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fix(trends): categorize caching #184

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Merged
OmarNabil005 merged 1 commit into from
Dec 15, 2025
Merged

fix(trends): categorize caching #184

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29 changes: 24 additions & 5 deletions src/post/services/hashtag-trends.service.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -180,7 +180,14 @@ export class HashtagTrendService {

if (trending.length === 0) {
this.logger.warn(`No trending data in Redis for ${category}, falling back to DB`);
return await this.getTrendingFromDB(limit, category);
const dbResults = await this.getTrendingFromDB(limit, category);

if (dbResults.length > 0) {
await this.redisService.setJSON(cacheKey, dbResults, this.CACHE_TTL);
this.logger.debug(`Cached ${dbResults.length} DB results for ${category}`);
}

return dbResults;
}

this.failureCount = 0;
Expand Down Expand Up @@ -326,7 +333,6 @@ export class HashtagTrendService {
return trends.map((trend) => ({
tag: `#${trend.hashtag.tag}`,
totalPosts: trend.post_count_7d,
score: trend.trending_score,
}));
} catch (error) {
this.logger.error('Failed to get trending from DB:', error);
Expand Down Expand Up @@ -404,16 +410,29 @@ export class HashtagTrendService {
}

private async determineCategories(event: PostCreatedEvent): Promise<TrendCategory[]> {
const categories: Set<TrendCategory> = new Set([TrendCategory.GENERAL]);
const categories: Set<TrendCategory> = new Set();

categories.add(TrendCategory.GENERAL);

if (event.interestSlug) {
for (const [category, slugs] of Object.entries(CATEGORY_TO_INTERESTS)) {
if (slugs.includes(event.interestSlug)) {
if (category === TrendCategory.GENERAL || category === TrendCategory.PERSONALIZED) {
continue;
}
Comment on lines +419 to +421
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Copilot AI Dec 15, 2025

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The logic for excluding GENERAL and PERSONALIZED is redundant since GENERAL is explicitly added at line 415, and PERSONALIZED should not be in CATEGORY_TO_INTERESTS. This filtering suggests a potential misunderstanding of the data structure. Consider validating that CATEGORY_TO_INTERESTS doesn't contain these categories, or document why this defensive check is necessary.

Suggested change
if (category === TrendCategory.GENERAL || category === TrendCategory.PERSONALIZED) {
continue;
}
// Assumption: CATEGORY_TO_INTERESTS does not contain GENERAL or PERSONALIZED

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if (slugs.length > 0 && slugs.includes(event.interestSlug)) {
categories.add(category as TrendCategory);
this.logger.debug(
`Post ${event.postId} with interest '${event.interestSlug}' mapped to category '${category}'`
);
}
}
}

return Array.from(categories);
const result = Array.from(categories);
this.logger.debug(
`Post ${event.postId} will be tracked in categories: ${result.join(', ')}`
);

return result;
}
}
6 changes: 2 additions & 4 deletions src/post/services/personalized-trends.service.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ export class PersonalizedTrendsService {
async getPersonalizedTrending(
userId: number,
limit: number = 10,
): Promise<Array<{ tag: string; totalPosts: number; score: number; categories: string[] }>> {
): Promise<Array<{ tag: string; totalPosts: number; }>> {
const cacheKey = `personalized:trending:${userId}:${limit}`;
const cached = await this.redisService.getJSON<any[]>(cacheKey);
if (cached && cached.length > 0) {
Expand All @@ -53,6 +53,7 @@ export class PersonalizedTrendsService {
const userInterests = await this.usersService.getUserInterests(userId);
const interestSlugs = userInterests.map((ui) => ui.slug);
const categories = this.mapInterestsToCategories(interestSlugs);

if (categories.length === 0) {
this.logger.debug(`User ${userId} has no interests, falling back to GENERAL`);
return await this.getTrendingForCategory(TrendCategory.GENERAL, limit);
Expand All @@ -71,7 +72,6 @@ export class PersonalizedTrendsService {
this.logger.warn(`No personalized trends for user ${userId}, using GENERAL`);
return await this.getTrendingForCategory(TrendCategory.GENERAL, limit);
}

const results = await Promise.all(
combinedTrends.map(async (trend) => {
let metadata = await this.redisTrendingService.getHashtagMetadata(
Expand Down Expand Up @@ -103,8 +103,6 @@ export class PersonalizedTrendsService {
return {
tag: `#${metadata.tag}`,
totalPosts: counts.count7d,
score: trend.combinedScore,
categories: trend.categories,
};
}),
);
Expand Down
41 changes: 26 additions & 15 deletions src/post/services/post.service.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -580,21 +580,32 @@ export class PostService {

// Emit post.created event for real-time hashtag tracking
if (hashtagIds.length > 0) {
let interestSlug: string | undefined;
if (post.interest_id) {
const interest = await this.prismaService.interest.findUnique({
where: { id: post.interest_id },
select: { slug: true },
});
interestSlug = interest?.slug;
}
this.eventEmitter.emit('post.created', {
postId: post.id,
userId: post.user_id,
hashtagIds,
interestSlug,
timestamp: post.created_at.getTime(),
});
setTimeout(async () => {
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Using setTimeout with a hardcoded delay of 1500ms is a fragile solution that creates a race condition. If the database update takes longer than 1.5 seconds, the interest_id may still be null. Consider using a more reliable approach such as refetching the post within the same transaction, using database triggers, or implementing a retry mechanism with exponential backoff.

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try {
let interestSlug: string | undefined;
const updatedPost = await this.prismaService.post.findUnique({
where: { id: post.id },
select: { interest_id: true },
});

if (updatedPost?.interest_id) {
const interest = await this.prismaService.interest.findUnique({
where: { id: updatedPost.interest_id },
select: { slug: true },
});
interestSlug = interest?.slug;
}
this.eventEmitter.emit('post.created', {
postId: post.id,
userId: post.user_id,
hashtagIds,
interestSlug,
timestamp: post.created_at.getTime(),
});
} catch (error) {
console.error('Failed to emit post.created event:', error);
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Direct console.error usage is inconsistent with the logging pattern typically used in services. Consider using a logger instance (e.g., this.logger.error) for consistent log formatting and level management.

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}
}, 1500);
}

// Update parent post stats cache if this is a reply or quote
Expand Down
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