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 , 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 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		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 →
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	*	A space-separated list of Netdata simple patterns to filter which charts are streamed. Read more →
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.

[API_KEY] and [MACHINE_GUID] sections

Setting	Default	Description
enabled	no	Whether this API KEY enabled or disabled.
allow from	*	A space-separated list of Netdata simple patterns matching the IPs of nodes that will stream metrics using this API key. Read more →
default history	3600	The default amount of child metrics history to retain when using the save, map, or ram memory modes.
default memory mode	ram	The database to use for all nodes using this API_KEY. Valid settings are dbengine, map, save, ram, or none. Read more →
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.

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:

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

send charts matching

A space-separated list of Netdata simple patterns 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.:

[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:

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

allow from

A space-separated list of Netdata simple patterns 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:

[API_KEY]
    allow from = 203.0.113.10

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

[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 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 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 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 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 mode	web mode	stream enabled	exporting	alarms	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 alarms are disabled.

[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

Streaming compression

OS dependencies

• Streaming compression is based on lz4 v1.9.0+. The lz4 v1.9.0+ 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 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, 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.

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.

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.

[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:

[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:

[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.

[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.

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.

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
• 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.

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