microsoft/garnet · error · RedisSerializationException

Unable to deserialize RedisOptions object. Line {lineCount}

Error message

Unable to deserialize RedisOptions object. Line {lineCount} not in expected format (keyword argument1 argument2 ... argumentN).

What it means

Thrown by RedisConfigSerializer.Deserialize when a non-comment, non-blank line in a Redis-format config file has no space character. Every directive in a Redis .conf file must follow 'keyword argument1 argument2 ... argumentN'. A line with only a keyword and no arguments (no space) is rejected because the parser cannot extract a value portion.

Source

Thrown at libs/host/Configuration/Redis/RedisConfigSerializer.cs:77

        /// <exception cref="RedisSerializationException"></exception>
        public static RedisOptions Deserialize(StreamReader reader, ILogger logger)
        {
            var options = new RedisOptions();

            int lineCount = 0;
            string line;
            while ((line = reader.ReadLine()) != null)
            {
                lineCount++;

                // Ignore whitespaces and comments
                if (string.IsNullOrWhiteSpace(line) || line.TrimStart().StartsWith('#'))
                    continue;

                // Expected line format: keyword argument1 argument2 ... argumentN
                var sepIdx = line.IndexOf(' ');
                if (sepIdx == -1)
                    throw new RedisSerializationException(
                        $"Unable to deserialize {nameof(RedisOptions)} object. Line {lineCount} not in expected format (keyword argument1 argument2 ... argumentN).");

                // Ignore key when no matching property found 
                var key = line.Substring(0, sepIdx);
                if (!KeyToProperty.Value.ContainsKey(key))
                {
                    logger?.LogWarning("Redis configuration option not supported: {key}.", key);
                    continue;
                }

                var value = line.Substring(sepIdx + 1);

                // Get matching property & the underlying option type (T in Option<T>)
                var prop = KeyToProperty.Value[key];
                var optType = prop.PropertyType.GenericTypeArguments.First();

                // Try to deserialize the value
                if (!TryChangeType(value, typeof(string), optType, out var newVal))

View on GitHub (pinned to 951b0fc683)

Solutions

Inspect the line number reported in the error message and add the missing argument(s) after the keyword.
If the directive genuinely takes no arguments, add a dummy value or remove the line if it's not needed.
Validate the config file format: each non-comment line must contain at least one space separating the keyword from its value.

Example fix

// before (line 3 of config file):
//   save

// after:
//   save 3600 1 300 100 60 10000

Defensive patterns

Strategy: validation

Validate before calling

foreach (var (line, num) in File.ReadLines(configPath).Select((l, i) => (l, i + 1)))
{
    var trimmed = line.TrimStart();
    if (string.IsNullOrWhiteSpace(trimmed) || trimmed.StartsWith('#')) continue;
    if (!line.Contains(' '))
        throw new FormatException($"Line {num}: directive '{trimmed}' has no arguments (expected 'keyword arg1 ...')");
}

Type guard

static bool IsValidConfigLine(string line)
{
    var t = line.TrimStart();
    if (string.IsNullOrWhiteSpace(t) || t.StartsWith('#')) return true;
    return line.Contains(' ');
}

Try / catch

try
{
    var redisOpts = RedisConfigSerializer.Deserialize(reader, logger);
}
catch (RedisSerializationException ex) when (ex.Message.Contains("not in expected format"))
{
    logger.LogError("Redis config file has a malformed line: {msg}", ex.Message);
    throw;
}

Prevention

Every directive line in a Redis config file must have at least one space after the keyword.
Validate config files with a linting tool before deploying.
Use comments starting with '#' for notes instead of bare keywords.

When it happens

Trigger: Loading a redis.conf-style file where a directive line is a single bare token with no space separator (e.g., a line containing only 'save' with no arguments). The code at line 75-76 uses IndexOf(' '); -1 means no space was found.

Common situations: Hand-edited Redis config files where a user accidentally deleted the argument portion; copy-paste from documentation that truncated the example; config generation tool that emitted keyword-only lines for boolean directives.

Related errors

AI-assisted analysis of microsoft/garnet@951b0fc683 (2026-08-13). Data as JSON: /api/errors/df2b4def3a461967. Report an issue: GitHub.