Move code for backend startup to separate file

This is code that runs in the backend process after forking, rather
than postmaster. Move it out of postmaster.c for clarity.

Reviewed-by: Tristan Partin, Andres Freund
Discussion: https://www.postgresql.org/message-id/7a59b073-5b5b-151e-7ed3-8b01ff7ce9ef@iki.fi

1 files changed, 41 insertions, 0 deletions

diff --git a/src/include/tcop/backend_startup.h b/src/include/tcop/backend_startup.h
new file mode 100644
index 00000000000..d29eaed1e97
--- /dev/null
+++ b/src/include/tcop/backend_startup.h
@@ -0,0 +1,41 @@
+/*-------------------------------------------------------------------------
+ *
+ * backend_startup.h
+ *	  prototypes for backend_startup.c.
+ *
+ *
+ * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/tcop/backend_startup.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef BACKEND_STARTUP_H
+#define BACKEND_STARTUP_H
+
+/*
+ * CAC_state is passed from postmaster to the backend process, to indicate
+ * whether the connection should be accepted, or if the process should just
+ * send an error to the client and close the connection.  Note that the
+ * connection can fail for various reasons even if postmaster passed CAC_OK.
+ */
+typedef enum CAC_state
+{
+	CAC_OK,
+	CAC_STARTUP,
+	CAC_SHUTDOWN,
+	CAC_RECOVERY,
+	CAC_NOTCONSISTENT,
+	CAC_TOOMANY,
+} CAC_state;
+
+/* Information passed from postmaster to backend process in 'startup_data' */
+typedef struct BackendStartupData
+{
+	CAC_state	canAcceptConnections;
+} BackendStartupData;
+
+extern void BackendMain(char *startup_data, size_t startup_data_len) pg_attribute_noreturn();
+
+#endif							/* BACKEND_STARTUP_H */