Adding upstream version 1.31.0.upstream/1.31.0

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+---
+title: "Streaming reference"
+description: "Each node running Netdata can stream the metrics it collects, in real time, to another node. See all of the available settings in this reference document."
+type: reference
+custom_edit_url: https://github.com/netdata/netdata/edit/master/docs/metrics-storage-management/reference-streaming.mdx
+---
+
+# Streaming reference
+
+Each node running Netdata can stream the metrics it collects, in real time, to another node. To learn more, read about
+[how streaming works](/docs/metrics-storage-management/how-streaming-works.mdx).
+
+For a quickstart guide for enabling a simple `parent-child` streaming relationship, see our [stream metrics between
+nodes](/docs/metrics-storage-management/enable-streaming.mdx) doc. All other configuration options and scenarios are
+covered in the sections below.
+
+## 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/configure/nodes.md) to
+open either `stream.conf` or `netdata.conf`.
+
+```
+sudo ./edit-config stream.conf
+sudo ./edit-config netdata.conf
+```
+
+## Settings
+
+As mentioned above, both `stream.conf` and `netdata.conf` contain settings relevant to streaming.
+
+### `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 →](#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](/libnetdata/simple_pattern/README.md) to filter which charts are streamed. [Read more →](#send-charts-matching)                                                                                                                                                                                  |
+| `buffer size bytes`                             | `1048576`                 | The size of the buffer to use when sending metrics. The default `1048576` equals a buffer of 1MB, which is good for 10-20 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.                                                                                                                                                                                                                                                                                              |
+
+### `[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](/libnetdata/simple_pattern/README.md) matching the IPs of nodes that will stream metrics using this API key. [Read more →](#allow-from)                                                                                                                                                          |
+| `default history`                               | `3600`                    | The default amount of child metrics history to retain when using the `save`, `map`, or `ram` memory modes.                                                                                                                                                                                                                                                |
+| [`default memory mode`](#default-memory-mode)   | `ram`                     | The [database](/database/README.md) to use for all nodes using this `API_KEY`. Valid settings are `dbengine`, `map`, `save`, `ram`, or `none`. [Read more →](#default-memory-mode)                                                                                                                                                                   |
+| `health enabled by default`                     | `auto`                    | Whether alarms and notifications should be enabled for nodes using this `API_KEY`. `auto` enables alarms when the child is connected. `yes` enables alarms always, and `no` disables alarms.                                                                                                                                                              |
+| `default postpone alarms on connect seconds`    | `60`                      | Postpone alarms and notifications for a period of time after the child connects.                                                                                                                                                                                                                                                                          |
+| `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).                                                                                                                                                                                                                                                                                                      |
+
+#### `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](/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](/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](/database/README.md) to use for all nodes using this `API_KEY`. Valid settings are `dbengine`, `ram`,
+`save`, `map`, 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.
+- `save`: Stores metrics in memory, but saves metrics to disk when Netdata stops or restarts, and loads historical
+  metrics on start.
+- `map`: Stores metrics in memory-mapped files, like swap, with constant disk write.
+- `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/store/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](/database/README.md) to be used on that node. Other options settings include `none`, `ram`, `save`, and `map`. `none` disables the database at this host. This also disables alarms and notifications, as those can't run without a database. |
+| **`[web]` section**                        |                   |                                                                                                                                                                                                                                                                              |
+| `mode`                                     | `static-threaded` | Determines the [web server](/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`.                                     |
+
+## Examples
+
+### 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 alarms are disabled.
+
+```conf
+[API_KEY]
+    enabled = yes
+    default memory mode = dbengine
+    health enabled by default = auto
+    allow from = *
+
+[MACHINE_GUID]
+    enabled = yes
+    memory mode = save
+    health enabled = 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](/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 (alarms 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
+
+    # alarms 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 alarms.
+
+```bash
+[global]
+    # disable the local database
+	  memory mode = none
+
+[health]
+    # disable health checks
+    enabled = no
+```
+
+## 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](/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.