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3 changes: 3 additions & 0 deletions linkerd.io/config/_default/menu.yaml
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- name: Linkerd edge
pageRef: /2-edge/
weight: 99
- name: Linkerd 2.17
pageRef: /2.17/
weight: 17
- name: Linkerd 2.16
pageRef: /2.16/
weight: 16
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2 changes: 1 addition & 1 deletion linkerd.io/config/_default/params.yaml
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twitter: Linkerd

# Latest major version of Linkerd
latestMajorVersion: "2.16"
latestMajorVersion: "2.17"
5 changes: 3 additions & 2 deletions linkerd.io/content/2-edge/features/egress.md
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---
title: Egress
description: Linkerd features capabilities to monitor and apply policies to egress traffic.
---

Linkerd features capabilities to monitor and apply policies to egress traffic.
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Related content:

* [Guide: Managing egress traffic]
({{< relref "../tasks/managing-egress-traffic" >}})
* [Guide: Managing egress traffic]({{< relref
"../tasks/managing-egress-traffic" >}})
* [EgressNetwork Reference]({{< relref "../reference/egress-network" >}})
1 change: 1 addition & 0 deletions linkerd.io/content/2-edge/reference/egress-network.md
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---
title: EgressNetwork
description: Reference guide to the EgressNetwork resource.
---

Linkerd's [egress functionality]({{< relref "../features/egress">}}) allows
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11 changes: 11 additions & 0 deletions linkerd.io/content/2.17/_index.md
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---
title: Docs
cascade:
type: docs

# Redirect
type: _default
layout: redirect
params:
redirect: ./overview
---
10 changes: 10 additions & 0 deletions linkerd.io/content/2.17/checks/index.md
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---
title: Checks

# Redirect
type: _default
layout: redirect
params:
unlisted: true
redirect: /2/tasks/troubleshooting/
---
21 changes: 21 additions & 0 deletions linkerd.io/content/2.17/common-errors/_index.md
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---
title: Common Errors
weight: 10
sitemap:
priority: 1.0
---

Linkerd is generally robust, but things can always go wrong! You'll find
information here about the most common things that cause people trouble.

## When in Doubt, Start With `linkerd check`

Whenever you see anything that looks unusual about your mesh, **always** start
with `linkerd check`. It will check a long series of things that have caused
trouble for others and make sure that your configuration is sane, and it will
point you to help for any problems it finds. It's hard to overstate how useful
this command is.

## Common Errors

{{< docs/section-toc >}}
18 changes: 18 additions & 0 deletions linkerd.io/content/2.17/common-errors/failfast.md
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---
title: Failfast
description: Failfast means that no endpoints are available.
---

If Linkerd reports that a given service is in the _failfast_ state, it
means that the proxy has determined that there are no available endpoints
for that service. In this situation there's no point in the proxy trying
to actually make a connection to the service - it already knows that it
can't talk to it - so it reports that the service is in failfast and
immediately returns an error from the proxy.

The error will be either a 503 or a 504; see below for more information,
but if you already know that the service is in failfast because you saw
it in the logs, that's the important part.

To get out of failfast, some endpoints for the service have to
become available.
11 changes: 11 additions & 0 deletions linkerd.io/content/2.17/common-errors/http-502.md
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---
title: HTTP 502 Errors
description: HTTP 502 means connection errors between proxies.
---

The Linkerd proxy will return a 502 error for connection errors between
proxies. Unfortunately it's fairly common to see an uptick in 502s when
first meshing a workload that hasn't previously been used with a mesh,
because the mesh surfaces errors that were previously invisible!

There's actually a whole page on [debugging 502s](../../tasks/debugging-502s/).
27 changes: 27 additions & 0 deletions linkerd.io/content/2.17/common-errors/http-503-504.md
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---
title: HTTP 503 and 504 Errors
description: HTTP 503 and 504 mean overloaded workloads.
---

503s and 504s show up when a Linkerd proxy is trying to make so many
requests to a workload that it gets overwhelmed.

When the workload next to a proxy makes a request, the proxy adds it
to an internal dispatch queue. When things are going smoothly, the
request is pulled from the queue and dispatched almost immediately.
If the queue gets too long, though (which can generally happen only
if the called service is slow to respond), the proxy will go into
_load-shedding_, where any new request gets an immediate 503. The
proxy can only get _out_ of load-shedding when the queue shrinks.

Failfast also plays a role here: if the proxy puts a service into
failfast while there are requests in the dispatch queue, all the
requests in the dispatch queue get an immediate 504 before the
proxy goes into load-shedding.

To get out of failfast, some endpoints for the service have to
become available.

To get out of load-shedding, the dispatch queue has to start
emptying, which implies that the service has to get more capacity
to process requests or that the incoming request rate has to drop.
36 changes: 36 additions & 0 deletions linkerd.io/content/2.17/common-errors/protocol-detection.md
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---
title: Protocol Detection Errors
description: Protocol detection errors indicate that Linkerd doesn't understand the
protocol in use.
---

Linkerd is capable of proxying all TCP traffic, including TLS connections,
WebSockets, and HTTP tunneling. In most cases where the client speaks first
when a new connection is made, Linkerd can detect the protocol in use,
allowing it to perform per-request routing and metrics.

If your proxy logs contain messages like `protocol detection timed out after
10s`, or you're experiencing 10-second delays when establishing connections,
you're probably running a situation where Linkerd cannot detect the protocol.
This is most common for protocols where the server speaks first, and the
client is waiting for information from the server. It may also occur with
non-HTTP protocols for which Linkerd doesn't yet understand the wire format of
a request.

You'll need to understand exactly what the situation is to fix this:

- A server-speaks-first protocol will probably need to be configured as a
`skip` or `opaque` port, as described in the [protocol detection
documentation](../../features/protocol-detection/#configuring-protocol-detection).

- If you're seeing transient protocol detection timeouts, this is more likely
to indicate a misbehaving workload.

- If you know the protocol is client-speaks-first but you're getting
consistent protocol detection timeouts, you'll probably need to fall back on
a `skip` or `opaque` port.

Note that marking ports as `skip` or `opaque` has ramifications beyond
protocol detection timeouts; see the [protocol detection
documentation](../../features/protocol-detection/#configuring-protocol-detection)
for more information.
14 changes: 14 additions & 0 deletions linkerd.io/content/2.17/features/_index.md
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---
title: Features
weight: 3
sitemap:
priority: 1.0
---

Linkerd offers many features, outlined below. For our walkthroughs and guides,
please see the [Linkerd task docs]({{< relref "../tasks" >}}). For a reference,
see the [Linkerd reference docs]({{< relref "../reference" >}}).

## Linkerd's features

{{< docs/section-toc >}}
62 changes: 62 additions & 0 deletions linkerd.io/content/2.17/features/access-logging.md
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---
title: HTTP Access Logging
description: Linkerd proxies can be configured to emit HTTP access logs.
---

Linkerd proxies can be configured to generate an HTTP access log that records
all HTTP requests that transit the proxy.

The `config.linkerd.io/access-log` annotation is used to enable proxy HTTP
access logging. Adding this annotation to a namespace or workload configures the
proxy injector to set an environment variable in the proxy container that
configures access logging.

HTTP access logging is disabled by default because it has a performance impact,
compared to proxies without access logging enabled. Enabling access logging may
increase tail latency and CPU consumption under load. The severity of
this performance cost may vary depending on the traffic being proxied, and may
be acceptable in some environments.

{{< note >}}
The proxy's HTTP access log is distinct from proxy debug logging, which is
configured separately. See the documentation on [modifying the proxy log
level](../../tasks/modifying-proxy-log-level/) for details on configuring the
proxy's debug logging.
{{< /note >}}

## Access Log Formats

The value of the `config.linkerd.io/access-log` annotation determines the format
of HTTP access log entries, and can be either "apache" or "json".

Setting the `config.linkerd.io/access-log: "apache"` annotation configures the
proxy to emit HTTP access logs in the [Apache Common Log
Format](https://en.wikipedia.org/wiki/Common_Log_Format). For example:

```text {class=disable-copy}
10.42.0.63:51160 traffic.booksapp.serviceaccount.identity.linkerd.cluster.local - [2022-08-23T20:28:20.071809491Z] "GET http://webapp:7000/ HTTP/2.0" 200
10.42.0.63:51160 traffic.booksapp.serviceaccount.identity.linkerd.cluster.local - [2022-08-23T20:28:20.187706137Z] "POST http://webapp:7000/authors HTTP/2.0" 303
10.42.0.63:51160 traffic.booksapp.serviceaccount.identity.linkerd.cluster.local - [2022-08-23T20:28:20.301798187Z] "GET http://webapp:7000/authors/104 HTTP/2.0" 200
10.42.0.63:51160 traffic.booksapp.serviceaccount.identity.linkerd.cluster.local - [2022-08-23T20:28:20.409177224Z] "POST http://webapp:7000/books HTTP/2.0" 303
10.42.0.1:43682 - - [2022-08-23T20:28:23.049685223Z] "GET /ping HTTP/1.1" 200
```

Setting the `config.linkerd.io/access-log: json` annotation configures the proxy
to emit access logs in a JSON format. For example:

```json {class=disable-copy}
{"client.addr":"10.42.0.70:32996","client.id":"traffic.booksapp.serviceaccount.identity.linkerd.cluster.local","host":"webapp:7000","method":"GET","processing_ns":"39826","request_bytes":"","response_bytes":"19627","status":200,"timestamp":"2022-08-23T20:33:42.321746212Z","total_ns":"14441135","trace_id":"","uri":"http://webapp:7000/","user_agent":"Go-http-client/1.1","version":"HTTP/2.0"}
{"client.addr":"10.42.0.70:32996","client.id":"traffic.booksapp.serviceaccount.identity.linkerd.cluster.local","host":"webapp:7000","method":"POST","processing_ns":"30036","request_bytes":"33","response_bytes":"0","status":303,"timestamp":"2022-08-23T20:33:42.436964052Z","total_ns":"14122403","trace_id":"","uri":"http://webapp:7000/authors","user_agent":"Go-http-client/1.1","version":"HTTP/2.0"}
{"client.addr":"10.42.0.70:32996","client.id":"traffic.booksapp.serviceaccount.identity.linkerd.cluster.local","host":"webapp:7000","method":"GET","processing_ns":"38664","request_bytes":"","response_bytes":"2350","status":200,"timestamp":"2022-08-23T20:33:42.551768300Z","total_ns":"6998222","trace_id":"","uri":"http://webapp:7000/authors/105","user_agent":"Go-http-client/1.1","version":"HTTP/2.0"}
{"client.addr":"10.42.0.70:32996","client.id":"traffic.booksapp.serviceaccount.identity.linkerd.cluster.local","host":"webapp:7000","method":"POST","processing_ns":"42492","request_bytes":"46","response_bytes":"0","status":303,"timestamp":"2022-08-23T20:33:42.659401621Z","total_ns":"9274163","trace_id":"","uri":"http://webapp:7000/books","user_agent":"Go-http-client/1.1","version":"HTTP/2.0"}
{"client.addr":"10.42.0.1:56300","client.id":"-","host":"10.42.0.69:7000","method":"GET","processing_ns":"35848","request_bytes":"","response_bytes":"4","status":200,"timestamp":"2022-08-23T20:33:49.254262428Z","total_ns":"1416066","trace_id":"","uri":"/ping","user_agent":"kube-probe/1.24","version":"HTTP/1.1"}
```

## Consuming Access Logs

The HTTP access log is written to the proxy container's `stderr` stream, while
the proxy's standard debug logging is written to the proxy container's `stdout`
stream. Currently, the `kubectl logs` command will always output both the
container's `stdout` and `stderr` streams. However, [KEP
3289](https://github.com/kubernetes/enhancements/pull/3289) will add support for
separating a container's `stdout` or `stderr` in the `kubectl logs` command.
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