> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/server-programming/archive-modules/archive-module-callbacks.md).

# 49.2. Archive Module Callbacks \#

[49.2.1. Startup Callback](#ARCHIVE-MODULE-STARTUP)

[49.2.2. Check Callback](#ARCHIVE-MODULE-CHECK)

[49.2.3. Archive Callback](#ARCHIVE-MODULE-ARCHIVE)

[49.2.4. Shutdown Callback](#ARCHIVE-MODULE-SHUTDOWN)

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

## 49.2.1. Startup Callback [#](#ARCHIVE-MODULE-STARTUP)

The `startup_cb` callback is called shortly after the module is loaded. This callback can be used to perform any additional initialization required. If the archive module has any state, it can use `state->private_data` to store it.

```

typedef void (*ArchiveStartupCB) (ArchiveModuleState *state);
```

## 49.2.2. Check Callback [#](#ARCHIVE-MODULE-CHECK)

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) (ArchiveModuleState *state);
```

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`.

## Note

When returning `false`, it may be useful to append some additional information to the generic warning message. To do that, provide a message to the `arch_module_check_errdetail` macro before returning `false`. Like `errdetail()`, this macro accepts a format string followed by an optional list of arguments. The resulting string will be emitted as the `DETAIL` line of the warning message.

## 49.2.3. Archive Callback [#](#ARCHIVE-MODULE-ARCHIVE)

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

```

typedef bool (*ArchiveFileCB) (ArchiveModuleState *state, 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 or an error is thrown, 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).

## Note

The `archive_file_cb` callback is called in a short-lived memory context that will be reset between invocations. If you need longer-lived storage, create a memory context in the module's `startup_cb` callback.

## 49.2.4. Shutdown Callback [#](#ARCHIVE-MODULE-SHUTDOWN)

The `shutdown_cb` callback is called when the archiver process exits (e.g., after an error) or the value of [archive\_library](/server-administration/runtime-config/runtime-config-wal.md#GUC-ARCHIVE-LIBRARY) changes. If no `shutdown_cb` is defined, no special action is taken in these situations. If the archive module has any state, this callback should free it to avoid leaks.

```

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

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/archive-module-callbacks.html)（英文原文，待翻譯）


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