|
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Caution:
Note that in earlier versions of syslog-ng Premium Edition, Advanced Log Transport Protocol is called Reliable Log Transfer Protocol (RLTP). |
You can use ALTP between multiple syslog-ng PE hosts, for example, in a client-relay-server scenario. In this case, the communication described in How ALTP connections work applies both between the client and the relay, and the relay and the server. However, note the following points:
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Unless you use disk-buffer on the relay, the relay waits for acknowledgment from the server before acknowledging the messages to the client. If you send the messages in large batches, and the server can process the messages slowly (or the network connection is slow), you might have to adjust the message-acknowledgment-timeout() on the client.
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If you use reliable disk-buffer on the relay, the relay will acknowledge the messages when the messages are written to the disk-buffer. That way, the client does not have to wait for the server to acknowledge the messages.
The following options are specific to the ALTP protocol. Note that when using ALTP in a source or a destination, the options of the syslog() or the network() driver can be used as well.
|
|
Caution:
Note that in earlier versions of syslog-ng Premium Edition, Advanced Log Transport Protocol is called Reliable Log Transfer Protocol (RLTP). |
allow-plain-compress()
| Accepted values: |
yes | no |
| Default: |
no |
Description: Enable on-the-wire compression in the ALTP communication. Note that this option must be enabled both on the server and the client side to have any effect. Enabling compression can significantly reduce the bandwidth required to transport the messages, but can slightly decrease the performance of syslog-ng PE, reducing the number of transferred messages. The allow-plain-compress() option can be used in source and destination drivers as well. Available in syslog-ng PE 7.0.12 and later. Note that in earlier versions, the name of this option was allow-compress().
batch-size()
| Accepted values: |
number |
| Default: |
1000 |
Description: Specifies the number of lines that are sent to a destination at a time. The syslog-ng PE application waits for this number of lines to accumulate and sends them off in a single batch. Setting this number high increases throughput as fully filled frames are sent to the network, but also increases message latency. Available in syslog-ng PE 7.0.10 and later.
message-acknowledgment-timeout()
| Type: |
number (seconds) |
| Default: |
900 |
Description: When the receiver (syslog-ng PE server) receives and successfully processes a message, it sends an acknowledgment to the sender (the syslog-ng PE client). If the receiver does not acknowledge receiving the messages within this period, the sender terminates the connection with the receiver. Use this option only in destination drivers.
response-timeout()
| Type: |
number (seconds) |
| Default: |
60 |
Description: If syslog-ng PE does not receive any protocol-related message in the given timeframe (except for message acknowledgment, which is governed by the message-acknowledgment-timeout() option), syslog-ng PE terminates the connection with the peer, and the "Connection broken" message appears in the logs of the sender (the syslog-ng PE client). This is normal, and happens when the sender does not send any new message to the receiver.
Under normal circumstances, you should not change the value of this option. The response-timeout() option can be used in source and destination drivers as well.
tls-required()
| Type: |
yes, optional, no |
| Default: |
optional |
Description: Determines whether STARTTLS is to be used during communication. If the option is set to yes, you must also configure the tls() option to specify other parameters of the TLS connection (for example, the authentication of the server and the client).
The tls-required() option can be used in source and destination drivers as well.
For example, if you configure tls-required(yes) on the server side and tls-required(no) on the client side, the connection is dropped. If one of them is set to optional, the configuration of the other side will decide if TLS is used or not. If both sides are set to optional, and the tls() option is properly configured, TLS encryption will be used. The following table summarizes the possible options and their results.
Note that the various parameters of the tls() option are considered in the connection only if the tls-required() settings of the peers result in TLS-encryption in the following table. In other words: the tls-required() option of ALTP determines if TLS should be used at all, while the peer-verify() option of the tls()setting determines if the TLS connection can be actually established.
| tls-required() setting on the client |
yes |
TLS-encryption |
rejected connection |
TLS-encryption |
| no |
rejected connection |
unencrypted connection |
unencrypted connection |
| optional |
TLS-encryption |
unencrypted connection |
TLS-encryption if the tls() option is set, unencrypted connection otherwise |
Setting tls-required(optional) on your server allows you to receive both encrypted and unencrypted connections on the same port.
|
|
Caution:
Note that in earlier versions of syslog-ng Premium Edition, Advanced Log Transport Protocol is called Reliable Log Transfer Protocol (RLTP). |
Example: Simple ALTP connection
The sender and the receiver use ALTP over the network() protocol. Since the tls() option is not configured neither on the sender nor on the receiver, the communication will be unencrypted.
Receiver configuration (syslog-ng PE server):
source s_network_altp {
network(
ip("127.0.0.1")
port("5555")
transport(altp)
ip-protocol(4)
);
};
Sender configuration (syslog-ng PE client):
destination d_network_altp {
network(
"127.0.0.1"
port("5555")
transport(altp)
ip-protocol(4)
);
};
Example: ALTP with TLS encryption
The following example configures a sender and a receiver to communicate using ALTP. Since the tls-required() option is set to optional on the receiver and yes on the sender, and the tls() option is configured, the communication will be TLS-encrypted. For the sender (syslog-ng PE client), reliable disk-buffering is enabled to prevent data loss.
Receiver configuration (syslog-ng PE server):
source s_syslog_altp {
syslog(
ip("127.0.0.1")
port("4444")
transport(altp(tls-required(optional)))
ip-protocol(4)
tls(
peer-verify(required-trusted)
ca-dir("/var/tmp/client/")
key-file("/var/tmp/server/server_priv.key")
cert-file("/var/tmp/server/server.crt")
)
);
};
Sender configuration (syslog-ng PE client):
destination d_syslog_altp {
syslog(
"127.0.0.1"
port("4444")
transport(altp(tls-required(yes)))
ip-protocol(4)
disk-buffer( mem-buf-size(200000) disk-buf-size(2000000) reliable(yes) )
tls(
peer-verify(required-trusted)
ca-dir("/var/tmp/server/")
key-file("/var/tmp/client/client_priv.key")
cert-file("/var/tmp/client/client.crt")
)
);
};
Reliability and minimizing the loss of log messages
