# 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. ## accept-encoding() | ---|--- Type: | `"identity"`, `"gzip"`, `"deflate"`, `"all"` Default: | N/A (disabled) _Description:_ Use `accept-encoding()` to request the server to compress the HTTP responses. (AxoSyslog doesn’t currently use them, but they still contribute to network traffic.) To compress the messages sent by AxoSyslog, see the [`content-compression()` option](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/reference-destination-http-nonjava/index.md#content-compression). * If you want to accept multiple compression types, list them separated by commas inside the quotation mark. * Use `"identity"` for no compression. * To enable all available compression types (including no compression), use `"all"`. * By default, AxoSyslog doesn’t send the `Accept-Encoding:` header, and the received response isn’t decompressed. For example: ``` destination d_http_compressed{ http(url("127.0.0.1:80") content-compression("deflate") accept-encoding("all")); }; ``` ## accept-redirects() | ---|--- Type: | `yes` or `no` Default: | _Description:_ Accept and follow redirect responses. ## azure-auth-header() See [The Azure auth header plugin](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/plugin-azure-auth-header/index.md). ## batch-bytes() | ---|--- Accepted values: | number [bytes] Default: | none _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. For details on how this option influences HTTP batch mode, see [Batch mode and load balancing](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/http-batch-mode/index.md) ## batch-idle-timeout() | ---|--- Type: | time in milliseconds Default: | `0` (disabled) Available in AxoSyslog 4.24 and later. _Description:_ `batch-idle-timeout()` measures the elapsed time since the last message was added to the batch (`batch-timeout()` defines the maximum time used to collect a batch, starting from the first message). If either `batch-idle-timeout()` or `batch-timeout()` expires, AxoSyslog closes and sends the batch. ## batch-lines() | ---|--- Type: | number Default: | 1 _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. To disable `batch-lines()`, set it to `0`. 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() / max-connections()` 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() | ---|--- Type: | time in milliseconds Default: | `-1` (disabled) _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. For details on how this option influences HTTP batch mode, see [Batch mode and load balancing](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/http-batch-mode/index.md) ## body() | ---|--- Type: | string or template Default: | _Description:_ The body of the HTTP request, for example, `body("${ISODATE} ${MESSAGE}")`. You can use strings, macros, and template functions in the body. If not set, it will contain the message received from the source by default. ## body-prefix() | ---|--- Accepted values: | string or template Default: | none Available in AxoSyslog version 3.18 and later. _Description:_ The string AxoSyslog puts at the beginning of the body of the HTTP request, before the log message. Starting with version 4.15, `body-prefix()` can include templates and macros as well. When using a template, note that: * Literal dollar signs (`$`) used in `body-prefix()` must be escaped like `$$`. * When using batching with a template, make sure to set the `worker-partition-key()` parameter appropriately to group similar messages together. For details on how this option influences HTTP batch mode, see [Batch mode and load balancing](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/http-batch-mode/index.md) ## body-suffix() | ---|--- Accepted values: | string Default: | none _Description:_ The string AxoSyslog puts to the end of the body of the HTTP request, after the log message. Available in AxoSyslog version 3.18 and later. For details on how this option influences HTTP batch mode, see [Batch mode and load balancing](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/http-batch-mode/index.md). ## cloud-auth() Authenticate to cloud-based services, for example, Azure and GCP, using service accounts. ### azure() Azure authentication currently supports authenticating to Azure Monitor, for example: ``` cloud-auth( azure( monitor( tenant-id("my-tenant-id") app-id("my-app-id") app-secret("my-app-secret") ) ) ) ``` To authenticate, you need to register a [Microsoft Entra application](). You’ll need the Tenant ID, App ID, and App Secret of this application to configure the AxoSyslog destination. #### app-id() | ---|--- Type: | string Default: | _Description:_ Application (client) ID of the Microsoft Entra application. #### app-secret() | ---|--- Type: | string Default: | _Description:_ The Client secret of the Microsoft Entra application. #### tenant-id() | ---|--- Type: | string Default: | _Description:_ Directory (tenant) ID of the Microsoft Entra application. ### gcp() Authenticate to GCP service accounts. For example: ``` cloud-auth( gcp( user-managed-service-account( name("your-user@your-project.iam.gserviceaccount.com") metadata-url("your-metadata-server:8080") ) ) ) ``` #### service-account() Authenticate to a service account using Service Account Key-Based Authentication. This method works both inside and outside GCP It uses a [service account key]() generated and downloaded through the GCP IAM & Admin console. The long-term service account key is used to generate short-term tokens for authentication (also called [self-signed JWT]()). ##### audience() | ---|--- Type: | string Default: | Note * When using the `google-pubsub()` destination, the `audience()` option is set to `https://pubsub.googleapis.com/google.pubsub.v1.Publisher`. Don’t change it. * When using the `google-pubsub()-grpc` destination, you don’t need to set the `audience()` option because the underlying gRPC API recognizes it automatically. * You cannot use `audience()` and `scope()` together. ##### key() | ---|--- Type: | string (path) Default: | Path to the service account key. ##### scope() | ---|--- Type: | string Default: | Available in AxoSyslog version 4.15 and later. URL for a scope claim for authentication [instead of audience](). For example: ``` ... cloud-auth( gcp( service-account( key("/path/to/secret.json") scope("https://www.googleapis.com/auth/example-scope") ) ) ) ``` Note You cannot use `audience()` and `scope()` together. ##### token-validity-duration() | ---|--- Type: | integer (seconds) Default: | `3600` #### user-managed-service-account() Available in AxoSyslog version 4.6 and later. Note The `user-managed-service-account()` method is only available for VMs running within GCP. Authenticate to a [user-managed service account]() of a GCP virtual machine using the VM Metadata Server Method. AxoSyslog interacts with the internal GCP metadata server, which provides an OAuth2 token for authentication. You can attach the [default service accounts]() as well. ##### metadata-url() | ---|--- Type: | string Default: | `http://metadata.google.internal/computeMetadata/v1/instance/service-accounts` The URL of the metadata server. When specifying the port, use the `URL:port` format. ##### name() | ---|--- Type: | string Default: | `default` Name of the service account to use. ## 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. An alternative way to specify this option is to put it into a `tls()` block, together with any other TLS options. This allows you to separate these options and ensure better readability. Make sure that you specify TLS options either using their own dedicated option (`ca-dir()`, `ca-file()`, `cert-file()`, `cipher-suite()`, `key-file()`, `peer-verify()`, and `ssl-version()`), 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. ### Declaration: ``` destination d_http { http( url("http://127.0.0.1:8080") tls( ca-dir("dir") cert-file("cert") cipher-suite("cipher") key-file("key") peer-verify(yes|no) ssl-version() ) ); }; ``` ## ca-file() | ---|--- Accepted values: | Filename Default: | none _Description:_ Name of a file that contains an X.509 CA certificate (or a certificate chain) in PEM format. The AxoSyslog application uses this certificate to validate the certificate of the HTTPS 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 it into a `tls()` block, together with any other TLS options. This allows you to separate these options and ensure better readability. Make sure that you specify TLS options either using their own dedicated option (`ca-dir()`, `ca-file()`, `cert-file()`, `cipher-suite()`, `key-file()`, `peer-verify()`, and `ssl-version()`), 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. ### Declaration: ``` destination d_http { http( url("http://127.0.0.1:8080") tls( ca-file("ca") cert-file("cert") cipher-suite("cipher") key-file("key") peer-verify(yes|no) ssl-version() ) ); }; ``` ## cert-file() | ---|--- Accepted values: | Filename Default: | none _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 it into a `tls()` block, together with any other TLS options. This allows you to separate these options and ensure better readability. Make sure that you specify TLS options either using their own dedicated option (`ca-dir()`, `ca-file()`, `cert-file()`, `cipher-suite()`, `key-file()`, `peer-verify()`, and `ssl-version()`), 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. ### Declaration: ``` destination d_http { http( url("http://127.0.0.1:8080") tls( ca-dir("dir") ca-file("ca") cert-file("cert") cipher-suite("cipher") key-file("key") peer-verify(yes|no) ssl-version() ) ); }; ``` ## cipher-suite() | ---|--- Accepted values: | Name of a cipher, or a colon-separated list Default: | Depends on the OpenSSL version that AxoSyslog uses _Description:_ Specifies the cipher, hash, and key-exchange algorithms used for the encryption, for example, `ECDHE-ECDSA-AES256-SHA384`. The list of available algorithms depends on the version of OpenSSL used to compile AxoSyslog. To specify multiple ciphers, separate the cipher names with a colon, and enclose the list between double-quotes, for example: ``` cipher-suite("ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384") ``` For a list of available algorithms, execute the `openssl ciphers -v` command. The first column of the output contains the name of the algorithms to use in the `cipher-suite()` option, the second column specifies which encryption protocol uses the algorithm (for example, `TLSv1.2`). That way, the `cipher-suite()` also determines the encryption protocol used in the connection: to disable SSLv3, use an algorithm that is available only in TLSv1.2, and that both the client and the server supports. You can also specify the encryption protocols using [ssl-options()](../../../docs/axosyslog-core/chapter-encrypted-transport-tls/tlsoptions/index.md). You can also use the following command to automatically list only ciphers permitted in a specific encryption protocol, for example, `TLSv1.2`: ``` echo "cipher-suite(\"$(openssl ciphers -v | grep TLSv1.2 | awk '{print $1}' | xargs echo -n | sed 's/ /:/g' | sed -e 's/:$//')\")" ``` Note that starting with version 3.10, when AxoSyslog receives TLS-encrypted connections, the order of ciphers set on the AxoSyslog server takes precedence over the client settings. An alternative way to specify this option is to put it into a `tls()` block, together with any other TLS options. This allows you to separate these options and ensure better readability. Make sure that you specify TLS options either using their own dedicated option (`ca-dir()`, `ca-file()`, `cert-file()`, `cipher-suite()`, `key-file()`, `peer-verify()`, and `ssl-version()`), 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. ### Declaration: ``` destination d_http { http( url("http://127.0.0.1:8080") tls( ca-dir("dir") ca-file("ca") cert-file("cert") cipher-suite("cipher") key-file("key") peer-verify(yes|no) ssl-version() ) ); }; ``` ## content-compression() | ---|--- Type: | `"identity"`, `"gzip"`, `"deflate"` Default: | `"identity"` _Description:_ Use `content-compression()` to compress the messages sent by AxoSyslog. Use `"identity"` for no compression. To accept compressed responses from the server, see the [`accept-encoding()` option](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/reference-destination-http-nonjava/index.md#accept-encoding). For example: ``` destination d_http_compressed{ http(url("127.0.0.1:80") content-compression("deflate") accept-encoding("all")); }; ``` Note that `content-compression()` keeps the original, plain-text content if the compressed payload would be larger than the compressed payload. If your destination server accepts only compressed payload, enable the [`force-content-compression(yes)`](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/reference-destination-http-nonjava/index.md#force-content-compression) option as well. ## delimiter() | ---|--- Accepted values: | string Default: | newline character _Description:_ By default, AxoSyslog separates the log messages of the batch with a newline character. You can specify a different delimiter by using the `delimiter()` option. Available in AxoSyslog version 3.18 and later. For details on how this option influences HTTP batch mode, see [Batch mode and load balancing](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/http-batch-mode/index.md) ## 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") ) ); }; ``` ## 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. ## flush-timeout() | ---|--- Type: | time in milliseconds Default: | 10000 [milliseconds] _Description:_ Specifies the time AxoSyslog waits for lines to accumulate in the output buffer. The AxoSyslog application sends flushes 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 `flush-timeout()` seconds. ## force-content-compression() | ---|--- Accepted values: | `yes`, `no` Default: | `no` Available in AxoSyslog 4.23 and later. _Description:_ If [`content-compression()`](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/reference-destination-http-nonjava/index.md#content-compression) is set to compress the messages, setting `force-content-compression(yes)` instructs AxoSyslog to always send the compressed payload, even when it’s larger than the original, uncompressed content. Use `force-content-compression(yes)` if your destination server accepts only compressed payload. ## 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. ## headers() | ---|--- Type: | string list Default: | see description _Description:_ Custom HTTP headers to include in the request, for example, `headers("HEADER1: header1", "HEADER2: header2")`. If not set, only the default headers are included, but no custom headers. The following headers are included by default: * X-Syslog-Host: `` * X-Syslog-Program: `` * X-Syslog-Facility: `` * X-Syslog-Level: `` Starting with AxoSyslog 4.18, you can use templates in the headers. Note that when using batching in the destination adn templates in `headers()`, the value of the template is calculated from the first message of the batch. Make sure to set the `worker-partition-key()` option properly to group similar messages. If you want to use literal dollar signs (`$`) in `headers()`, escape them like `$$`. ## 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")         )      ); }; ``` ## key-file() | ---|--- Accepted values: | Filename Default: | none _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. The `http()` destination supports only unencrypted key files (that is, the private key cannot be password-protected). An alternative way to specify this option is to put it into a `tls()` block, together with any other TLS options. This allows you to separate these options and ensure better readability. Make sure that you specify TLS options either using their own dedicated option (`ca-dir()`, `ca-file()`, `cert-file()`, `cipher-suite()`, `key-file()`, `peer-verify()`, and `ssl-version()`), 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. ### Declaration: ``` destination d_http { http( url("http://127.0.0.1:8080") tls( ca-dir("dir") ca-file("ca") cert-file("cert") cipher-suite("cipher") key-file("key") peer-verify(yes|no) ssl-version() ) ); }; ``` ## local-time-zone() | ---|--- Type: | name of the timezone, or the timezone offset Default: | The local timezone. _Description:_ Sets the timezone used when expanding filename and tablename templates. 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. ## log-fifo-size() | ---|--- Type: | number Default: | Use global setting. _Description:_ The number of messages that the output queue can store. ## method() | ---|--- Type: | `POST` or `PUT` Default: | POST _Description:_ Specifies the HTTP method to use when sending the message to the server. ## ocsp-stapling-verify | ---|--- Accepted values: | `yes`, `no` Default: | `no` Available in AxoSyslog 4.0 and later. _Description:_ When [OCSP stapling verification]() is enabled, AxoSyslog requests the server to send back its OCSP status. AxoSyslog verifies this status response using the trust store you have configured using the `ca-file()`, `ca-dir()`, or the `pkcs12-file()` options. Note RFC 6961 multi-stapling and TLS 1.3-provided multiple responses are currently not validated, only the peer certificate is verified. Example configuration: ``` destination { http(url("https://example.com") method("POST") tls(peer-verify(yes) ocsp-stapling-verify(yes))); }; ``` ## on-error() Type: | One of: `drop-message`, `drop-property`, `fallback-to-string`, `silently-drop-message`, `silently-drop-property`, `silently-fallback-to-string` ---|--- Default: | Use the global setting (which defaults to `drop-message`) _Description:_ Controls what happens when type-casting fails and AxoSyslog cannot convert some data to the specified type. By default, AxoSyslog drops the entire message and logs the error. Currently the `value-pairs()` option uses the settings of `on-error()`. * `drop-message`: Drop the entire message and log an error message to the `internal()` source. This is the default behavior of AxoSyslog. * `drop-property`: Omit the affected property (macro, template, or message-field) from the log message and log an error message to the `internal()` source. * `fallback-to-string`: Convert the property to string and log an error message to the `internal()` source. * `silently-drop-message`: Drop the entire message silently, without logging the error. * `silently-drop-property`: Omit the affected property (macro, template, or message-field) silently, without logging the error. * `silently-fallback-to-string`: Convert the property to string silently, without logging the error. ## password() | ---|--- Type: | string Default: | _Description:_ The password that AxoSyslog uses to authenticate on the server where it sends the messages. ## peer-verify() | ---|--- Accepted values: | `yes` or `no` Default: | `yes` _Description:_ Verification method of the peer. The following table summarizes the possible options and their results depending on the certificate of the peer. | The remote peer has: ---|--- no certificate | invalid certificate | valid certificate _Local peer-verify() setting_ | _no (optional-untrusted)_ | TLS-encryption | TLS-encryption | TLS-encryption _yes (required-trusted)_ | rejected connection | rejected connection | TLS-encryption 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. Warning When validating a certificate, the entire certificate chain must be valid, including the CA certificate. If any certificate of the chain is invalid, AxoSyslog will reject the connection. An alternative way to specify this option is to put it into a `tls()` block, together with any other TLS options. This allows you to separate these options and ensure better readability. Make sure that you specify TLS options either using their own dedicated option (`ca-dir()`, `ca-file()`, `cert-file()`, `cipher-suite()`, `key-file()`, `peer-verify()`, and `ssl-version()`), 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. ## persist-name() | ---|--- Type: | string Default: | N/A _Description:_ If you receive the following error message during AxoSyslog startup, set the `persist-name()` option of the duplicate drivers: ``` Error checking the uniqueness of the persist names, please override it with persist-name option. Shutting down. ``` This error happens if you use identical drivers in multiple sources, for example, if you configure two file sources to read from the same file. In this case, set the `persist-name()` of the drivers to a custom string, for example, `persist-name("example-persist-name1")`. ## proxy() Type: | The proxy server address, in `proxy("PROXY_IP:PORT")` format. For example, `proxy("http://myproxy:3128")` ---|--- Default: | None _Description:_ You can use the `proxy()` option to configure the HTTP driver in all HTTP-based destinations to use a specific HTTP proxy that is independent from the proxy configured for the system. Alternatively, you can leave the HTTP as-is, in which case the driver leaves the default `http_proxy` and `https_proxy` environment variables unmodified. Note ``` Configuring the proxy() option overwrites the default http_proxy and https_proxy environment variables. ``` ### Example: the proxy() option in configuration The following example illustrates including the `proxy()` option in your configuration. ``` destination { http( url("SYSLOG_SERVER_IP:PORT") proxy("PROXY_IP:PORT") method("POST")); }; ``` ## python-http-header() See [The Python HTTP header plugin](../../../docs/axosyslog-core/chapter-destinations/configuring-destinations-http-nonjava/plugin-python-http-header/index.md) ## response-action() | ---|--- Type: | list Default: | N/A (see below) _Description:_ Specifies what AxoSyslog does with the log message, based on the response code received from the HTTP server. If the server returns a status code beginning with 2 (for example, 200), AxoSyslog assumes the message was successfully sent. Otherwise, the action listed in the following table is applied. For status codes not listed in the following table, if the status code begins with 2 (for example, 299), AxoSyslog assumes the message was successfully sent. For other status codes, AxoSyslog disconnects. The following actions are possible: * `disconnect`: Keep trying to resend the message indefinitely. * `drop`: Drop the message without trying to resend it. * `retry`: Retry sending the message for a maximum of `retries()` times (3 by default). * `success`: Assume the message was successfully sent. code | explanation | action ---|---|--- 100 | “Continue” | disconnect 101 | “Switching Protocols” | disconnect 102 | “Processing” | retry 103 | “Early Hints” | retry 200 | “OK” | success 201 | “Created” | success 202 | “Accepted” | success 203 | “Non-Authoritative Information” | success 204 | “No Content” | success 205 | “Reset Content” | success 206 | “Partial Content” | success 300 | “Multiple Choices” | disconnect 301 | “Moved Permanently” | disconnect 302 | “Found” | disconnect 303 | “See Other” | disconnect 304 | “Not Modified” | retry 307 | “Temporary Redirect” | disconnect 308 | “Permanent Redirect” | disconnect 400 | “Bad Request” | disconnect 401 | “Unauthorized” | disconnect 402 | “Payment Required” | disconnect 403 | “Forbidden” | disconnect 404 | “Not Found” | disconnect 405 | “Method Not Allowed” | disconnect 406 | “Not Acceptable” | disconnect 407 | “Proxy Authentication Required” | disconnect 408 | “Request Timeout” | disconnect 409 | “Conflict” | disconnect 410 | “Gone” | drop 411 | “Length Required” | disconnect 412 | “Precondition Failed” | disconnect 413 | “Payload Too Large” | disconnect 414 | “URI Too Long” | disconnect 415 | “Unsupported Media Type” | disconnect 416 | “Range Not Satisfiable” | drop 417 | “Expectation Failed” | disconnect 418 | “I’m a teapot” | disconnect 421 | “Misdirected Request” | disconnect 422 | “Unprocessable Entity” | drop 423 | “Locked” | disconnect 424 | “Failed Dependency” | drop 425 | “Too Early” | drop 426 | “Upgrade Required” | disconnect 428 | “Precondition Required” | retry 429 | “Too Many Requests” | disconnect 431 | “Request Header Fields Too Large” | disconnect 451 | “Unavailable For Legal Reasons” | drop 500 | “Internal Server Error” | disconnect 501 | “Not Implemented” | disconnect 502 | “Bad Gateway” | disconnect 503 | “Service Unavailable” | disconnect 504 | “Gateway Timeout” | retry 505 | “HTTP Version Not Supported” | disconnect 506 | “Variant Also Negotiates” | disconnect 507 | “Insufficient Storage” | disconnect 508 | “Loop Detected” | drop 510 | “Not Extended” | disconnect 511 | “Network Authentication Required” | disconnect To customize the action to take for a particular response code, use the arrow operator in the following format: `response-action( => `. To customize multiple response code-action pairs, separate them with a comma, for example: ``` http( url("http://localhost:8080") response-action(418 => drop, 404 => retry) ); ``` ## 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. To handle HTTP error responses, if the HTTP server returns 5xx codes, AxoSyslog will attempt to resend messages until the number of attempts reaches `retries`. If the HTTP server returns 4xx codes, AxoSyslog will drop the messages. ## send-time-zone() | ---|--- Accepted values: | name of the timezone, or the timezone offset Default: | local timezone _Description:_ Specifies the time zone associated with the messages sent by `syslog-ng`, if not specified otherwise in the message or in the destination driver. For details, see [Timezones and daylight saving](../../../docs/axosyslog-core/chapter-concepts/timezone-handling/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. ## ssl-version() | ---|--- Type: | string Default: | None, uses the libcurl default _Description:_ Specifies the permitted SSL/TLS version. Possible values: `sslv2`, `sslv3`, `tlsv1`, `tlsv1_0`, `tlsv1_1`, `tlsv1_2`, `tlsv1_3`. An alternative way to specify this option is to put it into a `tls()` block, together with any other TLS options. This allows you to separate these options and ensure better readability. Make sure that you specify TLS options either using their own dedicated option (`ca-dir()`, `ca-file()`, `cert-file()`, `cipher-suite()`, `key-file()`, `peer-verify()`, and `ssl-version()`), 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. ### Declaration: ``` destination d_http { http( url("http://127.0.0.1:8080") tls( ca-dir("dir") ca-file("ca") cert-file("cert") cipher-suite("cipher") key-file("key") peer-verify(yes|no) ssl-version() ) ); }; ``` ## 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. ## time-reopen() | ---|--- Accepted values: | number [seconds] Default: | 60 _Description:_ The time to wait in seconds before a dead connection is reestablished. ## timeout() | ---|--- Type: | number [seconds] Default: | 0 _Description:_ The value (in seconds) to wait for an operation to complete, and attempt to reconnect the server if exceeded. By default, the timeout value is `0`, meaning that there is no timeout. Available in version 3.11 and later. ## 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. ## url() | ---|--- Type: | URL or list of URLs Default: | http://localhost/ _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. For example: `http://127.0.0.1:8000` In case the server on the specified URL returns a redirect request, AxoSyslog automatically follows maximum 3 redirects. Only HTTP and HTTPS based redirections are supported. ### Load balancing Starting with version 3.19, you can specify multiple URLs, for example, `url("site1" "site2")`. In this case, AxoSyslog sends log messages to the specified URLs in a load-balance fashion. This means that AxoSyslog sends each message to only one URL. For example, you can use this to send the messages to a set of ingestion nodes or indexers of your SIEM solution if a single node cannot handle the load. Note that the order of the messages as they arrive on the servers can differ from the order AxoSyslog has received them, so use load-balancing only if your server can use the timestamp from the messages. If the server uses the timestamp when it receives the messages, the order of the messages will be incorrect. Warning If you set multiple URLs in the `url()` option, set the `persist-name()` option as well to avoid data loss. Starting with version AxoSyslog version 3.22, you can use any of the following formats to specify multiple URLs: ``` url("server1", "server2", "server3"); # comma-separated strings url("server1" "server2" "server3"); # space-separated strings url("server1 server2 server3"); # space-separated within a single string ``` ### Templates in the url() Available in AxoSyslog version 4.5.0 and later. In AxoSyslog, a template can only be resolved on a single message, because the same template might have different resolutions on different messages. As a batch consists of multiple messages, it’s not trivial to decide which message should be used for the resolution. When batching is enabled and multiple workers are configured, it’s important to add only those messages to a batch which generate identical URLs. To achieve this, set the `worker-partition-key()` option with a template that contains all the templates used in the `url()` option, otherwise messages will be mixed. For security reasons, all the templated contents in the `url()` option are URL-encoded automatically. The following parts of the URL cannot be templated: * scheme * host * port * user * password ## user-agent() | ---|--- Type: | string Default: | `syslog-ng [version]'/`libcurl[version]` _Description:_ The value of the USER-AGENT header in the messages sent to the server. ## user() | ---|--- Type: | string Default: | _Description:_ The username that AxoSyslog uses to authenticate on the server where it sends the messages. ## use-system-cert-store() | ---|--- Type: | `yes` or `no` Default: | `no` _Description:_ Use the certificate store of the system for verifying HTTPS certificates. For details, see the [curl documentation](). ## worker-partition-autoscaling() | ---|--- Type: | `yes`, `no` Default: | `no` Available in version 4.21 and later. When using `worker-partition-key()` to categorize messages into different batches, the messages are hashed into workers by default. This prevents distributing across workers based on load. Setting `worker-partition-autoscaling(yes)` uses a 1-minute statistic to distribute high-traffic partitions among multiple workers, allowing each worker to maximize its batch size. When using `worker-partition-autoscaling(yes)`, set the number of `workers()` to higher than the expected number of partitions. ## worker-partition-buckets() | ---|--- Type: | template Default: | _Description:_ The `worker-partition-buckets()` option determines the number of worker threads used for the `worker-partition-key()`. Note that the number set by `worker-partition-buckets()` should be lower than the number of `workers()`. ## worker-partition-key() | ---|--- Type: | template Default: | _Description:_ The `worker-partition-key()` option specifies a template: messages that expand the template to the same value are mapped to the same partition. When batching is enabled and multiple workers are configured, it’s important to add only those messages to a batch which generate identical URLs. To achieve this, set the `worker-partition-key()` option with a template that contains all the templates used in the `url()` option, otherwise messages will be mixed. For example, you can partition messages based on the destination host: ``` worker-partition-key("$HOST") ``` ## workers() | ---|--- Type: | integer Default: | 1 _Description:_ Specifies the number of worker threads (at least 1) that AxoSyslog uses to send messages to the server. Increasing the number of worker threads can drastically improve the performance of the destination. Warning `Hazard of data loss.` When you use more than one worker threads together with disk-based buffering, AxoSyslog creates a separate disk buffer for each worker thread. This means that decreasing the number of workers can result in losing data currently stored in the disk buffer files. Do not decrease the number of workers when the disk buffer files are in use. If you are using load-balancing (that is, you have configured multiple servers in the `url()` option), increase the number of worker threads at least to the number of servers. For example, if you have set three URLs (`url("site1", "site2", "site3")`), set the `workers()` option to 3 or more. Last modified February 17, 2026: [http force-content-compression (d4e592cc)]()