java: Post messages over HTTP using Java

• 1: HTTP destination options

   java(
        class-path("/syslog-ng/install_dir/lib/syslog-ng/java-modules/*.jar")
        class-name("org.syslog_ng.http.HTTPDestination")
    
        option("url", "http://<server-address>:<port-number>")
    
    );

   destination d_http {
        java(
            class-path("/syslog-ng/install_dir/lib/syslog-ng/java-modules/*.jar")
            class-name("org.syslog_ng.http.HTTPDestination")
    
            option("url", "http://192.168.1.1:80")
        );
    };
    
    log
        { source(s_file); destination(d_http); flags(flow-control); };

1 - HTTP destination options

The http destination of AxoSyslog can directly post log messages to web services using the HTTP protocol. The http destination has the following options. Some of these options are directly used by the Java code underlying the http destination, therefore these options must be specified in the following format:

   option("<option-name>", "<option-value>")

For example, option("url", "http://<server-address>:<port-number>"). The exact format to use is indicated in the description of the option.

Required options

The following options are required: url().

ca-dir()

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. 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()

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")

class-name()

Description: The name of the class (including the name of the package) that includes the destination driver to use.

For the http destination, use this option as class-name("org.syslog_ng.http.HTTPDestination").

client-lib-dir()

Description: The list of the paths where the required Java classes are located. For example, class-path("/opt/syslog-ng/lib/syslog-ng/java-modules/:/opt/my-java-libraries/libs/"). If you set this option multiple times in your AxoSyslog configuration (for example, because you have multiple Java-based destinations), AxoSyslog will merge every available paths to a single list.

For the http destination, include the path to the java modules of AxoSyslog, for example, class-path("/syslog-ng/install_dir/lib/syslog-ng/java-modules/*.jar").

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 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")
        )
     );
};

jvm-options()

Description: Specify the Java Virtual Machine (JVM) settings of your Java destination from the AxoSyslog configuration file.

For example:

   jvm-options("-Xss1M -XX:+TraceClassLoading")

You can set this option only as a global option, by adding it to the options statement of the syslog-ng.conf configuration file.

log-fifo-size()

Description: The number of messages that the output queue can store.

method()

Description: Specifies the HTTP method to use when sending the message to the server. Available in AxoSyslog version 3.7.2 and newer.

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.

template()

Description: Specifies a template defining the logformat to be used in the destination. Macros are described in Macros of AxoSyslog. 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.

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.

url()

Description: Specifies the hostname or IP address and optionally the port number of the web service that can receive log data via HTTP. Use a colon (:) after the address to specify the port number of the server. You can also use macros, templates, and template functions in the URL, for example: http://host.example.com:8080/${MACRO1}/${MACRO2}/script")