docs(stage): add docker and cri (#1091)

Signed-off-by: Xiang Dai <764524258@qq.com>

docs/clients/promtail/pipelines.md

@@ -188,6 +188,8 @@ given log entry.
 
 Parsing stages:
 
+  * [docker](./stages/docker.md): Extract data by parsing the log line using the standard Docker format.
+  * [cri](./stages/cri.md): Extract data by parsing the log line using the standard CRI format.
   * [regex](./stages/regex.md): Extract data using a regular expression.
   * [json](./stages/json.md): Extract data by parsing the log line as JSON.
 

docs/clients/promtail/stages/cri.md

@@ -0,0 +1,46 @@
+# `cri` stage
+
+The `cri` stage is a parsing stage that reads the log line using the standard CRI logging format.
+
+## Schema
+
+```yaml
+cri: {}
+```
+
+Unlike most stages, the `cri` stage provides no configuration options and only
+supports the specific CRI log format. CRI specifies log lines log lines as
+space-delimited values with the following components:
+
+1. `time`: The timestamp string of the log
+2. `stream`: Either stdout or stderr
+3. `log`: The contents of the log line
+
+No whitespace is permitted between the components. In the following exmaple,
+only the first log line can be properly formatted using the `cri` stage:
+
+```
+"2019-01-01T01:00:00.000000001Z stderr P test\ngood"
+"2019-01-01 T01:00:00.000000001Z stderr testgood"
+"2019-01-01T01:00:00.000000001Z testgood"
+```
+
+## Examples
+
+For the given pipeline:
+
+```yaml
+- cri: {}
+```
+
+Given the following log line:
+
+```
+"2019-04-30T02:12:41.8443515Z stdout xx message"
+```
+
+The following key-value pairs would be created in the set of extracted data:
+
+- `output`: `message`
+- `stream`: `stdout`
+- `timestamp`: `2019-04-30T02:12:41.8443515`

docs/clients/promtail/stages/docker.md

@@ -0,0 +1,38 @@
+# `docker` stage
+
+The `docker` stage is a parsing stage that reads log lines in the standard
+format of Docker log files.
+
+## Schema
+
+```yaml
+docker: {}
+```
+
+Unlike most stages, the `docker` stage provides no configuration options and
+only supports the specific Docker log format. Each log line from Docker is
+written as JSON with the following keys:
+
+1. `log`: The content of log line
+2. `stream`: Either `stdout` or `stderr`
+3. `time`: The timestamp string of the log line
+
+## Examples
+
+For the given pipeline:
+
+```yaml
+- docker: {}
+```
+
+Given the following log line:
+
+```
+{"log":"log message\n","stream":"stderr","time":"2019-04-30T02:12:41.8443515Z"}
+```
+
+The following key-value pairs would be created in the set of extracted data:
+
+- `output`: `log message\n`
+- `stream`: `stderr`
+- `timestamp`: `2019-04-30T02:12:41.8443515`