# 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("", "") ``` For example, `option("url", "http://:")`. The exact format to use is indicated in the description of the option. ## Required options The following options are required: `url()`. ## 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`. ## class-name() | ---|--- Type: | string Default: | N/A _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() | ---|--- Type: | string Default: | The AxoSyslog module directory: /opt/syslog-ng/lib/syslog-ng/java-modules/ _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. 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") 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() | ---|--- Type: | list Default: | N/A _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](../../../docs/axosyslog-core/chapter-global-options/index.md), by adding it to the `options` statement of the `syslog-ng.conf` configuration file. ## log-fifo-size() | ---|--- Type: | number Default: | Use global setting. _Description:_ The number of messages that the output queue can store. ## method() | ---|--- Type: | DELETE Default: | PUT _Description:_ Specifies the HTTP method to use when sending the message to the server. Available in AxoSyslog version 3.7.2 and newer. ## retries() | ---|--- Type: | number (of attempts) Default: | 3 _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() | ---|--- 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. ## 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. ## url() | ---|--- Type: | URL Default: | _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")` Last modified May 8, 2026: [Renames hook-commands snippet (473feff3)]()