amqp() destination options

The amqp() driver publishes messages using the AMQP (Advanced Message Queuing Protocol).

The amqp() destination has the following options:

auth-method()

Description: The amqp() driver supports the following types of authentication:

• plain: Authentication happens using username and password. This is the default.

• external: Authentication happens using an out-of-band mechanism, for example, x509 certificate peer verification, client IP address range, or similar. For more information, see the RabbitMQ documentation.

batch-bytes()

Description: Sets the maximum size of payload in a batch. If the size of the messages reaches this value, AxoSyslog sends the batch to the destination even if the number of messages is less than the value of the batch-lines() option.

Note that if the batch-timeout() option is enabled and the queue becomes empty, AxoSyslog flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-bytes().

Available in AxoSyslog version 3.19 and later.

batch-lines()

Description: Specifies how many lines are flushed to a destination in one batch. The AxoSyslog application waits for this number of lines to accumulate and sends them off in a single batch. Increasing this number increases throughput as more messages are sent in a single batch, but also increases message latency.

For example, if you set batch-lines() to 100, AxoSyslog waits for 100 messages.

If the batch-timeout() option is disabled, the AxoSyslog application flushes the messages if it has sent batch-lines() number of messages, or the queue became empty. If you stop or reload AxoSyslog or in case of network sources, the connection with the client is closed, AxoSyslog automatically sends the unsent messages to the destination.

Note that if the batch-timeout() option is enabled and the queue becomes empty, AxoSyslog flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-lines().

For optimal performance, make sure that the AxoSyslog source that feeds messages to this destination is configured properly: the value of the log-iw-size() option of the source must be higher than the batch-lines()*workers() of the destination. Otherwise, the size of the batches cannot reach the batch-lines() limit.

batch-timeout()

Description: Specifies the time AxoSyslog waits for lines to accumulate in the output buffer. The AxoSyslog application sends batches to the destinations evenly. The timer starts when the first message arrives to the buffer, so if only few messages arrive, AxoSyslog sends messages to the destination at most once every batch-timeout() milliseconds.

body()

Description: The body of the AMQP message. You can also use macros and templates.

ca-file()

Description: Name of a file, that contains the trusted CA certificate in PEM format. For example: ca-file("/home/certs/syslog-ng/tls/cacert.pem"). The AxoSyslog application uses this CA certificate to validate the certificate of the peer.

An alternative way to specify this option is to put into a tls() block and specify it there, together with any other TLS options. This allows you to separate these options and ensure better readability.

Declaration:

   destination  d_ampqp {
        amqp(
            host("127.0.0.1")
            port(5672)
            username("test")
            password("test")
            tls(
                ca-file("ca")
                cert-file("cert") 
                key-file("key")
                peer-verify(yes|no)
            )
        );
    };

Make sure that you specify TLS options either using their own dedicated option (ca-file(), cert-file(), key-file(), and peer-verify()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

cert-file()

Description: Name of a file, that contains an X.509 certificate (or a certificate chain) in PEM format, suitable as a TLS certificate, matching the private key set in the key-file() option. The AxoSyslog application uses this certificate to authenticate the AxoSyslog client on the destination server. If the file contains a certificate chain, the file must begin with the certificate of the host, followed by the CA certificate that signed the certificate of the host, and any other signing CAs in order.

An alternative way to specify this option is to put into a tls() block and specify it there, together with any other TLS options. This allows you to separate these options and ensure better readability.

Declaration:

   destination  d_ampqp {
        amqp(
            host("127.0.0.1")
            port(5672)
            username("test")
            password("test")
            tls(
                ca-file("ca")
                cert-file("cert") 
                key-file("key")
                peer-verify(yes|no)
            )
        );
    };

Make sure that you specify TLS options either using their own dedicated option (ca-file(), cert-file(), key-file(), and peer-verify()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

disk-buffer()

Description: This option enables putting outgoing messages into the disk buffer of the destination to avoid message loss in case of a system failure on the destination side. It has the following options:

capacity-bytes()

Description: This is a required option. The maximum size of the disk-buffer in bytes. The minimum value is 1048576 bytes. If you set a smaller value, the minimum value will be used automatically. It replaces the old log-disk-fifo-size() option.

In AxoSyslog version 4.2 and earlier, this option was called disk-buf-size().

compaction()

Description: If set to yes, AxoSyslog prunes the unused space in the LogMessage representation, making the disk queue size smaller at the cost of some CPU time. Setting the compaction() argument to yes is recommended when numerous name-value pairs are unset during processing, or when the same names are set multiple times.

dir()

Description: Defines the folder where the disk-buffer files are stored.

flow-control-window-bytes()

Description: Use this option if the option reliable() is set to yes. This option contains the size of the messages in bytes that is used in the memory part of the disk buffer. It replaces the old log-fifo-size() option. It does not inherit the value of the global log-fifo-size() option, even if it is provided. Note that this option will be ignored if the option reliable() is set to no.

In AxoSyslog version 4.2 and earlier, this option was called mem-buf-size().

flow-control-window-size()

Description: Use this option if the option reliable() is set to no. This option contains the number of messages stored in overflow queue. It replaces the old log-fifo-size() option. It inherits the value of the global log-fifo-size() option if provided. If it is not provided, the default value is 10000 messages. Note that this option will be ignored if the option reliable() is set to yes.

In AxoSyslog version 4.2 and earlier, this option was called mem-buf-length().

front-cache-size()

Description: The number of messages stored in the output buffer of the destination. Note that if you change the value of this option and the disk-buffer already exists, the change will take effect when the disk-buffer becomes empty.

Options reliable() and capacity-bytes() are required options.

In AxoSyslog version 4.2 and earlier, this option was called qout-size().

prealloc()

Description:

By default, AxoSyslog doesn’t reserve the disk space for the disk-buffer file, since in a properly configured and sized environment the disk-buffer is practically empty, so a large preallocated disk-buffer file is just a waste of disk space. But a preallocated buffer can prevent other data from using the intended buffer space (and elicit a warning from the OS if disk space is low), preventing message loss if the buffer is actually needed. To avoid this problem, when using AxoSyslog 4.0 or later, you can preallocate the space for your disk-buffer files by setting prealloc(yes).

In addition to making sure that the required disk space is available when needed, preallocated disk-buffer files provide radically better (3-4x) performance as well: in case of an outage the amount of messages stored in the disk-buffer is continuously growing, and using large continuous files is faster, than constantly waiting on a file to change its size.

If you are running AxoSyslog on a dedicated host (always recommended for any high-volume settings), use prealloc(yes).

Available in AxoSyslog 4.0 and later.

reliable()

Description: If set to yes, AxoSyslog cannot lose logs in case of reload/restart, unreachable destination or AxoSyslog crash. This solution provides a slower, but reliable disk-buffer option. It is created and initialized at startup and gradually grows as new messages arrive. If set to no, the normal disk-buffer will be used. This provides a faster, but less reliable disk-buffer option.

truncate-size-ratio()

Description: Limits the truncation of the disk-buffer file. Truncating the disk-buffer file can slow down the disk IO operations, but it saves disk space. By default, AxoSyslog version 4.0 and later doesn’t truncate disk-buffer files by default (truncate-size-ratio(1)). Earlier versions freed the disk-space when at least 10% of the disk-buffer file could be freed (truncate-size-ratio(0.1)).

AxoSyslog only truncates the file if the possible disk gain is more than truncate-size-ratio() times capacity-bytes().

• Smaller values free disk space quicker.
• Larger ratios result in better performance.

If you want to avoid performance fluctuations:

• use truncate-size-ratio(1) (never truncate), or
• use prealloc(yes) to reserve the entire size of the disk-buffer on disk.

Example: Examples for using disk-buffer()

In the following case reliable disk-buffer() is used.

   destination d_demo {
        network(
            "127.0.0.1"
            port(3333)
            disk-buffer(
                flow-control-window-bytes(10000)
                capacity-bytes(2000000)
                reliable(yes)
                dir("/tmp/disk-buffer")
            )
        );
    };

In the following case normal disk-buffer() is used.

   destination d_demo {
        network(
            "127.0.0.1"
            port(3333)
               disk-buffer(
                flow-control-window-size(10000)
                capacity-bytes(2000000)
                reliable(no)
                dir("/tmp/disk-buffer")
            )
        );
    };

exchange()

Description: The name of the AMQP exchange where AxoSyslog sends the message. Exchanges take a message and route it into zero or more queues.

exchange-declare()

Description: By default, AxoSyslog does not create non-existing exchanges. Use the exchange-declare(yes) option to automatically create exchanges.

exchange-type()

Description: The type of the AMQP exchange.

frame-size()

Description: Sets maximal frame size (the frame-max option described in the AMQP Reference Guide.

heartbeat()

Description: If enabled, the AxoSyslog amqp destination sends heartbeat messages to the server periodically. During negotiation, both the amqp server and the client provide a heartbeat parameter, and the smaller is chosen for heartbeat interval. For example:

   destination { amqp(
        vhost("/")
        exchange("logs")
        body("hello world")
        heartbeat(10)
        username(guest) password(guest)
        );
    };

Available in AxoSyslog version 3.21 and later.

hook-commands()

Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.

Using hook-commands() when AxoSyslog starts or stops

To execute an external program when AxoSyslog starts or stops, use the following options:

startup()

Description: Defines the external program that is executed as AxoSyslog starts.

shutdown()

Description: Defines the external program that is executed as AxoSyslog stops.

Using the hook-commands() when AxoSyslog reloads

To execute an external program when the AxoSyslog configuration is initiated or torn down, for example, on startup/shutdown or during a AxoSyslog reload, use the following options:

setup()

Description: Defines an external program that is executed when the AxoSyslog configuration is initiated, for example, on startup or during a AxoSyslog reload.

teardown()

Description: Defines an external program that is executed when the AxoSyslog configuration is stopped or torn down, for example, on shutdown or during a AxoSyslog reload.

Example: Using the hook-commands() with a network source

In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as AxoSyslog is started/stopped.

The assumption in this example is that the LOGCHAIN chain is part of a larger ruleset that routes traffic to it. Whenever the AxoSyslog created rule is there, packets can flow, otherwise the port is closed.

   source {
       network(transport(udp)
        hook-commands(
              startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
              shutdown("iptables -D LOGCHAIN 1")
            )
         );
    };

host()

Description: The hostname or IP address of the AMQP server.

key-file()

Description: The name of a file that contains an unencrypted private key in PEM format, suitable as a TLS key. If properly configured, the AxoSyslog application uses this private key and the matching certificate (set in the cert-file() option) to authenticate the AxoSyslog client on the destination server.

max-channel()

Description: Sets maximal number of channels (the channel-max option described in the AMQP Reference Guide.

An alternative way to specify this option is to put into a tls() block and specify it there, together with any other TLS options. This allows you to separate these options and ensure better readability.

Declaration:

   destination  d_ampqp {
        amqp(
            host("127.0.0.1")
            port(5672)
            username("test")
            password("test")
            tls(
                ca-file("ca")
                cert-file("cert") 
                key-file("key")
                peer-verify(yes|no)
            )
        );
    };

Make sure that you specify TLS options either using their own dedicated option (ca-file(), cert-file(), key-file(), and peer-verify()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

password()

Description: The password used to authenticate on the AMQP server.

peer-verify()

Description: Verification method of the peer. The following table summarizes the possible options and their results depending on the certificate of the peer.

For untrusted certificates only the existence of the certificate is checked, but it does not have to be valid — AxoSyslog accepts the certificate even if it is expired, signed by an unknown CA, or its CN and the name of the machine mismatches.

An alternative way to specify this option is to put into a tls() block and specify it there, together with any other TLS options. This allows you to separate these options and ensure better readability.

Declaration:

   destination  d_ampqp {
        amqp(
            host("127.0.0.1")
            port(5672)
            username("test")
            password("test")
            tls(
                ca-file("ca")
                cert-file("cert") 
                key-file("key")
                peer-verify(yes|no)
            )
        );
    };

Make sure that you specify TLS options either using their own dedicated option (ca-file(), cert-file(), key-file(), and peer-verify()), or using the tls() block and inserting the relevant options within tls(). Avoid mixing the two methods. In case you do specify TLS options in both ways, the one that comes later in the configuration file will take effect.

persistent()

Description: If this option is enabled, the AMQP server or broker will store the messages on its hard disk. That way, the messages will be retained if the AMQP server is restarted, if the message queue is set to be durable on the AMQP server.

port()

Description: The port number of the AMQP server.

retries()

Description: If AxoSyslog cannot send a message, it will try again until the number of attempts reaches retries().

If the number of attempts reaches retries(), AxoSyslog will wait for time-reopen() time, then tries sending the message again.

routing-key()

Description: Specifies a routing key for the exchange. The routing key selects certain messages published to an exchange to be routed to the bound queue. In other words, the routing key acts like a filter. The routing key can include macros and templates.

time-reopen()

Description: The time to wait in seconds before a dead connection is reestablished.

throttle()

Description: Sets the maximum number of messages sent to the destination per second. Use this output-rate-limiting functionality only when using disk-buffer as well to avoid the risk of losing messages. Specifying 0 or a lower value sets the output limit to unlimited.

username()

Description: The username used to authenticate on the AMQP server.

value-pairs()

Description: The value-pairs() option creates structured name-value pairs from the data and metadata of the log message. For details on using value-pairs(), see Structuring macros, metadata, and other value-pairs.

vhost()

Description: The name of the AMQP virtual host to send the messages to.