[syslog-ng]Re: syslog-ng version 4.9.0 is now available

25 Aug 2025

      Hi Gyula,

Thanks for the report! I talked to the developer, who worked on it, and it is not a known issue. Please open a GitHub issue at https://github.com/syslog-ng/syslog-ng/issues/ for easier tracking, and also attach a minimal configuration to reproduce the problem, together with some information about your environment (number of log source hosts, message rate, etc.).

Thanks,
Peter

Peter Czanik (CzP) <peter.czanik@oneidentity.com>
Balabit (a OneIdentity company) / syslog-ng upstream
https://syslog-ng.com/community/
https://twitter.com/PCzanik

________________________________
From: Kerekes Gyula <gyula@harcinyul.hu>
Sent: Friday, August 22, 2025 10:35
To: syslog-ng@lists.balabit.hu <syslog-ng@lists.balabit.hu>
Subject: [syslog-ng]Re: syslog-ng version 4.9.0 is now available

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Hi,

I tried this stats exporter-dont-log() feature and it works well but it seems like it has a mem leak somewhere. I tried to switch off the prometheus data collection to one of the syslog-ng hosts and the mem consumption stayed fairly low. On the other hand all the others used 1-2 gigs of RSS mem. Is it a known issue?

Gyula

2025. 07. 17. 15:19 keltezéssel, Peter Czanik (pczanik) írta:
Hi,

I am happy to announce that version 4.9.0 of syslog-ng is now available. Thanks everyone who contributed code, documentation, testing, or in any other way.

Peter

4.9.0
Highlights

  *
stats-exporter: Added two new sources, stats-exporter() and stats-exporter-dont-log(), which directly serve the output of syslog-ng-ctl stats and syslog-ng-ctl query to a http scraper. The only difference is that stats-exporter-dont-log() suppresses log messages from incoming scraper requests, ensuring no messages appear in the log path. Meanwhile, stats-exporter() logs unparsed messages, storing incoming scraper HTTP requests in the MSG field.
Example usage for a Prometheus Scraper which logs the HTTP request of the scraper to /var/log/scraper.log:

@version: 4.9
@include "scl.conf"

source s_prometheus_stat {
    stats-exporter(
        ip("0.0.0.0")
        port(8080)
        stat-type("query")
        stat-query("*")
        scrape-freq-limit(30)
        single-instance(yes)
    );
};

log {
    source(s_prometheus_stat);
    destination { file(/var/log/scraper.log); };
};

Example usage for a generic HTTP Scraper which sends e.g. the GET /stats HTTP/1.1 HTTP request to get statistics of syslog-ng, do not want to log or further process the HTTP requests in the log pipe, and needs the response in CSV format:

@version: 4.9
@include "scl.conf"

source s_scraper_stat {
    stats-exporter-dont-log(
        ip("0.0.0.0")
        port(8080)
        stat-type("stats")
        stat-format("csv")
        scrape-pattern("GET /stats*")
        scrape-freq-limit(30)
        single-instance(yes)
    );
};

log {
    source(s_scraper_stat);
};

Note: A destination is not required for this to work; the stats-exporter() source will respond to the scraper regardless of whether a destination is present in the log path.
Available options:
stat-type(string) - query or stats, just like for the syslog-ng-ctl command line tool, see there for the details
stat-query(string) - the query regex string that can be used to filter the output of a query type request
stat-format(string) - the output format of the given stats request, like the -m option of the syslog-ng-ctl command line tool
scrape-pattern(string) – the pattern used to match the HTTP header of incoming scraping requests. A stat response will be generated and sent only if the header matches the pattern string
scrape-freq-limit(non-negative-int) - limits the frequency of repeated scraper requests to the specified number of seconds. Any repeated request within this period will be ignored. A value of 0 means no limit
single-instance(yes/no) - if set to yes only one scraper connection and request will be allowed at once
(#5259<https://github.com/syslog-ng/syslog-ng/pull/5259>)
  *
syslog() source driver: add support for RFC6587 style auto-detection of
octet-count based framing to avoid confusion that stems from the sender
using a different protocol to the server. This behaviour can be enabled
by using transport(auto) option for the syslog() source.
(#5322<https://github.com/syslog-ng/syslog-ng/pull/5322>)
  *
wildcard-file: Added inotify-based regular file change detection using the existing inotify-based directory monitor.
This improves efficiency on OSes like Linux, where only polling was available before, significantly reducing CPU usage while enhancing change detection accuracy.
To enable this feature, inotify kernel support is required, along with monitor-method() set to inotify or auto, and follow-freq() set to 0.
(#5315<https://github.com/syslog-ng/syslog-ng/pull/5315>)

Features

  *
cisco: Added support for Cisco Nexus NXOS 9.3 syslog format.
The parser now recognises NXOS 9.3 timestamps in YYYY MMM DD HH:MM:SS format and handles the different
sequence number prefix (: instead of seqno: ) used by NXOS 9.3 compared to traditional IOS formats.
Example Cisco configuration:
Example syslog-ng configuration:

@include "scl.conf"

source s_cisco {
    network(ip(0.0.0.0) transport("udp") port(2000) flags(no-parse));
};

parser p_cisco {
    cisco-parser();
};

destination d_placeholder {
    # Define your destination here
};

log {
    source(s_cisco);
    parser(p_cisco);
    destination(d_placeholder);
};

(#5412<https://github.com/syslog-ng/syslog-ng/pull/5412>)
     *   NXOS: (config)# logging server <syslog-ng-server-ip> port 2000
     *   IOS: (config)# logging host <syslog-ng-server-ip> transport udp port 2000
  *
bigquery(), google-pubsub-grpc(): Added service-account() authentication option.
Example usage:

destination {
    google-pubsub-grpc(
        project("test")
        topic("test")
        auth(service-account(key ("path_to_service_account_key.json")))
    );
};

Note: In contrary to the http() destination's similar option,
we do not need to manually set the audience here as it is
automatically recognized by the underlying gRPC API.
(#5270<https://github.com/syslog-ng/syslog-ng/pull/5270>)
  *
gRPC based destinations: Added response-action() option
With this option, it is possible to fine tune how syslog-ng
behaves in case of different gRPC results.
Supported by the following destination drivers:
Supported gRPC results:
Supported actions:
Usage:

google-pubsub-grpc(
  project("my-project")
  topic("my-topic")
  response-action(
    not-found => disconnect
    unavailable => drop
  )
);

(#5332<https://github.com/syslog-ng/syslog-ng/pull/5332>)
     *   opentelemetry()
     *   loki()
     *   bigquery()
     *   clickhouse()
     *   google-pubsub-grpc()
     *   ok
     *   unavailable
     *   cancelled
     *   deadline-exceeded
     *   aborted
     *   out-of-range
     *   data-loss
     *   unknown
     *   invalid-argument
     *   not-found
     *   already-exists
     *   permission-denied
     *   unauthenticated
     *   failed-precondition
     *   unimplemented
     *   internal
     *   resource-exhausted
     *   disconnect
     *   drop
     *   retry
     *   success
  *
s3: Added two new options
Example:

s3(
        url("http://localhost:9000"<http://localhost:9000>)
        bucket("testbucket")
        object_key("testobject")
        access_key("<ACCESS_KEY_ID>")
        secret_key("<SECRET_ACCESS_KEY>")
        content_type("text/plain")
        use_checksum("when_required")
);

(#5286<https://github.com/syslog-ng/syslog-ng/pull/5286>)
     *   content-type(): users now can change the content type of the objects uploaded by syslog-ng.
     *   use_checksum(): This option allows the users to change the default checksum settings for
S3 compatible solutions that don't support checksums. Requires botocore 1.36 or above. Acceptable values are
when_supported (default) and when_required.
  *
loki(): Added batch-bytes() and compression() options.
(#5174<https://github.com/syslog-ng/syslog-ng/pull/5174>)
  *
syslog-ng-ctl: Formatting the output of the syslog-ng-ctl stats and syslog-ng-ctl query commands is unified.
Both commands got a new --format (-m) argument that can control the output format of the given stat or query. The following formats are supported:
     *   kv - the legacy key-value-pairs e.g. center.queued.processed=0 (only for the query command yet)
     *   csv - comma separated values e.g. center;;queued;a;processed;0
     *   prometheus - the prometheus scraper ready format e.g. syslogng_center_processed{stat_instance="queued"} 0
(#5248<https://github.com/syslog-ng/syslog-ng/pull/5248>)
  *
network(), syslog() sources: add $PEERIP and $PEERPORT macros
The $PEERIP and $PEERPORT macros always display the address and port of the direct sender.
In most cases, these values are identical to $SOURCEIP and $SOURCEPORT.
However, when dealing with proxied protocols, $PEERIP and $PEERPORT reflect the proxy's address and port,
while $SOURCEIP and $SOURCEPORT indicate the original source of the message.
(#5291<https://github.com/syslog-ng/syslog-ng/pull/5291>)
  *
webhook(),opentelemetry() sources: support input_event_bytes metrics
(#5324<https://github.com/syslog-ng/syslog-ng/pull/5324>)
  *
freebsd-audit(): added a simple source SCL to collect FreeBSD audit logs using the built-in praudit program
https://www.syslog-ng.com/community/b/blog/posts/freebsd-audit-source-for-sy...
(#5383<https://github.com/syslog-ng/syslog-ng/pull/5383>)
  *
webhook(): headers support
include-request-headers(yes) stores request headers under the ${webhook.headers} key, allowing further processing
proxy-header("x-forwarded-for") helps retain the sender's original IP and the proxy's IP address
($SOURCEIP, $PEERIP).
(#5333<https://github.com/syslog-ng/syslog-ng/pull/5333>)
  *
check-program: Introduced as a flag for global or source options.
By default, this flag is set to false. Enabling the check-program flag triggers program name validation for RFC3164 messages. Valid program names must adhere to the following criteria:
Contain only these characters: [a-zA-Z0-9-_/().]
Include at least one alphabetical character.
If a program name fails validation, it will be considered part of the log message.
Example:

source { network(flags(check-hostname, check-program)); };

(#5264<https://github.com/syslog-ng/syslog-ng/pull/5264>)
  *
syslog(transport(proxied-*)) and network(transport(proxied-*)): changed
where HAProxy transport saved the original source and destination addresses.
Instead of using dedicated PROXIED_* name-value pairs, use the usual
$SOURCEIP, $SOURCEPORT, $DESTIP and $DESTPORT macros, making haproxy
based connections just like native ones.
$SOURCEPORT: added new macro which expands to the source port of the peer.
(#5305<https://github.com/syslog-ng/syslog-ng/pull/5305>)
  *
opentelemetry(), syslog-ng-otlp(): Added keep-alive() options.
Keepalive can be configured with the time(), timeout()
and max-pings-without-data() options of the keep-alive() block.

opentelemetry(
    ...
    keep-alive(time(20000) timeout(10000) max-pings-without-data(0))
);

(#5174<https://github.com/syslog-ng/syslog-ng/pull/5174>)
  *
bigquery(): Added auth() options.
Similarly to other gRPC based destination drivers, the bigquery()
destination now accepts different authentication methods, like
adc(), alts(), insecure() and tls().

bigquery (
    ...
    auth(
        tls(
            ca-file("/path/to/ca.pem")
            key-file("/path/to/key.pem")
            cert-file("/path/to/cert.pem")
        )
    )
);

(#5174<https://github.com/syslog-ng/syslog-ng/pull/5174>)
  *
cloud-auth: Added azure-monitor() destination
Added oauth2 authentication for azure monitor destinations.
Example usage:

azure-monitor(
     dcr-id("dcr id")
     dce-uri("dce uri")
     stream_name("stream name")
     auth(
          tenant-id("tenant id")
          app-id("app id")
          app-secret("app secret")
     )
)

(#5293<https://github.com/syslog-ng/syslog-ng/pull/5293>)
  *
multi-line-mode(): Added a new mutiline detection mode empty-line-separated that, as its name suggests, reads and treats all messages as one till it receives an empty line (which contains only a \r, \n or \r\n sequence).
(#5259<https://github.com/syslog-ng/syslog-ng/pull/5259>)
  *
google-pubsub-grpc(): Added a new destination that sends logs to Google Pub/Sub via the gRPC interface.
Example config:

google-pubsub-grpc(
  project("my_project")
  topic($topic)

  data($MESSAGE)
  attributes(
    timestamp => $S_ISODATE,
    host => $HOST,
  )

  workers(4)
  batch-timeout(1000) # ms
  batch-lines(1000)
);

The project() and topic() options are templatable.
The default service endpoint can be changed with the service_endpoint() option.
(#5266<https://github.com/syslog-ng/syslog-ng/pull/5266>)
  *
ivykis: We have switched to our own fork<https://github.com/balabit/ivykis> of ivykis as the source for builds when using syslog-ng’s internal ivykis option (--with-ivykis=internal in autotools or -DIVYKIS_SOURCE=internal in CMake).
We recommend switching to this internal version, as it includes new features not available in the original version<https://github.com/buytenh/ivykis> and likely never will be.
(#5307<https://github.com/syslog-ng/syslog-ng/pull/5307>)
  *
ivykis: Fixed and merged the in development phase io_uring based polling method solution to our ivykis fork<https://github.com/balabit/ivykis>.
This is am experimental integration and not selected by default, you must activate it directly either using the IV_EXCLUDE_POLL_METHOD or IV_SELECT_POLL_METHOD as described here<https://syslog-ng.github.io/admin-guide/060_Sources/020_File/001_File_following>.
(#5312<https://github.com/syslog-ng/syslog-ng/pull/5312>)
  *
file(), wildcard-file(): Added follow-method() option.
|Accepted values:| legacy | inotify | poll | system |
This option controls how syslog-ng will follow file changes.
The default legacy mode preserves the pre-4.9 version file follow-mode behavior of syslog-ng, which is based on the value of follow-freq().
The poll value forces syslog-ng to poll for file changes at the interval specified by the monitor-freq() option, even if a more efficient method (such as inotify or kqueue) is available.
If inotify is selected and supported by the platform, syslog-ng uses it to detect changes in source files. This is the most efficient and least resource-consuming option available on Linux for regular files.
The system value will use system poll methods (via ivykis) like port-timer port dev_poll epoll-timerfd epoll kqueue ppoll poll and uring. For more information about how to control the system polling methods used, see How content changes are followed in file() and wildcard-file() sources<https://syslog-ng.github.io/admin-guide/060_Sources/020_File/001_File_following>.
(#5338<https://github.com/syslog-ng/syslog-ng/pull/5338>)
  *
opentelemetry(), loki() destination: Add support for templated header() values
(#5184<https://github.com/syslog-ng/syslog-ng/pull/5184>)

Bugfixes

  *
syslog-ng-otlp() destination: Fixed a crash.
(#5267<https://github.com/syslog-ng/syslog-ng/pull/5267>)
  *
Fixed some time parsing and time formatting issues.
(#5386<https://github.com/syslog-ng/syslog-ng/pull/5386>)
  *
syslogformat: Fix integer overflow on set pri
(#5254<https://github.com/syslog-ng/syslog-ng/pull/5254>)
  *
network(), syslog(): Fixed a potential crash for TLS destinations during reload
In case of a TLS connection, if the handshake didn't happen before reloading syslog-ng,
it crashed on the first message sent to that destination.
(#5303<https://github.com/syslog-ng/syslog-ng/pull/5303>)
  *
collectd(): fix not reading server responses
(#5390<https://github.com/syslog-ng/syslog-ng/pull/5390>)
  *
metrics: syslog-ng-ctl --reset will no longer reset Prometheus metrics
(#5261<https://github.com/syslog-ng/syslog-ng/pull/5261>)
  *
rate-limit(): fix precision issue that could occur at a very low message rate
(#5346<https://github.com/syslog-ng/syslog-ng/pull/5346>)
  *
network(), syslog() sources and destinations: fix TCP/TLS shutdown
(#5271<https://github.com/syslog-ng/syslog-ng/pull/5271>)
  *
http: Fixed a batching related bug that happened with templated URLs and a single worker.
(#5281<https://github.com/syslog-ng/syslog-ng/pull/5281>)
  *
network(), syslog() destinations: handle async TLS messages (KeyUpdate, etc.)
(#5390<https://github.com/syslog-ng/syslog-ng/pull/5390>)

Notes to developers

  *   editorconfig: configure supported editors for the project's style
(#5331<https://github.com/syslog-ng/syslog-ng/pull/5331>)

Other changes

  *
java-modules: Upgrade java common and hdfs dependencies.
(#5366<https://github.com/syslog-ng/syslog-ng/pull/5366>)
  *
java-modules: Remove depricated java destinations: elasticsearch2, kafka-java and the java-http.
The following destinations can be used instead:
     *   elasticsearch2 - Both elastic-datastream()<https://syslog-ng.github.io/admin-guide/070_Destinations/035_elasticsearch-datastream/README> or the elastic-http()<https://syslog-ng.github.io/admin-guide/070_Destinations/030_Elasticsearch-http/README> can be used.
     *   kafka-java - The C based kafka-c()<https://syslog-ng.github.io/admin-guide/070_Destinations/100_Kafka-c/README> destination can be used instead. To help with migration check out the Shifting from Java implementation to C implementation<https://syslog-ng.github.io/admin-guide/070_Destinations/100_Kafka-c/001_Shifting_from_Java_to_C> page.
     *   java-http - the C based http()<https://syslog-ng.github.io/admin-guide/070_Destinations/081_http/README> destination can be used.
(#5366<https://github.com/syslog-ng/syslog-ng/pull/5366>)

Credits
syslog-ng is developed as a community project, and as such it relies
on volunteers, to do the work necessarily to produce syslog-ng.
Reporting bugs, testing changes, writing code or simply providing
feedback are all important contributions, so please if you are a user
of syslog-ng, contribute.
We would like to thank the following people for their contribution:
Alex Becker, Attila Szakacs, Balazs Scheidler, Bálint Horváth,
David Mandelberg, Eli Schwartz, Hofi, Kovács Gergő Ferenc,
László Várady, Peter Czanik (CzP), Petr Vaganov,
Shiraz, Szilard Parrag, Tamas Pal, Tamás Kosztyu, shifter

Peter Czanik (CzP) <peter.czanik@oneidentity.com><mailto:peter.czanik@oneidentity.com>
Balabit (a OneIdentity company) / syslog-ng upstream
https://syslog-ng.com/community/
https://twitter.com/PCzanik

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