feat(web-search): add DuckDuckGo search engine

[Malaydewangan09]

Adds support for DuckDuckGo as a web search engine.

• closes [FEATURE] Add Support for DuckDuckGo Web Search Engine langchain4j#3460

[Martin7-1]

@Malaydewangan09 Thanks for your contribution! There are some failed tests, could you please check?

[Malaydewangan09]

Hey, @Martin7-1 👋 yes, I’ll check this.
Thanks!

[Malaydewangan09]

Seems, more like a rate liming issue with DuckDuckGo 👀
I’ll have a look at this again!

[anna-geller]

@Malaydewangan09, is this PR still a draft or ready to be reviewed by maintainers? Do you still see rate-limiting issues?

[Martin7-1]

@Malaydewangan09 Hi! Thanks for your contribution. Could you please rebase master branch?

[Malaydewangan09]

Hey @Martin7-1, it's done, but I see spotless error in other modules too 🤔 Should I apply these?
Thanks!

[ERROR] Failed to execute goal com.diffplug.spotless:spotless-maven-plugin:2.44.4:check (default-cli) on project langchain4j-community-core: The following files had format violations:
[ERROR]     src/test/java/dev/langchain4j/community/chain/RetrievalQAChainTest.java
[ERROR]         @@ -84,10 +84,10 @@
[ERROR]          ········String·expectedUserMessage·=
[ERROR]          ················"""
[ERROR]          ················query
[ERROR]         -················
[ERROR]         +
[ERROR]          ················Answer·using·the·following·information:
[ERROR]          ················Segment·1
[ERROR]         -················
[ERROR]         +
[ERROR]          ················Segment·2""";
[ERROR]          ········assertThat(messagesCaptor.getValue()).isEqualTo(expectedUserMessage);
[ERROR]          ····}
[ERROR] Run 'mvn spotless:apply' to fix these violations.

[Martin7-1]

Hey @Martin7-1, it's done, but I see spotless error in other modules too 🤔 Should I apply these? Thanks!

[ERROR] Failed to execute goal com.diffplug.spotless:spotless-maven-plugin:2.44.4:check (default-cli) on project langchain4j-community-core: The following files had format violations:
[ERROR]     src/test/java/dev/langchain4j/community/chain/RetrievalQAChainTest.java
[ERROR]         @@ -84,10 +84,10 @@
[ERROR]          ········String·expectedUserMessage·=
[ERROR]          ················"""
[ERROR]          ················query
[ERROR]         -················
[ERROR]         +
[ERROR]          ················Answer·using·the·following·information:
[ERROR]          ················Segment·1
[ERROR]         -················
[ERROR]         +
[ERROR]          ················Segment·2""";
[ERROR]          ········assertThat(messagesCaptor.getValue()).isEqualTo(expectedUserMessage);
[ERROR]          ····}
[ERROR] Run 'mvn spotless:apply' to fix these violations.

Don't worry about it :) Looks like Github Action successfully passed spotless check. I'll review the PR asap.

[Malaydewangan09]

Its still red after adding small retry though 🤔
Works fine, when I launch multiple runs for these tests locally.
On it!

[Martin7-1]

Its still red after adding small retry though 🤔 Works fine, when I launch multiple runs for these tests locally. On it!

Great! Please ping me if you find ways to solve it.

[Malaydewangan09]

@Martin7-1, updated the tests to be more resilient and also took some inspiration from python DuckDuckGo wrapper used in langchain! 🤞

[Martin7-1]

Hmm...Looks like it stiil failed

[Malaydewangan09]

Humm, looks like a connection timeout now 🤔
Tried running parallel tests on my machine seems good there. Added an extra step to check for network availability in tests!

[Martin7-1]

@Malaydewangan09 I can passed all tests in my local env, looks like the GitHub Action may have some network problem :)

Great job! Thank you!

[Martin7-1]

Please add documents in langchain4j main repo. Thank you!

[Malaydewangan09]

Yeah, seems like that.
I'll add the docs in the main repo, thanks!