Apply metrics in rpc package

[trinhdn2]

Prerequisite

• Refactor metrics package with Prometheus and InfluxDB support #428

Checklist

• Adds JSON RPC call metrics.
• Implement serve time histograms, which allows us to have 2D heatmap plots: frequency of requests over time, groupped by serving times.

Added metrics:

• rpc_duration_all_count - all RPC methods serving timer
• rpc_duration_{method}_{success|failure} - RPC method level histogram metrics, separated by RPC method and execution status
• rpc_duration_{method}_{success|failure}_count - serving timer of a specific RPC method
• rpc_requests - total RPC requests served gauge
• rpc_success - total RPC success requests served gauge
• rpc_failure - total RPC failed requests served gauge

Example of new metrics under prometheus format:

# TYPE rpc_duration_GetBlockByHash_success_count counter
rpc_duration_GetBlockByHash_success_count 4

# TYPE rpc_duration_GetBlockByHash_success summary
rpc_duration_GetBlockByHash_success {quantile="0.5"} 74.5
rpc_duration_GetBlockByHash_success {quantile="0.75"} 162.25
rpc_duration_GetBlockByHash_success {quantile="0.95"} 181
rpc_duration_GetBlockByHash_success {quantile="0.99"} 181
rpc_duration_GetBlockByHash_success {quantile="0.999"} 181
rpc_duration_GetBlockByHash_success {quantile="0.9999"} 181

# TYPE rpc_duration_GetBlockByNumber_success_count counter
rpc_duration_GetBlockByNumber_success_count 7

# TYPE rpc_duration_GetBlockByNumber_success summary
rpc_duration_GetBlockByNumber_success {quantile="0.5"} 112
rpc_duration_GetBlockByNumber_success {quantile="0.75"} 127
rpc_duration_GetBlockByNumber_success {quantile="0.95"} 128
rpc_duration_GetBlockByNumber_success {quantile="0.99"} 128
rpc_duration_GetBlockByNumber_success {quantile="0.999"} 128
rpc_duration_GetBlockByNumber_success {quantile="0.9999"} 128

# TYPE rpc_duration_all_count counter
rpc_duration_all_count 26

# TYPE rpc_duration_all summary
rpc_duration_all {quantile="0.5"} 73416.5
rpc_duration_all {quantile="0.75"} 116281.5
rpc_duration_all {quantile="0.95"} 1.0382708499999982e+06
rpc_duration_all {quantile="0.99"} 1.468333e+06
rpc_duration_all {quantile="0.999"} 1.468333e+06
rpc_duration_all {quantile="0.9999"} 1.468333e+06

# TYPE rpc_failure gauge
rpc_failure 0

# TYPE rpc_requests gauge
rpc_requests 26

# TYPE rpc_success gauge
rpc_success 26

References:

• rpc: add metrics for generic json rpc ethereum/go-ethereum#20847
• rpc: swap out timer metrics to histograms ethereum/go-ethereum#25044