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Node Cache and Session Reuse

Overview

The ESP RainMaker CLI includes an optional caching layer that dramatically improves performance for local control operations. When enabled, the cache stores node details, configuration, POP (Proof of Possession), local control capability, and session crypto state on disk. This eliminates redundant cloud API calls, enables session reuse across CLI invocations, and auto-discovers nodes that support Security 0 local control.

Cache is disabled by default and must be explicitly enabled.

What Gets Cached

File Description TTL
node_details.json Full node details from cloud API 1 hour
node_config.json Node configuration 1 hour
local_control_info.json POP, security version, transport, port 1 hour
local_control_capability.json Empirically discovered sec0/sec1 support 24 hours
session.json AES-CTR crypto state, resolved IP, cookie 7 days

Enabling Cache

Cache can be enabled at multiple levels:

Profile Level

Enable cache when creating a new profile:

esp-rainmaker-cli profile add my-profile --base-url https://api.example.com/ --cache

Enable cache on an existing profile:

esp-rainmaker-cli cache enable

Disable cache on the current profile:

esp-rainmaker-cli cache disable

Environment Variable

Override the profile setting for all commands in the current shell:

# Enable cache regardless of profile setting
export RM_NODE_CACHE=1

# Disable cache regardless of profile setting
export RM_NODE_CACHE=0

Per-Command Override

Skip cache for a single command using --no-cache:

esp-rainmaker-cli getparams <nodeid> --local --no-cache

Resolution Order

The cache-enabled decision follows this priority (highest to lowest):

  1. --no-cache flag (always wins)
  2. RM_NODE_CACHE environment variable
  3. Profile configuration (cache enable / profile add --cache)
  4. Default: disabled

Cache Management Commands

Show Cache Contents

# Show all cached nodes for the current profile/user
esp-rainmaker-cli cache show

# Show cache for a specific node
esp-rainmaker-cli cache show --nodeid <nodeid>

Clear Cache

# Clear all cached data for the current profile/user
esp-rainmaker-cli cache clear

# Clear cache for a specific node only
esp-rainmaker-cli cache clear --nodeid <nodeid>

Enable/Disable

esp-rainmaker-cli cache enable
esp-rainmaker-cli cache disable

How Each Command Uses Cache

Commands That Populate Cache

Command Caches
getnodedetails node_details, local_control_info (POP)
getnodeconfig node_config
getnodeconfig --local node_config
getparams (cloud) local_control_info (POP)
getparams --local local_control_info (POP), session, capability
setparams --local session, capability

Commands That Read From Cache

Command Reads
getparams --local POP (from local_control_info or capability), session (for reuse)
setparams --local POP, session
getnodeconfig --local POP, session
getparams --auto POP, session, capability
setparams --auto POP, session, capability
getnodeconfig --auto POP, session, capability

Session Reuse

Session reuse is the most impactful optimization. Without it, every --local command performs a full X25519 key exchange handshake. With session reuse, the saved crypto state is restored from disk and a lightweight probe verifies the session is alive.

How It Works

  1. After a successful local control operation, the CLI saves the session crypto state (shared key, nonce, AES-CTR counter offset, HTTP cookie) and the resolved IP address to disk.
  2. On the next invocation, the CLI loads the saved state, reconstructs the AES-CTR cipher, connects directly to the saved IP (skipping mDNS resolution), and sends a lightweight probe to verify the session.
  3. If the probe succeeds, the operation proceeds immediately -- no handshake, no mDNS.
  4. If the probe fails (device rebooted, IP changed), the CLI automatically falls back to a fresh session establishment.

Performance Impact

Scenario Without Cache With Cache
getparams --local (first time) ~10s ~10s (mDNS + handshake)
getparams --local (subsequent) ~10s < 1s (cached IP + session)
setparams --local (subsequent) ~10s < 1s
Cloud getparams (reference) ~1.5s ~1.5s

What Triggers a Fresh Session

  • Device reboot: Session probe fails, fresh handshake is performed automatically.
  • Device IP change: TCP connection to cached IP fails (3-second timeout), falls back to mDNS resolution.
  • cache clear: Manually removes saved sessions.
  • 7-day TTL expiry: Sessions unused for 7 days are considered expired.

In all cases, the fallback is automatic and transparent.

Capability Discovery

For nodes that support local control with Security 0 but do not advertise a "Local Control" service in their cloud configuration (no POP field), the CLI can empirically discover this capability:

  1. When --local is used with cache enabled, no POP is available, and no cached capability exists, the CLI enters discovery mode.
  2. It first attempts a Security 0 connection (no POP required). If the device responds, it records sec_ver=0, pop_required=false.
  3. If Security 0 fails and a POP is available, it tries Security 1.
  4. The discovered capability is cached in local_control_capability.json (24-hour TTL), so subsequent commands skip the probe entirely.

This means you can use --local on Security 0 nodes without needing to specify --sec_ver 0 manually, as long as cache is enabled.

Storage Layout

~/.espressif/rainmaker/node_cache/
└── <profile_name>/
    └── <user_id>/
        ├── <nodeid_1>/
        │   ├── node_details.json
        │   ├── node_config.json
        │   ├── local_control_info.json
        │   ├── local_control_capability.json
        │   ├── session.json
        │   └── cache_meta.json
        └── <nodeid_2>/
            └── ...

Each node has its own directory. Cache is scoped by profile and user ID, so switching users or profiles never mixes data.

Custom Cache Directory

By default, cache is stored under ~/.espressif/rainmaker/node_cache/. You can override this with an environment variable:

export RM_NODE_CACHE_DIR=/path/to/custom/cache

This is useful for CI/CD pipelines or containerized environments where ~/.espressif may not be appropriate.

Environment Variables Summary

Variable Values Description
RM_NODE_CACHE 0 or 1 Override profile cache setting
RM_NODE_CACHE_DIR path Override cache storage location

Troubleshooting

Session resume is slow or failing

Clear the session cache to force a fresh connection:

esp-rainmaker-cli cache clear --nodeid <nodeid>

Stale data after firmware update

If a device's configuration changed after a firmware update, clear its cache:

esp-rainmaker-cli cache clear --nodeid <nodeid>

Cache is enabled but not being used

Check the resolution order:

  1. Is --no-cache being passed?
  2. Is RM_NODE_CACHE=0 set in the environment?
  3. Run esp-rainmaker-cli cache show to verify cache is active.

Debug logging

Use --debug to see cache-related log messages:

esp-rainmaker-cli getparams <nodeid> --local --debug

Look for messages like:

  • Using cached POP for node ...
  • Attempting session resume to ...
  • Session resumed for node ...
  • Saved session with resolved IP ...