Prometheus

imgproxy can collect metrics for Prometheus. To use this feature, do the following:

Set the IMGPROXY_PROMETHEUS_BIND environment variable to the address and port that will be listened to by the Prometheus server. Note that you can't bind the main server and Prometheus to the same port.
(optional) Set the IMGPROXY_PROMETHEUS_NAMESPACE to prepend prefix to the names of metrics, i.e. with IMGPROXY_PROMETHEUS_NAMESPACE=imgproxy names will appear like imgproxy_requests_total.
Collect the metrics from any path on the specified binding.

imgproxy will collect the following metrics:

requests_total: a counter with the total number of HTTP requests imgproxy has processed
errors_total: a counter of the occurred errors separated by type (timeout, downloading, processing)
request_duration_seconds: a histogram of the request latency (in seconds)
request_span_duration_seconds: a histogram of the request latency (in seconds) separated by span (queue, downloading, processing)
requests_in_progress: the number of requests currently in progress
images_in_progress: the number of images currently in progress
buffer_size_bytes: a histogram of the download buffers sizes (in bytes)
buffer_default_size_bytes: calibrated default buffer size (in bytes)
buffer_max_size_bytes: calibrated maximum buffer size (in bytes)
vips_memory_bytes: libvips memory usage
vips_max_memory_bytes: libvips maximum memory usage
vips_allocs: the number of active vips allocations
Some useful Go metrics like memstats and goroutines count

The following metrics are deprecated and can be removed in future versions. Use request_span_duration_seconds instead.

download_duration_seconds: a histogram of the source image downloading latency (in seconds)
processing_duration_seconds: a histogram of the image processing latency (in seconds)