_connection_failures` counter. When that counter
|
|
exceeds the `consecutive_connection_failures_before_delay` configuration value,
|
|
KumoMTA will then delay all of the messages currently in the ready queue,
|
|
generating a transient failure log record with code `451 4.4.1 No answer from
|
|
any hosts listed in MX`.
|
|
|
|
The default value for this setting is 100.
|
|
|
|
## ehlo_domain
|
|
|
|
Optional string. Specifies the EHLO domain when initiating a connection to the
|
|
destination. The default value is the `ehlo_domain` specified by
|
|
[make_egress_source](make_egress_source.md), if any, otherwise, the local
|
|
machine hostname.
|
|
|
|
## enable_tls
|
|
|
|
Controls whether and how TLS will be used when connecting to the destination.
|
|
Possible values are:
|
|
|
|
* `"Opportunistic"` - use TLS if advertised by the `EHLO` response. If the peer
|
|
has invalid or self-signed certificates, then the delivery will fail. KumoMTA
|
|
will NOT fallback to not using TLS on that same host.
|
|
|
|
* `"OpportunisticInsecure"` - use TLS if advertised by the `EHLO` response.
|
|
Validation of the certificate will be skipped. Not recommended for sending to
|
|
the public internet; this is intended for local or lab testing scenarios.
|
|
|
|
* `"Required"` - Require that TLS be advertised in the `EHLO` response. The
|
|
remote host must have valid certificates in order to deliver to the site.
|
|
|
|
* `"RequiredInsecure"` - Require that TLS be advertised in the `EHLO` response.
|
|
Validation of the certificate will be skipped. Not recommended for sending
|
|
to the public internet; this is intended for local or lab testing scenarios.
|
|
|
|
* `"Disabled" - do not try to use TLS.
|
|
|
|
The default value is `"Opportunistic"`.
|
|
|
|
```lua
|
|
kumo.on('get_egress_path_config', function(domain, source_name, site_name)
|
|
return kumo.make_egress_path {
|
|
enable_tls = 'Opportunistic',
|
|
}
|
|
end)
|
|
```
|
|
|
|
## connect_timeout
|
|
## starttls_timeout
|
|
## ehlo_timeout
|
|
## mail_from_timeout
|
|
## rcpt_to_timeout
|
|
## data_timeout
|
|
## data_dot_timeout
|
|
## rset_timeout
|
|
|
|
Controls the timeouts waiting for responses to various SMTP commands.
|
|
|
|
The value is specified as a integer in seconds, or as a string using syntax
|
|
like `"2min"` for a two minute duration.
|
|
|
|
## idle_timeout
|
|
how long a connection will remain open and idle, waiting to be
|
|
reused for another delivery attempt, before being closed.
|
|
|
|
The value is specified as a integer in seconds, or as a string using syntax
|
|
like `"2min"` for a two minute duration.
|
|
|
|
|
|
```lua
|
|
kumo.on('get_egress_path_config', function(domain, source_name, site_name)
|
|
return kumo.make_egress_path {
|
|
idle_timeout = 60,
|
|
}
|
|
end)
|
|
```
|
|
|
|
## max_connection_rate
|
|
|
|
Optional string.
|
|
|
|
Specifies the maximum permitted rate at which connections can be established
|
|
from this source to the corresponding destination site.
|
|
|
|
The value is of the form `quantity/period`
|
|
where quantity is a number and period can be a measure of time.
|
|
|
|
Examples of throttles:
|
|
|
|
```
|
|
"10/s" -- 10 per second
|
|
"10/sec" -- 10 per second
|
|
"10/second" -- 10 per second
|
|
|
|
"50/m" -- 50 per minute
|
|
"50/min" -- 50 per minute
|
|
"50/minute" -- 50 per minute
|
|
|
|
"1,000/hr" -- 1000 per hour
|
|
"1_000/h" -- 1000 per hour
|
|
"1000/hour" -- 1000 per hour
|
|
|
|
"10_000/d" -- 10,000 per day
|
|
"10,000/day" -- 10,000 per day
|
|
```
|
|
|
|
Throttles are implemented using a Generic Cell Rate Algorithm.
|
|
|
|
```lua
|
|
kumo.on('get_egress_path_config', function(domain, source_name, site_name)
|
|
return kumo.make_egress_path {
|
|
max_connection_rate = '100/min',
|
|
}
|
|
end)
|
|
```
|
|
|
|
If the throttle is exceeded and the delay before a connection be established
|
|
is longer than the `idle_timeout`, then the messages in the ready queue
|
|
will be delayed until the throttle would permit them to be delievered again.
|
|
|
|
## max_deliveries_per_connection
|
|
|
|
Optional number.
|
|
|
|
If set, no more than this number of messages will be attempted on any
|
|
given connection.
|
|
|
|
|Version|Default|
|
|
|-------|-------|
|
|
|{{since('dev', inline=True)}}|The default is 1024|
|
|
|Prior versions|The default is unlimited|
|
|
|
|
## max_message_rate
|
|
|
|
Optional string.
|
|
|
|
Specifies the maximum permitted rate at which messages can be delivered
|
|
from this source to the corresponding destination site.
|
|
|
|
The throttle is specified the same was as for `max_connection_rate` above.
|
|
|
|
If the throttle is exceeded and the delay before the current message can be
|
|
sent is longer than the `idle_timeout`, then the messages in the ready queue
|
|
will be delayed until the throttle would permit them to be delievered again.
|
|
|
|
## max_ready
|
|
|
|
Specifies the maximum number of messages that can be in the *ready queue*.
|
|
The ready queue is the set of messages that are immediately eligible for delivery.
|
|
|
|
If a message is promoted from its delayed queue to the ready queue and it would
|
|
take the size of the ready queue above *max_ready*, the message will be delayed
|
|
by a randomized interval of up to 60 seconds and placed back into the scheduled
|
|
queue before being considered again.
|
|
|
|
Moving a message from *ready* to *scheduled* as a result of hitting this limit
|
|
may trigger disk IO to save the content of the message if the message was
|
|
received with deferred spooling enabled. In addition, other in-memory state
|
|
is discarded to reduce memory utilization, and it will need to be re-loaded
|
|
from the spool when the message is tried again later.
|
|
|
|
The default for `max_ready` is 1024 messages.
|
|
|
|
Raising the limit will increase RAM utilization in exchange for decreasing
|
|
the IO load to your spool storage.
|
|
|
|
## prohibited_hosts
|
|
|
|
A CIDR list of hosts that should be considered "poisonous", for example, because
|
|
they might cause a mail loop.
|
|
|
|
When resolving the hosts for the destination MX, if any of the hosts are
|
|
present in the `prohibited_hosts` list then the ready queue will be immediately
|
|
failed with a `550 5.4.4` status.
|
|
|
|
## skip_hosts
|
|
|
|
A CIDR list of hosts that should be removed from the list of hosts returned
|
|
when resolving the MX for the destination domain.
|
|
|
|
This can be used for example to skip a host that is experiencing issues.
|
|
|
|
If all of the hosts returned for an MX are filtered out by `skip_hosts` then
|
|
the ready queue will be immediately failed with a `550 5.4.4` status.
|
|
|
|
## smtp_port
|
|
|
|
Specifies the port to connect to when making an SMTP connection to a destination
|
|
MX host.
|
|
|
|
The default is port 25.
|
|
|
|
See also [kumo.make_egress_source().remote_port](make_egress_source.md#remote_port)
|
|
|
|
## smtp_auth_plain_username
|
|
|
|
When set, connecting to the destination requires a successful AUTH PLAIN using the
|
|
specified username.
|
|
|
|
AUTH PLAIN will only be attempted if TLS is also enabled, unless
|
|
`allow_smtp_auth_plain_without_tls = true`. This is to prevent leaking
|
|
of the credential over an unencrypted link.
|
|
|
|
```lua
|
|
kumo.on('get_egress_path_config', function(domain, site_name)
|
|
return kumo.make_egress_path {
|
|
enable_tls = 'Required',
|
|
smtp_auth_plain_username = 'scott',
|
|
-- The password can be any keysource value
|
|
smtp_auth_plain_password = {
|
|
key_data = 'tiger',
|
|
},
|
|
}
|
|
end)
|
|
```
|
|
|
|
## smtp_auth_plain_password
|
|
|
|
Specifies the password that should be used together with `smtp_auth_plain_username`
|
|
when an authenticated SMTP connection is desired.
|
|
|
|
The value is any [keysource](../keysource.md), which allows for specifying the
|
|
password inline in the configuration file, or managing it via a credential manager
|
|
such as HashiCorp Vault.
|
|
|
|
```lua
|
|
kumo.on('get_egress_path_config', function(domain, site_name)
|
|
return kumo.make_egress_path {
|
|
enable_tls = 'Required',
|
|
smtp_auth_plain_username = 'scott',
|
|
-- The password can be any keysource value.
|
|
-- Here we are loading the credential for the domain
|
|
-- from HashiCorp vault
|
|
smtp_auth_plain_password = {
|
|
vault_mount = 'secret',
|
|
vault_path = 'smtp-auth/' .. domain,
|
|
},
|
|
}
|
|
end)
|
|
```
|
|
|
|
## allow_smtp_auth_plain_without_tls
|
|
|
|
Optional boolean. Defaults to `false`.
|
|
|
|
When `false`, and the connection is not using TLS, SMTP AUTH PLAIN will be
|
|
premptively failed in order to prevent the credential from being passed over
|
|
the network in clear text.
|
|
|
|
You can set this to `true` to allow sending the credential in clear text.
|
|
|
|
!!! danger
|
|
Do not enable this option on an untrusted network, as the credential
|
|
will then be passed in clear text and visible to anyone else on the
|
|
network
|