From 0666812c55faa6bfd8e17e693f125a447331009b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Carlos=20P=C3=A9rez-Aradros=20Herce?= <exekias@gmail.com>
Date: Fri, 15 Jun 2018 09:43:53 +0200
Subject: [PATCH] Cherry-pick #7165 to 6.3: Negotiate Docker API version
 (#7177)

* Negotiate Docker API version (#7165)

New Docker versions have deprecated our hardcoded client API version
(1.22), this change uses an API version negotiation mechanism to ensure
compatibility.

We should still upgrade to a newer client in the future, let's keep an
eye on https://github.com/moby/moby/issues/33989 and do it once we have
something we can vendor.

(cherry picked from commit 253bc71cbc7c8d76e8c8a3cd419b2d65ce2b7998)

* Update CHANGELOG.asciidoc
---
 CHANGELOG.asciidoc                 |  2 ++
 libbeat/common/docker/client.go    | 44 ++++++++++++++++++++++++++++++
 libbeat/common/docker/watcher.go   |  6 ++--
 metricbeat/module/docker/docker.go |  3 +-
 4 files changed, 50 insertions(+), 5 deletions(-)
 create mode 100644 libbeat/common/docker/client.go

diff --git a/CHANGELOG.asciidoc b/CHANGELOG.asciidoc
index d3ba9154638e..0992a4e0d17f 100644
--- a/CHANGELOG.asciidoc
+++ b/CHANGELOG.asciidoc
@@ -29,6 +29,8 @@ https://github.com/elastic/beats/compare/v6.3.0...6.3[Check the HEAD diff]
 
 *Affecting all Beats*
 
+- Negotiate Docker API version from our client instead of using a hardcoded one. {pull}7165[7165]
+
 *Auditbeat*
 
 *Filebeat*
diff --git a/libbeat/common/docker/client.go b/libbeat/common/docker/client.go
new file mode 100644
index 000000000000..965fbb442c35
--- /dev/null
+++ b/libbeat/common/docker/client.go
@@ -0,0 +1,44 @@
+package docker
+
+import (
+	"net/http"
+
+	"github.com/elastic/beats/libbeat/logp"
+
+	"github.com/docker/docker/api"
+	"github.com/docker/docker/api/types/versions"
+	"github.com/docker/docker/client"
+	"golang.org/x/net/context"
+)
+
+// Select Docker API version
+const dockerAPIVersion = api.DefaultVersion
+
+// NewClient builds and returns a new Docker client
+// It uses version 1.26 by default, and negotiates it with the server so it is downgraded if 1.26 is too high
+func NewClient(host string, httpClient *http.Client, httpHeaders map[string]string) (*client.Client, error) {
+	c, err := client.NewClient(host, dockerAPIVersion, httpClient, nil)
+	if err != nil {
+		return c, err
+	}
+
+	logp.Debug("docker", "Negotiating client version")
+	ping, err := c.Ping(context.Background())
+	if err != nil {
+		logp.Debug("docker", "Failed to perform ping: %s", err)
+	}
+
+	// try the latest version before versioning headers existed
+	if ping.APIVersion == "" {
+		ping.APIVersion = "1.24"
+	}
+
+	// if server version is lower than the client version, downgrade
+	if versions.LessThan(ping.APIVersion, dockerAPIVersion) {
+		c.UpdateClientVersion(ping.APIVersion)
+	}
+
+	logp.Debug("docker", "Client version set to %s", c.ClientVersion())
+
+	return c, nil
+}
diff --git a/libbeat/common/docker/watcher.go b/libbeat/common/docker/watcher.go
index 02c4a0cb11cc..5c2e03fea4cc 100644
--- a/libbeat/common/docker/watcher.go
+++ b/libbeat/common/docker/watcher.go
@@ -9,7 +9,6 @@ import (
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/events"
 	"github.com/docker/docker/api/types/filters"
-	"github.com/docker/docker/client"
 	"github.com/docker/go-connections/tlsconfig"
 	"golang.org/x/net/context"
 
@@ -19,8 +18,7 @@ import (
 
 // Select Docker API version
 const (
-	dockerAPIVersion = "1.22"
-	shortIDLen       = 12
+	shortIDLen = 12
 )
 
 // Watcher reads docker events and keeps a list of known containers
@@ -106,7 +104,7 @@ func NewWatcher(host string, tls *TLSConfig, storeShortID bool) (Watcher, error)
 		}
 	}
 
-	client, err := client.NewClient(host, dockerAPIVersion, httpClient, nil)
+	client, err := NewClient(host, httpClient, nil)
 	if err != nil {
 		return nil, err
 	}
diff --git a/metricbeat/module/docker/docker.go b/metricbeat/module/docker/docker.go
index 1023409419cb..02408c365430 100644
--- a/metricbeat/module/docker/docker.go
+++ b/metricbeat/module/docker/docker.go
@@ -11,6 +11,7 @@ import (
 	"github.com/docker/docker/client"
 	"github.com/docker/go-connections/tlsconfig"
 
+	"github.com/elastic/beats/libbeat/common/docker"
 	"github.com/elastic/beats/metricbeat/mb"
 	"github.com/elastic/beats/metricbeat/mb/parse"
 )
@@ -67,7 +68,7 @@ func NewDockerClient(endpoint string, config Config) (*client.Client, error) {
 		}
 	}
 
-	client, err := client.NewClient(endpoint, dockerAPIVersion, httpClient, nil)
+	client, err := docker.NewClient(endpoint, httpClient, nil)
 	if err != nil {
 		return nil, err
 	}