More context store docs

Author: knolleary

_includes/api-toc.html

@@ -32,6 +32,8 @@
         <ul>
             <li class="toctitle{% if page.url == "/docs/api/context/" %} active{% endif %}"><a href="/docs/api/context/">Context Store API</a>
             <li {% if page.url contains "/docs/api/context/methods" %}class="active"{% endif %}><a href="/docs/api/context/methods">Methods</a>
+            <li {% if page.url contains "/docs/api/context/store/memory" %}class="active"{% endif %}><a href="/docs/api/context/store/memory">Memory store</a>
+            <li {% if page.url contains "/docs/api/context/store/localfilesystem" %}class="active"{% endif %}><a href="/docs/api/context/store/localfilesystem">File store</a>
         </ul>
     </li>
     <li class="tocheader">

docs/api/context/index.md

@@ -9,10 +9,10 @@ title: Context Store API
 The Context Store API provides a pluggable way to configure where context data is
 stored.
 
-By default, Node-RED uses a memory-based implementation of this API. It also provides
-a file-based implementation.
+By default, Node-RED uses a [memory-based implementation](store/memory) of this API. It also provides
+a [file-based implementation](store/localfilesystem).
 
-The API functions are documented [here](methods/).
+To create a custom Context Store, a module should create that implements the [Store Module API](#store-module-api).
 
 ### Configuration
 

docs/api/context/store/localfilesystem.md

@@ -0,0 +1,66 @@
+---
+layout: docs
+toc: api-toc.html
+title: Local Filesystem Context Store
+---
+
+**New in 0.19**
+
+The Local Filesystem Context store holds context data in local files. By default it
+caches context data in memory, allowing both synchronous and asynchronous access.
+
+If the caching mode is disabled, the store only supports asynchronous access.
+
+### Configuration
+
+To create a file store, the following configuration can be used.
+
+{% highlight javascript %}
+contextStorage: {
+   default: {
+       module:"file",
+       config: {
+           // see below
+       }
+   }
+}
+{% endhighlight %}
+
+### Options
+
+The file store can take the following configuration options:
+
+Options         | Description
+----------------|------------------------------
+`dir`           | The directory to store the `base` directory in. Default: the user directory, `~/.node-red`
+`base`          | The base directory under which context data is stored. Default: `"context"`
+`cache`         | Whether to cache context in memory. Default: `true`
+`flushInterval` | If caching is enabled, the minimum interval between writes to storage, in seconds. Default: `30`
+
+The default configuration for a `file` context store is to use the directory `~/.node-red/context`, with caching
+enabled and writes to storage happening every 30 seconds.
+
+The `flushInterval` is provided to minimise wear on the underlying storage, such
+as on a Raspberry Pi's SD card. Note that if Node-RED is unexpectedly killed, any data
+that has not yet been flushed will be lost.
+
+### Implementation details
+
+This context store uses a separate file for each context scope. At the top level
+is a directory for each flow scope and one for the global scope. Within each
+flow scope directory is a file containing the flow scope, `flow.json` and a file
+for each node context.
+
+```
+   $HOME/.node-red/context
+     ├── global
+     │     └── global.json
+     ├── <id of Flow 1>
+     │     ├── flow.json
+     │     ├── <id of Node a>.json
+     │     └── <id of Node b>.json
+     └── <id of Flow 2>
+           ├── flow.json
+           ├── <id of Node x>.json
+           └── <id of Node y>.json
+```

docs/api/context/store/memory.md

@@ -0,0 +1,27 @@
+---
+layout: docs
+toc: api-toc.html
+title: Memory Context Store
+---
+
+**New in 0.19**
+
+The Memory Context store is the default store used by Node-RED. It holds all
+context data in memory and is wiped whenever Node-RED restarts. It provides both
+synchronous and asynchronous access.
+
+### Configuration
+
+To create a memory store, the following configuration can be used.
+
+{% highlight javascript %}
+contextStorage: {
+   default: {
+       module:"memory",
+   }
+}
+{% endhighlight %}
+
+### Options
+
+The memory store does not provide any configuration options.

docs/user-guide/context.md

@@ -63,7 +63,10 @@ contextStorage: {
 {% endhighlight %}
 
 Node-RED provides two built-in store modules: `memory` and `file`. It is also
-possible to create custom store plugins - full details are on the [api pages](../api/context/).
+possible to create custom store plugins.
+
+Full details on the built-in modules, and how to create custom modules, is
+available on the [api pages](../api/context/).
 
 Stores can provide either synchronous or asynchronous access. Synchronous access
 means a call to get data from the store returns immediately with the value. Asynchronous