The client field is not reset to null after being closed in the shutdown method. Since the initialize method (lines 80-82) only creates a new client if the field is null, calling initialize again after a shutdown will result in the provider attempting to use a closed client, leading to errors. Setting the field to null ensures that a fresh client is created upon re-initialization.

    public void shutdown() {
        if (client != null) {
            try {
                client.close();
            } catch (Exception e) {
                log.warn("Error closing ParameterManagerClient", e);
            }
            client = null;
        }
        log.info("GcpParameterManagerProvider shut down");
    }

The client field is not reset to null after being closed in the shutdown method. Since the initialize method (lines 80-82) only creates a new client if the field is null, calling initialize again after a shutdown will result in the provider attempting to use a closed client. Resetting the field to null allows for proper re-initialization.

    public void shutdown() {
        if (client != null) {
            try {
                client.close();
            } catch (Exception e) {
                log.warn("Error closing SecretManagerServiceClient", e);
            }
            client = null;
        }
        log.info("GcpSecretManagerProvider shut down");
    }

The PR description mentions that the gcp-parameter-manager provider supports a configurable version (defaulting to "latest"), similar to the gcp-secret-manager provider. However, the GcpParameterManagerProviderOptions class is missing a field for this configuration, and the provider implementation (line 165 in GcpParameterManagerProvider.java) has the version hardcoded to "latest". Consider adding a parameterVersion field to this options class to align with the intended functionality and the Secret Manager implementation.

The evictOldest method performs a full scan of the ConcurrentHashMap ($O(N)$ complexity) to find the entry with the minimum expiry time. While acceptable for the default maxSize of 500, this will become a performance bottleneck if the cache size is increased or if evictions occur frequently under high load. Consider using a data structure that maintains order (like a LinkedHashMap with access order, though it requires external synchronization) or a dedicated caching library like Caffeine if more advanced eviction is needed.