Health check
You can check the health of the server by making a request to /healthz, which
should return a 200 OK response.
Monitoring
For monitoring, ew-vod2cbm generates Prometheus data available at /metrics.
There are different metrics for the response times for segments for different media types.
All bucket and counter names start with ew_, or more precisely:
ew_audio_segment_request_duration_milliseconds_bucket
ew_audio_segment_requests_total
ew_subs_segment_request_duration_milliseconds_bucket
ew_subs_segment_requests_total
ew_video_segment_request_duration_milliseconds_bucket
ew_video_segment_requests_total
Logging
To provide context to each log message, structured logging is used. Thus
instead of free text log messages without any specific format, the log data is
to some extent divided into fields of name-value pairs, making the logs more
coherent and more suitable for processing by external tools.
Log messages related to a specific HTTP request include the log field named
request_id which can be used to filter out specific requests.
The log field named topic is always present and is used to separate different
areas of logging. The current topics are access, messages and error, and
are used to log HTTP access, debug messages and panic stack traces,
respectively.
As a comparison, the topics are similar to having separate files for access logging, debug messages and errors in a conventional file-based logging system.
Log formats
When run from the command line ew-vod2cbm can log in one of the formats
consolepretty, consolejson or journald depending on the value of the
-logformat parameter. Logging can be disabled by using the value discard.
$ ew-vod2cbm -upstream http://127.0.0.1 -logformat consolejson
consolepretty logs to standard output (stdout) in a human-readable format.
Each log line starts with the date and the log message followed by the context-
dependent log fields:
2022-02-07T11:54:42Z INF Incoming request bytes_out=27592 latency_ms=6.18251 method=GET ...
consolejson logs to stdout using a JSON object for each message:
{"level":"info","topic":"access","time":"2022-02-07T12:06:07Z","bytes_out":27592, ...}
When run as a systemd service, ew-vod2cbm logs directly to journald using
the logjournald configuration parameter. When stored in journald, field
names are upper case whereas the values keep their format. Some examples:
To see entries with the topic access:
$ journalctl -u ew-vod2cbm TOPIC=access -o verbose
To see entries with a specific request ID:
$ journalctl -u ew-vod2cbm REQUEST_ID="host/B1Po0eYz1d-000006" -o verbose
To see the call stack in the event of a crash:
$ journalctl -u ew-vod2cbm TOPIC=error -o verbose
Using the verbose output includes all available name-value fields. Without
this only the log message is printed. The field named JSON contains the
original structured log message as sent by the service. To filter out only
this field --output-fields=JSON can be used, however this requires a systemd
version of at least 236.
$ journalctl -u ew-vod2cbm --output-fields=JSON TOPIC=access
To continuously monitor the service:
$ journalctl -fu ew-vod2cbm
Log levels
At startup the log level is set to info.
The log level can be changed by posting a form-field named level to the
loglevel endpoint on the ew-vod2cbm server:
$ curl -F level=debug ew-vod2cbm-server:8090/loglevel
The available log levels and how they relate to systemd priority values is listed below:
Log level Systemd priority
trace 7
debug 7
info 6
warn 4
error 3
fatal 2
panic 0
To e.g. see all error and warning messages using journalctl:
$ journalctl -u ew-vod2cbm PRIORITY=3 PRIORITY=4
Use a GET request to see the current log level:
$ curl ew-vod2cbm-server:8090/loglevel
Messages with higher level than the configured one will not be logged.