Postfix Exporter installation on rhel 8.10 stuck

[Mamita2012]

Hello team,

I'm trying to install postfix_exporter on a SMTP server in order to monitor and get alerts via grafana and alertmanager regarding mailq and so one. So have download the code compiled

total 14436
-rwxrwxr-x. 1 root root 285 19 oct. 2021 build_static.sh
-rw-rw-r--. 1 root root 298 19 oct. 2021 CHANGELOG.md
-rw-rw-r--. 1 root root 492 19 oct. 2021 Dockerfile
-rw-rw-r--. 1 root root 614 19 oct. 2021 go.mod
-rw-rw-r--. 1 root root 12094 19 oct. 2021 go.sum
-rw-rw-r--. 1 root root 11357 19 oct. 2021 LICENSE
-rw-rw-r--. 1 root root 2475 19 oct. 2021 logsource_docker.go
-rw-rw-r--. 1 root root 1939 19 oct. 2021 logsource_docker_test.go
-rw-rw-r--. 1 root root 2040 19 oct. 2021 logsource_file.go
-rw-rw-r--. 1 root root 1691 19 oct. 2021 logsource_file_test.go
-rw-rw-r--. 1 root root 1686 19 oct. 2021 logsource.go
-rw-rw-r--. 1 root root 3719 19 oct. 2021 logsource_systemd.go
-rw-rw-r--. 1 root root 3733 19 oct. 2021 logsource_systemd_test.go
-rw-rw-r--. 1 root root 1866 19 oct. 2021 main.go
drwxrwxr-x. 2 root root 58 19 oct. 2021 mock
-rwxr-xr-x. 1 root root 14657496 18 mars 10:17 postfix_exporter
-rw-rw-r--. 1 root root 24881 19 oct. 2021 postfix_exporter.go
-rw-rw-r--. 1 root root 10727 19 oct. 2021 postfix_exporter_test.go
-rw-rw-r--. 1 root root 3436 19 oct. 2021 README.md
-rw-rw-r--. 1 root root 1103 19 oct. 2021 showq_test.go
drwxrwxr-x. 2 root root 23 19 oct. 2021 testdata

Unfortunately, the installation of postfix_exporter-0.3.0 stuck with the error
2025/04/02 17:05:19 Reading log events from /var/log/mail.log
2025/04/02 17:05:19 Listening on :9154

A the moment the installltion is stuck
root 2455048 0.0 0.7 1613472 14668 pts/0 Sl+ 17:05 0:00 ./postfix_exporter
root 2459738 0.0 0.0 12108 1052 pts/1 S+ 17:16 0:00 grep --color=auto postfix_exporter
May someone help me please ?

[maxkratz]

(Disclaimer: Maybe I'm incorrect here, so if you find this comment irritating, please correct me.)

The binary postfix_exporter is not an installer. It is an executable file that directly runs the HTTP server to connect to and gather metrics from.
Listening on :9154 indicates that the exporter is listening on port 9154 for HTTP requests. So at least if I'm not mistaken here, everything is working as expected. You can check that after running the binary by connecting to your port 9154, e.g., with curl or wget.

If you want the exporter to be "installed", you have to do it manually after compiling the binary. Typically, you want a systemd service (or something similar) to run the binary when the system has booted. There are additional configuration steps necessary for this setup.

[Mamita2012]

(Disclaimer: Maybe I'm incorrect here, so if you find this comment irritating, please correct me.)

The binary postfix_exporter is not an installer. It is an executable file that directly runs the HTTP server to connect to and gather metrics from. Listening on :9154 indicates that the exporter is listening on port 9154 for HTTP requests. So at least if I'm not mistaken here, everything is working as expected. You can check that after running the binary by connecting to your port 9154, e.g., with curl or wget.

If you want the exporter to be "installed", you have to do it manually after compiling the binary. Typically, you want a systemd service (or something similar) to run the binary when the system has booted. There are additional configuration steps necessary for this setup.

[Mamita2012]

Hi maxkratz,

Thanks a lot for your feedback. Well appreciated.
As you can see here, the curl show connection refused. So instead of compiling the binary and how I can make the metric gathering works please ?

[root@OPSMTPPUB01 postfix_exporter-0.3.0]# curl http://localhost:9154/metrics
curl: (7) Failed to connect to localhost port 9154: Connexion refusée
[root@OPGOSVTBSMTPPUB01 postfix_exporter-0.3.0]#

[maxkratz]

Hi maxkratz,

Thanks a lot for your feedback. Well appreciated. As you can see here, the curl show connection refused. So instead of compiling the binary and how I can make the metric gathering works please ?

[root@OPSMTPPUB01 postfix_exporter-0.3.0]# curl http://localhost:9154/metrics curl: (7) Failed to connect to localhost port 9154: Connexion refusée [root@OPGOSVTBSMTPPUB01 postfix_exporter-0.3.0]#

Just to be completely sure: before using curl to request the metrics via HTTP, you did (re)start your compiled binary (e.g., in another terminal window) and it was running as you mentioned above?

Maybe you have a firewall (like ufw) on your server that is blocking your requests? (If I think about it, this seems unlikely to me because you are trying to access the port locally on the same machine.)

While running your compiled binary (as you commented above), you can use nmap to check for the open port like so: $ nmap -p 9154 localhost
What does it return?

[Mamita2012]

Hi maxkratz,
Thanks a lot for your feedback. Well appreciated. As you can see here, the curl show connection refused. So instead of compiling the binary and how I can make the metric gathering works please ?
[root@OPSMTPPUB01 postfix_exporter-0.3.0]# curl http://localhost:9154/metrics curl: (7) Failed to connect to localhost port 9154: Connexion refusée [root@OPGOSVTBSMTPPUB01 postfix_exporter-0.3.0]#

Just to be completely sure: before using curl to request the metrics via HTTP, you did (re)start your compiled binary (e.g., in another terminal window) and it was running as you mentioned above?

Maybe you have a firewall (like ufw) on your server that is blocking your requests? (If I think about it, this seems unlikely to me because you are trying to access the port locally on the same machine.)

While running your compiled binary (as you commented above), you can use nmap to check for the open port like so: $ nmap -p 9154 localhost What does it return?

Hi maxkratz,

Sorry for my late answer, I was OOO.
I try to use nmap as you asked at same time the binary is being run
[root@OPSMTPPUB01 ~]# cd postfix_exporter-0.3.0/
[root@OPSMTPPUB01 postfix_exporter-0.3.0]# ./postfix_exporter
2025/05/02 09:31:26 Reading log events from /var/log/mail.log
2025/05/02 09:31:26 Listening on :9154

[root@OPSMTPPUB01 osadmin]# nmap -p 9154 localhost
Starting Nmap 7.70 ( https://nmap.org ) at 2025-05-02 09:31 GMT
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000042s latency).
Other addresses for localhost (not scanned): ::1

PORT STATE SERVICE
9154/tcp open unknown

Nmap done: 1 IP address (1 host up) scanned in 0.27 seconds
[root@OPSMTPPUB01 osadmin]# ps aux | grep postfix_exporter
root 3033101 0.4 0.6 1613472 11916 pts/0 Sl+ 09:31 0:00 ./postfix_exporter
root 3033762 0.0 0.0 12108 992 pts/1 S+ 09:31 0:00 grep --color=auto postfix_exporter

But once the binary run is stopped, the exporter service is down. So, my question is how can i keep the service running in order to gather metrics via http ?
[root@OPSMTPPUB01 postfix_exporter-0.3.0]# ./postfix_exporter
2025/05/02 09:31:26 Reading log events from /var/log/mail.log
2025/05/02 09:31:26 Listening on :9154

[root@OPSMTPPUB01 postfix_exporter-0.3.0]# ps aux | grep postfix_exporter
root 3035547 0.0 0.0 12108 1092 pts/0 S+ 09:36 0:00 grep --color=auto postfix_exporter

[maxkratz]

Hi maxkratz,

Sorry for my late answer, I was OOO.

No problem :-).

I try to use nmap as you asked at same time the binary is being run [root@OPSMTPPUB01 ~]# cd postfix_exporter-0.3.0/ [root@OPSMTPPUB01 postfix_exporter-0.3.0]# ./postfix_exporter 2025/05/02 09:31:26 Reading log events from /var/log/mail.log 2025/05/02 09:31:26 Listening on :9154

[root@OPSMTPPUB01 osadmin]# nmap -p 9154 localhost Starting Nmap 7.70 ( https://nmap.org ) at 2025-05-02 09:31 GMT Nmap scan report for localhost (127.0.0.1) Host is up (0.000042s latency). Other addresses for localhost (not scanned): ::1

PORT STATE SERVICE 9154/tcp open unknown

Nmap done: 1 IP address (1 host up) scanned in 0.27 seconds [root@OPSMTPPUB01 osadmin]# ps aux | grep postfix_exporter root 3033101 0.4 0.6 1613472 11916 pts/0 Sl+ 09:31 0:00 ./postfix_exporter root 3033762 0.0 0.0 12108 992 pts/1 S+ 09:31 0:00 grep --color=auto postfix_exporter

Allright, this seems to me as if the binary itself is working correctly. Great!
Could you also check the access of the provided metrics while running the binary, e.g., with curl or wget?

My next steps of checking would be to:

• check the metrics with curl on the same machine, and ...
• ... check the metrics with curl from another machine (both while running the binary).

If both steps succeed, everything is working normally and you "just" have to find a way to run the binary as a service, i.e., keep it running at all time in the background, start it after booting up, etc.

But once the binary run is stopped, the exporter service is down. So, my question is how can i keep the service running in order to gather metrics via http ?

My go-to solution for this is Docker, so I created a Docker image with the postfix exporter and keep it running via docker-compose. But I understand Docker is not for everyone and it would probably be overkill for you to install Docker just for this one use case.

Maybe have a look at this systemd service file (https://github.com/prometheus/node_exporter/blob/master/examples/systemd/node_exporter.service) for the node_exporter of Prometheus. You could adapt it to your needs and the postfix exporter, install it in the system, and run your postfix exporter as systemd service. The necessary steps can be found online, e.g., in the Debian wiki (https://wiki.debian.org/systemd/Services).

I hope this helps you out :-).

[Mamita2012]

Curl from the same machine, report all metrics. Don't understand curl you ask from another machine ?
Ok, I'll look into the link you provide in order to configure postfix as systemd service. Thanks a lot

[maxkratz]

Curl from the same machine, report all metrics. Don't understand curl you ask from another machine ?

I just wanted to ensure your local service (the metrics exporter) is available from outside your machine to be queried by Prometheus.

Ok, I'll look into the link you provide in order to configure postfix as systemd service. Thanks a lot

You are welcome :-).

[Mamita2012]

Hi Max,
Thanks I follow your instruction and was able to configure postfix as systemd. The service is working fine and I'm able to see the the metrics

[root@OPSMTPPUB01 ~]# curl http://localhost:9154/metrics | grep postfix_
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 11312 0 11312 0 0 3682k 0 --:--:-- --:--:-- --:--:-- 3682k

HELP postfix_cleanup_messages_not_accepted_total Total number of messages not accepted by cleanup.

TYPE postfix_cleanup_messages_not_accepted_total counter

postfix_cleanup_messages_not_accepted_total 0

HELP postfix_cleanup_messages_processed_total Total number of messages processed by cleanup.

TYPE postfix_cleanup_messages_processed_total counter

postfix_cleanup_messages_processed_total 18

HELP postfix_cleanup_messages_rejected_total Total number of messages rejected by cleanup.

TYPE postfix_cleanup_messages_rejected_total counter

postfix_cleanup_messages_rejected_total 0

HELP postfix_qmgr_messages_inserted_receipients Number of receipients per message inserted into the mail queues.

TYPE postfix_qmgr_messages_inserted_receipients histogram

postfix_qmgr_messages_inserted_receipients_bucket{le="1"} 18
postfix_qmgr_messages_inserted_receipients_bucket{le="2"} 18
postfix_qmgr_messages_inserted_receipients_bucket{le="4"} 18
postfix_qmgr_messages_inserted_receipients_bucket{le="8"} 18
postfix_qmgr_messages_inserted_receipients_bucket{le="16"} 18
postfix_qmgr_messages_inserted_receipients_bucket{le="32"} 18
postfix_qmgr_messages_inserted_receipients_bucket{le="64"} 18
postfix_qmgr_messages_inserted_receipients_bucket{le="128"} 18
postfix_qmgr_messages_inserted_receipients_bucket{le="+Inf"} 18
postfix_qmgr_messages_inserted_receipients_sum 18
postfix_qmgr_messages_inserted_receipients_count 18

HELP postfix_qmgr_messages_inserted_size_bytes Size of messages inserted into the mail queues in bytes.

TYPE postfix_qmgr_messages_inserted_size_bytes histogram

postfix_qmgr_messages_inserted_size_bytes_bucket{le="1000"} 0
postfix_qmgr_messages_inserted_size_bytes_bucket{le="10000"} 0
postfix_qmgr_messages_inserted_size_bytes_bucket{le="100000"} 18
postfix_qmgr_messages_inserted_size_bytes_bucket{le="1e+06"} 18
postfix_qmgr_messages_inserted_size_bytes_bucket{le="1e+07"} 18
postfix_qmgr_messages_inserted_size_bytes_bucket{le="1e+08"} 18
postfix_qmgr_messages_inserted_size_bytes_bucket{le="1e+09"} 18
postfix_qmgr_messages_inserted_size_bytes_bucket{le="+Inf"} 18
postfix_qmgr_messages_inserted_size_bytes_sum 1.347469e+06
postfix_qmgr_messages_inserted_size_bytes_count 18

HELP postfix_qmgr_messages_removed_total Total number of messages removed from mail queues.

TYPE postfix_qmgr_messages_removed_total counter

postfix_qmgr_messages_removed_total 18

HELP postfix_smtp_connection_timed_out_total Total number of messages that have been deferred on SMTP.

TYPE postfix_smtp_connection_timed_out_total counter

postfix_smtp_connection_timed_out_total 0

HELP postfix_smtp_deferred_messages_total Total number of messages that have been deferred on SMTP.

TYPE postfix_smtp_deferred_messages_total counter

postfix_smtp_deferred_messages_total 0

HELP postfix_smtp_delivery_delay_seconds SMTP message processing time in seconds.

TYPE postfix_smtp_delivery_delay_seconds histogram

postfix_smtp_delivery_delay_seconds_bucket{stage="",le="0.001"} 4
postfix_smtp_delivery_delay_seconds_bucket{stage="",le="0.01"} 14
postfix_smtp_delivery_delay_seconds_bucket{stage="",le="0.1"} 20
postfix_smtp_delivery_delay_seconds_bucket{stage="",le="1"} 20
postfix_smtp_delivery_delay_seconds_bucket{stage="",le="10"} 20
postfix_smtp_delivery_delay_seconds_bucket{stage="",le="60"} 20
postfix_smtp_delivery_delay_seconds_bucket{stage="",le="3600"} 20
postfix_smtp_delivery_delay_seconds_bucket{stage="",le="86400"} 20
postfix_smtp_delivery_delay_seconds_bucket{stage="",le="172800"} 20
postfix_smtp_delivery_delay_seconds_bucket{stage="",le="+Inf"} 20
postfix_smtp_delivery_delay_seconds_sum{stage=""} 0.31000000000000005
postfix_smtp_delivery_delay_seconds_count{stage=""} 20

HELP postfix_smtp_status_deferred Total number of messages deferred.

TYPE postfix_smtp_status_deferred counter

postfix_smtp_status_deferred 0

HELP postfix_smtpd_connects_total Total number of incoming connections.

TYPE postfix_smtpd_connects_total counter

postfix_smtpd_connects_total 23

HELP postfix_smtpd_disconnects_total Total number of incoming disconnections.

TYPE postfix_smtpd_disconnects_total counter

postfix_smtpd_disconnects_total 23

HELP postfix_smtpd_forward_confirmed_reverse_dns_errors_total Total number of connections for which forward-confirmed DNS cannot be resolved.

TYPE postfix_smtpd_forward_confirmed_reverse_dns_errors_total counter

postfix_smtpd_forward_confirmed_reverse_dns_errors_total 0

HELP postfix_smtpd_messages_processed_total Total number of messages processed.

TYPE postfix_smtpd_messages_processed_total counter

postfix_smtpd_messages_processed_total{sasl_method=""} 18

HELP postfix_smtpd_sasl_authentication_failures_total Total number of SASL authentication failures.

TYPE postfix_smtpd_sasl_authentication_failures_total counter

postfix_smtpd_sasl_authentication_failures_total 0

HELP postfix_unsupported_log_entries_total Log entries that could not be processed.

TYPE postfix_unsupported_log_entries_total counter

postfix_unsupported_log_entries_total{service=""} 13

HELP postfix_up Whether scraping Postfix's metrics was successful.

TYPE postfix_up gauge

postfix_up{path="/var/spool/postfix/public/showq"} 0

The think that doesn't work at the moment is the fact I'm having this metric below value is equal to 0
postfix_up{path="/var/spool/postfix/public/showq"} 0
the exporter isn't be able to read the queue status. I spent a lot of time in checjikg this and have modified the selinux without success

mai 09 15:59:39 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 15:59:39 Reading log events from /var/log/mail.log
mai 09 15:59:39 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 15:59:39 Listening on :9154
mai 09 15:59:57 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 15:59:57 Failed to scrape showq socket: dial unix /var/spool/postfix/public/showq: connect: permission denied
mai 09 16:01:37 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 16:01:37 Failed to scrape showq socket: dial unix /var/spool/postfix/public/showq: connect: permission denied
mai 09 16:02:41 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 16:02:41 Failed to scrape showq socket: dial unix /var/spool/postfix/public/showq: connect: permission denied

[root@OPSMTPPUB01 ~]# ls -lZ /var/spool/postfix/public/showq
Your help please
srw-rw-rw-. 1 postfix postfix system_u:object_r:postfix_public_t:s0 0 9 mai 15:44 /var/spool/postfix/public/showq

[maxkratz]

The think that doesn't work at the moment is the fact I'm having this metric below value is equal to 0 postfix_up{path="/var/spool/postfix/public/showq"} 0 the exporter isn't be able to read the queue status. I spent a lot of time in checjikg this and have modified the selinux without success

mai 09 15:59:39 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 15:59:39 Reading log events from /var/log/mail.log mai 09 15:59:39 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 15:59:39 Listening on :9154 mai 09 15:59:57 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 15:59:57 Failed to scrape showq socket: dial unix /var/spool/postfix/public/showq: connect: permission denied mai 09 16:01:37 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 16:01:37 Failed to scrape showq socket: dial unix /var/spool/postfix/public/showq: connect: permission denied mai 09 16:02:41 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 16:02:41 Failed to scrape showq socket: dial unix /var/spool/postfix/public/showq: connect: permission denied

[root@OPSMTPPUB01 ~]# ls -lZ /var/spool/postfix/public/showq Your help please srw-rw-rw-. 1 postfix postfix system_u:object_r:postfix_public_t:s0 0 9 mai 15:44 /var/spool/postfix/public/showq

I'm no expert here, but this seems to me like a permission problem.

There is a similar issue open for quite some time: #93

[Mamita2012]

Ok I'll check. Thanks again for your responsiveness. Rallye appreciate Le ven. 9 mai 2025, 16:20, Max Kratz ***@***.***> a écrit :

…

*maxkratz* left a comment (kumina/postfix_exporter#120) <#120 (comment)> The think that doesn't work at the moment is the fact I'm having this metric below value is equal to 0 postfix_up{path="/var/spool/postfix/public/showq"} 0 the exporter isn't be able to read the queue status. I spent a lot of time in checjikg this and have modified the selinux without success mai 09 15:59:39 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 15:59:39 Reading log events from /var/log/mail.log mai 09 15:59:39 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 15:59:39 Listening on :9154 mai 09 15:59:57 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 15:59:57 Failed to scrape showq socket: dial unix /var/spool/postfix/public/showq: connect: permission denied mai 09 16:01:37 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 16:01:37 Failed to scrape showq socket: dial unix /var/spool/postfix/public/showq: connect: permission denied mai 09 16:02:41 OPGOSVTBSMTPPUB01 postfix_exporter[3102375]: 2025/05/09 16:02:41 Failed to scrape showq socket: dial unix /var/spool/postfix/public/showq: connect: permission denied ***@***.*** ~]# ls -lZ /var/spool/postfix/public/showq Your help please srw-rw-rw-. 1 postfix postfix system_u:object_r:postfix_public_t:s0 0 9 mai 15:44 /var/spool/postfix/public/showq I'm no expert here, but this seems to me like a permission problem. There is a similar issue open for quite some time: #93 <#93> — Reply to this email directly, view it on GitHub <#120 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BCYFYS552LJHL3UFHA7DDRT25TIUXAVCNFSM6AAAAAB2KEIYSSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDQNRXGE2DIMRSG4> . You are receiving this because you authored the thread.Message ID: ***@***.***>