Overview

A router is one way to get traffic into the cluster. The HAProxy Template Router plug-in is one of the available router plugins.

HAProxy Template Router

The template router has two components:

  • a wrapper that watches endpoints and routes and causes a HAProxy reload based on changes.

  • a controller that builds the HAProxy configuration file based on routes and endpoints.

The HAProxy router uses version 1.5.18.

The controller and HAProxy are housed inside a pod, which is managed by a deployment configuration. The process of setting up the router is automated by the oc adm router command.

The controller watches the routes and endpoints for changes, as well as HAProxy’s health. When a change is detected, it builds a new haproxy-config file and restarts HAProxy. The haproxy-config file is constructed based on the router’s template file and information from OKD.

The HAProxy template file can be customized as needed to support features that are not currently supported by OKD. The HAProxy manual describes all of the features supported by HAProxy.

The following diagram illustrates how data flows from the master through the plug-in and finally into an HAProxy configuration:

HAProxy Router Data Flow
Figure 1. HAProxy Router Data Flow

HAProxy Template Router Metrics

The HAProxy router exposes or publishes metrics in Prometheus format for consumption by external metrics collection and aggregation systems (e.g. Prometheus, statsd). The router can be configured to provide HAProxy CSV format metrics, or provide no router metrics at all.

The metrics are collected from both the router controller and from HAProxy every 5 seconds. The router metrics counters start at zero when the router is deployed and increase over time. The HAProxy metrics counters are reset to zero every time haproxy is reloaded. The router collects HAProxy statistics for each frontend, backend and server. To reduce resource usage when there are more than 500 servers, the backends are reported instead of the servers since a backend can have multiple servers.

The statistics are a subset of the available HAProxy Statistics.

The following HAProxy metrics are collected on a periodic basis and converted to Prometheus format. For every frontend the "F" counters are collected. When the counters are collected for each backend and the "S" server counters are collected for each server. Otherwise, the "B" counters are collected for each backend and no server counters are collected.

See router environment variables for more information.

In the following table:

Column 1 - Index from HAProxy CSV statistics

Column 2

F

Frontend metrics

b

Backend metrics when not showing Server metrics due to the Server Threshold,

B

Backend metrics when showing Server metrics

S

Server metrics.

Column 3 - The counter

Column 4 - Counter description

Index

Usage

Counter

Description

2

bBS

current_queue

Current number of queued requests not assigned to any server.

4

FbS

current_sessions

Current number of active sessions.

5

FbS

max_sessions

Maximum observed number of active sessions.

7

FbBS

connections_total

Total number of connections.

8

FbS

bytes_in_total

Current total of incoming bytes.

9

FbS

bytes_out_total

Current total of outgoing bytes.

13

bS

connection_errors_total

Total of connection errors.

14

bS

response_errors_total

Total of response errors.

17

bBS

up

Current health status of the backend (1 = UP, 0 = DOWN).

21

S

check_failures_total

Total number of failed health checks.

24

S

downtime_seconds_total

Total downtime in seconds.", nil),

33

FbS

current_session_rate

Current number of sessions per second over last elapsed second.

35

FbS

max_session_rate

Maximum observed number of sessions per second.

40

FbS

http_responses_total

Total of HTTP responses, code 2xx

43

FbS

http_responses_total

Total of HTTP responses, code 5xx

60

bS

http_average_response_latency_milliseconds

of the last 1024 requests in milliseconds.

The router controller scrapes the following items. These are only available with Prometheus format metrics.

Name

Description

template_router_reload_seconds

Measures the time spent reloading the router in seconds.

template_router_write_config_seconds

Measures the time spent writing out the router configuration to disk in seconds.

haproxy_exporter_up

Was the last scrape of haproxy successful.

haproxy_exporter_csv_parse_failures

Number of errors while parsing CSV.

haproxy_exporter_scrape_interval

The time in seconds before another scrape is allowed, proportional to size of data.

haproxy_exporter_server_threshold

Number of servers tracked and the current threshold value.

haproxy_exporter_total_scrapes

Current total HAProxy scrapes.

http_request_duration_microseconds

The HTTP request latencies in microseconds.

http_request_size_bytes

The HTTP request sizes in bytes.

http_response_size_bytes

The HTTP response sizes in bytes.

openshift_build_info

A metric with a constant '1' value labeled by major, minor, git commit & git version from which OpenShift was built.

ssh_tunnel_open_count

Counter of SSH tunnel total open attempts

ssh_tunnel_open_fail_count

Counter of SSH tunnel failed open attempts