# 51.2. Archive Module Callbacks

The archive callbacks define the actual archiving behavior of the module. The server will call them as required to process each individual WAL file.

## 51.2.1. Check Callback

The `check_configured_cb` callback is called to determine whether the module is fully configured and ready to accept WAL files (e.g., its configuration parameters are set to valid values). If no `check_configured_cb` is defined, the server always assumes the module is configured.

```
typedef bool (*ArchiveCheckConfiguredCB) (void);
```

If `true` is returned, the server will proceed with archiving the file by calling the `archive_file_cb` callback. If `false` is returned, archiving will not proceed, and the archiver will emit the following message to the server log:

```
WARNING:  archive_mode enabled, yet archiving is not configured
```

In the latter case, the server will periodically call this function, and archiving will proceed only when it returns `true`.

## 51.2.2. Archive Callback

The `archive_file_cb` callback is called to archive a single WAL file.

```
typedef bool (*ArchiveFileCB) (const char *file, const char *path);
```

If `true` is returned, the server proceeds as if the file was successfully archived, which may include recycling or removing the original WAL file. If `false` is returned, the server will keep the original WAL file and retry archiving later. *`file`* will contain just the file name of the WAL file to archive, while *`path`* contains the full path of the WAL file (including the file name).

## 51.2.3. Shutdown Callback

The `shutdown_cb` callback is called when the archiver process exits (e.g., after an error) or the value of [archive\_library](https://www.postgresql.org/docs/current/runtime-config-wal.html#GUC-ARCHIVE-LIBRARY) changes. If no `shutdown_cb` is defined, no special action is taken in these situations.

```
typedef void (*ArchiveShutdownCB) (void);
```