HAProxy Environment Variables – How to Use Environment Variables in haproxy.conf

environment-variableshaproxy

My haproxy.cfg file has one backend servers using hostnames:

backend servers
    server myapp ${PORTAL_PORT_3000_TCP_ADDR}:${PORTAL_PORT_3000_TCP_PORT} maxconn 32

myapp is running in other docker container linked to haproxy docker container. The mentioned environment variable have values inside haproxy container but when it container start raise this error

[ALERT] 244/134924 (8) : parsing [/etc/haproxy.cfg:16] : Unknown host in '${PORTAL_PORT_3000_TCP_ADDR}:${PORTAL_PORT_3000_TCP_PORT}'
[ALERT] 244/134924 (8) : Error(s) found in configuration file : /etc/haproxy.cfg
[ALERT] 244/134934 (8) : Fatal errors found in configuration.

Best Answer

You are, most likely, using version 1.4 or older. The possibility to use environment variables has been introduced in haproxy 1.5.

Related Solutions

Linux – Check Environment Variables of a Running Process on Unix

cat /proc/<pid>/environ

If you want to have pid(s) of a given running executable you can, among a number of other possibilities, use pidof:

AlberT$ pidof sshd   
30690 6512

EDIT:

I totally quote Dennis Williamson and Teddy comments to achieve a more readable output. My solution is the following:

tr '\0' '\n' < /proc/<pid>/environ

Hostnames in HAProxy configuration file

In haproxy >= 1.7, you should be able to use the init-addr option, specifying none to prevent DNS resolution at startup.

From the docs:

init-addr {last | libc | none | <ip>},[...]*

Indicate in what order the server's address should be resolved upon startup if it uses an FQDN. Attempts are made to resolve the address by applying in turn each of the methods mentionned in the comma-delimited list. The first method which succeeds is used. If the end of the list is reached without finding a working method, an error is thrown. Method "last" suggests to pick the address which appears in the state file (see "server-state-file"). Method "libc" uses the libc's internal resolver (gethostbyname() or getaddrinfo() depending on the operating system and build options). Method "none" specifically indicates that the server should start without any valid IP address in a down state. It can be useful to ignore some DNS issues upon startup, waiting for the situation to get fixed later. Finally, an IP address (IPv4 or IPv6) may be provided.

So your config line could be:

server s1 myhostname init-addr none

Best Answer

Related Solutions

Linux – Check Environment Variables of a Running Process on Unix

Hostnames in HAProxy configuration file

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