# network() destination options

The `network()` driver sends messages to a remote host (for example, a server or relay) on the local intranet or internet using the RFC3164 syslog protocol (for details about the protocol, see [BSD-syslog or legacy-syslog messages](../../../docs/axosyslog-core/chapter-concepts/concepts-message-structure/concepts-message-bsdsyslog/index.md)). The `network()` driver supports sending messages using the UDP, TCP or the encrypted TLS networking protocols.

These destinations have the following options:

## ca-dir()

|   
---|---  
Accepted values: | Directory name  
Default: | none  
  
_Description:_ The name of a directory that contains a set of trusted CA certificates in PEM format. The CA certificate files have to be named after the 32-bit hash of the subject’s name. This naming can be created using the c_rehash utility in openssl. For an example, see [Configuring TLS on the AxoSyslog clients](../../../docs/axosyslog-core/chapter-encrypted-transport-tls/tls-serverauth/procedure-configuring-tls-client/index.md). The AxoSyslog application uses the CA certificates in this directory to validate the certificate of the peer.

This option can be used together with the optional `ca-file()` option.

## ca-file()

|   
---|---  
Accepted values: | File name  
Default: | empty  
  
_Description:_ Optional. The name of a file that contains a set of trusted CA certificates in PEM format. The AxoSyslog application uses the CA certificates in this file to validate the certificate of the peer.

Example format in configuration:
```
 
       ca-file("/etc/pki/tls/certs/ca-bundle.crt")
    
```

Note The `ca-file()` option can be used together with the `ca-dir()` option, and it is relevant when `peer-verify()` is set to other than `no` or `optional-untrusted`. 

## close-on-input()

|   
---|---  
Type: | `yes  
Default: | yes  
  
_Description:_ By default, AxoSyslog closes destination sockets if it receives any input from the socket (for example, a reply). If this option is set to no, AxoSyslog just ignores the input, but does not close the socket.

## 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()

Type: | number (bytes)  
---|---  
Default: | 1MiB  
  
_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()

Type: | yes/no  
---|---  
Default: | no  
  
_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.

Note Simply unsetting these name-value pairs by using the `unset()` rewrite operation is not enough, as due to performance reasons that help when AxoSyslog is CPU bound, the internal representation of a `LogMessage` will not release the memory associated with these name-value pairs. In some cases, however, the size of this overhead becomes significant (the raw message size can grow up to four times its original size), which unnecessarily increases the disk queue file size. For these cases, the compaction will drop `unset` values, making the `LogMessage` representation smaller at the cost of some CPU time required to perform compaction. 

### dir()

Type: | string  
---|---  
Default: | N/A  
  
_Description:_ Defines the folder where the disk-buffer files are stored.

Warning

When creating a new `dir()` option for a disk buffer, or modifying an existing one, make sure you delete the persist file.

AxoSyslog creates disk-buffer files based on the path recorded in the persist file. Therefore, if the persist file is not deleted after modifying the `dir()` option, then following a restart, AxoSyslog will look for or create disk-buffer files in their old location. To ensure that AxoSyslog uses the new `dir()` setting, the persist file must not contain any information about the destinations which the disk-buffer file in question belongs to.

Note If the `dir()` path provided by the user does not exist, AxoSyslog creates the path with the same permission as the running instance. 

### flow-control-window-bytes()

Type: | number (bytes)  
---|---  
Default: | 163840000  
  
_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()

Type: | number(messages)  
---|---  
Default: | 10000  
  
_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()

Type: | number(messages)  
---|---  
Default: | 1000  
  
_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()

Type: | yes/no  
---|---  
Default: | no  
  
_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()

Type: | yes/no  
---|---  
Default: | no  
  
_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.

Warning Hazard of data loss! If you change the value of `reliable()` option when there are messages in the disk-buffer, the messages stored in the disk-buffer will be lost. 

### truncate-size-ratio()

Type: | number((between 0 and 1))  
---|---  
Default: | 1 (do not truncate)  
  
_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.



Warning Axoflow does not recommend you to change `truncate-size-ratio()`. Only change its value if you understand the performance implications of doing so. 

### 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")
            )
        );
    };
    
```

## failover()

_Description:_ Available only in AxoSyslog version 3.17 and later. For details about how client-side failover works, see [Client-side failover](../../../docs/axosyslog-core/chapter-destinations/concepts-failover/index.md).

### servers()

Type: | list of IP addresses and fully-qualified domain names  
---|---  
Default: | empty  
  
_Description:_ Specifies a secondary destination server where log messages are sent if the primary server becomes inaccessible. To list several failover servers, separate the address of the servers with comma. By default, AxoSyslog waits for the a server before switching to the next failover server is set in the `time-reopen()` option.

If `failback()` is not set, AxoSyslog does not attempt to return to the primary server even if it becomes available. In case the failover server fails, AxoSyslog attempts to connect the next failover server in the list in round-robin fashion.

Warning The failover servers must be accessible on the same port as the primary server. 

### failback()

_Description:_ Available only in AxoSyslog version 3.17 and later.

When AxoSyslog starts up, it always connects to the primary server first. In the `failover()` option there is a possibility to customize the failover modes.

Depending on how you set the `failback()` option, AxoSyslog behaves as follows:

  * `round-robin mode`: If `failback()` is not set, AxoSyslog does not attempt to return to the primary server even if it becomes available. In case the failover server fails, AxoSyslog attempts to connect the next failover server in the list in round-robin fashion.

In the following example AxoSyslog handles the logservers in round-robin fashion if the primary logserver becomes inaccessible (therefore `failback()` option is not set).
```
 destination d_network {
                 network(
                      "primary-server.com"
                      port(601)
                      failover( servers("failover-server1", "failover-server2") )
            );  
            };
        
```

    * `failback mode`: If `failback()` is set, AxoSyslog attempts to return to the primary server.

After AxoSyslog connects a secondary server during a failover, it sends a probe every `tcp-probe-interval()` seconds towards the primary server. If the primary logserver responds with a TCP ACK packet, the probe is successful. When the number of successful probes reaches the value set in the `successful-probes-required()` option, AxoSyslog tries to connect the primary server using the last probe.

Note AxoSyslog always waits for the result of the last probe before sending the next message. So if one connection attempt takes longer than the configured interval, that is, it waits for connection time out, you may experience longer intervals between actual probes. 

In the following example AxoSyslog attempts to return to the primary logserver, as set in the `failback()` option: it will check if the server is accessible every `tcp-probe-interval()` seconds, and reconnect to the primary logserver after three successful connection attempts.
```
 destination d_network_2 {
                   network(
                        "primary-server.com"
                        port(601)
                        failover( 
                      servers("failover-server1", "failover-server2")
                             failback(
                                  successful-probes-required()
                                  tcp-probe-interval()
                             )
                        )
              );  
              };
          
```




Default value for `tcp-probe-interval()`: 60 seconds

Default value for `successful-probes-required()`: 3

### Example: Configuring failover servers

In the following example AxoSyslog handles the logservers in round-robin fashion if the primary logserver becomes uneccassible (therefore `failback()` option is not set).
```
 
       destination demo_failover_roundrobin{
              syslog("primary-logserver.example.com"
                    failover(
                          servers("first-failover-logserver.example.com", "second-failover-logserver.example.com")
                    )
              transport("tcp")
              port(514)
              time-reopen(60)
              );
        };
    
```

In the following example AxoSyslog attempts to return to the primary logserver, as set in the `failback()` option: it will check if the server is accessible every `tcp-probe-interval()` seconds, and reconnect to the primary logserver after three successful connection attempts.
```
 
       destination demo_failover_returntoprimary{
              syslog("primary-logserver.example.com"
                    failover(
                          servers("first-failover-logserver.example.com", "second-failover-logserver.example.com")
                          failback(
                                tcp-probe-interval(120)
                                successful-probes-required(3)
                          )
                    )
              transport("tcp")
              port(514)
              time-reopen(60)
              );
        };
    
```

Note This option is not available for the connection-less UDP protocol, because in this case the client does not detect that the destination becomes inaccessible. 

## flags()

|   
---|---  
Type: | no-multi-line, syslog-protocol  
Default: | empty set  
  
_Description:_ Flags influence the behavior of the destination driver.

  * _no-multi-line_ : The `no-multi-line` flag disables line-breaking in the messages: the entire message is converted to a single line.
  * _syslog-protocol_ : The `syslog-protocol` flag instructs the driver to format the messages according to the new IETF syslog protocol standard (RFC5424), but without the frame header. If this flag is enabled, macros used for the message have effect only for the text of the message, the message header is formatted to the new standard. Note that this flag is not needed for the `syslog` driver, and that the `syslog` driver automatically adds the frame header to the messages.



## flush-lines()

|   
---|---  
Type: | number  
Default: | Use global setting (exception: for http() destination, the default is 1).  
  
_Description:_ Specifies how many lines are flushed to a destination at a time. 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.

The AxoSyslog application flushes the messages if it has sent `flush-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.

For optimal performance when sending messages to an AxoSyslog server, make sure that the value of `flush-lines()` is smaller than the window size set in the `log-iw-size()` option in the source of your server.

## frac-digits()

|   
---|---  
Type: | number  
Default: | 0  
  
_Description:_ The AxoSyslog application can store fractions of a second in the timestamps according to the ISO8601 format. The `frac-digits()` parameter specifies the number of digits stored. The digits storing the fractions are padded by zeros if the original timestamp of the message specifies only seconds. Fractions can always be stored for the time the message was received.

Note The AxoSyslog application can add the fractions to non-ISO8601 timestamps as well. 

Note As AxoSyslog is precise up to the microsecond, when the `frac-digits()` option is set to a value higher than 6, AxoSyslog will truncate the fraction seconds in the timestamps after 6 digits. 

## 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.

Note The AxoSyslog application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable AxoSyslog to execute external applications. 

### Using `hook-commands()` when AxoSyslog starts or stops

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

#### `startup()`

Type: | string  
---|---  
Default: | N/A  
  
_Description:_ Defines the external program that is executed as AxoSyslog starts.

#### `shutdown()`

Type: | string  
---|---  
Default: | N/A  
  
_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()`

Type: | string  
---|---  
Default: | N/A  
  
_Description:_ Defines an external program that is executed when the AxoSyslog configuration is initiated, for example, on startup or during a AxoSyslog reload.

#### `teardown()`

Type: | string  
---|---  
Default: | N/A  
  
_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 hook-commands() with a network source

In the following example, the `hook-commands()` is used with the `network()` driver and it opens an [iptables](<https://en.wikipedia.org/wiki/Iptables> "https://en.wikipedia.org/wiki/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")
            )
         );
    };
    
```

## ip-protocol()

|   
---|---  
Type: | number  
Default: | 4  
  
_Description:_ Determines the internet protocol version of the given driver (`network()` or `syslog()`). The possible values are `4` and `6`, corresponding to IPv4 and IPv6. The default value is `ip-protocol(4)`.

Note that listening on a port using IPv6 automatically means that you are also listening on that port using IPv4. That is, if you want to have receive messages on an IP-address/port pair using both IPv4 and IPv6, create a source that uses the `ip-protocol(6)`. You cannot have two sources with the same IP-address/port pair, but with different `ip-protocol()` settings (it causes an `Address already in use` error).

For example, the following source receives messages on TCP, using the `network()` driver, on every available interface of the host on both IPv4 and IPv6.
```
 
       source s_network_tcp { network( transport("tcp") ip("::") ip-protocol(6) port(601) ); };
    
```

## ip-tos()

|   
---|---  
Type: | number  
Default: | 0  
  
_Description:_ Specifies the Type-of-Service value of outgoing packets.

## ip-ttl()

|   
---|---  
Type: | number  
Default: | 0  
  
_Description:_ Specifies the Time-To-Live value of outgoing packets.

## keep-alive()

|   
---|---  
Type: | yes or no  
Default: | yes  
  
_Description:_ Specifies whether connections to destinations should be closed when `syslog-ng` is reloaded. Note that this applies to the client (destination) side of the connections, server-side (source) connections are always reopened after receiving a HUP signal unless the `keep-alive` option is enabled for the source.

## localip()

|   
---|---  
Type: | string  
Default: | 0.0.0.0  
  
_Description:_ The IP address to bind to before connecting to target.

## localport()

|   
---|---  
Type: | number  
Default: | 0  
  
_Description:_ The port number to bind to. Messages are sent from this port.

## log-fifo-size()

|   
---|---  
Type: | number  
Default: | Use global setting.  
  
_Description:_ The number of messages that the output queue can store.

## mark-freq()

|   
---|---  
Accepted values: | number [seconds]  
Default: | 1200  
  
_Description:_ An alias for the obsolete `mark()` option, retained for compatibility with version 1.6.x.

The number of seconds between two `MARK` messages. `MARK` messages are generated when there was no message traffic to inform the receiver that the connection is still alive. If set to zero (`0`), no `MARK` messages are sent. The `mark-freq()` can be set for global option and/or every `MARK` capable destination driver if `mark-mode()` is periodical or dst-idle or host-idle. If `mark-freq()` is not defined in the destination, then the `mark-freq()` will be inherited from the global options. If the destination uses internal `mark-mode()`, then the global `mark-freq()` will be valid (does not matter what `mark-freq()` set in the destination side).

## mark-mode()

Accepted values: | `internal` | `dst-idle` | `host-idle` | `periodical` | `none` | `global`  
---|---  
Default: | `internal` for pipe, program drivers `none` for file, unix-dgram, unix-stream drivers `global` for syslog, tcp, udp destinations `host-idle` for global option  
  
_Description:_ The `mark-mode()` option can be set for the following destination drivers: file(), program(), unix-dgram(), unix-stream(), network(), pipe(), syslog() and in global option.

  * `internal`: When internal mark mode is selected, internal source should be placed in the log path as this mode does not generate mark by itself at the destination. This mode only yields the mark messages from internal source. This is the mode as AxoSyslog 3.3 worked. `MARK` will be generated by internal source if there was NO traffic on local sources:

`file()`, `pipe()`, `unix-stream()`, `unix-dgram()`, `program()`

  * `dst-idle`: Sends `MARK` signal if there was NO traffic on destination drivers. `MARK` signal from internal source will be dropped.

`MARK` signal can be sent by the following destination drivers: `network()`, `syslog()`, `program()`, `file()`, `pipe()`, `unix-stream()`, `unix-dgram()`.

  * `host-idle`: Sends `MARK` signal if there was NO local message on destination drivers. for example, `MARK` is generated even if messages were received from tcp. `MARK` signal from internal source will be dropped.

`MARK` signal can be sent by the following destination drivers: `network()`, `syslog()`, `program()`, `file()`, `pipe()`, `unix-stream()`, `unix-dgram()`.

  * `periodical`: Sends `MARK` signal perodically, regardless of traffic on destination driver. `MARK` signal from internal source will be dropped.

`MARK` signal can be sent by the following destination drivers: `network()`, `syslog()`, `program()`, `file()`, `pipe()`, `unix-stream()`, `unix-dgram()`.

  * `none`: Destination driver drops all `MARK` messages. If an explicit mark-mode() is not given to the drivers where `none` is the default value, then `none` will be used.

  * `global`: Destination driver uses the global `mark-mode()` setting. Note that setting the global `mark-mode()` to global causes a syntax error in AxoSyslog.




Note In case of `dst-idle`, `host-idle` and `periodical`, the `MARK` message will not be written in the destination, if it is not open yet. 

Available in AxoSyslog 3.4 and later.

## port() or destport()

|   
---|---  
Type: | number  
Default: | 601  
  
_Description:_ The port number to connect to. Note that the default port numbers used by AxoSyslog do not comply with the latest RFC which was published after the release of AxoSyslog 3.0.2, therefore the default port numbers will change in the future releases.

## so-broadcast()

|   
---|---  
Type: | yes or no  
Default: | no  
  
_Description:_ This option controls the `SO_BROADCAST` socket option required to make AxoSyslog send messages to a broadcast address. For details, see the `socket(7)` manual page.

## so-keepalive()

|   
---|---  
Type: | yes or no  
Default: | no  
  
_Description:_ Enables keep-alive messages, keeping the socket open. This only effects TCP and UNIX-stream sockets. For details, see the `socket(7)` manual page.

## so-rcvbuf()

|   
---|---  
Type: | number  
Default: | 0  
  
_Description:_ Specifies the size of the socket receive buffer in bytes. For details, see the `socket(7)` manual page.

## so-sndbuf()

|   
---|---  
Type: | number  
Default: | 0  
  
_Description:_ Specifies the size of the socket send buffer in bytes. For details, see the `socket(7)` manual page.

## spoof-source()

|   
---|---  
Type: | yes or no  
Default: | no  
  
_Description:_ Enables source address spoofing. This means that the host running AxoSyslog generates UDP packets with the source IP address matching the original sender of the message. It is useful when you want to perform some kind of preprocessing using AxoSyslog then forward messages to your central log management solution with the source address of the original sender. This option only works for UDP destinations though the original message can be received by TCP as well. This option is only available if `syslog-ng` was compiled using the `--enable-spoof-source` configuration option.

The maximum size of spoofed datagrams in udp() destinations is set to 1024 bytes by default. To change the maximum size, use the `spoof-source-max-msglen()` option.

Note

Anything above the size of the maximum transmission unit (MTU), which is 1500 bytes by default, is not recommended because of fragmentation.

The maximum datagram in IP protocols (both IPv4 and IPv6) is 65535 bytes including the IP and UDP headers. The minimum size of the IPv4 header is 20 bytes, the IPv6 is 40 bytes, and the UDP is 8 bytes.

Warning To use spoofing on Microsoft Windows platforms, you must also set the `spoof-interface()` option as well. 

## suppress()

|   
---|---  
Type: | seconds  
Default: | 0 (disabled)  
  
_Description:_ If several identical log messages would be sent to the destination without any other messages between the identical messages (for example, an application repeated an error message ten times), AxoSyslog can suppress the repeated messages and send the message only once, followed by the `Last message repeated n times.` message. The parameter of this option specifies the number of seconds AxoSyslog waits for identical messages.

## tcp-keepalive-intvl()

|   
---|---  
Type: | number [seconds]  
Default: | 0  
  
_Description:_ Specifies the interval (number of seconds) between subsequential keepalive probes, regardless of the traffic exchanged in the connection. This option is equivalent to `/proc/sys/net/ipv4/tcp_keepalive_intvl`. The default value is `0`, which means using the kernel default.

Warning

The `tcp-keepalive-time()`, `tcp-keepalive-probes()`, and `tcp-keepalive-intvl()` options only work on platforms which support the `TCP_KEEPCNT`, `TCP_KEEPIDLE`,and `TCP_KEEPINTVL` setsockopts. Currently, this is Linux.

A connection that has no traffic is closed after `tcp-keepalive-time() + tcp-keepalive-intvl() * tcp-keepalive-probes()` seconds.

Available in AxoSyslog version 3.4 and later.

## tcp-keepalive-probes()

|   
---|---  
Type: | number  
Default: | 0  
  
_Description:_ Specifies the number of unacknowledged probes to send before considering the connection dead. This option is equivalent to `/proc/sys/net/ipv4/tcp_keepalive_probes`. The default value is `0`, which means using the kernel default.

Warning

The `tcp-keepalive-time()`, `tcp-keepalive-probes()`, and `tcp-keepalive-intvl()` options only work on platforms which support the `TCP_KEEPCNT`, `TCP_KEEPIDLE`,and `TCP_KEEPINTVL` setsockopts. Currently, this is Linux.

A connection that has no traffic is closed after `tcp-keepalive-time() + tcp-keepalive-intvl() * tcp-keepalive-probes()` seconds.

Available in AxoSyslog version 3.4 and later.

## tcp-keepalive-time()

|   
---|---  
Type: | number [seconds]  
Default: | 0  
  
_Description:_ Specifies the interval (in seconds) between the last data packet sent and the first keepalive probe. This option is equivalent to `/proc/sys/net/ipv4/tcp_keepalive_time`. The default value is `0`, which means using the kernel default.

Warning

The `tcp-keepalive-time()`, `tcp-keepalive-probes()`, and `tcp-keepalive-intvl()` options only work on platforms which support the `TCP_KEEPCNT`, `TCP_KEEPIDLE`,and `TCP_KEEPINTVL` setsockopts. Currently, this is Linux.

A connection that has no traffic is closed after `tcp-keepalive-time() + tcp-keepalive-intvl() * tcp-keepalive-probes()` seconds.

Available in AxoSyslog version 3.4 and later.

## template()

|   
---|---  
Type: | string  
Default: | A format conforming to the default logfile format.  
  
_Description:_ Specifies a template defining the logformat to be used in the destination. Macros are described in [Macros of AxoSyslog](../../../docs/axosyslog-core/chapter-manipulating-messages/customizing-message-format/reference-macros/index.md). Please note that for network destinations it might not be appropriate to change the template as it changes the on-wire format of the syslog protocol which might not be tolerated by stock syslog receivers (like `syslogd` or `syslog-ng` itself). For network destinations make sure the receiver can cope with the custom format defined.

Note If a message uses the IETF-syslog format (RFC5424), only the text of the message can be customized (that is, the $MESSAGE part of the log), the structure of the header is fixed. 

## template-escape()

|   
---|---  
Type: | yes or no  
Default: | no  
  
_Description:_ Turns on escaping for the `'`, `"`, and backspace characters in templated output files. This is useful for generating SQL statements and quoting string contents so that parts of the log message are not interpreted as commands to the SQL server.

> Note: Starting with AxoSyslog version 4.5, `template-escape(yes)` escapes the top-level template function in case of nested template functions.

## time-reopen()

|   
---|---  
Accepted values: | number [seconds]  
Default: | 60  
  
_Description:_ The time to wait in seconds before a dead connection is reestablished.

## throttle()

|   
---|---  
Type: | number  
Default: | 0  
  
_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.

## time-zone()

|   
---|---  
Type: | name of the timezone, or the timezone offset  
Default: | unspecified  
  
_Description:_ Convert timestamps to the timezone specified by this option. If this option is not set, then the original timezone information in the message is used. Converting the timezone changes the values of all date-related macros derived from the timestamp, for example, `HOUR`. For the complete list of such macros, see [Date-related macros](../../../docs/axosyslog-core/chapter-manipulating-messages/customizing-message-format/date-macros/index.md).

The timezone can be specified by using the name, for example, `time-zone("Europe/Budapest")`), or as the timezone offset in +/-HH:MM format, for example, `+01:00`). On Linux and UNIX platforms, the valid timezone names are listed under the `/usr/share/zoneinfo` directory.

## tls()

|   
---|---  
Type: | tls options  
Default: | n/a  
  
_Description:_ This option sets various options related to TLS encryption, for example, key/certificate files and trusted CA locations. TLS can be used only with tcp-based transport protocols. For details, see [TLS options](../../../docs/axosyslog-core/chapter-encrypted-transport-tls/tlsoptions/index.md).

## transport()

|   
---|---  
Type: | udp, tcp, or tls  
Default: | tcp  
  
_Description:_ Specifies the protocol used to send messages to the destination server.

If you use the `udp` transport, AxoSyslog automatically sends multicast packets if a multicast destination address is specified. The `tcp` transport does not support multicasting.

## ts-format()

|   
---|---  
Type: | rfc3164, bsd, rfc3339, iso  
Default: | rfc3164  
  
_Description:_ Override the global timestamp format (set in the global `ts-format()` parameter) for the specific destination. For details, see [ts-format()](../../../docs/axosyslog-core/chapter-global-options/reference-options/index.md).

Note This option applies only to file and file-like destinations. Destinations that use specific protocols (for example, `network()`, or `syslog()`) ignore this option. For protocol-like destinations, use a template locally in the destination, or use the [proto-template](../../../docs/axosyslog-core/chapter-global-options/reference-options/index.md) option. 

Last modified January 4, 2024: [Delete some leftover RLTP references (cf172d7)](<https://github.com/axoflow/axosyslog-core-docs/commit/cf172d7b057a8a622f89f58d99624f99e9495e10>)