--- title: "Metrics reference" url: "https://axoflow.com/docs/axosyslog-core/4.28/chapter-log-statistics/metrics-reference/" last_modified: "2026-06-24T14:45:40+02:00" --- > For the complete documentation index, see [llms.txt](https://axoflow.com/docs/axosyslog-core/4.28/llms.txt). # Metrics reference The following list shows the metrics available in AxoSyslog. AxoSyslog provides detailed metrics about its performance and status for observability and monitoring. We recommend using Prometheus to scrape these metrics, see [Collect metrics with Prometheus](https://axoflow.com/docs/axosyslog-core/4.28/chapter-log-statistics/prometheus-exporter/index.md) for details. To display the current metrics locally in Prometheus-compatible format, run: ```shell syslog-ng-ctl stats prometheus ``` Note that which metrics are shown depends on the current value of the [`stats(level())` global option](https://axoflow.com/docs/axosyslog-core/4.28/chapter-global-options/reference-options/index.md#global-option-stats-level) (you can list the available metrics by running `syslog-ng --metrics-registry`). For details on what the metrics mean, see [Metrics reference](https://axoflow.com/docs/axosyslog-core/4.28/chapter-log-statistics/metrics-reference/index.md). > **Note:** > > - Metrics that have the `_total` suffix reset to zero when AxoSyslog is restarted. Reloading AxoSyslog doesn’t cause a reset. > - Different metrics are available on different [`stats(level())`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-global-options/reference-options/index.md#global-option-stats-level). ## classified_events_total *Description*: Default metric of the [`metrics-probe()`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-parsers/metrics-probe/index.md) parser. ## disk_queue_capacity_bytes *Description*: Maximal size of the disk queue (in bytes), as set in the `capacity-bytes()` disk-buffer option. ## disk_queue_capacity *Description*: The size of the overflow queue of the destination, as set in the `flow-control-window-size()` disk-buffer option. ## disk_queue_dir_available_bytes *Description*: The size of the space available in the directories where disk-buffer files are stored (including directories storing abandoned disk-buffers), in bytes. ## disk_queue_disk_allocated_bytes *Description*: The actual size of the disk-buffer files, in bytes. ## disk_queue_disk_usage_bytes *Description*: Total size of data waiting in each disk-buffer, in bytes. ## disk_queue_events *Description*: Number of messages waiting in each disk-buffer by destination. ## disk_queue_memory_usage_bytes *Description*: Amount of memory used for caching disk-buffers, in bytes. ## disk_queue_processed_events_total *Description*: The number of events processed since startup by each disk-buffer. ## event_processing_latency_seconds *Description*: Histogram of the latency (time from receiving the message to fully processing it), from the source or destination perspective. ## events_allocated_bytes *Description*: The total amount of memory used by log messages in AxoSyslog. ## filtered_events_total *Description*: The total number of messages that matched and didn’t match a filter, for each filter in the configuration file. ## input_event_bytes_total *Description*: Incoming log messages processed by each source, measured in bytes. ## input_events_total *Description*: Number of incoming log messages processed by each source. ## input_transport_errors_total *Description*: Number of various transport errors that prevent AxoSyslog from ingesting messages, for example, TLS handshake errors or syslog framing errors. Labels include the source `id`, `peer_address`, and the `reason` for the error. ```shell syslogng_input_transport_errors_total{address="127.0.0.1:5513",driver="syslog",peer_address="127.0.0.1",reason="invalid-frame-header",transport="tcp"} 1 syslogng_input_transport_errors_total{address="127.0.0.1:5515",driver="syslog",id="s_tls_req#0",peer_address="127.0.0.1",reason="tls-handshake",tls_error="0A0000C7",tls_error_string="SSL routines::peer did not return a certificate",transport="tls"} 1 ``` ## input_window_available *Description*: Available on `stats(level(3))`. Shows the current size of the flow-control window (how much is still free from `log-iw-size()`). ## input_window_capacity *Description*: Available on `stats(level(3))`. Shows the value of `log-iw-size()` (the size of the flow-control window). ## input_window_full_total *Description*: The total number of input window full events, for the entire configuration. These events cause AxoSyslog to throttle the source. Available on `stats(level(1))`. ## internal_events_queue_capacity *Description*: The internal queue size of the [`internal()`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-sources/configuring-sources-internal/index.md) source. ## internal_events_total *Description*: The number of messages the [`internal()`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-sources/configuring-sources-internal/index.md) source has queued, processed, or dropped. ## io_worker_latency_seconds *Description*: Shows how overloaded the IO workers of AxoSyslog are. ## last_config_file_modification_timestamp_seconds *Description*: The date when the configuration file was last modified. ## last_config_reload_timestamp_seconds *Description*: The date when the AxoSyslog configuration was last reloaded. If it differs from `last_successful_config_reload_timestamp_seconds`, reloading the configuration has failed. ## last_successful_config_reload_timestamp_seconds *Description*: The date when the AxoSyslog configuration was last reloaded successfully. ## mainloop_io_worker_roundtrip_latency_seconds *Description*: Shows how overloaded the main AxoSyslog loop is (how much time it takes to start a new worker). Values close to 0 are good, high values indicate high load or processing bottleneck. ## memory_queue_capacity *Description*: Shows the capacity (maximum possible size) of each queue. Note that this metric publishes `log-fifo-size()`, which only limits non-flow-controlled messages. Messages coming from flow-controlled paths aren’t limited by `log-fifo-size()`, but by the `log-iw-size()` of their corresponding source. For metrics on `log-iw-size()`, see [`input_window_available`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-log-statistics/metrics-reference/index.md#input_window_available) and [`input_window_capacity`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-log-statistics/metrics-reference/index.md#input_window_capacity). ## memory_queue_events *Description*: Number of messages waiting in each memory queue by destination. ## memory_queue_memory_usage_bytes *Description*: Total bytes of data waiting in each memory queue. ## memory_queue_processed_events_total *Description*: The number of events processed since startup by each queue. ## output_active_worker_partitions *Description*: The number of active partitions when `worker-partition-autoscaling()` is set to `yes`. ## output_batch_size_bytes *Description*: Histogram-style metrics for the destination. ## output_batch_size_events *Description*: Histogram-style metrics for the destination. ## output_batch_timedout_total *Description*: For destinations that use batching, it shows the number of batches that were sent because of timeout (either `batch-timeout()` or `batch-idle-timeout()` expired). ## output_event_bytes_total *Description*: Log messages sent to each destination, measured in bytes. ## output_event_latency_seconds *Description*: Histogram of the latency: time from receiving the message to delivering it to the destination. ## output_event_retries_total *Description*: Shows the number of events when AxoSyslog retried sending a message. ## output_event_size_bytes *Description*: Histogram-style metrics for the destination. ## output_events_total *Description*: Number of log messages sent to each destination, showing sent and dropped messages. ## output_grpc_requests_total *Description*: The total number of gRPC requests. ## output_http_requests_total *Description*: Available on `stats(level(1))` The total number of HTTP requests. ## output_request_latency_seconds *Description*: Histogram-style metrics for the destination. ## output_unreachable *Description*: A bool-like metric, which shows whether a destination is reachable or not. ## output_workers *Description*: The number of workers configured for each destination. ## parallelize_failed_events_total *Description*: The number of events that [`parallelize()`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-nonsequential-processing/index.md) couldn’t process in parallel. Such messages were sent without parallelization. A high number of such events can signal a configuration issue or a bottleneck. ## parallelized_assigned_events_total *Description*: The number of events each worker has received when using [`parallelize()`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-nonsequential-processing/index.md). Can show if the workers receive the load unevenly. ## parallelized_batch_size Available in AxoSyslog 4.26 and later at `stats-level(4)` *Description*: Prometheus-style histograms to that show how logscheduler batches messages. Useful only for low-level debugging and troubleshooting. ```shell syslogng_parallelized_batch_size_sum{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5"} 1000000 syslogng_parallelized_batch_size_count{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5"} 13962 syslogng_parallelized_batch_size_bucket{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5",le="1"} 4686 syslogng_parallelized_batch_size_bucket{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5",le="2"} 2857 syslogng_parallelized_batch_size_bucket{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5",le="4"} 2757 syslogng_parallelized_batch_size_bucket{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5",le="8"} 1401 ``` ## parallelized_input_batch_size Available in AxoSyslog 4.26 and later at `stats-level(4)` *Description*: Prometheus-style histograms to that show how logscheduler batches messages. Useful only for low-level debugging and troubleshooting. Example: ```shell syslogng_parallelized_input_batch_size_sum{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5"} 1000000 syslogng_parallelized_input_batch_size_count{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5"} 11979 syslogng_parallelized_input_batch_size_bucket{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5",le="1"} 4545 syslogng_parallelized_input_batch_size_bucket{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5",le="2"} 2784 syslogng_parallelized_input_batch_size_bucket{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5",le="4"} 2729 syslogng_parallelized_input_batch_size_bucket{parallelize="/install/etc/callgrind-syslog-ng.conf:30:5",le="8"} 1429 ``` ## parallelized_processed_events_total *Description*: The number of events processed using [`parallelize()`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-nonsequential-processing/index.md). ## parsed_events_total *Description*: Shows the number of messages processed by each parser. ## route_egress_total *Description*: The number of messages delivered by each [named log path](https://axoflow.com/docs/axosyslog-core/4.28/chapter-routing-filters/logpath/index.md#name-log-path). ## route_ingress_total *Description*: The number of messages entering each [named log path](https://axoflow.com/docs/axosyslog-core/4.28/chapter-routing-filters/logpath/index.md#name-log-path). ## scratch_buffers_bytes *Description*: The number of bytes allocated to internal string buffers. ## scratch_buffers_count *Description*: The number of allocated internal string buffers. ## socket_connections *Description*: Number of active connections for the sources. ## socket_max_connections *Description*: Maximum permitted number of connections for the sources. ## socket_receive_buffer_max_bytes *Description*: The maximal size socket receive buffer in bytes, as configured in the `so-rcvbuf()` option of the destination. ## socket_receive_buffer_used_bytes *Description*: The number of bytes used from the socket receive buffer. ## socket_receive_dropped_packets_total *Description*: Number of UDP packets dropped by the OS before processing. ## socket_rejected_connections_total *Description*: The number of connections rejected because the `max-connections()` limit of the source was reached, for each source. ## stats_level *Description*: Shows the current verbosity [`level()`](https://axoflow.com/docs/axosyslog-core/4.28/chapter-global-options/reference-options/index.md#global-option-stats-level) of statistics and metrics. ## tagged_events_total *Description*: The number of messages marked with a [tag](https://axoflow.com/docs/axosyslog-core/4.28/chapter-manipulating-messages/modifying-messages/rewrite-tags/index.md), for each tag. (Every message automatically has the tag of its source in `.source.` format.) Last modified June 24, 2026: [Adds new histograms to metrics reference (879ad916)](https://github.com/axoflow/axosyslog-core-docs/commit/879ad916c6800037ed3f7728f7bbc74724bdd768)