Prometheus

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

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

imgproxy will collect the following metrics:

requests_total - a counter of the total number of HTTP requests imgproxy processed;
errors_total - a counter of the occurred errors separated by type (timeout, downloading, processing);
request_duration_seconds - a histogram of the response latency (seconds);
download_duration_seconds - a histogram of the source image downloading latency (seconds);
processing_duration_seconds - a histogram of the image processing latency (seconds);
buffer_size_bytes - a histogram of the download/gzip buffers sizes (bytes);
buffer_default_size_bytes - calibrated default buffer size (bytes);
buffer_max_size_bytes - calibrated maximum buffer size (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.