github.com/yankunsam/loki/v2@v2.6.3-0.20220817130409-389df5235c27/docs/sources/operations/loki-canary.md

---
title: Loki Canary
weight: 60
---
# Loki Canary

![canary](../canary.png)

Loki Canary is a standalone app that audits the log-capturing performance of
a Grafana Loki cluster.

Loki Canary generates artificial log lines.
These log lines are sent to the Loki cluster.
Loki Canary communicates with the Loki cluster to capture metrics about the
artificial log lines,
such that Loki Canary forms information about the performance of the
Loki cluster.
The information is available as Prometheus time series metrics.

![block_diagram](../loki-canary-block.png)

Loki Canary writes a log to a file and stores the timestamp in an internal
array. The contents look something like this:

```nohighlight
1557935669096040040 ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp
```

The relevant part of the log entry is the timestamp; the `p`s are just filler
bytes to make the size of the log configurable.

An agent (like Promtail) should be configured to read the log file and ship it
to Loki.

Meanwhile, Loki Canary will open a WebSocket connection to Loki and will tail
the logs it creates. When a log is received on the WebSocket, the timestamp
in the log message is compared to the internal array.

If the received log is:

- The next in the array to be received, it is removed from the array and the
  (current time - log timestamp) is recorded in the `response_latency`
  histogram. This is the expected behavior for well behaving logs.
- Not the next in the array to be received, it is removed from the array, the
  response time is recorded in the `response_latency` histogram, and the
  `out_of_order_entries` counter is incremented.
- Not in the array at all, it is checked against a separate list of received
  logs to either increment the `duplicate_entries` counter or the
  `unexpected_entries` counter.

In the background, Loki Canary also runs a timer which iterates through all of
the entries in the internal array. If any of the entries are older than the
duration specified by the `-wait` flag (defaulting to 60s), they are removed
from the array and the `websocket_missing_entries` counter is incremented. An
additional query is then made directly to Loki for any missing entries to
determine if they are truly missing or only missing from the WebSocket. If
missing entries are not found in the direct query, the `missing_entries` counter
is incremented.

### Additional Queries

#### Spot Check

Starting with version 1.6.0, the canary will spot check certain results over time
to make sure they are present in Loki, this is helpful for testing the transition
of inmemory logs in the ingester to the store to make sure nothing is lost.

`-spot-check-interval` and `-spot-check-max` are used to tune this feature,
`-spot-check-interval` will pull a log entry from the stream at this interval
and save it in a separate list up to `-spot-check-max`.

Every `-spot-check-query-rate`, Loki will be queried for each entry in this list and
`loki_canary_spot_check_entries_total` will be incremented, if a result
is missing `loki_canary_spot_check_missing_entries_total` will be incremented.

The defaults of `15m` for `spot-check-interval` and `4h` for `spot-check-max`
means that after 4 hours of running the canary will have a list of 16 entries
it will query every minute (default `spot-check-query-rate` interval is 1m),
so be aware of the query load this can put on Loki if you have a lot of canaries.

__NOTE:__ if you are using `out-of-order-percentage` to test ingestion of out-of-order
log lines be sure not to set the two out of order time range flags too far in the past.
The defaults are already enough to test this functionality properly, and setting them
too far in the past can cause issues with the spot check test.


When using `out-of-order-percentage` you also need to make use of pipeline stages
in your Promtail configuration in order to set the timestamps correctly as the logs are pushed
to Loki. The `client/promtail/pipelines` docs have examples of how to do this.

#### Metric Test

Loki Canary will run a metric query `count_over_time` to
verify that the rate of logs being stored in Loki corresponds to the rate they are being
created by Loki Canary.

`-metric-test-interval` and `-metric-test-range` are used to tune this feature, but
by default every `15m` the canary will run a `count_over_time` instant-query to Loki
for a range of `24h`.

If the canary has not run for `-metric-test-range` (`24h`) the query range is adjusted
to the amount of time the canary has been running such that the rate can be calculated
since the canary was started.

The canary calculates what the expected count of logs would be for the range
(also adjusting this based on canary runtime) and compares the expected result with
the actual result returned from Loki.  The _difference_ is stored as the value in
the gauge `loki_canary_metric_test_deviation`

It's expected that there will be some deviation, the method of creating an expected
calculation based on the query rate compared to actual query data is imperfect
and will lead to a deviation of a few log entries.

It's not expected for there to be a deviation of more than 3-4 log entries.

### Control

Loki Canary responds to two endpoints to allow dynamic suspending/resuming of the
canary process.  This can be useful if you'd like to quickly disable or reenable the
canary.  To stop or start the canary issue an HTTP GET request against the `/suspend` or
`/resume` endpoints.

## Installation

### Binary

Loki Canary is provided as a pre-compiled binary as part of the
[Loki Releases](https://github.com/grafana/loki/releases) on GitHub.

### Docker

Loki Canary is also provided as a Docker container image:

```bash
# change tag to the most recent release
$ docker pull grafana/loki-canary:2.0.0
```

### Kubernetes

To run on Kubernetes, you can do something simple like:

`kubectl run loki-canary --generator=run-pod/v1
--image=grafana/loki-canary:latest --restart=Never --image-pull-policy=IfNotPresent
--labels=name=loki-canary -- -addr=loki:3100`

Or you can do something more complex like deploy it as a DaemonSet, there is a
Tanka setup for this in the `production` folder, you can import it using
`jsonnet-bundler`:

```shell
jb install github.com/grafana/loki-canary/production/ksonnet/loki-canary
```

Then in your Tanka environment's `main.jsonnet` you'll want something like
this:

```jsonnet
local loki_canary = import 'loki-canary/loki-canary.libsonnet';

loki_canary {
  loki_canary_args+:: {
    addr: "loki:3100",
    port: 80,
    labelname: "instance",
    interval: "100ms",
    size: 1024,
    wait: "3m",
  },
  _config+:: {
    namespace: "default",
  }
}
```
#### Examples

Standalone Pod Implementation of loki-canary

```
---
apiVersion: v1
kind: Pod
metadata:
  labels:
    app: loki-canary
    name: loki-canary
  name: loki-canary
spec:
  containers:
  - args:
    - -addr=loki:3100
    image: grafana/loki-canary:latest
    imagePullPolicy: IfNotPresent
    name: loki-canary
    resources: {}
---
apiVersion: v1
kind: Service
metadata:
  name: loki-canary
  labels:
    app: loki-canary
spec:
  type: ClusterIP
  selector:
    app: loki-canary
  ports:
  - name: metrics
    protocol: TCP
    port: 3500
    targetPort: 3500
```

DaemonSet Implementation of loki-canary

```
---
kind: DaemonSet
apiVersion: extensions/v1beta1
metadata:
  labels:
    app: loki-canary
    name: loki-canary
  name: loki-canary
spec:
  template:
    metadata:
      name: loki-canary
      labels:
        app: loki-canary
    spec:
      containers:
      - args:
        - -addr=loki:3100
        image: grafana/loki-canary:latest
        imagePullPolicy: IfNotPresent
        name: loki-canary
        resources: {}
---
apiVersion: v1
kind: Service
metadata:
  name: loki-canary
  labels:
    app: loki-canary
spec:
  type: ClusterIP
  selector:
    app: loki-canary
  ports:
  - name: metrics
    protocol: TCP
    port: 3500
    targetPort: 3500
```


### From Source

If the other options are not sufficient for your use case, you can compile
`loki-canary` yourself:

```bash
# clone the source tree
$ git clone https://github.com/grafana/loki

# build the binary
$ make loki-canary

# (optionally build the container image)
$ make loki-canary-image
```

## Configuration

The address of Loki must be passed in with the `-addr` flag, and if your Loki
server uses TLS, `-tls=true` must also be provided. Note that using TLS will
cause the WebSocket connection to use `wss://` instead of `ws://`.

The `-labelname` and `-labelvalue` flags should also be provided, as these are
used by Loki Canary to filter the log stream to only process logs for the
current instance of the canary. Ensure that the values provided to the flags are
unique to each instance of Loki Canary. Grafana Labs' Tanka config
accomplishes this by passing in the pod name as the label value.

If Loki Canary reports a high number of `unexpected_entries`, Loki Canary may
not be waiting long enough and the value for the `-wait` flag should be
increased to a larger value than 60s.

__Be aware__ of the relationship between `pruneinterval` and the `interval`.
For example, with an interval of 10ms (100 logs per second) and a prune interval
of 60s, you will write 6000 logs per minute. If those logs were not received
over the WebSocket, the canary will attempt to query Loki directly to see if
they are completely lost. __However__ the query return is limited to 1000
results so you will not be able to return all the logs even if they did make it
to Loki.

__Likewise__, if you lower the `pruneinterval` you risk causing a denial of
service attack as all your canaries attempt to query for missing logs at
whatever your `pruneinterval` is defined at.

All options:

```
  -addr string
        The Loki server URL:Port, e.g. loki:3100
  -buckets int
        Number of buckets in the response_latency histogram (default 10)
  -interval duration
        Duration between log entries (default 1s)
  -labelname string
        The label name for this instance of Loki Canary to use in the log selector
        (default "name")
  -labelvalue string
        The unique label value for this instance of Loki Canary to use in the log selector
        (default "loki-canary")
  -metric-test-interval duration
        The interval the metric test query should be run (default 1h0m0s)
  -metric-test-range duration
        The range value [24h] used in the metric test instant-query. This value is truncated
        to the running time of the canary until this value is reached (default 24h0m0s)
  -out-of-order-max duration
    	  Maximum amount of time (in seconds) in the past an out of order entry may have as a
          timestamp. (default 60s)
  -out-of-order-min duration
    	  Minimum amount of time (in seconds) in the past an out of order entry may have as a
          timestamp. (default 30s)
  -out-of-order-percentage int
      	Percentage (0-100) of log entries that should be sent out of order
  -pass string
        Loki password
  -port int
        Port which Loki Canary should expose metrics (default 3500)
  -pruneinterval duration
        Frequency to check sent versus received logs, and also the frequency at which queries
        for missing logs will be dispatched to Loki, and the frequency spot check queries are run
        (default 1m0s)
  -query-timeout duration
        How long to wait for a query response from Loki (default 10s)
  -size int
        Size in bytes of each log line (default 100)
  -spot-check-interval duration
        Interval that a single result will be kept from sent entries and spot-checked against
        Loki. For example, with the 15 minute default, one entry every 15 minutes will be saved,
        and then queried again every 15 minutes until the time defined by spot-check-max is
        reached (default 15m0s)
  -spot-check-max duration
        How far back to check a spot check an entry before dropping it (default 4h0m0s)
  -spot-check-query-rate duration
        Interval that Loki Canary will query Loki for the current list of all spot check entries
        (default 1m0s)
  -streamname string
        The stream name for this instance of Loki Canary to use in the log selector
        (default "stream")
  -streamvalue string
        The unique stream value for this instance of Loki Canary to use in the log selector
        (default "stdout")
  -tenant-id string
        Tenant ID to be set in X-Scope-OrgID header.
  -tls
        Does the Loki connection use TLS?
  -user string
        Loki user name
  -version
        Print this build's version information
  -wait duration
        Duration to wait for log entries before reporting them as lost (default 1m0s)
```