pnoltes opened a new issue, #830:
URL: https://github.com/apache/celix/issues/830
### Description
ASF Celix bundles are currently distributed and loaded as ZIP files, which
requires a runtime dependency on `libzip`. This proposal details the concept of
a **Bundle Store** architecture designed to decouple the distribution format
from runtime execution. By adopting a Content-Addressable Storage (CAS) model
(aligned with the **OCI Registry as Storage (ORAS)** concept) bundles can be
provisioned via ZIP, TAR, or OCI layers, while moving the bundle runtime usage
to a directory-based system.
### Rationale
* **Removal of Runtime Overhead:** Transitioning to a directory-based store
eliminates the need for `libzip` and runtime decompression.
* **OCI Ecosystem Alignment:** Leveraging the ORAS concept for bundle
distribution and possible signing.
* **Security & Reliability:** Explicitly separates immutable bundle code
from application state.
### Storage Management: `celix-bnd-storage`
The management of the bundle store and the association of storage tiers is
handled by a new utility: **`celix-bnd-storage`**.
#### Configuration (`~/.config/celix/bnd-storage.json`)
This human-editable file defines the global environment settings:
* **Storage Roots:** Base paths for the **Bundle Store**, **Persistent
Storage**, and **Volatile Storage**.
* **Policy Settings:** Default garbage collection (GC) rules and retention
periods.
#### Instance (Bundle) State (`/var/run/celix/instances.d/` or
`~/.local/share/celix/state/instances.d/`)
To ensure concurrency safety and remove the usage of a state directory in
the CWD, a directory-based **Instance State** is introduced. Each active
framework instance maintains its own JSON entry named after its SHA-256 ID.
This registry tracks:
* **Instance Mapping:** Linkage between the **Framework Instance SHA-256**
and its assigned **Friendly Name**.
* **Process Tracking:** The current **Process ID (PID)** and start time.
### Framework Instance Identification
The framework transitions from random UUIDs to deterministic **SHA-256
Framework Instance IDs**.
1. **Identity Derivation:** If an instance ID is not explicitly provided,
the Celix launcher generates a SHA-256 hash based on:
* The absolute path of the application executable
* The absolute path of the current working directory (CWD).
2. **Naming Approach:** Instances are assigned "friendly names" (e.g.,
`focused_hawking`) mapped to the SHA-256 ID within the State Registry entries
(nice to have).
3. **Launcher Integration:** The launcher supports the `--instance_id`
argument to manually specify a SHA-256 ID. And optionally support a
`--instance_name` argument.
### Architecture: The 3-Tier Filesystem Model
The framework interacts with three distinct filesystem areas:
1. **Bundle Store (Immutable):**
* `blobs/sha256/`: Contains unpacked bundle content, indexed by the SHA-256
hash. If possible, these directories should be mounted or marked as
**read-only** to ensure integrity.
* `tags/<bundle_symbolic_name>/<bundle_version>`: A structure of symbolic
links, linking to unpacked bundle blob entries.
2. **Volatile Storage:**
* Located at `<volatile_root>/<instance_sha256>/`. Intended for `tmpfs`
storage.
3. **Persistent Storage:**
* Located at `<persistent_root>/<instance_sha256>/`. Reserved for long-term
state that survives restarts.
### Proposed API Changes
The `celix_bundle.h` and `celix_framework.h` interfaces are extended:
* **Immutable Resources:**
* `const char* celix_bundle_getBundleStorePath(const celix_bundle_t* bnd,
const char* path)`: Returns the absolute path to a file within the **Bundle
Store** for the specific bundle.
* **Instance Storage:**
* `char* celix_bundle_getPersistentStoragePath(const celix_bundle_t*
bnd)`: Returns the path to the persistent directory dedicated to the bundle for
the specific framework instance.
* `char* celix_bundle_getVolatileStoragePath(const celix_bundle_t* bnd)`:
Returns the path to the volatile directory for the current run.
* **Framework**
* `const char* celix_framework_getInstanceId(const celix_framework_t*
fw)`: Returns the framework instance id (SHA256).
* `const char* celix_framework_getName(const celix_framework_t* fw)`:
Returns the framework (human friendly) name.
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