The mongodb() driver sends messages to a MongoDB database. MongoDB is a schema-free, document-oriented database.
The mongodb() destination has the following options:
collection()
| Type: | template |
| Default: | messages |
Description: The name of the MongoDB collection where the log messages are stored (collections are similar to SQL tables). You can use templates to change the collection dynamically based on the source or the content of the message, for example, collection("${HOST}").
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Caution:
Hazard of data loss! The syslog-ng OSE application does not verify that the specified collection name does not contain invalid characters. If you specify a collection with an invalid name, the log messages sent to the MongoDB database will be irrevocably lost without any warning. |
disk-buffer()
Description: This option enables putting outgoing messages into the disk buffer of the destination to avoid message loss in case of a system failure on the destination side. It has the following options:
| reliable() | |||
| Type: | yes|no | ||
| Default: | no | ||
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Description: If set to yes, syslog-ng OSE cannot lose logs in case of reload/restart, unreachable destination or syslog-ng OSE crash. This solution provides a slower, but reliable disk-buffer option. It is created and initialized at startup and gradually grows as new messages arrive. If set to no, the normal disk-buffer will be used. This provides a faster, but less reliable disk-buffer option.
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| compaction() | |
| Type: | yes|no |
| Default: | no |
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Description: If set to yes, syslog-ng OSE prunes the unused space in the LogMessage representation, making the disk queue size smaller at the cost of some CPU time. Setting the compaction() argument to yes is recommended when numerous name-value pairs are unset during processing, or when the same names are set multiple times. | |
NOTE: Simply unsetting these name-value pairs by using the unset() rewrite operation is not enough, as due to performance reasons that help when syslog-ng OSE is CPU bound, the internal representation of a LogMessage will not release the memory associated with these name-value pairs. In some cases, however, the size of this overhead becomes significant (the raw message size can grow up to four times its original size), which unnecessarily increases the disk queue file size. For these cases, the compaction will drop unset values, making the LogMessage representation smaller at the cost of some CPU time required to perform compaction.
| disk-buf-size() | |
| Type: | number (bytes) |
| Default: | |
| Description: This is a required option. The maximum size of the disk-buffer in bytes. The minimum value is 1048576 bytes. If you set a smaller value, the minimum value will be used automatically. It replaces the old log-disk-fifo-size() option. | |
| mem-buf-length() | |
| Type: | number (messages) |
| Default: | 10000 |
| Description: Use this option if the option reliable() is set to no. This option contains the number of messages stored in overflow queue. It replaces the old log-fifo-size() option. It inherits the value of the global log-fifo-size() option if provided. If it is not provided, the default value is 10000 messages. Note that this option will be ignored if the option reliable() is set to yes. | |
| mem-buf-size() | |
| Type: | number (bytes) |
| Default: | 163840000 |
| Description: Use this option if the option reliable() is set to yes. This option contains the size of the messages in bytes that is used in the memory part of the disk buffer. It replaces the old log-fifo-size() option. It does not inherit the value of the global log-fifo-size() option, even if it is provided. Note that this option will be ignored if the option reliable() is set to no. | |
| qout-size() | |
| Type: | number (messages) |
| Default: | 64 |
| Description: The number of messages stored in the output buffer of the destination. Note that if you change the value of this option and the disk-buffer already exists, the change will take effect when the disk-buffer becomes empty. | |
Options reliable() and disk-buf-size() are required options.
Example: Examples for using disk-buffer()
In the following case reliable disk-buffer() is used.
destination d_demo {
network(
"127.0.0.1"
port(3333)
disk-buffer(
mem-buf-size(10000)
disk-buf-size(2000000)
reliable(yes)
dir("/tmp/disk-buffer")
)
);
};
In the following case normal disk-buffer() is used.
destination d_demo {
network(
"127.0.0.1"
port(3333)
disk-buffer(
mem-buf-length(10000)
disk-buf-size(2000000)
reliable(no)
dir("/tmp/disk-buffer")
)
);
};| Type: | number (between 0 and 1) | ||
| Default: | 0.1 (10%) | ||
|
Description: Limits the truncation of the disk-buffer file. Truncating the disk-buffer file can slow down the disk IO operations, but it saves disk space, so syslog-ng only truncates the file, if the possible disk gain is more than truncate-size-ratio() times disk-buf-size().
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batch-bytes()
| Accepted values: | number [bytes] |
| Default: | none |
Description: Sets the maximum size of payload in a batch. If the size of the messages reaches this value, syslog-ng OSE sends the batch to the destination even if the number of messages is less than the value of the batch-lines() option.
Note that if the batch-timeout() option is enabled and the queue becomes empty, syslog-ng OSE flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-bytes().
Available in syslog-ng OSE version
batch-lines()
| Type: | number |
| Default: | 1 |
Description: Specifies how many lines are flushed to a destination in one batch. The syslog-ng OSE application waits for this number of lines to accumulate and sends them off in a single batch. Increasing this number increases throughput as more messages are sent in a single batch, but also increases message latency.
For example, if you set batch-lines() to 100, syslog-ng OSE waits for 100 messages.
If the batch-timeout() option is disabled, the syslog-ng OSE application flushes the messages if it has sent batch-lines() number of messages, or the queue became empty. If you stop or reload syslog-ng OSE or in case of network sources, the connection with the client is closed, syslog-ng OSE automatically sends the unsent messages to the destination.
Note that if the batch-timeout() option is enabled and the queue becomes empty, syslog-ng OSE flushes the messages only if batch-timeout() expires, or the batch reaches the limit set in batch-lines().
For optimal performance, make sure that the syslog-ng OSE source that feeds messages to this destination is configured properly: the value of the log-iw-size() option of the source must be higher than the batch-lines()*workers() of the destination. Otherwise, the size of the batches cannot reach the batch-lines() limit.
batch-timeout()
| Type: | time in milliseconds |
| Default: | -1 (disabled) |
Description: Specifies the time syslog-ng OSE waits for lines to accumulate in the output buffer. The syslog-ng OSE application sends batches to the destinations evenly. The timer starts when the first message arrives to the buffer, so if only few messages arrive, syslog-ng OSE sends messages to the destination at most once every batch-timeout() milliseconds.
Description: The syslog-ng application can store fractions of a second in the timestamps according to the ISO8601 format. The frac-digits() parameter specifies the number of digits stored. The digits storing the fractions are padded by zeros if the original timestamp of the message specifies only seconds. Fractions can always be stored for the time the message was received.
NOTE: The syslog-ng OSE application can add the fractions to non-ISO8601 timestamps as well.
NOTE: As syslog-ng OSE is precise up to the microsecond, when the frac-digits() option is set to a value higher than 6, syslog-ng OSE will truncate the fraction seconds in the timestamps after 6 digits.
hook-commands()
Description: This option makes it possible to execute external programs when the relevant driver is initialized or torn down. The hook-commands() can be used with all source and destination drivers with the exception of the usertty() and internal() drivers.
NOTE: The syslog-ng OSE application must be able to start and restart the external program, and have the necessary permissions to do so. For example, if your host is running AppArmor or SELinux, you might have to modify your AppArmor or SELinux configuration to enable syslog-ng OSE to execute external applications.
Using the hook-commands() when syslog-ng OSE starts or stops
To execute an external program when syslog-ng OSE starts or stops, use the following options:
| startup() | |
| Type: | string |
| Default: | N/A |
|
Description: Defines the external program that is executed as syslog-ng OSE starts. | |
| shutdown() | |
| Type: | string |
| Default: | N/A |
|
Description: Defines the external program that is executed as syslog-ng OSE stops. | |
Using the hook-commands() when syslog-ng OSE reloads
To execute an external program when the syslog-ng OSE configuration is initiated or torn down, for example, on startup/shutdown or during a syslog-ng OSE reload, use the following options:
| setup() | |
| Type: | string |
| Default: | N/A |
|
Description: Defines an external program that is executed when the syslog-ng OSE configuration is initiated, for example, on startup or during a syslog-ng OSE reload. | |
| teardown() | |
| Type: | string |
| Default: | N/A |
|
Description: Defines an external program that is executed when the syslog-ng OSE configuration is stopped or torn down, for example, on shutdown or during a syslog-ng OSE reload. | |
Example: Using the hook-commands() with a network source
In the following example, the hook-commands() is used with the network() driver and it opens an iptables port automatically as syslog-ng OSE is started/stopped.
The assumption in this example is that the LOGCHAIN chain is part of a larger ruleset that routes traffic to it. Whenever the syslog-ng OSE created rule is there, packets can flow, otherwise the port is closed.
source {
network(transport(udp)
hook-commands(
startup("iptables -I LOGCHAIN 1 -p udp --dport 514 -j ACCEPT")
shutdown("iptables -D LOGCHAIN 1")
)
);
};local-time-zone()
| Type: | name of the timezone, or the timezone offset |
| Default: | The local timezone. |
Description: Sets the timezone used when expanding filename and tablename templates.
The timezone can be specified by using the name, 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.
log-fifo-size()
| Type: | number |
| Default: | Use global setting. |
Description: The number of messages that the output queue can store.
on-error()
| Accepted values: |
drop-message|drop-property|fallback-to-string| silently-drop-message|silently-drop-property|silently-fallback-to-string |
| Default: | Use the global setting (which defaults to drop-message) |
Description: Controls what happens when type-casting fails and syslog-ng OSE cannot convert some data to the specified type. By default, syslog-ng OSE drops the entire message and logs the error. Currently the value-pairs() option uses the settings of on-error().
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drop-message: Drop the entire message and log an error message to the internal() source. This is the default behavior of syslog-ng OSE.
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drop-property: Omit the affected property (macro, template, or message-field) from the log message and log an error message to the internal() source.
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fallback-to-string: Convert the property to string and log an error message to the internal() source.
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silently-drop-message: Drop the entire message silently, without logging the error.
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silently-drop-property: Omit the affected property (macro, template, or message-field) silently, without logging the error.
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silently-fallback-to-string: Convert the property to string silently, without logging the error.
retries()
| Type: | number (of attempts) |
| Default: | 3 |
Description: If syslog-ng OSE cannot send a message, it will try again until the number of attempts reaches retries().
If the number of attempts reaches retries(), syslog-ng OSE will wait for time-reopen() time, then tries sending the message again.
For MongoDB operations, syslog-ng OSE uses a one-minute timeout: if an operation times out, syslog-ng OSE assumes the operation has failed.
time-reopen()
| Accepted values: | number [seconds] |
| Default: | 60 |
Description: The time to wait in seconds before a dead connection is reestablished.
throttle()
| Type: | number |
| Default: | 0 |
Description: Sets the maximum number of messages sent to the destination per second. Use this output-rate-limiting functionality only when using disk-buffer as well to avoid the risk of losing messages. Specifying 0 or a lower value sets the output limit to unlimited.
uri()
| Type: | string |
| Default: | mongodb://127.0.0.1:27017/syslog?wtimeoutMS=60000&socketTimeoutMS=60000&connectTimeoutMS=60000 |
Description: Available in syslog-ng OSE 3.8 and later. Please refer to the MongoDB URI format documentation for detailed syntax.
value-pairs()
| Type: | parameter list of the value-pairs() option |
| Default: | scope("selected-macros" "nv-pairs") |
Description: The value-pairs() option creates structured name-value pairs from the data and metadata of the log message. For details on using value-pairs(), see Structuring macros, metadata, and other value-pairs.
NOTE: Empty keys are not logged.
NOTE: By default, syslog-ng OSE handles every message field as a string. For details on how to send selected fields as other types of data (for example, handle the PID as a number), see Specifying data types in value-pairs.
workers()
| Type: | integer |
| Default: | 1 |
Description: Specifies the number of worker threads (at least 1) that syslog-ng OSE uses to send messages to the server. Increasing the number of worker threads can drastically improve the performance of the destination.
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Caution:
Hazard of data loss. When you use more than one worker threads together with disk-based buffering, syslog-ng OSE creates a separate disk buffer for each worker thread. This means that decreasing the number of workers can result in losing data currently stored in the disk buffer files. Do not decrease the number of workers when the disk buffer files are in use. |