deno-openmetrics_exporter

OpenMetrics / Prometheus metrics exporting for Deno's runtime

Repository Migrated!

A metrics effort focused only on OpenMetrics/Prometheus is too narrow in scope for such a young ecosystem, so further development on this code has been moved to /x/observability instead. This widens the scope of the module so please get in touch if you have Opinions™ about monitoring Deno programs.

Example

It's pretty typical to run a Prometheus exporter on its own dedicated port to keep it separate from whatever API you may be hosting. Or if you aren't hosting an API at all, you may not already have any HTTP server.

Here's an example of that:

import { runMetricsServer } from "https://raw.githubusercontent.com/cloudydeno/deno-openmetrics_exporter/main/mod.ts";

runMetricsServer({ port: 9090 });
console.log("Now serving http://localhost:9090/metrics");

You can also run the demo directly, which simulates extra HTTP traffic to make the metrics more full:

deno run --allow-net https://raw.githubusercontent.com/cloudydeno/deno-openmetrics_exporter/main/demo.ts

If you would like to expose metrics on your existing web server, you'll want to look at mod.ts for inspiration instead of importing it as-is.

Deno Metrics

• deno_ops_dispatched: # of operations started, split into 3 categories
• deno_ops_completed: # of operations finished, split into 3 categories
• deno_ops_sent_bytes_total: # of data bytes dispatched with all operations so far
• deno_ops_sent_control_bytes: # of control bytes dispatched with all operations so far
  • Note from Deno's source code:

    The 'bytes' metrics seem pretty useless, especially now that the distinction between 'control' and 'data' buffers has become blurry.

• deno_ops_received_bytes: # of bytes received in response to an operation so far
• deno_open_resources: # of currently registered Deno resources, split by resource type.
  • A process starts up with 3: stdin, stdout, err.
  • Starting the metrics server will add 1 tcpListener.
  • Your metrics HTTP request seemingly always shows up as an additional tcpStream.
  • All other resources are from your application's own code (or libraries in use).

Please note that the ops_..._bytes metrics refer to bytes transfered within your process, between Javascript and the actual Deno runtime. They are not directly related to bytes transfered over the network or similar metrics. You'll want to monitor network bytes from a lower level source such as Docker or Kubernetes metrics if that is an interesting metric to you.

Here's an example of the payload:

# TYPE deno_ops_dispatched counter
deno_ops_dispatched_total{op_type="sync"} 179
deno_ops_dispatched_total{op_type="async"} 252
deno_ops_dispatched_total{op_type="async_unref"} 0
# TYPE deno_ops_completed counter
deno_ops_completed_total{op_type="sync"} 179
deno_ops_completed_total{op_type="async"} 245
deno_ops_completed_total{op_type="async_unref"} 0
# TYPE deno_ops_sent_bytes counter
# UNIT deno_ops_sent_bytes bytes
deno_ops_sent_bytes_total 1214641
# TYPE deno_ops_sent_control_bytes counter
# UNIT deno_ops_sent_control_bytes bytes
deno_ops_sent_control_bytes_total 13178
# TYPE deno_ops_received_bytes counter
# UNIT deno_ops_received_bytes bytes
deno_ops_received_bytes_total 23640
# TYPE deno_open_resources gauge
deno_open_resources{res_type="stdin"} 1
deno_open_resources{res_type="stdout"} 1
deno_open_resources{res_type="stderr"} 1
deno_open_resources{res_type="tcpListener"} 1
deno_open_resources{res_type="child"} 30
deno_open_resources{res_type="tcpStream"} 2

HTTP Server Metrics

• denohttp_handled_requests: Number of HTTP requests that have been received and responded to in full.
• denohttp_requests_in_flight: Current number of HTTP requests being served.
• denohttp_request_duration_seconds: A histogram of the HTTP request durations, including writing a response.
• denohttp_response_bytes_total: Number of bytes transmitted in response to HTTP requests. Includes a facet for which aspect of the HTTP response the bytes were a part of.

# TYPE denohttp_handled_requests counter
# HELP denohttp_handled_requests Number of HTTP requests that have been received and responded to in full.
denohttp_handled_requests{code="404",method="get"} 1218
denohttp_handled_requests{code="200",method="get"} 6
# TYPE denohttp_requests_in_flight gauge
# HELP denohttp_requests_in_flight Current number of HTTP requests being served.
denohttp_requests_in_flight 1
# TYPE denohttp_request_duration_seconds histogram
# UNIT denohttp_request_duration_seconds seconds
# HELP denohttp_request_duration_seconds A histogram of the HTTP request durations, including writing a response.
denohttp_request_duration_seconds_bucket{le="0.01"} 1219
denohttp_request_duration_seconds_bucket{le="0.1"} 1224
denohttp_request_duration_seconds_bucket{le="1"} 1224
denohttp_request_duration_seconds_bucket{le="+Inf"} 1224
denohttp_request_duration_seconds_sum 0.704
denohttp_request_duration_seconds_count 1224
# TYPE denohttp_response_bytes counter
# UNIT denohttp_response_bytes bytes
# HELP denohttp_response_bytes Number of bytes transmitted in response to HTTP requests.
denohttp_response_bytes_total{purpose="body"} 25247
denohttp_response_bytes_total{purpose="framing"} 31782
denohttp_response_bytes_total{purpose="header"} 24936

TODO

• Serve data from Deno.metrics()
• Serve data from Deno.resources()
• Accept custom metrics from the user's code
• Include 'created' timestamp on counters to aid in monotonic tracking
• Publish on deno.land
• Keep track of previous metrics to include zero gauges in future bodies

License

MIT