#metrics #facade #macros

app metrics-observer

Text-based UI for metrics-exporter-tcp

2 unstable releases

0.3.0 Dec 24, 2023
0.2.0 Apr 16, 2023

#503 in Debugging

46 downloads per month

MIT license

495KB
5K SLoC

metrics-observer

A text-based UI for observing metrics exported by metrics-exporter-tcp.

quick start

# Install it:
cargo install metrics-observer

# Connect to an application using the defaults of metrics-exporter-tcp
# which is 127.0.0.1:5000:
metrics-observer

# Specify a custom address to connect to:
metrics-observer 192.168.1.1:5000

understanding the output

status bar

The status bar at the top will track the connection status, as well as list as the possible controls that can be used. Here's a shot where the observer is disconnected from the target process and is waiting to retry its connection:

observer disconnected

basic data display

As metrics are emitted by the process, they'll be shipped to the observer and displayed. As metrics-exporter-tcp doesn't store any metrics itself, when reconnecting, all of the previous values will be gone, and the observer will start collecting from scratch.

For counters, you'll see values in the form of total: <value>, where <value> is the counter total since we connected to the endpoint. For gauges, instead of total:, you'll see current: as the prefix. For histograms, a pre-defined set of percentiles will be calculated: minimum, p50, p99, p999, and maximum.

Labels are shown in square brackets after the metric name. In this example, you can see a metrics where the system label is set to the value foo.

Here's a simple example:

observer connected, histogram with same timebase for each percentile

unit support

If a given metric has its units defined, then metrics-observer will display them accordingly. We use the canonical label value for the given unit, which is based on the official abbreviation for a unit or the most commonplace label. For example, a data rate-based unit such as terabits per second will show as Tbps while a data-based unit such as mebibytes will show as MiB. However, in the case of the count per second unit, which is not an official unit, we use the commonplace label of /s.

Beyond the way that metrics with units will be labeled, we also specifically scale time-based units in a more human-friendly way. For example, if a value is defined as being nanoseconds, but the value itself is actually representative of 1.5 milliseconds, we would display it as 1.5ms instead of the full value in nanoseconds only. This also applies for histograms using time-based units, where each percentile will be displayed in the most appropriate timebase.

Here's an example where some metrics have a unit, and we have a histogram where percentiles have values across different timebases:

observer connected, histogram with percentiles in different timebases

Dependencies

~4–13MB
~129K SLoC