ollama - Align `keep-alive` handling across OllamaEmbeddingModel and OllamaChatModel

[dev-jonghoonpark]

Issue
Currently, the keep-alive option is handled inconsistently between models.

• In OllamaEmbeddingModel, a duration parser is used to process the keep-alive option.
• In OllamaChatModel, the raw user input is passed directly without parsing.

spring-ai/models/spring-ai-ollama/src/main/java/org/springframework/ai/ollama/OllamaEmbeddingModel.java

Lines 203 to 232 in d83c826

	public static class DurationParser {
	private static final Pattern PATTERN = Pattern.compile("(-?\\d+)(ms|s|m|h)");
	public static Duration parse(String input) {
	if (!StringUtils.hasText(input)) {
	return null;
	}
	Matcher matcher = PATTERN.matcher(input);
	if (matcher.matches()) {
	long value = Long.parseLong(matcher.group(1));
	String unit = matcher.group(2);
	return switch (unit) {
	case "ms" -> Duration.ofMillis(value);
	case "s" -> Duration.ofSeconds(value);
	case "m" -> Duration.ofMinutes(value);
	case "h" -> Duration.ofHours(value);
	default -> throw new IllegalArgumentException("Unsupported time unit: " + unit);
	};
	}
	else {
	throw new IllegalArgumentException("Invalid duration format: " + input);
	}
	}
	}

Proposed Solution
For better consistency, we should either:

1. Remove the duration parser from OllamaEmbeddingModel, or
2. Apply the duration parser to OllamaChatModel as well.

[MattiaDiProfio]

Hi, I'd like to have a go at this issue, could you assign it to me? Thanks 🙂

[dev-jonghoonpark]

@MattiaDiProfio
Nice! Once the maintainer confirms the direction, it should be all set to move forward. Cheering you on 🙂

[ilayaperumalg]

@MattiaDiProfio Thanks for your interest in contributing! @dev-jonghoonpark thanks to your contributions and helping the community as always!

It would be better to move DurationParser as a separate class and use it for both the models. We also need to add tests to verify the backwards compatibility.

[ilayaperumalg]

@dev-jonghoonpark @MattiaDiProfio As per the issue reported #4619 @Aelentel, we shouldn't be using java.util.Duration format for keep-alive parameter and the PR #4621 from @leelance go with the removal of Duration parser. I believe that's the right thing to do here. What do you think?

[leehaut]

If keepAlive uses the Duration type, it would be better to define Duration as the type in OllamaEmbeddingOptions as well. This eliminates the need for the public static Duration parse(String input) conversion, and Spring also supports configuration properties of this type.

However, in EmbeddingsRequest, for the field @JsonProperty("keep_alive") Duration keepAlive, we need to add @JsonSerialize(using = DurationToStringSerializer.class).

public class DurationToStringSerializer extends JsonSerializer<Duration> {
 //Duration =>5m, 2h...
}

[dev-jonghoonpark]

@ilayaperumalg
I also think using Duration isn't strictly necessary.
and I think that @leelance’s PR is appropriate. 👍