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+---
+labels:
+- 'Stage-Beta'
+summary: 'Log to in-memory ringbuffer'
+...
+
+Introduction
+============
+
+Sometimes debug logs are too verbose for continuous logging to disk. However
+occasionally you may be interested in the debug logs when a certain event occurs.
+
+This module allows you to store all logs in a fixed-size buffer in Prosody's memory,
+and dump them to a file whenever you want.
+
+# Configuration
+
+First of all, you need to load the module by adding it to your global `modules_enabled`:
+
+``` {.lua}
+modules_enabled = {
+    ...
+    "log_ringbuffer";
+    ...
+}
+```
+
+By default the module will do nothing - you need to configure a log sink, using Prosody's
+usual [logging configuration](https://prosody.im/doc/advanced_logging).
+
+``` {.lua}
+log = {
+    -- Log errors to a file
+    error = "/var/log/prosody/prosody.err";
+
+    -- Log debug and higher to a 2MB buffer
+    { to = "ringbuffer", size = 1024*1024*2, filename_template = "debug-logs-{pid}-{count}.log", signal = "SIGUSR2" };
+}
+```
+
+The possible fields of the logging config entry are:
+
+`to`
+:   Set this to `"ringbuffer"`.
+
+`levels`
+:   The log levels to capture, e.g. `{ min = "debug" }`. By default, all levels are captured.
+
+`size`
+:   The size, in bytes, of the buffer. When the buffer fills,
+    old data will be overwritten by new data.
+
+`lines`
+:   If specified, preserves the latest N complete lines in the
+    buffer. The `size` option is ignored when this option is set.
+
+`filename`
+:   The name of the file to dump logs to when triggered.
+
+`filename_template`
+:   This parameter may optionally be specified instead of `filename. It
+    may contain a number of variables, described below. Defaults to
+    `"{paths.data}/ringbuffer-logs-{pid}-{count}.log"`.
+
+Only one of the following triggers may be specified:
+
+`signal`
+:   A signal that will cause the buffer to be dumped, e.g. `"SIGUSR2"`.
+    Do not use any signal that is used by any other Prosody module, to
+    avoid conflicts.
+
+`event`
+:   Alternatively, the name of a Prosody global event that will trigger
+    the logs to be dumped, e.g. `"config-reloaded"`.
+
+## Filename variables
+
+If `filename_template` is specified instead of `filename`, it may contain
+any of the following variables in curly braces, e.g. `{pid}`.
+
+`pid`
+:   The PID of the current process
+
+`count`
+:   A counter that begins at 0 and increments for each dump made by
+    the current process.
+
+`time`
+:   The unix timestamp at which the dump is made. It can be formatted
+    to human-readable local time using `{time|yyyymmdd}` and `{time|hhmmss}`.
+
+`paths`
+:   Allows access to Prosody's known filesystem paths, use e.g. `{paths.data}`
+    for the path to Prosody's data directory.
+
+The filename does not have to be unique for every dump - if a file with the same
+name already exists, it will be appended to.
+
+## Integration with mod_debug_traceback
+
+This module can be used in combination with [mod_debug_traceback] so that debug
+logs are dumped at the same time as the traceback. Use the following configuration:
+
+``` {.lua}
+log = {
+	---
+	-- other optional logging config here --
+	---
+
+	{
+		to = "ringbuffer";
+		filename_template = "{paths.data}/traceback-{pid}-{count}.log";
+		event = "debug_traceback/triggered";
+	};
+}
+```
+
+If the filename template matches the traceback path, both logs and traceback will
+be combined into the same file. Of course separate files can be specified if preferred.
+
+# Compatibility
+
+0.12 and later.