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:
| Type: | number (bytes) |
|---|---|
| Default: | 1MiB |
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.
In {{% param "product.ose" %}} version 4.2 and earlier, this option was called disk-buf-size().
| Type: | yes/no |
|---|---|
| Default: | no |
Description: If set to yes, {{% param "product.abbrev" %}} 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.
{{% alert title="Note" color="info" %}}
Simply unsetting these name-value pairs by using the unset() rewrite operation is not enough, as due to performance reasons that help when {{% param "product.abbrev" %}} 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.
{{% /alert %}}
| Type: | string |
|---|---|
| Default: | N/A |
Description: Defines the folder where the disk-buffer files are stored.
{{< include-headless "wnt/warning-disk-buffer-new-directory-delete-persist-file.md" >}}
{{% alert title="Note" color="info" %}}
If the dir() path provided by the user does not exist, {{% param "product.ose" %}} creates the path with the same permission as the running instance.
{{% /alert %}}
| 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.
In {{% param "product.ose" %}} version 4.2 and earlier, this option was called mem-buf-size().
| 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.
In {{% param "product.ose" %}} version 4.2 and earlier, this option was called mem-buf-length().
| Type: | number(messages) |
|---|---|
| Default: | 1000 |
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 capacity-bytes() are required options.
In {{% param "product.ose" %}} version 4.2 and earlier, this option was called qout-size().
| Type: | yes/no |
|---|---|
| Default: | no |
Description: {{< include-headless "chunk/option-description-destination-diskbuffer-prealloc.md" >}}
Available in {{% param "product.abbrev" %}} 4.0 and later.
| Type: | yes/no |
|---|---|
| Default: | no |
Description: If set to yes, {{% param "product.abbrev" %}} cannot lose logs in case of reload/restart, unreachable destination or {{% param "product.abbrev" %}} 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.
{{% alert title="Warning" color="warning" %}}
Hazard of data loss! If you change the value of reliable() option when there are messages in the disk-buffer, the messages stored in the disk-buffer will be lost.
{{% /alert %}}
| Type: | number [minutes] |
|---|---|
| Default: | 5 |
Available in {{% param "product.abbrev" %}} 4.2 and later.
Description: Set the frequency of generating [disk-buffer related metrics]({{< relref "/metrics/reference-metrics/_index.md#disk-buffer-metrics" >}}). Set it to zero to disable metrics.
options {
disk-buffer(
stats(
freq(10)
)
);
};```
### truncate-size-ratio() {#diskbuf-trunkate-size-ratio}
| Type: | number((between 0 and 1)) |
|--------------|-----------|
| Default: | 1 (do not truncate) |
*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. By default, {{% param "product.abbrev" %}} version 4.0 and later doesn't truncate disk-buffer files by default (`truncate-size-ratio(1)`). Earlier versions freed the disk-space when at least 10% of the disk-buffer file could be freed (`truncate-size-ratio(0.1)`).
{{% param "product.abbrev" %}} only truncates the file if the possible disk gain is more than `truncate-size-ratio()` times `capacity-bytes()`.
- Smaller values free disk space quicker.
- Larger ratios result in better performance.
If you want to avoid performance fluctuations:
- use `truncate-size-ratio(1)` (never truncate), or
- use `prealloc(yes)` to [reserve the entire size of the disk-buffer on disk](#diskbuf-prealloc).
{{% alert title="Warning" color="warning" %}}
{{% param "product.companyabbrev" %}} does not recommend you to change `truncate-size-ratio()`. Only change its value if you understand the performance implications of doing so.
{{% /alert %}}
### Example: Examples for using disk-buffer()
In the following case reliable disk-buffer() is used.
```shell
destination d_demo {
network(
"127.0.0.1"
port(3333)
disk-buffer(
flow-control-window-bytes(10000)
capacity-bytes(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(
flow-control-window-size(10000)
capacity-bytes(2000000)
reliable(no)
dir("/tmp/disk-buffer")
)
);
};