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+# Metrics long term archiving
+
+netdata supports backends for archiving the metrics, or providing long term dashboards,
+using Grafana or other tools, like this:
+
+![image](https://cloud.githubusercontent.com/assets/2662304/20649711/29f182ba-b4ce-11e6-97c8-ab2c0ab59833.png)
+
+Since netdata collects thousands of metrics per server per second, which would easily congest any backend
+server when several netdata servers are sending data to it, netdata allows sending metrics at a lower
+frequency, by resampling them.
+
+So, although netdata collects metrics every second, it can send to the backend servers averages or sums every
+X seconds (though, it can send them per second if you need it to).
+
+## features
+
+1. Supported backends
+
+ - **graphite** (`plaintext interface`, used by **Graphite**, **InfluxDB**, **KairosDB**,
+ **Blueflood**, **ElasticSearch** via logstash tcp input and the graphite codec, etc)
+
+ metrics are sent to the backend server as `prefix.hostname.chart.dimension`. `prefix` is
+ configured below, `hostname` is the hostname of the machine (can also be configured).
+
+ - **opentsdb** (`telnet interface`, used by **OpenTSDB**, **InfluxDB**, **KairosDB**, etc)
+
+ metrics are sent to opentsdb as `prefix.chart.dimension` with tag `host=hostname`.
+
+ - **json** document DBs
+
+ metrics are sent to a document db, `JSON` formatted.
+
+ - **prometheus** is described at [prometheus page](prometheus/) since it pulls data from netdata.
+
+2. Only one backend may be active at a time.
+
+3. Netdata can filter metrics (at the chart level), to send only a subset of the collected metrics.
+
+4. Netdata supports three modes of operation for all backends:
+
+ - `as-collected` sends to backends the metrics as they are collected, in the units they are collected.
+ So, counters are sent as counters and gauges are sent as gauges, much like all data collectors do.
+ For example, to calculate CPU utilization in this format, you need to know how to convert kernel ticks to percentage.
+
+ - `average` sends to backends normalized metrics from the netdata database.
+ In this mode, all metrics are sent as gauges, in the units netdata uses. This abstracts data collection
+ and simplifies visualization, but you will not be able to copy and paste queries from other sources to convert units.
+ For example, CPU utilization percentage is calculated by netdata, so netdata will convert ticks to percentage and
+ send the average percentage to the backend.
+
+ - `sum` or `volume`: the sum of the interpolated values shown on the netdata graphs is sent to the backend.
+ So, if netdata is configured to send data to the backend every 10 seconds, the sum of the 10 values shown on the
+ netdata charts will be used.
+
+Time-series databases suggest to collect the raw values (`as-collected`). If you plan to invest on building your monitoring around a time-series database and you already know (or you will invest in learning) how to convert units and normalize the metrics in Grafana or other visualization tools, we suggest to use `as-collected`.
+
+If, on the other hand, you just need long term archiving of netdata metrics and you plan to mainly work with netdata, we suggest to use `average`. It decouples visualization from data collection, so it will generally be a lot simpler. Furthermore, if you use `average`, the charts shown in the back-end will match exactly what you see in Netdata, which is not necessarily true for the other modes of operation.
+
+5. This code is smart enough, not to slow down netdata, independently of the speed of the backend server.
+
+## configuration
+
+In `/etc/netdata/netdata.conf` you should have something like this (if not download the latest version
+of `netdata.conf` from your netdata):
+
+```
+[backend]
+ enabled = yes | no
+ type = graphite | opentsdb | json
+ host tags = list of TAG=VALUE
+ destination = space separated list of [PROTOCOL:]HOST[:PORT] - the first working will be used
+ data source = average | sum | as collected
+ prefix = netdata
+ hostname = my-name
+ update every = 10
+ buffer on failures = 10
+ timeout ms = 20000
+ send charts matching = *
+ send hosts matching = localhost *
+ send names instead of ids = yes
+```
+
+- `enabled = yes | no`, enables or disables sending data to a backend
+
+- `type = graphite | opentsdb | json`, selects the backend type
+
+- `destination = host1 host2 host3 ...`, accepts **a space separated list** of hostnames,
+ IPs (IPv4 and IPv6) and ports to connect to.
+ Netdata will use the **first available** to send the metrics.
+
+ The format of each item in this list, is: `[PROTOCOL:]IP[:PORT]`.
+
+ `PROTOCOL` can be `udp` or `tcp`. `tcp` is the default and only supported by the current backends.
+
+ `IP` can be `XX.XX.XX.XX` (IPv4), or `[XX:XX...XX:XX]` (IPv6).
+ For IPv6 you can to enclose the IP in `[]` to separate it from the port.
+
+ `PORT` can be a number of a service name. If omitted, the default port for the backend will be used
+ (graphite = 2003, opentsdb = 4242).
+
+ Example IPv4:
+
+```
+ destination = 10.11.14.2:4242 10.11.14.3:4242 10.11.14.4:4242
+```
+
+ Example IPv6 and IPv4 together:
+
+```
+ destination = [ffff:...:0001]:2003 10.11.12.1:2003
+```
+
+ When multiple servers are defined, netdata will try the next one when the first one fails. This allows
+ you to load-balance different servers: give your backend servers in different order on each netdata.
+
+ netdata also ships [`nc-backend.sh`](nc-backend.sh),
+ a script that can be used as a fallback backend to save the metrics to disk and push them to the
+ time-series database when it becomes available again. It can also be used to monitor / trace / debug
+ the metrics netdata generates.
+
+- `data source = as collected`, or `data source = average`, or `data source = sum`, selects the kind of
+ data that will be sent to the backend.
+
+- `hostname = my-name`, is the hostname to be used for sending data to the backend server. By default
+ this is `[global].hostname`.
+
+- `prefix = netdata`, is the prefix to add to all metrics.
+
+- `update every = 10`, is the number of seconds between sending data to the backend. netdata will add
+ some randomness to this number, to prevent stressing the backend server when many netdata servers send
+ data to the same backend. This randomness does not affect the quality of the data, only the time they
+ are sent.
+
+- `buffer on failures = 10`, is the number of iterations (each iteration is `[backend].update every` seconds)
+ to buffer data, when the backend is not available. If the backend fails to receive the data after that
+ many failures, data loss on the backend is expected (netdata will also log it).
+
+- `timeout ms = 20000`, is the timeout in milliseconds to wait for the backend server to process the data.
+ By default this is `2 * update_every * 1000`.
+
+- `send hosts matching = localhost *` includes one or more space separated patterns, using ` * ` as wildcard
+ (any number of times within each pattern). The patterns are checked against the hostname (the localhost
+ is always checked as `localhost`), allowing us to filter which hosts will be sent to the backend when
+ this netdata is a central netdata aggregating multiple hosts. A pattern starting with ` ! ` gives a
+ negative match. So to match all hosts named `*db*` except hosts containing `*slave*`, use
+ `!*slave* *db*` (so, the order is important: the first pattern matching the hostname will be used - positive
+ or negative).
+
+- `send charts matching = *` includes one or more space separated patterns, using ` * ` as wildcard (any
+ number of times within each pattern). The patterns are checked against both chart id and chart name.
+ A pattern starting with ` ! ` gives a negative match. So to match all charts named `apps.*`
+ except charts ending in `*reads`, use `!*reads apps.*` (so, the order is important: the first pattern
+ matching the chart id or the chart name will be used - positive or negative).
+
+- `send names instead of ids = yes | no` controls the metric names netdata should send to backend.
+ netdata supports names and IDs for charts and dimensions. Usually IDs are unique identifiers as read
+ by the system and names are human friendly labels (also unique). Most charts and metrics have the same
+ ID and name, but in several cases they are different: disks with device-mapper, interrupts, QoS classes,
+ statsd synthetic charts, etc.
+
+- `host tags = list of TAG=VALUE` defines tags that should be appended on all metrics for the given host.
+ These are currently only sent to opentsdb and prometheus. Please use the appropriate format for each
+ time-series db. For example opentsdb likes them like `TAG1=VALUE1 TAG2=VALUE2`, but prometheus like
+ `tag1="value1",tag2="value2"`. Host tags are mirrored with database replication (streaming of metrics
+ between netdata servers).
+
+## monitoring operation
+
+netdata provides 5 charts:
+
+1. **Buffered metrics**, the number of metrics netdata added to the buffer for dispatching them to the
+ backend server.
+
+2. **Buffered data size**, the amount of data (in KB) netdata added the buffer.
+
+3. ~~**Backend latency**, the time the backend server needed to process the data netdata sent.
+ If there was a re-connection involved, this includes the connection time.~~
+ (this chart has been removed, because it only measures the time netdata needs to give the data
+ to the O/S - since the backend servers do not ack the reception, netdata does not have any means
+ to measure this properly).
+
+4. **Backend operations**, the number of operations performed by netdata.
+
+5. **Backend thread CPU usage**, the CPU resources consumed by the netdata thread, that is responsible
+ for sending the metrics to the backend server.
+
+![image](https://cloud.githubusercontent.com/assets/2662304/20463536/eb196084-af3d-11e6-8ee5-ddbd3b4d8449.png)
+
+## alarms
+
+The latest version of the alarms configuration for monitoring the backend is [here](../health/health.d/backend.conf)
+
+netdata adds 4 alarms:
+
+1. `backend_last_buffering`, number of seconds since the last successful buffering of backend data
+2. `backend_metrics_sent`, percentage of metrics sent to the backend server
+3. `backend_metrics_lost`, number of metrics lost due to repeating failures to contact the backend server
+4. ~~`backend_slow`, the percentage of time between iterations needed by the backend time to process the data sent by netdata~~ (this was misleading and has been removed).
+
+![image](https://cloud.githubusercontent.com/assets/2662304/20463779/a46ed1c2-af43-11e6-91a5-07ca4533cac3.png)
+
+
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