help folks read logs (#112)

*   add more description to the troubleshooting guide
*   adjust the log format to match more recent glog
*   include a config for the lnav tool, which will help colorize,
    browse, and search the logs.

Next up: install an ffmpeg log callback for consistency.

guide/troubleshooting.md

@@ -35,6 +35,88 @@ Logging options are controlled by environment variables:
 
 If you use Docker, set these via Docker's `--env` argument.
 
+With the default `MOONFIRE_FORMAT=glog`, log lines are in the following
+format:
+
+```text
+I20210308 21:31:24.255 main moonfire_nvr] Success.
+LYYYYmmdd HH:MM:SS.FFF TTTT PPPPPPPPPPPP] ...
+L    = level:
+       E = error
+       W = warn
+       I = info
+       D = debug
+       T = trace
+YYYY = year
+mm   = month
+dd   = day
+HH   = hour (using a 24-hour clock)
+MM   = minute
+SS   = section
+FFF  = fractional portion of the second
+TTTT = thread name (if set) or tid (otherwise)
+PPPP = module path
+...  = message body
+```
+
+You can use the following command to teach [lnav](http://lnav.org/) Moonfire
+NVR's log format:
+
+```
+$ lnav -i misc/moonfire_log.json
+```
+
+### Flush log lines
+
+During normal operation, Moonfire NVR will periodically flush changes to its
+SQLite3 database. Every flush is logged, as in the following message:
+
+```
+I20210308 23:14:18.388 sync-/media/14tb/sample moonfire_db::db] Flush 3810 (why: 120 sec after start of 1 minute 14 seconds courtyard-main recording 3/1842086):
+/media/6tb/sample: added 98M 864K 842B in 8 recordings (4/1839795, 7/1503516, 6/1853939, 1/1838087, 2/1852096, 12/1516945, 8/1514942, 10/1506111), deleted 111M 435K 587B in 5 (4/1801170, 4/1801171, 6/1799708, 1/1801528, 2/1815572), GCed 9 recordings (6/1799707, 7/1376577, 4/1801168, 1/1801527, 4/1801167, 4/1801169, 10/1243252, 2/1815571, 12/1418785).
+/media/14tb/sample: added 8M 364K 643B in 3 recordings (3/1842086, 9/1505359, 11/1516695), deleted 0B in 0 (), GCed 0 recordings ().
+```
+
+This log message is packed with debugging information:
+
+*   the date and time: `20210308 23:14:18.388`.
+*   the name of the thread that prompted the flush: `sync-/media/14tb/sample`.
+*   a sequence number: `3810`. This is handy for checking how often Moonfire NVR
+    is flushing.
+*   a reason for the flush: `120 sec after start of 1 minute 14 seconds courtyard-main recording 3/1842086`.
+    This was a regular periodic flush at the `flush_if_sec` for the stream,
+    as described in [install.md](install.md). `3/1842086` is an identifier for
+    the recording, in the form `stream_id/recording_id`. It corresponds to the
+    file `/media/14tb/sample/00000003001c1ba6`. On-disk files are named by
+    a fixed eight hexadecimal digits for the stream id and eight hexadecimal
+    digits for the recording id. You can convert with Python:
+    ```
+    $ python3
+    >>> '%08x%08x' % (3, 1842086)
+    '00000003001c1ba6'
+    >>>
+    ```
+*   For each affected sample file directory (`/media/6tb/sample` and
+    `/media/14tb/sample`), a line showing the exact changes included in the
+    flush. There are three kinds of changes:
+
+    *   added recordings–these files are already fully written in the sample
+        file directory and now are being added to the database.
+    *   deleted recordings–these are being removed from the database's
+        `recording` table (and added to the `garbage` table) in preparation
+        for being deleted from the sample file directory. They can no longer
+        be accessed after this flush.
+    *   GCed (garbage-collected) recordings—these have been fully removed from
+        disk and no longer will be referenced in the database at all.
+
+    You can learn more about these in the "Lifecycle of a recording" section
+    of the [recording schema design document](../design/schema.md).
+
+    For added and deleted recordings, the line includes sizes in bytes
+    (`98M 864K 842B` represents 10,3646,026 bytes, or about 99 MiB), numbers
+    of recordings, and the IDs of each recording. For GCed recordings, the
+    sizes are omitted (as this information is not stored).
+
 ## Problems
 
 ### `Error: pts not monotonically increasing; got 26615520 then 26539470`

misc/moonfire_log.json

@@ -0,0 +1,41 @@
+{
+    "$schema": "https://lnav.org/schemas/format-v1.schema.json",
+    "moonfire_log": {
+        "title": "Moonfire Log",
+        "description": "The Moonfire NVR log format.",
+        "timestamp-format": ["%Y%m%d %H:%M:%S.%L"],
+        "url": "https://github.com/scottlamb/mylog/blob/master/src/lib.rs",
+        "regex": {
+            "std": {
+                "pattern": "^(?<level>[EWIDT])(?<timestamp>\\d{4} \\d{2}\\d{2}\\d{2}\\.\\d{3}) +(?<thread>[^ ]+) (?<module_path>[^ \\]]+)\\] (?<body>(?:.|\\n)*)"
+            }
+        },
+        "level-field": "level",
+        "level": {
+            "error": "E",
+            "warning": "W",
+            "info": "I",
+            "debug": "D",
+            "trace": "T"
+        },
+        "opid-field": "thread",
+        "value": {
+            "thread": {
+                "kind": "string",
+                "identifier": true
+            },
+            "module_path": {
+                "kind": "string",
+                "identifier": true
+            }
+        },
+        "sample": [
+            {
+                "line": "I20210308 21:31:24.255 main moonfire_nvr] Success."
+            },
+            {
+                "line": "W20210303 22:20:53.081 s-west_side-main moonfire_base::clock] getting next packet took PT8.153173367S!"
+            }
+        ]
+    }
+}

server/Cargo.lock

@@ -1274,7 +1274,7 @@ dependencies = [
 [[package]]
 name = "mylog"
 version = "0.1.0"
-source = "git+https://github.com/scottlamb/mylog#45cdec74e11b05d02b55d49cfb1a8391e0f281a5"
+source = "git+https://github.com/scottlamb/mylog#64519c6d9d4587d803900b82a83b45b35939b8f7"
 dependencies = [
  "chrono",
  "log",