一个应用程序实例可以在 FCM 中订阅多少个主题？
How many topics an app instance can subscribe in FCM?
正如 FCM 文档中提到的，可以为一个 Firebase 应用程序创建无限的主题。但是正如 Firebase Admin SDK document: 解释了一个错误：
messaging/too-many-topics:- A registration token has been subscribed to the maximum number of topics and cannot be subscribed to any more.
我找不到这个最大主题数的阈值。任何人都可以解释一下，限制是什么？ 一个应用程序实例可以在 FCM 中订阅多少个主题？
我通过 运行 应用程序实例的订阅脚本找到了答案。订阅 1999 主题后，下一次订阅开始出现错误：messaging/too-many-topics.
所以阈值为1999。
尽管选择的答案是正确的，但我想 post 在这里给出一个绝对的答案。
Google Firebase Cloud Messaging
Some things to keep in mind about topics:
Topic messaging supports unlimited subscriptions for each topic.
However, FCM enforces limits in these areas:
One app instance can be subscribed to no more than 2000 topics.
If you are using batch import to subscribe app instances, each request is limited to 1000 app instances.
The frequency of new subscriptions is rate-limited per project. If you send too many subscription requests in a short period of time, FCM servers will respond with a 429 RESOURCE_EXHAUSTED ("quota exceeded") response. Retry with exponential backoff.
正如 FCM 文档中提到的，可以为一个 Firebase 应用程序创建无限的主题。但是正如 Firebase Admin SDK document: 解释了一个错误：
messaging/too-many-topics:- A registration token has been subscribed to the maximum number of topics and cannot be subscribed to any more.
我找不到这个最大主题数的阈值。任何人都可以解释一下，限制是什么？ 一个应用程序实例可以在 FCM 中订阅多少个主题？
我通过 运行 应用程序实例的订阅脚本找到了答案。订阅 1999 主题后，下一次订阅开始出现错误：messaging/too-many-topics.
所以阈值为1999。
尽管选择的答案是正确的，但我想 post 在这里给出一个绝对的答案。 Google Firebase Cloud Messaging
Some things to keep in mind about topics:
Topic messaging supports unlimited subscriptions for each topic. However, FCM enforces limits in these areas:
One app instance can be subscribed to no more than 2000 topics.
If you are using batch import to subscribe app instances, each request is limited to 1000 app instances.
The frequency of new subscriptions is rate-limited per project. If you send too many subscription requests in a short period of time, FCM servers will respond with a 429 RESOURCE_EXHAUSTED ("quota exceeded") response. Retry with exponential backoff.