astreamer_inject.c

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/*-------------------------------------------------------------------------
 *
 * astreamer_inject.c
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *        src/bin/pg_basebackup/astreamer_inject.c
 *-------------------------------------------------------------------------
 */
 
#include "postgres_fe.h"
 
#include "astreamer_inject.h"
#include "common/file_perm.h"
#include "common/logging.h"
 
typedef struct astreamer_recovery_injector
{
    astreamer   base;
    bool        skip_file;
    bool        is_recovery_guc_supported;
    bool        is_postgresql_auto_conf;
    bool        found_postgresql_auto_conf;
    PQExpBuffer recoveryconfcontents;
    astreamer_member member;
} astreamer_recovery_injector;
 
static void astreamer_recovery_injector_content(astreamer *streamer,
                                                astreamer_member *member,
                                                const char *data, int len,
                                                astreamer_archive_context context);
static void astreamer_recovery_injector_finalize(astreamer *streamer);
static void astreamer_recovery_injector_free(astreamer *streamer);
 
static const astreamer_ops astreamer_recovery_injector_ops = {
    .content = astreamer_recovery_injector_content,
    .finalize = astreamer_recovery_injector_finalize,
    .free = astreamer_recovery_injector_free
};
 
/*
 * Create a astreamer that can edit recoverydata into an archive stream.
 *
 * The input should be a series of typed chunks (not ASTREAMER_UNKNOWN) as
 * per the conventions described in astreamer.h; the chunks forwarded to
 * the next astreamer will be similarly typed, but the
 * ASTREAMER_MEMBER_HEADER chunks may be zero-length in cases where we've
 * edited the archive stream.
 *
 * Our goal is to do one of the following three things with the content passed
 * via recoveryconfcontents: (1) if is_recovery_guc_supported is false, then
 * put the content into recovery.conf, replacing any existing archive member
 * by that name; (2) if is_recovery_guc_supported is true and
 * postgresql.auto.conf exists in the archive, then append the content
 * provided to the existing file; and (3) if is_recovery_guc_supported is
 * true but postgresql.auto.conf does not exist in the archive, then create
 * it with the specified content.
 *
 * In addition, if is_recovery_guc_supported is true, then we create a
 * zero-length standby.signal file, dropping any file with that name from
 * the archive.
 */
astreamer *
astreamer_recovery_injector_new(astreamer *next,
                                bool is_recovery_guc_supported,
                                PQExpBuffer recoveryconfcontents)
{
    astreamer_recovery_injector *streamer;
 
    streamer = palloc0(sizeof(astreamer_recovery_injector));
    *((const astreamer_ops **) &streamer->base.bbs_ops) =
        &astreamer_recovery_injector_ops;
    streamer->base.bbs_next = next;
    streamer->is_recovery_guc_supported = is_recovery_guc_supported;
    streamer->recoveryconfcontents = recoveryconfcontents;
 
    return &streamer->base;
}
 
/*
 * Handle each chunk of tar content while injecting recovery configuration.
 */
static void
astreamer_recovery_injector_content(astreamer *streamer,
                                    astreamer_member *member,
                                    const char *data, int len,
                                    astreamer_archive_context context)
{
    astreamer_recovery_injector *mystreamer;
 
    mystreamer = (astreamer_recovery_injector *) streamer;
    Assert(member != NULL || context == ASTREAMER_ARCHIVE_TRAILER);
 
    switch (context)
    {
        case ASTREAMER_MEMBER_HEADER:
            /* Must copy provided data so we have the option to modify it. */
            memcpy(&mystreamer->member, member, sizeof(astreamer_member));
 
            /*
             * On v12+, skip standby.signal and edit postgresql.auto.conf; on
             * older versions, skip recovery.conf.
             */
            if (mystreamer->is_recovery_guc_supported)
            {
                mystreamer->skip_file =
                    (strcmp(member->pathname, "standby.signal") == 0);
                mystreamer->is_postgresql_auto_conf =
                    (strcmp(member->pathname, "postgresql.auto.conf") == 0);
                if (mystreamer->is_postgresql_auto_conf)
                {
                    /* Remember we saw it so we don't add it again. */
                    mystreamer->found_postgresql_auto_conf = true;
 
                    /* Increment length by data to be injected. */
                    mystreamer->member.size +=
                        mystreamer->recoveryconfcontents->len;
 
                    /*
                     * Zap data and len because the archive header is no
                     * longer valid; some subsequent astreamer must regenerate
                     * it if it's necessary.
                     */
                    data = NULL;
                    len = 0;
                }
            }
            else
                mystreamer->skip_file =
                    (strcmp(member->pathname, "recovery.conf") == 0);
 
            /* Do not forward if the file is to be skipped. */
            if (mystreamer->skip_file)
                return;
            break;
 
        case ASTREAMER_MEMBER_CONTENTS:
            /* Do not forward if the file is to be skipped. */
            if (mystreamer->skip_file)
                return;
            break;
 
        case ASTREAMER_MEMBER_TRAILER:
            /* Do not forward it the file is to be skipped. */
            if (mystreamer->skip_file)
                return;
 
            /* Append provided content to whatever we already sent. */
            if (mystreamer->is_postgresql_auto_conf)
                astreamer_content(mystreamer->base.bbs_next, member,
                                  mystreamer->recoveryconfcontents->data,
                                  mystreamer->recoveryconfcontents->len,
                                  ASTREAMER_MEMBER_CONTENTS);
            break;
 
        case ASTREAMER_ARCHIVE_TRAILER:
            if (mystreamer->is_recovery_guc_supported)
            {
                /*
                 * If we didn't already find (and thus modify)
                 * postgresql.auto.conf, inject it as an additional archive
                 * member now.
                 */
                if (!mystreamer->found_postgresql_auto_conf)
                    astreamer_inject_file(mystreamer->base.bbs_next,
                                          "postgresql.auto.conf",
                                          mystreamer->recoveryconfcontents->data,
                                          mystreamer->recoveryconfcontents->len);
 
                /* Inject empty standby.signal file. */
                astreamer_inject_file(mystreamer->base.bbs_next,
                                      "standby.signal", "", 0);
            }
            else
            {
                /* Inject recovery.conf file with specified contents. */
                astreamer_inject_file(mystreamer->base.bbs_next,
                                      "recovery.conf",
                                      mystreamer->recoveryconfcontents->data,
                                      mystreamer->recoveryconfcontents->len);
            }
 
            /* Nothing to do here. */
            break;
 
        default:
            /* Shouldn't happen. */
            pg_fatal("unexpected state while injecting recovery settings");
    }
 
    astreamer_content(mystreamer->base.bbs_next, &mystreamer->member,
                      data, len, context);
}
 
/*
 * End-of-stream processing for this astreamer.
 */
static void
astreamer_recovery_injector_finalize(astreamer *streamer)
{
    astreamer_finalize(streamer->bbs_next);
}
 
/*
 * Free memory associated with this astreamer.
 */
static void
astreamer_recovery_injector_free(astreamer *streamer)
{
    astreamer_free(streamer->bbs_next);
    pfree(streamer);
}
 
/*
 * Inject a member into the archive with specified contents.
 */
void
astreamer_inject_file(astreamer *streamer, char *pathname, char *data,
                      int len)
{
    astreamer_member member;
 
    strlcpy(member.pathname, pathname, MAXPGPATH);
    member.size = len;
    member.mode = pg_file_create_mode;
    member.is_directory = false;
    member.is_link = false;
    member.linktarget[0] = '\0';
 
    /*
     * There seems to be no principled argument for these values, but they are
     * what PostgreSQL has historically used.
     */
    member.uid = 04000;
    member.gid = 02000;
 
    /*
     * We don't know here how to generate valid member headers and trailers
     * for the archiving format in use, so if those are needed, some successor
     * astreamer will have to generate them using the data from 'member'.
     */
    astreamer_content(streamer, &member, NULL, 0,
                      ASTREAMER_MEMBER_HEADER);
    astreamer_content(streamer, &member, data, len,
                      ASTREAMER_MEMBER_CONTENTS);
    astreamer_content(streamer, &member, NULL, 0,
                      ASTREAMER_MEMBER_TRAILER);
}