Available router plug-ins
- The HAProxy Template Router

Available router plug-ins

A router can be assigned to a node to control traffic in an OKD cluster. OKD uses HAProxy as the default router, but options are available.

The HAProxy Template Router

The HAProxy template router implementation is the reference implementation for a template router plug-in. It uses the openshift/origin-haproxy-router repository to run an HAProxy instance alongside the template router plug-in.

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 1.8.1.

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:

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 five 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, back end, and server. To reduce resource usage when there are more than 500 servers, the back ends are reported instead of the servers because a back end 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 front end the “F” counters are collected. When the counters are collected for each back end and the “S” server counters are collected for each server. Otherwise, the “B” counters are collected for each back end 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	Front end metrics
b	Back end metrics when not showing Server metrics due to the Server Threshold,
B	Back end 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 back end (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