# Streaming and replication reference

This document contains advanced streaming options and suggested deployment options for production. 
If you haven't already done so, we suggest you first go through the 
[quick introduction to streaming](/docs/observability-centralization-points/README.md)
, for your first, basic parent child setup.

## Configuration

There are two files responsible for configuring Netdata's streaming capabilities: `stream.conf` and `netdata.conf`.

From within your Netdata config directory (typically `/etc/netdata`), [use `edit-config`](/docs/netdata-agent/configuration/README.md) to
open either `stream.conf` or `netdata.conf`.

```
sudo ./edit-config stream.conf
sudo ./edit-config netdata.conf
```

### `stream.conf`

The `stream.conf` file contains three sections. The `[stream]` section is for configuring child nodes.

The `[API_KEY]` and `[MACHINE_GUID]` sections are both for configuring parent nodes, and share the same settings.
`[API_KEY]` settings affect every child node using that key, whereas `[MACHINE_GUID]` settings affect only the child
node with a matching GUID.

The file `/var/lib/netdata/registry/netdata.public.unique.id` contains a random GUID that **uniquely identifies each
node**. This file is automatically generated by Netdata the first time it is started and remains unaltered forever.

#### `[stream]` section

| Setting                                         | Default                   | Description                                                                                                                                                                                                                                          |
|-------------------------------------------------|---------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `enabled`                                       | `no`                      | Whether this node streams metrics to any parent. Change to `yes` to enable streaming.                                                                                                                                                                |
| [`destination`](#destination)                   |                           | A space-separated list of parent nodes to attempt to stream to, with the first available parent receiving metrics, using the following format: `[PROTOCOL:]HOST[%INTERFACE][:PORT][:SSL]`. [Read more &rarr;](#destination)                          |
| `ssl skip certificate verification`             | `yes`                     | If you want to accept self-signed or expired certificates, set to `yes` and uncomment.                                                                                                                                                               |
| `CApath`                                        | `/etc/ssl/certs/`         | The directory where known certificates are found. Defaults to OpenSSL's default path.                                                                                                                                                                |
| `CAfile`                                        | `/etc/ssl/certs/cert.pem` | Add a parent node certificate to the list of known certificates in `CAPath`.                                                                                                                                                                         |
| `api key`                                       |                           | The `API_KEY` to use as the child node.                                                                                                                                                                                                              |
| `timeout seconds`                               | `60`                      | The timeout to connect and send metrics to a parent.                                                                                                                                                                                                 |
| `default port`                                  | `19999`                   | The port to use if `destination` does not specify one.                                                                                                                                                                                               |
| [`send charts matching`](#send-charts-matching) | `*`                       | A space-separated list of [Netdata simple patterns](/src/libnetdata/simple_pattern/README.md) to filter which charts are streamed. [Read more &rarr;](#send-charts-matching)                           |
| `buffer size bytes`                             | `10485760`                | The size of the buffer to use when sending metrics. The default `10485760` equals a buffer of 10MB, which is good for 60 seconds of data. Increase this if you expect latencies higher than that. The buffer is flushed on reconnect.                |
| `reconnect delay seconds`                       | `5`                       | How long to wait until retrying to connect to the parent node.                                                                                                                                                                                       |
| `initial clock resync iterations`               | `60`                      | Sync the clock of charts for how many seconds when starting.                                                                                                                                                                                         |
| `parent using h2o`                              | `no`                      | Set to yes if you are connecting to parent trough it's h2o webserver/port. Currently there is no reason to set this to `yes` unless you are testing the new h2o based netdata webserver. When production ready this will be set to `yes` as default. |

### `[API_KEY]` and `[MACHINE_GUID]` sections

| Setting                                       | Default  | Description                                                                                                                                                                                                                                        |
|-----------------------------------------------|----------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `enabled`                                     | `no`     | Whether this API KEY enabled or disabled.                                                                                                                                                                                                          |
| [`allow from`](#allow-from)                   | `*`      | A space-separated list of [Netdata simple patterns](/src/libnetdata/simple_pattern/README.md) matching the IPs of nodes that will stream metrics using this API key. [Read more &rarr;](#allow-from) |
| `default history`                             | `3600`   | The default amount of child metrics history to retain when using the `ram` memory mode.                                                                                                                                                            |
| [`default memory mode`](#default-memory-mode) | `ram`    | The [database](/src/database/README.md) to use for all nodes using this `API_KEY`. Valid settings are `dbengine`, `ram`, or `none`. [Read more &rarr;](#default-memory-mode)                         |
| `health enabled by default`                   | `auto`   | Whether alerts and notifications should be enabled for nodes using this `API_KEY`. `auto` enables alerts when the child is connected. `yes` enables alerts always, and `no` disables alerts.                                                       |
| `default postpone alarms on connect seconds`  | `60`     | Postpone alerts and notifications for a period of time after the child connects.                                                                                                                                                                   |
| `default health log history`                  | `432000` | History of health log events (in seconds) kept in the database.                                                                                                                                                                                    |
| `default proxy enabled`                       |          | Route metrics through a proxy.                                                                                                                                                                                                                     |
| `default proxy destination`                   |          | Space-separated list of `IP:PORT` for proxies.                                                                                                                                                                                                     |
| `default proxy api key`                       |          | The `API_KEY` of the proxy.                                                                                                                                                                                                                        |
| `default send charts matching`                | `*`      | See [`send charts matching`](#send-charts-matching).                                                                                                                                                                                               |
| `enable compression`                          | `yes`    | Enable/disable stream compression.                                                                                                                                                                                                                 |
| `enable replication`                          | `yes`    | Enable/disable replication.                                                                                                                                                                                                                        |
| `seconds to replicate`                        | `86400`  | How many seconds of data to replicate from each child at a time                                                                                                                                                                                    |
| `seconds per replication step`                | `600`    | The duration we want to replicate per each replication step.                                                                                                                                                                                       |
| `is ephemeral node`                           | `no`     | Indicate whether this child is an ephemeral node. An ephemeral node will become unavailable after the specified duration of "cleanup ephemeral hosts after secs" from the time of the node's last connection.                                      |

#### `destination`

A space-separated list of parent nodes to attempt to stream to, with the first available parent receiving metrics, using
the following format: `[PROTOCOL:]HOST[%INTERFACE][:PORT][:SSL]`.

- `PROTOCOL`: `tcp`, `udp`, or `unix`. (only tcp and unix are supported by parent nodes)
- `HOST`: A IPv4, IPv6 IP, or a hostname, or a unix domain socket path. IPv6 IPs should be given with brackets
  `[ip:address]`.
- `INTERFACE` (IPv6 only): The network interface to use.
- `PORT`: The port number or service name (`/etc/services`) to use.
- `SSL`: To enable TLS/SSL encryption of the streaming connection.

To enable TCP streaming to a parent node at `203.0.113.0` on port `20000` and with TLS/SSL encryption: 

```conf
[stream]
    destination = tcp:203.0.113.0:20000:SSL
```

#### `send charts matching`

A space-separated list of [Netdata simple patterns](/src/libnetdata/simple_pattern/README.md) to filter which charts are streamed.

The default is a single wildcard `*`, which streams all charts.

To send only a few charts, list them explicitly, or list a group using a wildcard. To send _only_ the `apps.cpu` chart
and charts with contexts beginning with `system.`: 

```conf
[stream]
    send charts matching = apps.cpu system.*
```

To send all but a few charts, use `!` to create a negative match. To send _all_ charts _but_ `apps.cpu`:

```conf
[stream]
    send charts matching = !apps.cpu *
```

#### `allow from`

A space-separated list of [Netdata simple patterns](/src/libnetdata/simple_pattern/README.md) matching the IPs of nodes that
will stream metrics using this API key. The order is important, left to right, as the first positive or negative match is used.

The default is `*`, which accepts all requests including the `API_KEY`.

To allow from only a specific IP address:

```conf
[API_KEY]
    allow from = 203.0.113.10
```

To allow all IPs starting with `10.*`, except `10.1.2.3`:

```conf
[API_KEY]
    allow from = !10.1.2.3 10.*
```

> If you set specific IP addresses here, and also use the `allow connections` setting in the `[web]` section of
> `netdata.conf`, be sure to add the IP address there so that it can access the API port.

#### `default memory mode`

The [database](/src/database/README.md) to use for all nodes using this `API_KEY`.
Valid settings are `dbengine`, `ram`, , or `none`.

- `dbengine`: The default, recommended time-series database (TSDB) for Netdata. Stores recent metrics in memory, then
  efficiently spills them to disk for long-term storage.
- `ram`: Stores metrics _only_ in memory, which means metrics are lost when Netdata stops or restarts. Ideal for
  streaming configurations that use ephemeral nodes.
- `none`: No database.

When using `default memory mode = dbengine`, the parent node creates a separate instance of the TSDB to store metrics
from child nodes. The [size of _each_ instance is configurable](/docs/netdata-agent/configuration/optimizing-metrics-database/change-metrics-storage.md) with the `page
cache size` and `dbengine multihost disk space` settings in the `[global]` section in `netdata.conf`.

### `netdata.conf`

| Setting                                    | Default           | Description                                                                                                                                                                                                                                                                                                     |
|--------------------------------------------|-------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `[global]` section                         |                   |                                                                                                                                                                                                                                                                                                                 |
| `memory mode`                              | `dbengine`        | Determines the [database type](/src/database/README.md) to be used on that node. Other options settings include `none`, and `ram`. `none` disables the database at this host. This also disables alerts and notifications, as those can't run without a database. |
| `[web]` section                            |                   |                                                                                                                                                                                                                                                                                                                 |
| `mode`                                     | `static-threaded` | Determines the [web server](/src/web/server/README.md) type. The other option is `none`, which disables the dashboard, API, and registry.                                                                                                                             |
| `accept a streaming request every seconds` | `0`               | Set a limit on how often a parent node accepts streaming requests from child nodes. `0` equals no limit. If this is set, you may see `... too busy to accept new streaming request. Will be allowed in X secs` in Netdata's `error.log`.                                                                        |

### Basic use cases

This is an overview of how the main options can be combined:

| target             | memory<br/>mode | web<br/>mode | stream<br/>enabled |               exporting               |    alerts    | dashboard |
|--------------------|:---------------:|:------------:|:------------------:|:-------------------------------------:|:------------:|:---------:|
| headless collector |     `none`      |    `none`    |       `yes`        | only for `data source = as collected` | not possible |    no     |
| headless proxy     |     `none`      |  not `none`  |       `yes`        | only for `data source = as collected` | not possible |    no     |
| proxy with db      |   not `none`    |  not `none`  |       `yes`        |               possible                |   possible   |    yes    |
| central netdata    |   not `none`    |  not `none`  |        `no`        |               possible                |   possible   |    yes    |

### Per-child settings

While the `[API_KEY]` section applies settings for any child node using that key, you can also use per-child settings
with the `[MACHINE_GUID]` section.

For example, the metrics streamed from only the child node with `MACHINE_GUID` are saved in memory, not using the
default `dbengine` as specified by the `API_KEY`, and alerts are disabled.

```conf
[API_KEY]
    enabled = yes
    default memory mode = dbengine
    health enabled by default = auto
    allow from = *

[MACHINE_GUID]
    enabled = yes
    memory mode = ram
    health enabled = no
```

### Streaming compression

[![Supported version Netdata Agent release](https://img.shields.io/badge/Supported%20Netdata%20Agent-v1.33%2B-brightgreen)](https://github.com/netdata/netdata/releases/latest)

[![Supported version Netdata Agent release](https://img.shields.io/badge/Supported%20Netdata%20stream%20version-v5%2B-blue)](https://github.com/netdata/netdata/releases/latest)

#### OS dependencies
* Streaming compression is based on [lz4 v1.9.0+](https://github.com/lz4/lz4). The [lz4 v1.9.0+](https://github.com/lz4/lz4) library must be installed in your OS in order to enable streaming compression. Any lower version will disable Netdata streaming compression for compatibility purposes between the older versions of Netdata agents.

To check if your Netdata Agent supports stream compression run the following GET request in your browser or terminal:

```
curl -X GET http://localhost:19999/api/v1/info | grep 'Stream Compression'
```

**Output**
```
"buildinfo": "dbengine|Native HTTPS|Netdata Cloud|ACLK Next Generation|New Cloud Protocol Support|ACLK Legacy|TLS Host Verification|Machine Learning|Stream Compression|protobuf|JSON-C|libcrypto|libm|LWS v3.2.2|mosquitto|zlib|apps|cgroup Network Tracking|EBPF|perf|slabinfo",
```
> Note: If your OS doesn't support Netdata compression the `buildinfo` will not contain the `Stream Compression` statement.

To check if your Netdata Agent has stream compression enabled, run the following GET request in your browser or terminal: 

```
 curl -X GET http://localhost:19999/api/v1/info | grep 'stream-compression'
```
**Output**
```
"stream-compression": "enabled"
```
Note: The `stream-compression` status can be `"enabled" | "disabled" | "N/A"`.

A compressed data packet is determined and decompressed on the fly.

#### Limitations
This limitation will be withdrawn asap and is work-in-progress.

The current implementation of streaming data compression can support only a few number of dimensions in a chart with names that cannot exceed the size of 16384 bytes. In case your instance hit this limitation, the agent will deactivate compression during runtime to avoid stream corruption. This limitation can be seen in the error.log file with the sequence of the following messages: 
```
netdata INFO  : STREAM_SENDER[child01] : STREAM child01 [send to my.parent.IP]: connecting...
netdata INFO  : STREAM_SENDER[child01] : STREAM child01 [send to my.parent.IP]: initializing communication...
netdata INFO  : STREAM_SENDER[child01] : STREAM child01 [send to my.parent.IP]: waiting response from remote netdata...
netdata INFO  : STREAM_SENDER[child01] : STREAM_COMPRESSION: Compressor Reset
netdata INFO  : STREAM_SENDER[child01] : STREAM child01 [send to my.parent.IP]: established communication with a parent using protocol version 5 - ready to send metrics...
...
netdata ERROR : PLUGINSD[go.d] : STREAM_COMPRESSION: Compression Failed - Message size 27847 above compression buffer limit: 16384 (errno 9, Bad file descriptor)
netdata ERROR : PLUGINSD[go.d] : STREAM_COMPRESSION: Deactivating compression to avoid stream corruption
netdata ERROR : PLUGINSD[go.d] : STREAM_COMPRESSION child01 [send to my.parent.IP]: Restarting connection without compression
...
netdata INFO  : STREAM_SENDER[child01] : STREAM child01 [send to my.parent.IP]: connecting...
netdata INFO  : STREAM_SENDER[child01] : STREAM child01 [send to my.parent.IP]: initializing communication...
netdata INFO  : STREAM_SENDER[child01] : STREAM child01 [send to my.parent.IP]: waiting response from remote netdata...
netdata INFO  : STREAM_SENDER[child01] : Stream is uncompressed! One of the agents (my.parent.IP <-> child01) does not support compression OR compression is disabled.
netdata INFO  : STREAM_SENDER[child01] : STREAM child01 [send to my.parent.IP]: established communication with a parent using protocol version 4 - ready to send metrics...
netdata INFO  : WEB_SERVER[static4] : STREAM child01 [send]: sending metrics...
```

#### How to enable stream compression
Netdata Agents are shipped with data compression enabled by default. You can also configure which streams will use compression.

With enabled stream compression, a Netdata Agent can negotiate streaming compression with other Netdata Agents. During the negotiation of streaming compression both Netdata Agents should support and enable compression in order to communicate over a compressed stream. The negotiation will result into an uncompressed stream, if one of the Netdata Agents doesn't support **or** has compression disabled.

To enable stream compression: 

1. Edit `stream.conf` by using the `edit-config` script: 
`/etc/netdata/edit-config stream.conf`. 

2. In the `[stream]` section, set `enable compression` to `yes`.
```
# This is the default stream compression flag for an agent.

[stream]
    enable compression = yes | no
```


| Parent                               | Stream compression | Child                                |
|--------------------------------------|--------------------|--------------------------------------|
| Supported & Enabled                  | compressed         | Supported & Enabled                  |
| (Supported & Disabled)/Not supported | uncompressed       | Supported & Enabled                  |
| Supported & Enabled                  | uncompressed       | (Supported & Disabled)/Not supported |
| (Supported & Disabled)/Not supported | uncompressed       | (Supported & Disabled)/Not supported |

In case of parents with multiple children you can select which streams will be compressed by using the same configuration under the `[API_KEY]`, `[MACHINE_GUID]` section. 

This configuration uses AND logic with the default stream compression configuration under the `[stream]` section. This means the stream compression from child to parent will be enabled only if the outcome of the AND logic operation is true (`default compression enabled` && `api key compression enabled`). So both should be enabled to get stream compression otherwise  stream compression is disabled.
```  
[API_KEY]
    enable compression = yes | no
```
Same thing applies with the `[MACHINE_GUID]` configuration.
```
[MACHINE_GUID]
    enable compression = yes | no
```

### Securing streaming with TLS/SSL

Netdata does not activate TLS encryption by default. To encrypt streaming connections, you first need to [enable TLS
support](/src/web/server/README.md#enabling-tls-support) on the parent. With encryption enabled on the receiving side, you
need to instruct the child to use TLS/SSL as well. On the child's `stream.conf`, configure the destination as follows:

```
[stream]
    destination = host:port:SSL
```

The word `SSL` appended to the end of the destination tells the child that connections must be encrypted.

> While Netdata uses Transport Layer Security (TLS) 1.2 to encrypt communications rather than the obsolete SSL protocol,
> it's still common practice to refer to encrypted web connections as `SSL`. Many vendors, like Nginx and even Netdata
> itself, use `SSL` in configuration files, whereas documentation will always refer to encrypted communications as `TLS`
> or `TLS/SSL`.

#### Certificate verification

When TLS/SSL is enabled on the child, the default behavior will be to not connect with the parent unless the server's
certificate can be verified via the default chain. In case you want to avoid this check, add the following to the
child's `stream.conf` file:

```
[stream]
    ssl skip certificate verification = yes
```

#### Trusted certificate

If you've enabled [certificate verification](#certificate-verification), you might see errors from the OpenSSL library
when there's a problem with checking the certificate chain (`X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT_LOCALLY`). More
importantly, OpenSSL will reject self-signed certificates.

Given these known issues, you have two options. If you trust your certificate, you can set the options `CApath` and
`CAfile` to inform Netdata where your certificates, and the certificate trusted file, are stored.

For more details about these options, you can read about [verify
locations](https://www.openssl.org/docs/man1.1.1/man3/SSL_CTX_load_verify_locations.html).

Before you changed your streaming configuration, you need to copy your trusted certificate to your child system and add
the certificate to OpenSSL's list.

On most Linux distributions, the `update-ca-certificates` command searches inside the `/usr/share/ca-certificates`
directory for certificates. You should double-check by reading the `update-ca-certificate` manual (`man
update-ca-certificate`), and then change the directory in the below commands if needed.

If you have `sudo` configured on your child system, you can use that to run the following commands. If not, you'll have
to log in as `root` to complete them.

```
# mkdir /usr/share/ca-certificates/netdata
# cp parent_cert.pem /usr/share/ca-certificates/netdata/parent_cert.crt
# chown -R netdata.netdata /usr/share/ca-certificates/netdata/
```

First, you create a new directory to store your certificates for Netdata. Next, you need to change the extension on your
certificate from `.pem` to `.crt` so it's compatible with `update-ca-certificate`. Finally, you need to change
permissions so the user that runs Netdata can access the directory where you copied in your certificate.

Next, edit the file `/etc/ca-certificates.conf` and add the following line:

```
netdata/parent_cert.crt
```

Now you update the list of certificates running the following, again either as `sudo` or `root`:

```
# update-ca-certificates
```

> Some Linux distributions have different methods of updating the certificate list. For more details, please read this
> guide on [adding trusted root certificates](https://github.com/Busindre/How-to-Add-trusted-root-certificates).

Once you update your certificate list, you can set the stream parameters for Netdata to trust the parent certificate.
Open `stream.conf` for editing and change the following lines:

```
[stream]
    CApath = /etc/ssl/certs/
    CAfile = /etc/ssl/certs/parent_cert.pem
```

With this configuration, the `CApath` option tells Netdata to search for trusted certificates inside `/etc/ssl/certs`.
The `CAfile` option specifies the Netdata parent certificate is located at `/etc/ssl/certs/parent_cert.pem`. With this
configuration, you can skip using the system's entire list of certificates and use Netdata's parent certificate instead.

#### Expected behaviors

With the introduction of TLS/SSL, the parent-child communication behaves as shown in the table below, depending on the
following configurations:

-   **Parent TLS (Yes/No)**: Whether the `[web]` section in `netdata.conf` has `ssl key` and `ssl certificate`.
-   **Parent port TLS (-/force/optional)**: Depends on whether the `[web]` section `bind to` contains a `^SSL=force` or
    `^SSL=optional` directive on the port(s) used for streaming.
-   **Child TLS (Yes/No)**: Whether the destination in the child's `stream.conf` has `:SSL` at the end.
-   **Child TLS Verification (yes/no)**: Value of the child's `stream.conf` `ssl skip certificate verification`
    parameter (default is no).

| Parent TLS enabled | Parent port SSL  | Child TLS | Child SSL Ver. | Behavior                                                                                                                                 |
|:-------------------|:-----------------|:----------|:---------------|:-----------------------------------------------------------------------------------------------------------------------------------------|
| No                 | -                | No        | no             | Legacy behavior. The parent-child stream is unencrypted.                                                                                 |
| Yes                | force            | No        | no             | The parent rejects the child connection.                                                                                                 |
| Yes                | -/optional       | No        | no             | The parent-child stream is unencrypted (expected situation for legacy child nodes and newer parent nodes)                                |
| Yes                | -/force/optional | Yes       | no             | The parent-child stream is encrypted, provided that the parent has a valid TLS/SSL certificate. Otherwise, the child refuses to connect. |
| Yes                | -/force/optional | Yes       | yes            | The parent-child stream is encrypted.                                                                                                    |

### Proxy

A proxy is a node that receives metrics from a child, then streams them onward to a parent. To configure a proxy,
configure it as a receiving and a sending Netdata at the same time.

Netdata proxies may or may not maintain a database for the metrics passing through them. When they maintain a database,
they can also run health checks (alerts and notifications) for the remote host that is streaming the metrics.

In the following example, the proxy receives metrics from a child node using the `API_KEY` of
`66666666-7777-8888-9999-000000000000`, then stores metrics using `dbengine`. It then uses the `API_KEY` of
`11111111-2222-3333-4444-555555555555` to proxy those same metrics on to a parent node at `203.0.113.0`.

```conf
[stream]
    enabled = yes 
    destination = 203.0.113.0
    api key = 11111111-2222-3333-4444-555555555555

[66666666-7777-8888-9999-000000000000]
    enabled = yes
    default memory mode = dbengine
```

### Ephemeral nodes

Netdata can help you monitor ephemeral nodes, such as containers in an auto-scaling infrastructure, by always streaming
metrics to any number of permanently-running parent nodes.

On the parent, set the following in `stream.conf`:

```conf
[11111111-2222-3333-4444-555555555555]
	# enable/disable this API key
    enabled = yes

    # one hour of data for each of the child nodes
    default history = 3600

    # do not save child metrics on disk
    default memory = ram

    # alerts checks, only while the child is connected
    health enabled by default = auto
```

On the child nodes, set the following in `stream.conf`:

```bash
[stream]
    # stream metrics to another Netdata
    enabled = yes

    # the IP and PORT of the parent
    destination = 10.11.12.13:19999

	  # the API key to use
    api key = 11111111-2222-3333-4444-555555555555
```

In addition, edit `netdata.conf` on each child node to disable the database and alerts.

```bash
[global]
    # disable the local database
	  memory mode = none

[health]
    # disable health checks
    enabled = no
```

## Replication

Netdata streaming automatically replicates data from child nodes to parent nodes, ensuring that the parent node has a complete and up-to-date view of all metrics.
This replication process ensures data continuity even if child nodes temporarily disconnect.

Replication is enabled by default in Netdata, but you can customize the replication behavior by modifying the `[API_KEY]` section of the `stream.conf` file. Here's an example configuration:

```conf
[11111111-2222-3333-4444-555555555555]
    # Enable replication for all hosts using this api key. Default: yes.
    enable replication = yes

    # How many seconds of data to replicate from each child at a time. Default: a day (86400 seconds).
    seconds to replicate = 86400

    # The duration we want to replicate per each replication step. Default: 600 seconds (10 minutes).
    seconds per replication step = 600
```

You can monitor the replication process in two ways:

1. **Netdata Monitoring**: access the Netdata Monitoring section and look for the Replication charts. 
2. **Streaming Function**: use the Streaming function (Top) to see the replication status of children nodes. This function provides real-time insights into the replication status of each child node.

### Replication history

Replication history in [dbengine](/src/database/README.md) mode is limited
by [Tier 0 retention](/docs/netdata-agent/configuration/optimizing-metrics-database/change-metrics-storage.md#effect-of-storage-tiers-and-disk-space-on-retention):

- Child instances replicate only Tier 0 data.
- Parent instance calculates higher-level tiers using Tier 0 as the basis.

Extend replication history by increasing Tier 0 retention.

Checking Tier 0 retention:

- Using a web browser:
    - Navigate to `http://{CHILD_IP}:19999/api/v2/node_instances`.
    - Locate the `expected_retention` value for Tier 0 of your Agent.
    - Convert the value from seconds to days for a more meaningful representation.
- Using `curl` and `jq`:
    - Execute the following command:
      ```bash
      $ curl -s "http://{CHILD_IP}:19999/api/v2/node_instances" | jq '.agents[] | {nm, retention: (.db_size[0].retention / 86400 | .*100 | round/100) }'
      ```
    - Example output:
      ```json
       {
         "nm": "myhost",
         "retention": 12.73
       }
      ```

## Troubleshooting

Both parent and child nodes log information at `/var/log/netdata/error.log`.

If the child manages to connect to the parent you will see something like (on the parent):

```
2017-03-09 09:38:52: netdata: INFO : STREAM [receive from [10.11.12.86]:38564]: new client connection.
2017-03-09 09:38:52: netdata: INFO : STREAM xxx [10.11.12.86]:38564: receive thread created (task id 27721)
2017-03-09 09:38:52: netdata: INFO : STREAM xxx [receive from [10.11.12.86]:38564]: client willing to stream metrics for host 'xxx' with machine_guid '1234567-1976-11e6-ae19-7cdd9077342a': update every = 1, history = 3600, memory mode = ram, health auto
2017-03-09 09:38:52: netdata: INFO : STREAM xxx [receive from [10.11.12.86]:38564]: initializing communication...
2017-03-09 09:38:52: netdata: INFO : STREAM xxx [receive from [10.11.12.86]:38564]: receiving metrics...
```

and something like this on the child:

```
2017-03-09 09:38:28: netdata: INFO : STREAM xxx [send to box:19999]: connecting...
2017-03-09 09:38:28: netdata: INFO : STREAM xxx [send to box:19999]: initializing communication...
2017-03-09 09:38:28: netdata: INFO : STREAM xxx [send to box:19999]: waiting response from remote netdata...
2017-03-09 09:38:28: netdata: INFO : STREAM xxx [send to box:19999]: established communication - sending metrics...
```

The following sections describe the most common issues you might encounter when connecting parent and child nodes.

### Slow connections between parent and child

When you have a slow connection between parent and child, Netdata raises a few different errors. Most of the
errors will appear in the child's `error.log`.

```bash
netdata ERROR : STREAM_SENDER[CHILD HOSTNAME] : STREAM CHILD HOSTNAME [send to PARENT IP:PARENT PORT]: too many data pending - buffer is X bytes long,
Y unsent - we have sent Z bytes in total, W on this connection. Closing connection to flush the data.
```

On the parent side, you may see various error messages, most commonly the following:

```
netdata ERROR : STREAM_PARENT[CHILD HOSTNAME,[CHILD IP]:CHILD PORT] : read failed: end of file
```

Another common problem in slow connections is the child sending a partial message to the parent. In this case, the
parent will write the following to its `error.log`:

```
ERROR : STREAM_RECEIVER[CHILD HOSTNAME,[CHILD IP]:CHILD PORT] : sent command 'B' which is not known by netdata, for host 'HOSTNAME'. Disabling it.
```

In this example, `B` was part of a `BEGIN` message that was cut due to connection problems.

Slow connections can also cause problems when the parent misses a message and then receives a command related to the
missed message. For example, a parent might miss a message containing the child's charts, and then doesn't know
what to do with the `SET` message that follows. When that happens, the parent will show a message like this:

```
ERROR : STREAM_RECEIVER[CHILD HOSTNAME,[CHILD IP]:CHILD PORT] : requested a SET on chart 'CHART NAME' of host 'HOSTNAME', without a dimension. Disabling it.
```

### Child cannot connect to parent

When the child can't connect to a parent for any reason (misconfiguration, networking, firewalls, parent
down), you will see the following in the child's `error.log`.

```
ERROR : STREAM_SENDER[HOSTNAME] : Failed to connect to 'PARENT IP', port 'PARENT PORT' (errno 113, No route to host)
```

### 'Is this a Netdata?'

This question can appear when Netdata starts the stream and receives an unexpected response. This error can appear when
the parent is using SSL and the child tries to connect using plain text. You will also see this message when
Netdata connects to another server that isn't Netdata. The complete error message will look like this:

```
ERROR : STREAM_SENDER[CHILD HOSTNAME] : STREAM child HOSTNAME [send to PARENT HOSTNAME:PARENT PORT]: server is not replying properly (is it a netdata?).
```

### Stream charts wrong

Chart data needs to be consistent between child and parent nodes. If there are differences between chart data on
a parent and a child, such as gaps in metrics collection, it most often means your child's `memory mode`
does not match the parent's. To learn more about the different ways Netdata can store metrics, and thus keep chart
data consistent, read our [memory mode documentation](/src/database/README.md).

### Forbidding access

You may see errors about "forbidding access" for a number of reasons. It could be because of a slow connection between
the parent and child nodes, but it could also be due to other failures. Look in your parent's `error.log` for errors
that look like this: 

```
STREAM [receive from [child HOSTNAME]:child IP]: `MESSAGE`. Forbidding access."
```

`MESSAGE` will have one of the following patterns:

- `request without KEY` : The message received is incomplete and the KEY value can be API, hostname, machine GUID.
- `API key 'VALUE' is not valid GUID`: The UUID received from child does not have the format defined in [RFC
  4122](https://tools.ietf.org/html/rfc4122)
- `machine GUID 'VALUE' is not GUID.`: This error with machine GUID is like the previous one.
- `API key 'VALUE' is not allowed`: This stream has a wrong API key.
- `API key 'VALUE' is not permitted from this IP`: The IP is not allowed to use STREAM with this parent.
- `machine GUID 'VALUE' is not allowed.`: The GUID that is trying to send stream is not allowed.
- `Machine GUID 'VALUE' is not permitted from this IP. `: The IP does not match the pattern or IP allowed to connect to
  use stream.

### Netdata could not create a stream

The connection between parent and child is a stream. When the parent can't convert the initial connection into
a stream, it will write the following message inside `error.log`:

```
file descriptor given is not a valid stream
```

After logging this error, Netdata will close the stream.
