---
name: "cpg_initialize"
section: "3"
platform: "linux"
package: "libcpg-dev"
version: "3.1.9-2+deb13u1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/cpg_initialize"
---

# cpg\_initialize(3)

Create a new connection to the CPG service

## NAME

cpg\_initialize - Create a new connection to the CPG service

## SYNOPSIS

**#include \<corosync/cpg.h\>**

**int cpg\_initialize(cpg\_handle\_t \****handle***, cpg\_callbacks\_t \****callbacks***);**

## DESCRIPTION

The **cpg\_initialize** function is used to initialize a connection to the closed process groups API. This function is deprecated and **cpg\_model\_initialize** should be used in newly written code.

Each application may have several connections to the CPG API.  Each application uses the *handle* argument to uniquely identify the connection.  The *handle* argument is then used in other function calls to identify the connection to be used for communication with the CPG service.

Every time an CPG event occurs within the joined group, one of the callbacks specified by the argument *callbacks* is called.  The callback functions are described by the following type definitions:

-

  ```
  typedef void (*cpg_deliver_fn_t) (
          cpg_handle_t handle,
          const struct cpg_name *group_name,
          uint32_t nodeid,
          uint32_t pid,
          const void *msg,
          size_t msg_len);
  typedef void (*cpg_confchg_fn_t) (
          cpg_handle_t handle,
          const struct cpg_name *group_name,
          const struct cpg_address *member_list, size_t member_list_entries,
          const struct cpg_address *left_list, size_t left_list_entries,
          const struct cpg_address *joined_list, size_t joined_list_entries);
  ```

-

  The *callbacks* argument is of the type:

-

  ```

  ```

  typedef struct {\
           cpg\_deliver\_fn\_t cpg\_deliver\_fn;\
           cpg\_confchg\_fn\_t cpg\_confchg\_fn; } cpg\_callbacks\_t;

-

  When a configuration change occurs or a message is to be delivered one of the callbacks is called from the **cpg\_dispatch()** function.  If a configuration change occurs, *cpg\_confchg\_fn* is called.  If a delivery of a message occurs, *cpg\_deliver\_fn* is called.

The *cpg\_address* structure is defined

-

  ```

  ```

  struct cpg\_address {\
           unsigned int nodeid;\
           unsigned int pid;\
           unsigned int reason; };

-

  where nodeid is a 32 bit unique node identifier, pid is the process ID of the process that has joined/left the group or sent the message, and reason is an integer code indicating why the node joined/left the group (this value is not set for the member\_list items).

-

  ```

  ```

  CPG\_REASON\_JOIN      - the process joined a group using cpg\_join(). CPG\_REASON\_LEAVE     - the process left a group using cpg\_leave() CPG\_REASON\_NODEDOWN  - the process left a group because the node left the cluster. CPG\_REASON\_NODEUP    - the process joined a group because it was already a member of a group on a node that has just joined the cluster CPG\_REASON\_PROCDOWN  - the process left a group without calling cpg\_leave() CPG\_REASON\_UNDEFINED - a special value used for the member\_list items

-

  ## RETURN VALUE

This call returns the CS\_OK value if successful, otherwise an error is returned.

## ERRORS

The errors are undocumented.

## SEE ALSO

[**cpg\_overview**(3)](/cpg_overview/3.md), [**cpg\_initialize**(3)](/cpg_initialize/3.md), [**cpg\_finalize**(3)](/cpg_finalize/3.md), [**cpg\_fd\_get**(3)](/cpg_fd_get/3.md), [**cpg\_dispatch**(3)](/cpg_dispatch/3.md), [**cpg\_join**(3)](/cpg_join/3.md), [**cpg\_leave**(3)](/cpg_leave/3.md), [**cpg\_mcast\_joined**(3)](/cpg_mcast_joined/3.md), [**cpg\_membership\_get**(3)](/cpg_membership_get/3.md) [**cpg\_zcb\_alloc**(3)](/cpg_zcb_alloc/3.md) [**cpg\_zcb\_free**(3)](/cpg_zcb_free/3.md) [**cpg\_zcb\_mcast\_joined**(3)](/cpg_zcb_mcast_joined/3.md) [**cpg\_context\_get**(3)](/cpg_context_get/3.md) [**cpg\_context\_set**(3)](/cpg_context_set/3.md) [**cpg\_local\_get**(3)](/cpg_local_get/3.md) [**cpg\_model\_initialize**(3)](/cpg_model_initialize/3.md)

**CS\_ERR\_TRY\_AGAIN** Resource temporarily unavailable

**CS\_ERR\_INVALID\_PARAM** Invalid argument

**CS\_ERR\_ACCESS** Permission denied

**CS\_ERR\_LIBRARY** The connection failed

**CS\_ERR\_INTERRUPT** System call interrupted by a signal

**CS\_ERR\_NOT\_SUPPORTED** The requested protocol/functionality not supported

**CS\_ERR\_MESSAGE\_ERROR** Incorrect auth message received

**CS\_ERR\_NO\_MEMORY** Not enough memory to complete the requested task