Kubernetes Client Library for C

This is the official Kubernetes client library for the C programming language.

Building the library

# Clone the repo
git clone https://github.com/kubernetes-client/c
CLIENT_REPO_ROOT=${PWD}/c

# Install pre-requisites
sudo apt-get install libssl-dev libcurl4-openssl-dev uncrustify

# Build pre-requisite: libwebsockets
git clone https://libwebsockets.org/repo/libwebsockets --depth 1 --branch v4.2-stable
cd libwebsockets
mkdir build
cd build
cmake -DLWS_WITHOUT_TESTAPPS=ON -DLWS_WITHOUT_TEST_SERVER=ON-DLWS_WITHOUT_TEST_SERVER_EXTPOLL=ON \
      -DLWS_WITHOUT_TEST_PING=ON -DLWS_WITHOUT_TEST_CLIENT=ON -DCMAKE_C_FLAGS="-fpic" -DCMAKE_INSTALL_PREFIX=/usr/local ..
make
sudo make install

# Build pre-requisite: libyaml
git clone https://github.com/yaml/libyaml --depth 1 --branch release/0.2.5
cd libyaml
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=/usr/local -DBUILD_TESTING=OFF  -DBUILD_SHARED_LIBS=ON ..
make
sudo make install

# Move into the Kubernetes directory
cd ${CLIENT_REPO_ROOT}/kubernetes

# Build
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX=/usr/local ..
make
sudo make install

(Optional) Installing using vcpkg on Windows

If you want to install the C client using vcpkg, please refer to vcpkg.md

Building an example

cd ${CLIENT_REPO_ROOT}/examples/list_pod
make

Running the example

./list_pod_bin

Usage example

list all pods:

    char *basePath = NULL;
    sslConfig_t *sslConfig = NULL;
    list_t *apiKeys = NULL;
    int rc = load_kube_config(&basePath, &sslConfig, &apiKeys, NULL);/* NULL means loading configuration from $HOME/.kube/config */
    if (rc != 0) {
        printf("Cannot load kubernetes configuration.\n");
        return -1;
    }
    apiClient_t *apiClient = apiClient_create_with_base_path(basePath, sslConfig, apiKeys);
    if (!apiClient) {
        printf("Cannot create a kubernetes client.\n");
        return -1;
    }

    v1_pod_list_t *pod_list = NULL;
    pod_list = CoreV1API_listNamespacedPod(apiClient,
                                          "default",    /*namespace */
                                           NULL,    /* pretty */
                                           0,       /* allowWatchBookmarks */
                                           NULL,    /* continue */
                                           NULL,    /* fieldSelector */
                                           NULL,    /* labelSelector */
                                           0,       /* limit */
                                           NULL,    /* resourceVersion */
                                           NULL,    /* resourceVersionMatch */
                                           0,       /* timeoutSeconds */
                                           0        /* watch */
        );
    printf("return code=%ld\n", apiClient->response_code);
    if (pod_list) {
      ...
    }

    apiClient_free(apiClient);
    apiClient = NULL;
    free_client_config(basePath, sslConfig, apiKeys);
    basePath = NULL;
    sslConfig = NULL;
    apiKeys = NULL;
    apiClient_unsetupGlobalEnv();

list all pods in cluster:

    char *basePath = NULL;
    sslConfig_t *sslConfig = NULL;
    list_t *apiKeys = NULL;
    int rc = load_incluster_config(&basePath, &sslConfig, &apiKeys);
    if (rc != 0) {
        printf("Cannot load kubernetes configuration in cluster.\n");
        return -1;
    }
    apiClient_t *apiClient = apiClient_create_with_base_path(basePath, sslConfig, apiKeys);
    if (!apiClient) {
        printf("Cannot create a kubernetes client.\n");
        return -1;
    }

    v1_pod_list_t *pod_list = NULL;
    pod_list = CoreV1API_listNamespacedPod(apiClient,
                                          "default",    /*namespace */
                                           NULL,    /* pretty */
                                           0,       /* allowWatchBookmarks */
                                           NULL,    /* continue */
                                           NULL,    /* fieldSelector */
                                           NULL,    /* labelSelector */
                                           0,       /* limit */
                                           NULL,    /* resourceVersion */
                                           NULL,    /* resourceVersionMatch */
                                           0,       /* timeoutSeconds */
                                           0        /* watch */
        );
    printf("return code=%ld\n", apiClient->response_code);
    if (pod_list) {
      ...
    }

    apiClient_free(apiClient);
    apiClient = NULL;
    free_client_config(basePath, sslConfig, apiKeys);
    basePath = NULL;
    sslConfig = NULL;
    apiKeys = NULL;
    apiClient_unsetupGlobalEnv();

Aggregated APIs and CRD-based APIs

If you want to implement a client for aggregated APIs (such as the metrics server API apis/metrics.k8s.io ) or CRD-based APIs, use the generic client. See example.

Multi-threaded Usage

If the C client library is used in multi-threaded program, the following 2 actions are required:

After the program starts up, main thread must call the function apiClient_setupGlobalEnv() before any worker thread is created.
If the C client is no longer used, main thread must call the function apiClient_unsetupGlobalEnv() after all worker threads end.

Refer to the example for detail.

Documentation

All APIs and Models' documentation can be found at the Generated client's README file

Community, discussion, contribution, and support

Learn how to engage with the Kubernetes community on the community page.

You can reach the maintainers of this project at:

Code of conduct

Participation in the Kubernetes community is governed by the Kubernetes Code of Conduct.

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