Healthchecks

Healthchecks are used for determine service status of backend nodes pool. If discovery return only a nodes list and there are no healthchecks on discovery service side it needs to use mechanism to determine service real status (failed or ok ). In this case healthchecks can be used. There are two different type of healthchecks in gobetween.

Healthchecks are optional since 0.2 release.

If there are no healthcheck server section defined - backend nodes marked as "ok" and can be deleted from backend according to discovery rules and intervals

ping

This is a simple healthcheck. It is simple sheck connection to backend nodes by initiate new connection from gobetween side to each backend node from discovery list. In case of connection created successfully - check passed. This is a simple mechanism. Checks success are only mean that connection created . No data verification made during this checks.

Example of ping healthcheck:

[servers.default.healthcheck]
kind = "ping"
interval = "2s"
ping_timeout_duration = "500ms"

exec

This is a more complicated healthcheck type. During Gobetween development we made a decision provide users a flexible mechanism to create own healthchecks. No one except end user know how exactly check service status of nodes in discovery pools. There are uncountable quantity of usage cases and services. Anyone can create it's own script and call it as healthcheck. Script execute by gobetween with arguments: /path/to/script [ip] [port] output of script to stdout should be 1 if check passed successfully and 0 if failed by default (may be overriden).

Example of exec healthcheck:

[servers.default.healthcheck] 
kind = "exec"
interval = "2s"  
timeout = "1s"                  # (required) max time for script to execute until mark as failed 
                                # this value should be less then interval

exec_command = "/usr/share/exec_healthcheck.sh"  # (required) command to execute
exec_expected_positive_output = "1"           # (required) expected output of command in case of success
exec_expected_negative_output = "0"           # (required) expected output of command in case of failure

Examples

Please note that in all operating systems healthcheck response should not contain newline after output result.

Windows

healthcheck.bat

@ECHO OFF
echo|set /p Dummy=1

Linux (Actually any Unix family)

healthcheck.sh

#!/usr/bin/env bash
echo -n 1 ;

probe

(since 0.7.0)

Probe sends string to backend and expects specific string in response to check if backend is alive. Only the beginning of received buffer will be compared with expected value, so that backend response can contain extra data, not being checked. probe_send and probe_recv are configured as strings and support escape sequences: \n \r or \xNN for hex. First probe_recv_len bytes of server response could be also matched using regular expression.

Probe healthcheck supports tcp, udp and tls (since 0.8.0) protocols. When using tls, backend should provide valid server certificate. Healtcheck protocol may differ from the configured server protocol.

Example of probe healthcheck:

[servers.default.healthcheck] 
kind = "probe"
interval = "2s"  
timeout = "1s"                  # (required) max time for script to execute until mark as failed 
                                # this value should be less then interval
probe_protocol = "udp"          # (required) "udp" | "tcp" | "tls"
probe_strategy = "starts_with"  # (optional) "starts_with" | "regexp"
probe_send    = 'PING\xFF\n'    # (required) string to send
probe_recv    = 'PONG\xAA\n'    # (required) string to expect in response (response starts with or regexp)
probe_recv_len = 0              # (optional) number of bytes to read (value > 0 is required for regexp strategy)