recovery_gen.c

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/*-------------------------------------------------------------------------
 *
 * recovery_gen.c
 *      Generator for recovery configuration
 *
 * Portions Copyright (c) 2011-2025, PostgreSQL Global Development Group
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"
 
#include "common/logging.h"
#include "fe_utils/recovery_gen.h"
#include "fe_utils/string_utils.h"
 
static char *escape_quotes(const char *src);
static char *FindDbnameInConnOpts(PQconninfoOption *conn_opts);
 
/*
 * Write recovery configuration contents into a fresh PQExpBuffer, and
 * return it.
 *
 * This accepts the dbname which will be appended to the primary_conninfo.
 * The dbname will be ignored by walreceiver process but slotsync worker uses
 * it to connect to the primary server.
 */
PQExpBuffer
GenerateRecoveryConfig(PGconn *pgconn, const char *replication_slot,
                       char *dbname)
{
    PQconninfoOption *connOptions;
    PQExpBufferData conninfo_buf;
    char       *escaped;
    PQExpBuffer contents;
 
    Assert(pgconn != NULL);
 
    contents = createPQExpBuffer();
    if (!contents)
        pg_fatal("out of memory");
 
    /*
     * In PostgreSQL 12 and newer versions, standby_mode is gone, replaced by
     * standby.signal to trigger a standby state at recovery.
     */
    if (PQserverVersion(pgconn) < MINIMUM_VERSION_FOR_RECOVERY_GUC)
        appendPQExpBufferStr(contents, "standby_mode = 'on'\n");
 
    connOptions = PQconninfo(pgconn);
    if (connOptions == NULL)
        pg_fatal("out of memory");
 
    initPQExpBuffer(&conninfo_buf);
    for (PQconninfoOption *opt = connOptions; opt && opt->keyword; opt++)
    {
        /* Omit empty settings and those libpqwalreceiver overrides. */
        if (strcmp(opt->keyword, "replication") == 0 ||
            strcmp(opt->keyword, "dbname") == 0 ||
            strcmp(opt->keyword, "fallback_application_name") == 0 ||
            (opt->val == NULL) ||
            (opt->val != NULL && opt->val[0] == '\0'))
            continue;
 
        /* Separate key-value pairs with spaces */
        if (conninfo_buf.len != 0)
            appendPQExpBufferChar(&conninfo_buf, ' ');
 
        /*
         * Write "keyword=value" pieces, the value string is escaped and/or
         * quoted if necessary.
         */
        appendPQExpBuffer(&conninfo_buf, "%s=", opt->keyword);
        appendConnStrVal(&conninfo_buf, opt->val);
    }
 
    if (dbname)
    {
        /*
         * If dbname is specified in the connection, append the dbname. This
         * will be used later for logical replication slot synchronization.
         */
        if (conninfo_buf.len != 0)
            appendPQExpBufferChar(&conninfo_buf, ' ');
 
        appendPQExpBuffer(&conninfo_buf, "%s=", "dbname");
        appendConnStrVal(&conninfo_buf, dbname);
    }
 
    if (PQExpBufferDataBroken(conninfo_buf))
        pg_fatal("out of memory");
 
    /*
     * Escape the connection string, so that it can be put in the config file.
     * Note that this is different from the escaping of individual connection
     * options above!
     */
    escaped = escape_quotes(conninfo_buf.data);
    termPQExpBuffer(&conninfo_buf);
    appendPQExpBuffer(contents, "primary_conninfo = '%s'\n", escaped);
    free(escaped);
 
    if (replication_slot)
    {
        /* unescaped: ReplicationSlotValidateName allows [a-z0-9_] only */
        appendPQExpBuffer(contents, "primary_slot_name = '%s'\n",
                          replication_slot);
    }
 
    if (PQExpBufferBroken(contents))
        pg_fatal("out of memory");
 
    PQconninfoFree(connOptions);
 
    return contents;
}
 
/*
 * Write the configuration file in the directory specified in target_dir,
 * with the contents already collected in memory appended.  Then write
 * the signal file into the target_dir.  If the server does not support
 * recovery parameters as GUCs, the signal file is not necessary, and
 * configuration is written to recovery.conf.
 */
void
WriteRecoveryConfig(PGconn *pgconn, const char *target_dir, PQExpBuffer contents)
{
    char        filename[MAXPGPATH];
    FILE       *cf;
    bool        use_recovery_conf;
 
    Assert(pgconn != NULL);
 
    use_recovery_conf =
        PQserverVersion(pgconn) < MINIMUM_VERSION_FOR_RECOVERY_GUC;
 
    snprintf(filename, MAXPGPATH, "%s/%s", target_dir,
             use_recovery_conf ? "recovery.conf" : "postgresql.auto.conf");
 
    cf = fopen(filename, use_recovery_conf ? "w" : "a");
    if (cf == NULL)
        pg_fatal("could not open file \"%s\": %m", filename);
 
    if (fwrite(contents->data, contents->len, 1, cf) != 1)
        pg_fatal("could not write to file \"%s\": %m", filename);
 
    fclose(cf);
 
    if (!use_recovery_conf)
    {
        snprintf(filename, MAXPGPATH, "%s/%s", target_dir, "standby.signal");
        cf = fopen(filename, "w");
        if (cf == NULL)
            pg_fatal("could not create file \"%s\": %m", filename);
 
        fclose(cf);
    }
}
 
/*
 * Escape a string so that it can be used as a value in a key-value pair
 * a configuration file.
 */
static char *
escape_quotes(const char *src)
{
    char       *result = escape_single_quotes_ascii(src);
 
    if (!result)
        pg_fatal("out of memory");
    return result;
}
 
/*
 * FindDbnameInConnOpts
 *
 * This is a helper function for GetDbnameFromConnectionOptions(). Extract
 * the value of dbname from PQconninfoOption parameters, if it's present.
 * Returns a strdup'd result or NULL.
 */
static char *
FindDbnameInConnOpts(PQconninfoOption *conn_opts)
{
    for (PQconninfoOption *conn_opt = conn_opts;
         conn_opt->keyword != NULL;
         conn_opt++)
    {
        if (strcmp(conn_opt->keyword, "dbname") == 0 &&
            conn_opt->val != NULL && conn_opt->val[0] != '\0')
            return pg_strdup(conn_opt->val);
    }
    return NULL;
}
 
/*
 * GetDbnameFromConnectionOptions
 *
 * This is a special purpose function to retrieve the dbname from either the
 * 'connstr' specified by the caller or from the environment variables.
 *
 * Returns NULL, if dbname is not specified by the user in the given
 * connection options.
 */
char *
GetDbnameFromConnectionOptions(const char *connstr)
{
    PQconninfoOption *conn_opts;
    char       *err_msg = NULL;
    char       *dbname;
 
    /* First try to get the dbname from connection string. */
    if (connstr)
    {
        conn_opts = PQconninfoParse(connstr, &err_msg);
        if (conn_opts == NULL)
            pg_fatal("%s", err_msg);
 
        dbname = FindDbnameInConnOpts(conn_opts);
 
        PQconninfoFree(conn_opts);
        if (dbname)
            return dbname;
    }
 
    /*
     * Next try to get the dbname from default values that are available from
     * the environment.
     */
    conn_opts = PQconndefaults();
    if (conn_opts == NULL)
        pg_fatal("out of memory");
 
    dbname = FindDbnameInConnOpts(conn_opts);
 
    PQconninfoFree(conn_opts);
    return dbname;
}