The google-pubsub() source utilizes the At-Least-Once delivery behavior of Google Pub/Sub. This behavior is intentional, and its purpose is to avoid potential log loss. However, in certain cases, the At-Least-Once delivery behavior results in message duplication on the syslog-ng PE side.
Issue
On the Google Cloud Platform side, you can set the value of the Acknowledgment deadline (the default value is 10 seconds) when creating your Google Pub/Sub Subscription.
For more information, see Set up your Google Cloud project and Pub/Sub topic and subscriptions.
The syslog-ng PE application has to acknowledge log-fetch-limit() number of messages within the Acknowledgement deadline time limit. If syslog-ng PE does not acknowledge Google Pub/Sub messages no later than the time limit specified in the Acknowledgment deadline, the Google Pub/Sub service will attempt to redeliver the message to syslog-ng PE.
As a result, any acknowledgement sent later than the Acknowledgment deadline will result in message duplication on the syslog-ng PE side. This issue occurs most often if you have flow-control turned on, and your syslog-ng PE destinations are slow.
Workaround
To avoid message duplication, you can use one of these methods:
-
Using the disk-buffer option if flow control is on
When using the disk-buffer option, syslog-ng PE acknowledges Pub/Sub messages as soon as they are sent to the output queue or overflow queue, instead of acknowledging them when the destination sends or rewrites them.
-
Adjusting the value of your ack-tracker-timeout() to the Acknowledgment deadline, and the value of your ack-tracker-batch-size() to your log-fetch-limit()
The syslog-ng PE application acknowledges messages in batches. You can set the size (ack-tracker-batch-size(), the default value is 100), and timeout (ack-tracker-timeout(), the default value is 3000 milliseconds, or 3 seconds) of these batches.
To avoid message duplication, set your ack-tracker-timeout() to a value not larger than the value of your Acknowledgment deadline, and your ack-tracker-batch-size() to a value not larger than your log-fetch-limit().
Common error messages with workaround solutions
The following table describes the possible error messages that you may encounter while using the google-pubsub() source.
DefaultCredentialsError: Could not automatically determine credentials. Please set GOOGLE_APPLICATION_CREDENTIALS or explicitly create credentials and re-run the application. |
Use the credentials() option to specify a key file.
For more information, see Create service account credentials. |
404 Resource not found (resource=...). |
The specified subscription is not valid. Check the value of the subscription() option. Make sure you specify the Subscription ID, not the name of the subscription.
For more information, see Set up your Google Cloud project and Pub/Sub topic and subscriptions. |
400 Invalid resource name given (name=...). |
The specified subscription is not valid. Check the value of the subscription() option. Make sure you specify the Subscription ID, not the name of the subscription.
For more information, see Set up your Google Cloud project and Pub/Sub topic and subscriptions. |
404 Requested project not found or user does not have access to it (project=nonproj). Make sure to specify the unique project identifier and not the Google Cloud Console display name. |
Make sure to specify the unique project identifier and not the Google Cloud Console display name. |
PubSubSource init, failed to load credentials file, path=... |
The file specified in the credentials() option does not exist, or it is not accessible. Check the path and its permissions. |
Error messages that require assistance from our Support Team
In some cases, you may encounter different error messages that require assistance from our Support Team. If you encounter similar error messages as those listed in the following table, One Identity recommends that you contact our Support Team for assistance.
PubSubSource error while pulling messages, error: ... |
A non-retryable error occurred.
If you encounter an error message other than those listed in the previous table, contact our Support Team with the complete error message. |
PubSubSource error while acking messages, error: ... |
A non-retryable error occurred.
If you encounter an error message other than those listed in the previous table, contact our Support Team with the complete error message. |
The wildcard-file() source collects log messages from multiple plain-text files from multiple directories. The wildcard-file() source is available in syslog-ng PE version 7.0.3 and later.
The syslog-ng PE application notices if a file is renamed or replaced with a new file, so it can correctly follow the file even if logrotation is used. When syslog-ng PE is restarted, it records the position of the last sent log message in the /opt/syslog-ng/var/syslog-ng.persist file, and continues to send messages from this position after the restart.
Declaration
wildcard-file(
base-dir("<pathname>")
filename-pattern("<filename>")
);
Note the following important points:
-
You can use the * and ? wildcard characters in the filename (the filename-pattern() option), but not in the path (the base-dir() option).
-
When using the wildcard-file() source, always set how often syslog-ng PE should check the files for new messages using the follow-freq() parameter.
-
If you use multiple wildcard-file() sources in your configuration, make sure that the files and folders that match the wildcards do not overlap. That is, every file and folder should belong to only one file source. Monitoring a file from multiple wildcard sources can lead to data loss.
-
When using wildcards, syslog-ng PE monitors every matching file (up to the limit set in the max-files() option), and can receive new log messages from any of the files. However, monitoring (polling) many files (that is, more than ten) has a significant overhead and may affect performance. On Linux this overhead is not so significant, because syslog-ng PE uses the inotify feature of the kernel. Set the max-files() option at least to the number of files you want to monitor. If the wildcard-file source matches more files than the value of the max-files() option, it is random which files will syslog-ng PE actually monitor. The default value of max-files() is 100.
-
If the message does not have a proper syslog header, syslog-ng PE treats messages received from files as sent by the kern facility. Use the default-facility() and default-priority() options in the source definition to assign a different facility if needed.
Required parameters: base-dir(), filename-pattern(). For the list of available optional parameters, see wildcard-file() source options.
Example: Using the wildcard-file() driver
The following example monitors every file with the .log extension in the /var/log directory for log messages.
The wildcard-file() driver has the following options:
base-dir()
| Type: |
path without filename |
| Default: |
|
Description: The path to the directory that contains the log files to monitor, for example, base-dir("/var/log"). To monitor also the subdirectories of the base directory, use the recursive(yes) option. For details, see recursive().
|
|
Caution:
If you use multiple wildcard-file() sources in your configuration, make sure that the files and folders that match the wildcards do not overlap. That is, every file and folder should belong to only one file source. Monitoring a file from multiple wildcard sources can lead to data loss. |
source s_files {
wildcard-file(
base-dir("/var/log")
filename-pattern("*.log")
recursive(no)
follow-freq(1)
);
};
default-facility()
| Type: |
facility string |
| Default: |
kern |
default-priority()
| Type: |
priority string |
| Default: |
|
Description: This parameter assigns an emergency level to the messages received from the file source, if the message does not specify one. For example, default-priority(warning).
encoding()
Description: Specifies the characterset (encoding, for example, UTF-8) of messages using the legacy BSD-syslog protocol. To list the available character sets on a host, execute the iconv -l command. For details on how encoding affects the size of the message, see Message size and encoding.
filename-pattern()
| Type: |
filename without path |
| Default: |
|
Description: The filename to read messages from, without the path. You can use the * and ? wildcard characters, without regular expression and character range support. You cannot use the * and ? literally in the pattern.
For example, filename-pattern("*.log") matches the syslog.log and auth.log files, but does not match the access_log file. The filename-pattern("*log") pattern matches all three.
|
|
Caution:
If you use multiple wildcard-file() sources in your configuration, make sure that the files and folders that match the wildcards do not overlap. That is, every file and folder should belong to only one file source. Monitoring a file from multiple wildcard sources can lead to data loss. |
source s_files {
wildcard-file(
base-dir("/var/log")
filename-pattern("*.log")
recursive(no)
follow-freq(1)
);
};
flags()
| Type: |
assume-utf8, empty-lines, expect-hostname, guess-timezone, kernel, no-hostname, no-multi-line, no-parse, sanitize-utf8, store-legacy-msghdr, store-raw-message, syslog-protocol, validate-utf8 |
| Default: |
empty set |
Description: Specifies the log parsing options of the source.
-
assume-utf8: The assume-utf8 flag assumes that the incoming messages are UTF-8 encoded, but does not verify the encoding. If you explicitly want to validate the UTF-8 encoding of the incoming message, use the validate-utf8 flag.
-
empty-lines: Use the empty-lines flag to keep the empty lines of the messages. By default, syslog-ng PE removes empty lines automatically.
-
expect-hostname: If the expect-hostname flag is enabled, syslog-ng PE will assume that the log message contains a hostname and parse the message accordingly. This is the default behavior for TCP sources. Note that pipe sources use the no-hostname flag by default.
-
kernel: The kernel flag makes the source default to the LOG_KERN | LOG_NOTICE priority if not specified otherwise.
-
no-hostname: Enable the no-hostname flag if the log message does not include the hostname of the sender host. That way syslog-ng PE assumes that the first part of the message header is ${PROGRAM} instead of ${HOST}. For example:
source s_dell {
network(
port(2000)
flags(no-hostname)
);
};
-
no-multi-line: The no-multi-line flag disables line-breaking in the messages: the entire message is converted to a single line. Note that this happens only if the underlying transport method actually supports multi-line messages. Currently the file() and pipe() drivers support multi-line messages.
-
no-parse: By default, syslog-ng PE parses incoming messages as syslog messages. The no-parse flag completely disables syslog message parsing and processes the complete line as the message part of a syslog message. The syslog-ng PE application will generate a new syslog header (timestamp, host, and so on) automatically and put the entire incoming message into the MESSAGE part of the syslog message (available using the ${MESSAGE} macro). This flag is useful for parsing messages not complying to the syslog format.
If you are using the flags(no-parse) option, then syslog message parsing is completely disabled, and the entire incoming message is treated as the ${MESSAGE} part of a syslog message. In this case, syslog-ng PE generates a new syslog header (timestamp, host, and so on) automatically. Note that since flags(no-parse) disables message parsing, it interferes with other flags, for example, disables flags(no-multi-line).
-
dont-store-legacy-msghdr: By default, syslog-ng stores the original incoming header of the log message. This is useful if the original format of a non-syslog-compliant message must be retained (syslog-ng automatically corrects minor header errors, for example, adds a whitespace before msg in the following message: Jan 22 10:06:11 host program:msg). If you do not want to store the original header of the message, enable the dont-store-legacy-msghdr flag.
-
sanitize-utf8: When using the sanitize-utf8 flag, syslog-ng PE converts non-UTF-8 input to an escaped form, which is valid UTF-8.
-
store-raw-message: Save the original message as received from the client in the ${RAWMSG} macro. You can forward this raw message in its original form to another syslog-ng node using the syslog-ng() destination, or to a SIEM system, ensuring that the SIEM can process it. Available only in 7.0.9 and later.
-
syslog-protocol: The syslog-protocol flag specifies that incoming messages are expected to be formatted according to the new IETF syslog protocol standard (RFC5424), but without the frame header. Note that this flag is not needed for the syslog driver, which handles only messages that have a frame header.
-
validate-utf8: The validate-utf8 flag enables encoding-verification for messages formatted according to the new IETF syslog standard (for details, see IETF-syslog messages). If theBOMcharacter is missing, but the message is otherwise UTF-8 compliant, syslog-ng automatically adds the BOM character to the message.
follow-freq()
Description: Indicates that the source should be checked periodically. This is useful for files which always indicate readability, even though no new lines were appended. If this value is higher than zero, syslog-ng will not attempt to use poll() on the file, but checks whether the file changed every time the follow-freq() interval (in seconds) has elapsed. Floating-point numbers (for example, 1.5) can be used as well.
keep-timestamp()
| Type: |
yes or no |
| Default: |
yes |
Description: Specifies whether syslog-ng should accept the timestamp received from the sending application or client. If disabled, the time of reception will be used instead. This option can be specified globally, and per-source as well. The local setting of the source overrides the global option if available.
|
|
Caution:
To use the S_ macros, the keep-timestamp() option must be enabled (this is the default behavior of syslog-ng PE). |
log-fetch-limit()
Description: The maximum number of messages fetched from a source during a single poll loop. The destination queues might fill up before flow-control could stop reading if log-fetch-limit() is too high.
log-iw-size()
| Type: |
number |
| Default: |
10000 |
Description: The size of the initial window, this value is used during flow control. Make sure that log-iw-size() is larger than the value of log-fetch-limit().
When using wildcards in the filenames, syslog-ng PE attempts to read log-fetch-limit() number of messages from each file. For optimal performance, make sure that log-iw-size() is greater than log-fetch-limit()*max-files(). Note that to avoid performance problems, if log-iw-size()/max-files() is smaller than 100, syslog-ng PE automatically sets log-iw-size() to max-files()*100.
Example: Initial window size of file sources
If log-fetch-limit() is 100, and your wildcard file source has 200 files, then log-iw-size() should be at least 20000.
log-msg-size()
| Type: |
number (bytes) |
| Default: |
Use the global log-msg-size() option, which defaults to 65536 (64 KiB). |
Description: Maximum length of a message in bytes. This length includes the entire message (the data structure and individual fields). The maximum value that you can set is 268435456 bytes (256 MiB).
For messages using the IETF-syslog message format (RFC5424), the maximal size of the value of an SDATA field is 64 KiB.
NOTE: In most cases, you do not need to set log-msg-size() higher than 10 MiB.
For details on how encoding affects the size of the message, see Message size and encoding.
You can use human-readable units when setting configuration options. For details, see Notes about the configuration syntax.
Uses the value of the global option if not specified.
log-prefix() (DEPRECATED)
Description: A string added to the beginning of every log message. It can be used to add an arbitrary string to any log source, though it is most commonly used for adding kernel: to the kernel messages on Linux. NOTE: This option is deprecated. Use program-override() instead.
max-files()
| Type: |
integer |
| Default: |
100 |
Description: Limits the number of files that the wildcard-file source monitors.
When using wildcards, syslog-ng PE monitors every matching file (up to the limit set in the max-files() option), and can receive new log messages from any of the files. However, monitoring (polling) many files (that is, more than ten) has a significant overhead and may affect performance. On Linux this overhead is not so significant, because syslog-ng PE uses the inotify feature of the kernel. Set the max-files() option at least to the number of files you want to monitor. If the wildcard-file source matches more files than the value of the max-files() option, it is random which files will syslog-ng PE actually monitor. The default value of max-files() is 100.
monitor-method()
| Type: |
auto | inotify | poll |
| Default: |
auto |
Description: If the platform supports inotify, syslog-ng PE uses it automatically to detect changes to the source files. If inotify is not available, syslog-ng PE polls the files as set in the follow-freq() option. To force syslog-ng PE poll the files even if inotify is available, set this option to poll.
multi-line-garbage()
| Type: |
regular expression |
| Default: |
empty string |
Description: Use the multi-line-garbage() option when processing multi-line messages that contain unneeded parts between the messages. Specify a string or regular expression that matches the beginning of the unneeded message parts. If the multi-line-garbage() option is set, syslog-ng PE ignores the lines between the line matching the multi-line-garbage() and the next line matching multi-line-prefix(). See also the multi-line-prefix() option.
When receiving multi-line messages from a source when the multi-line-garbage() option is set, but no matching line is received between two lines that match multi-line-prefix(), syslog-ng PE will continue to process the incoming lines as a single message until a line matching multi-line-garbage() is received.
To use the multi-line-garbage() option, set the multi-line-mode() option to prefix-garbage.
|
|
Caution:
If the multi-line-garbage() option is set, syslog-ng PE discards lines between the line matching the multi-line-garbage() and the next line matching multi-line-prefix(). |
multi-line-mode()
| Type: |
indented|regexp |
| Default: |
empty string |
Description: Use the multi-line-mode() option when processing multi-line messages. The syslog-ng PE application provides the following methods to process multi-line messages: multi-line-mode(indented), and multi-line-mode(prefix-garbage).
-
The indented mode can process messages where each line that belongs to the previous line is indented by whitespace, and the message continues until the first non-indented line. For example, the Linux kernel (starting with version 3.5) uses this format for /dev/log, as well as several applications, like Apache Tomcat.
Example: Processing indented multi-line messages
source s_tomcat {
file("/var/log/tomcat/xxx.log"
multi-line-mode(indented)
);
};
-
The prefix-garbage mode uses a string or regular expression (set in multi-line-prefix()) that matches the beginning of the log messages, ignores newline characters from the source until a line matches the regular expression again, and treats the lines between the matching lines as a single message. For details on using multi-line-mode(prefix-garbage), see the multi-line-prefix() and multi-line-garbage() options.
-
The prefix-suffix mode uses a string or regular expression (set in multi-line-prefix()) that matches the beginning of the log messages, ignores newline characters from the source until a line matches the regular expression set in multi-line-suffix(), and treats the lines between multi-line-prefix() and multi-line-suffix() as a single message. Any other lines between the end of the message and the beginning of a new message (that is, a line that matches the multi-line-prefix() expression) are discarded. For details on using multi-line-mode(prefix-suffix), see the multi-line-prefix() and multi-line-suffix() options.
The prefix-suffix mode is similar to the prefix-garbage mode, but it appends the garbage part to the message instead of discarding it.
TIP:
-
To make multi-line messages more readable when written to a file, use a template in the destination and instead of the ${MESSAGE} macro, use the following: $(indent-multi-line ${MESSAGE}). This expression inserts a tab after every newline character (except when a tab is already present), indenting every line of the message after the first. For example:
destination d_file {
file ("/var/log/messages"
template("${ISODATE} ${HOST} $(indent-multi-line ${MESSAGE})\n")
);
};
For details on using templates, see Templates and macros.
-
To actually convert the lines of multi-line messages to single line (by replacing the newline characters with whitespaces), use the flags(no-multi-line) option in the source.
multi-line-prefix()
| Type: |
regular expression starting with the ^ character |
| Default: |
empty string |
Description: Use the multi-line-prefix() option to process multi-line messages, that is, log messages that contain newline characters (for example, Tomcat logs). Specify a string or regular expression that matches the beginning of the log messages (always start with the ^ character). Use as simple regular expressions as possible, because complex regular expressions can severely reduce the rate of processing multi-line messages. If the multi-line-prefix() option is set, syslog-ng PE ignores newline characters from the source until a line matches the regular expression again, and treats the lines between the matching lines as a single message. See also the multi-line-garbage() option.
TIP:
-
To make multi-line messages more readable when written to a file, use a template in the destination and instead of the ${MESSAGE} macro, use the following: $(indent-multi-line ${MESSAGE}). This expression inserts a tab after every newline character (except when a tab is already present), indenting every line of the message after the first. For example:
destination d_file {
file ("/var/log/messages"
template("${ISODATE} ${HOST} $(indent-multi-line ${MESSAGE})\n")
);
};
For details on using templates, see Templates and macros.
-
To actually convert the lines of multi-line messages to single line (by replacing the newline characters with whitespaces), use the flags(no-multi-line) option in the source.
Example: Processing Tomcat logs
The log messages of the Apache Tomcat server are a typical example for multi-line log messages. The messages start with the date and time of the query in the YYYY.MM.DD HH:MM:SS format, as you can see in the following example.
2010.06.09. 12:07:39 org.apache.catalina.startup.Catalina start
SEVERE: Catalina.start:
LifecycleException: service.getName(): "Catalina"; Protocol handler start failed: java.net.BindException: Address already in use null:8080
at org.apache.catalina.connector.Connector.start(Connector.java:1138)
at org.apache.catalina.core.StandardService.start(StandardService.java:531)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
at org.apache.catalina.startup.Catalina.start(Catalina.java:583)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.commons.daemon.support.DaemonLoader.start(DaemonLoader.java:177)
2010.06.09. 12:07:39 org.apache.catalina.startup.Catalina start
INFO: Server startup in 1206 ms
2010.06.09. 12:45:08 org.apache.coyote.http11.Http11Protocol pause
INFO: Pausing Coyote HTTP/1.1 on http-8080
2010.06.09. 12:45:09 org.apache.catalina.core.StandardService stop
INFO: Stopping service Catalina
To process these messages, specify a regular expression matching the timestamp of the messages in the multi-line-prefix() option. Such an expression is the following:
source s_file{file("/var/log/tomcat6/catalina.2010-06-09.log" follow-freq(0) multi-line-prefix("[0-9]{4}\.[0-9]{2}\.[0-9]{2}\.") flags(no-parse));};
};
Note that flags(no-parse) is needed to prevent syslog-ng PE trying to interpret the date in the message.
multi-line-suffix()
| Type: |
regular expression |
| Default: |
empty string |
Description: Use the multi-line-suffix() option when processing multi-line messages. Specify a string or regular expression that matches the end of the multi-line message.
To use the multi-line-suffix() option, set the multi-line-mode() option to prefix-suffix. See also the multi-line-prefix() option.
multi-line-timeout()
| Type: |
number [seconds] |
| Default: |
[0 == disable] |
Description: If any multi-line option is enabled, there are two possible scenarios:
- the requirement specified in any multi-line option is met, which results in syslog-ng PE sending the full message (even multi-line messages)
- the number of seconds specified in multi-line-timeout() passes, which results in syslog-ng PE sending the current message, which could be partial
NOTE: One Identity recommends that you set multi-line-timeout() to a higher value than (preferably a multiple of) follow-freq().
The recommended minimum value is 10 seconds.
pad-size()
Description: Specifies input padding. Some operating systems (such as HP-UX) pad all messages to block boundary. This option can be used to specify the block size. The syslog-ng PE application will pad reads from the associated device to the number of bytes set in pad-size(). Mostly used on HP-UX where /dev/log is a named pipe and every write is padded to 2048 bytes. If pad-size() was given and the incoming message does not fit into pad-size(), syslog-ng will not read anymore from this pipe and displays the following error message:
Padding was set, and couldn't read enough bytes
program-override()
Description: Replaces the ${PROGRAM} part of the message with the parameter string. For example, to mark every message coming from the kernel, include the program-override("kernel") option in the source containing /proc/kmsg.
recursive()
| Type: |
yes | no |
| Default: |
no |
Description: When enabled, syslog-ng PE monitors every subdirectory of the path set in the base-dir() option, and reads log messages from files with matching filenames. The recursive option can be used together with wildcards in the filename.
|
|
Caution:
If you use multiple wildcard-file() sources in your configuration, make sure that the files and folders that match the wildcards do not overlap. That is, every file and folder should belong to only one file source. Monitoring a file from multiple wildcard sources can lead to data loss. |
Example: Monitoring multiple directories
The following example reads files having the .log extension from the /var/log/ directory and its subdirectories, including for example, the /var/log/apt/history.log file.
source s_file_subdirectories {
wildcard-file(
base-dir("/var/log")
filename-pattern("*.log")
recursive(yes)
follow-freq(1)
log-fetch-limit(100)
);
};
tags()
Description: Label the messages received from the source with custom tags. Tags must be unique, and enclosed between double quotes. When adding multiple tags, separate them with comma, for example, tags("dmz", "router"). This option is available only in syslog-ng 3.1 and later.
time-zone()
| Type: |
name of the timezone, or the timezone offset |
| Default: |
|
Description: The default timezone for messages read from the source. Applies only if no timezone is specified within the message itself.
The timezone can be specified as using the name of the (for example, time-zone("Europe/Budapest")), or as the timezone offset in +/-HH:MM format (for example, +01:00). On Linux and UNIX platforms, the valid timezone names are listed under the /usr/share/zoneinfo directory.
